dataset.py

# DISCLAIMER
#
# The majority of the data below is NOT original and has been sourced from publicly available articles, websites, and other internet content.
# This dataset is intended solely for training and educational purposes. Full credit and rights belong to the original authors and creators of the content.
#
#


dataset = [
    (
        "Photosynthesis is the process by which green plants convert sunlight into chemical energy, producing oxygen and glucose from carbon dioxide and water.",
        100),
    ("Hey everyone!", 0),
    ("Ladies and gentlemen, welcome to today's conference!", 0),
    ("Photosynthesis allows green plants to convert sunlight into energy, producing oxygen and glucose in the process.",
     90),
    ("Photosynthesis, which plants do, is just really cool and fascinating to think about.", 5),
    (
        "Photosynthesis in plants is amazing because they convert sunlight into energy while we benefit from the oxygen they produce.",
        60),
    ("The mitochondria is the powerhouse of the cell, generating ATP through cellular respiration.", 100),
    ("Wow, isn't that interesting?", 0),
    ("Thank you all for being here tonight!", 0),
    ("Mitochondria generate ATP, the cell's energy currency, through cellular respiration.", 80),
    ("Mitochondria, which are found in cells, are really vital for energy.", 20),
    ("In cellular respiration, mitochondria generate ATP, which powers cellular activities.", 60),
    (
        "DNA, or deoxyribonucleic acid, contains the genetic instructions for development and functioning of living organisms.",
        100),
    ("That's cool!", 0),
    ("Welcome to our event!", 0),
    ("DNA carries genetic information crucial for development and functioning.", 70),
    ("DNA, which is the genetic material, is so fascinating and important.", 30),
    ("Genetic instructions are encoded in DNA, guiding development and cellular activities.", 50),
    (
        "The theory of relativity, developed by Albert Einstein, revolutionized our understanding of space, time, and gravity.",
        100),
    ("Wow, what a concept!", 0),
    ("Good afternoon, everyone!", 0),
    ("Einstein's theory of relativity altered our perception of space, time, and gravity.", 70),
    ("Relativity, proposed by Einstein, is just so mind-blowing.", 20),
    ("Space and time are interconnected in Einstein's theory of relativity.", 90),
    (
        "Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles.",
        100),
    ("Amazing, isn't it?", 0),
    ("Welcome, everyone!", 0),
    ("Quantum mechanics describes the behavior of particles on an atomic and subatomic level.", 100),
    ("Quantum mechanics, which is really fascinating, deals with tiny particles.", 30),
    ("Atoms and particles behave according to the principles of quantum mechanics.", 60),
    ("Evolution by natural selection, a theory proposed by Charles Darwin, explains the diversity of life on Earth.",
     95),
    ("Isn't that something?", 0),
    ("Hello, everyone!", 0),
    ("Darwin's theory of evolution explains how species adapt and change over time.", 80),
    ("Evolution, which Darwin proposed, is super interesting.", 20),
    ("Species evolve over time through the process of natural selection.", 50),
    (
        "Plate tectonics is the theory explaining the movement of the Earth's lithosphere, which is divided into tectonic plates.",
        100),
    ("Wow, isn't that cool?", 0),
    ("Good morning, everyone!", 0),
    ("The theory of plate tectonics describes the large-scale movement of Earth's lithosphere.", 80),
    ("Plate tectonics, which explain earthquakes, are fascinating.", 20),
    ("Earth's lithosphere is divided into tectonic plates that move.", 50),
    ("The water cycle describes the continuous movement of water on, above, and below the surface of the Earth.", 100),
    ("Isn't that neat?", 0),
    ("Welcome to today's session!", 0),
    ("The water cycle involves evaporation, condensation, and precipitation.", 80),
    ("The water cycle, which is essential, involves several stages.", 20),
    ("Water moves through evaporation, condensation, and precipitation in the water cycle.", 50),
    (
        "The Pythagorean theorem states that in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.",
        100),
    ("Isn't math fun?", 0),
    ("Hello and welcome!", 0),
    ("The Pythagorean theorem is a fundamental principle in geometry.", 80),
    ("The Pythagorean theorem, which relates to triangles, is important.", 20),
    ("In a right-angled triangle, the Pythagorean theorem applies.", 50),
    ("The cell membrane controls the movement of substances in and out of cells.", 100),
    ("Isn't that fascinating?", 0),
    ("Hello, good to see you all!", 0),
    ("Cell membranes regulate what enters and exits the cell.", 80),
    ("The cell membrane, which is essential, regulates movement.", 40),
    ("Substances move in and out of cells through the cell membrane.", 50),
    ("Newton's laws of motion describe the relationship between the motion of an object and the forces acting on it.",
     100),
    ("Isn't that amazing?", 0),
    ("Good evening, everyone!", 0),
    ("Newton's laws explain how objects move and interact with forces.", 80),
    ("Newton's laws, which are fundamental, describe motion.", 20),
    ("Motion and forces are described by Newton's laws.", 50),
    ("Black holes are regions of spacetime where gravity is so strong that nothing, not even light, can escape.", 100),
    ("Wow, isn't that intriguing?", 0),
    ("Welcome to our talk!", 0),
    ("Black holes have such strong gravity that even light can't escape.", 80),
    ("Black holes, which are incredibly dense, are fascinating.", 20),
    ("Regions with intense gravity, like black holes, trap everything.", 50),
    (
        "Artificial intelligence (AI) involves creating machines that can perform tasks that typically require human intelligence.",
        70),
    ("Isn't that exciting?", 0),
    ("Good afternoon and welcome!", 0),
    ("AI systems can perform tasks that usually require human intelligence.", 80),
    ("AI, which is rapidly advancing, is amazing.", 30),
    ("Machines with AI can perform intelligent tasks.", 60),
    (
        "CRISPR-Cas9 is a revolutionary technology that allows for precise editing of the genome, potentially curing genetic diseases.",
        100),
    ("Isn't that revolutionary?", 0),
    ("Hi everyone, glad to see you!", 0),
    ("CRISPR-Cas9 enables scientists to edit genes with high precision.", 80),
    ("CRISPR, which is used in genetics, is groundbreaking.", 20),
    ("Genome editing is possible with CRISPR-Cas9 technology.", 50),
    ("Blockchain is a decentralized ledger technology that securely records transactions across multiple computers.",
     100),
    ("Isn't that secure?", 0),
    ("Good evening, everyone!", 0),
    ("Blockchain technology records transactions in a decentralized and secure way.", 80),
    ("Blockchain, which is used for cryptocurrencies, is innovative.", 20),
    ("Transactions are securely recorded using blockchain technology.", 50),
    ("Global warming refers to the long-term rise in the average temperature of the Earth's climate system.", 100),
    ("Isn't that concerning?", 0),
    ("Welcome to today's lecture!", 0),
    ("The Earth's average temperature is rising due to global warming.", 80),
    ("Global warming, which affects climates, is a major issue.", 20),
    ("The climate system is warming over time due to global warming.", 50),
    (
        "The human immune system defends the body against infectious organisms and other invaders through a complex network of cells and proteins.",
        100),
    ("Isn't that impressive?", 0),
    ("Good to see you all here today!", 0),
    ("The immune system protects the body from infections and diseases.", 80),
    ("The immune system, which fights invaders, is crucial.", 20),
    ("Our body fights off infections with the immune system.", 50),
    (
        "Dark matter makes up about 27% of the universe and does not emit light or energy, making it invisible and detectable only through its gravitational effects.",
        100),
    ("Isn't that mysterious?", 0),
    ("Welcome to the presentation!", 0),
    ("Dark matter, although invisible, has significant gravitational effects.", 80),
    ("Dark matter, which is undetectable by light, is intriguing.", 20),
    ("The universe contains a large amount of dark matter affecting gravity.", 50),
    ("The Large Hadron Collider (LHC) is the world's largest and most powerful particle accelerator, located at CERN.",
     100),
    ("Isn't that incredible?", 0),
    ("Hello, everyone, glad to have you here!", 0),
    ("The LHC is used to collide particles at high energies to study fundamental physics.", 80),
    ("The LHC, which is at CERN, is an amazing tool for physics.", 20),
    ("Particles are accelerated and collided in the LHC to study physics.", 50),
    ("Photosynthesis in green plants converts sunlight into chemical energy, producing oxygen and glucose.", 100),
    ("Hey everyone, welcome!", 0),
    ("Ladies and gentlemen, thanks for coming!", 0),
    ("Green plants use photosynthesis to produce energy and oxygen.", 90),
    ("Photosynthesis, a process in plants, is fascinating and vital.", 10),
    ("Green plants convert sunlight into energy via photosynthesis.", 50),
    (
        "The internet is a global network that connects millions of private, public, academic, business, and government networks.",
        100),
    ("Isn't that vast?", 0),
    ("Welcome to the seminar!", 0),
    ("The internet connects various networks globally, facilitating communication.", 80),
    ("The internet, which links many networks, is expansive.", 20),
    ("Globally, the internet connects different networks.", 50),
    (
        "Machine learning is a subset of artificial intelligence that enables computers to learn from data and improve from experience without being explicitly programmed.",
        100),
    ("Isn't that smart?", 0),
    ("Hello, welcome to the talk!", 0),
    ("Machine learning allows computers to improve their performance by learning from data.", 80),
    ("Machine learning, which is part of AI, is highly advanced.", 20),
    ("Computers can learn from data using machine learning.", 50),
    (
        "Antibiotics are medicines that help stop infections caused by bacteria by killing the bacteria or preventing them from reproducing.",
        100),
    ("Isn't that lifesaving?", 0),
    ("Good afternoon, everyone!", 0),
    ("Antibiotics treat bacterial infections by killing or inhibiting bacteria.", 80),
    ("Antibiotics, which fight bacteria, are crucial for health.", 20),
    ("Bacterial infections are treated using antibiotics.", 50),
    (
        "The periodic table organizes all known chemical elements in an informative array based on atomic number, electron configuration, and recurring chemical properties.",
        100),
    ("Isn't that organized?", 0),
    ("Hello everyone, glad you're here!", 0),
    ("The periodic table arranges elements by atomic number and properties.", 80),
    ("The periodic table, which lists elements, is very useful.", 20),
    ("Elements are organized in the periodic table by various properties.", 50),
    (
        "Electric cars use electric motors powered by batteries, reducing the reliance on fossil fuels and decreasing emissions.",
        100),
    ("Isn't that eco-friendly?", 0),
    ("Welcome to our discussion!", 0),
    ("Electric cars reduce emissions by using battery-powered motors.", 80),
    ("Electric cars, which use batteries, are environmentally friendly.", 20),
    ("Using batteries, electric cars help reduce fossil fuel reliance.", 50),
    (
        "The Hubble Space Telescope has provided stunning images and valuable data, advancing our understanding of the universe.",
        100),
    ("Isn't that awe-inspiring?", 0),
    ("Hi everyone, thanks for coming!", 0),
    ("The Hubble Space Telescope has revolutionized astronomy with its images.", 80),
    ("The Hubble, which orbits Earth, has greatly advanced space science.", 20),
    ("Stunning images from Hubble have deepened our understanding of space.", 50),
    ("Vaccines stimulate the immune system to develop immunity to a specific disease, preventing illness.", 100),
    ("Isn't that preventative?", 0),
    ("Welcome to our health seminar!", 0),
    ("Vaccines help prevent diseases by boosting the immune system.", 80),
    ("Vaccines, which prevent illnesses, are essential for public health.", 20),
    ("The immune system is strengthened by vaccines to fight diseases.", 50),
    ("Photosynthesis in green plants converts sunlight into chemical energy, producing oxygen and glucose.", 100),
    ("Hey everyone, welcome!", 0),
    ("Ladies and gentlemen, thanks for coming!", 0),
    ("Green plants use photosynthesis to produce energy and oxygen.", 90),
    ("Photosynthesis, a process in plants, is fascinating and vital.", 10),
    ("Green plants convert sunlight into energy via photosynthesis.", 50),
    (
        "The internet is a global network that connects millions of private, public, academic, business, and government networks.",
        100),
    ("Isn't that vast?", 0),
    ("Welcome to the seminar!", 0),
    ("The internet connects various networks globally, facilitating communication.", 80),
    ("The internet, which links many networks, is expansive.", 20),
    ("Globally, the internet connects different networks.", 50),
    (
        "Machine learning is a subset of artificial intelligence that enables computers to learn from data and improve from experience without being explicitly programmed.",
        100),
    ("Isn't that smart?", 0),
    ("Hello, welcome to the talk!", 0),
    ("Machine learning allows computers to improve their performance by learning from data.", 80),
    ("Machine learning, which is part of AI, is highly advanced.", 20),
    ("Computers can learn from data using machine learning.", 50),
    (
        "Antibiotics are medicines that help stop infections caused by bacteria by killing the bacteria or preventing them from reproducing.",
        100),
    ("Isn't that lifesaving?", 0),
    ("Good afternoon, everyone!", 0),
    ("Antibiotics treat bacterial infections by killing or inhibiting bacteria.", 80),
    ("Antibiotics, which fight bacteria, are crucial for health.", 20),
    ("Bacterial infections are treated using antibiotics.", 50),
    (
        "The periodic table organizes all known chemical elements in an informative array based on atomic number, electron configuration, and recurring chemical properties.",
        100),
    ("Isn't that organized?", 0),
    ("Hello everyone, glad you're here!", 0),
    ("The periodic table arranges elements by atomic number and properties.", 80),
    ("The periodic table, which lists elements, is very useful.", 20),
    ("Elements are organized in the periodic table by various properties.", 50),
    (
        "Electric cars use electric motors powered by batteries, reducing the reliance on fossil fuels and decreasing emissions.",
        100),
    ("Isn't that eco-friendly?", 0),
    ("Welcome to our discussion!", 0),
    ("Electric cars reduce emissions by using battery-powered motors.", 80),
    ("Electric cars, which use batteries, are environmentally friendly.", 20),
    ("Using batteries, electric cars help reduce fossil fuel reliance.", 50),
    (
        "The Hubble Space Telescope has provided stunning images and valuable data, advancing our understanding of the universe.",
        100),
    ("Isn't that awe-inspiring?", 0),
    ("Hi everyone, thanks for coming!", 0),
    ("The Hubble Space Telescope has revolutionized astronomy with its images.", 80),
    ("The Hubble, which orbits Earth, has greatly advanced space science.", 20),
    ("Stunning images from Hubble have deepened our understanding of space.", 50),
    ("Vaccines stimulate the immune system to develop immunity to a specific disease, preventing illness.", 100),
    ("Isn't that preventative?", 0),
    ("Welcome to our health seminar!", 0),
    ("Vaccines help prevent diseases by boosting the immune system.", 80),
    ("Vaccines, which prevent illnesses, are essential for public health.", 20),
    ("The immune system is strengthened by vaccines to fight diseases.", 50),
    (
        "A black hole is a region of space where the gravitational pull is so strong that not even light can escape.",
        100),
    ("Wow, isn't that mysterious?", 0),
    ("Good day, everyone!", 0),
    ("In a black hole, the gravitational pull is incredibly strong.", 80),
    ("Black holes, with their strong gravity, are truly fascinating.", 20),
    ("Nothing can escape the gravity of a black hole.", 50),
    (
        "String theory suggests that the fundamental particles of the universe are one-dimensional strings rather than point particles.",
        100),
    ("Isn't that intriguing?", 0),
    ("Hi, everyone, good to see you!", 0),
    ("String theory posits that particles are actually tiny strings.", 80),
    ("String theory, which deals with particles, is quite complex.", 20),
    ("Fundamental particles might be strings, according to string theory.", 50),
    ("Climate change refers to significant changes in global temperatures and weather patterns over time.", 100),
    ("Isn't that concerning?", 0),
    ("Welcome to our climate talk!", 0),
    ("Climate change is causing shifts in weather patterns worldwide.", 80),
    ("Climate change, which affects the entire planet, is a critical issue.", 20),
    ("Global temperatures are rising due to climate change.", 50),
    ("The human brain consists of approximately 86 billion neurons that communicate through synapses.", 100),
    ("Isn't that amazing?", 0),
    ("Hi everyone, great to have you here!", 0),
    ("The brain's neurons communicate via synapses to process information.", 80),
    ("The human brain, with its billions of neurons, is incredibly complex.", 20),
    ("Neurons in the brain communicate to process thoughts and actions.", 50),
    ("Renewable energy sources, such as solar and wind power, are essential for reducing greenhouse gas emissions.",
     100),
    ("Isn't that sustainable?", 0),
    ("Welcome to our energy seminar!", 0),
    ("Renewable energy helps reduce greenhouse gas emissions.", 80),
    ("Solar and wind power, as renewable energy sources, are crucial.", 20),
    ("Greenhouse gas emissions can be reduced with renewable energy.", 50),
    ("The theory of general relativity describes gravity as a warping of spacetime by mass and energy.", 100),
    ("Isn't that profound?", 0),
    ("Hello, and thanks for joining us!", 0),
    ("General relativity explains gravity as a curvature of spacetime.", 80),
    ("General relativity, proposed by Einstein, is a key theory.", 20),
    ("Gravity is described by the warping of spacetime in general relativity.", 50),
    ("CRISPR is a technology that can be used to edit genes and has the potential to treat genetic disorders.", 100),
    ("Isn't that revolutionary?", 0),
    ("Good day, everyone, welcome!", 0),
    ("CRISPR technology allows for precise editing of genetic material.", 80),
    ("CRISPR, which can edit genes, is a groundbreaking tool.", 20),
    ("Genetic disorders might be treated with CRISPR gene editing.", 50),
    ("The Mariana Trench is the deepest part of the world's oceans, located in the western Pacific Ocean.", 100),
    ("Isn't that deep?", 0),
    ("Hello and welcome!", 0),
    ("The Mariana Trench is the deepest oceanic trench on Earth.", 80),
    ("The Mariana Trench, which is extremely deep, is fascinating.", 20),
    ("In the Pacific Ocean lies the deepest trench, the Mariana Trench.", 50),
    (
        "Quantum entanglement is a physical phenomenon that occurs when pairs of particles become interconnected and the state of one particle instantly influences the state of the other, no matter the distance between them.",
        100),
    ("Isn't that mind-bending?", 0),
    ("Hi, everyone, great to see you!", 0),
    ("Quantum entanglement involves particles instantaneously affecting each other.", 80),
    ("Quantum entanglement, which connects particles, is a strange phenomenon.", 20),
    ("Particles in quantum entanglement affect each other instantly, regardless of distance.", 50),
    (
        "DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules.",
        100),
    ("Isn't that precise?", 0),
    ("Good morning, everyone!", 0),
    ("DNA replication creates two identical copies of a DNA molecule.", 80),
    ("DNA replication, essential for cell division, is very accurate.", 20),
    ("In DNA replication, the molecule is copied to produce identical DNA.", 50),
    (
        "The speed of light in a vacuum is approximately 299,792,458 meters per second, a fundamental constant in physics.",
        100),
    ("Isn't that fast?", 0),
    ("Hello everyone, thanks for joining!", 0),
    ("The speed of light is a crucial constant in physics, at nearly 300 million meters per second.", 80),
    ("The speed of light, which is very fast, is fundamental to physics.", 20),
    ("Light travels in a vacuum at about 299,792,458 meters per second.", 50),
    (
        "The Richter scale measures the magnitude of earthquakes, with each whole number increase representing a tenfold increase in measured amplitude.",
        100),
    ("Isn't that powerful?", 0),
    ("Welcome to our geology talk!", 0),
    ("The Richter scale quantifies earthquake magnitude logarithmically.", 80),
    ("The Richter scale, which measures earthquakes, is logarithmic.", 20),
    ("Earthquake magnitude is measured on the Richter scale.", 50),
    (
        "The Amazon rainforest is the largest tropical rainforest in the world, known for its biodiversity and role in regulating the Earth's climate.",
        100),
    ("Isn't that important?", 0),
    ("Hello everyone, glad to have you here!", 0),
    ("The Amazon rainforest is crucial for biodiversity and climate regulation.", 80),
    ("The Amazon, which is vast, helps regulate the Earth's climate.", 20),
    ("Biodiversity and climate are supported by the Amazon rainforest.", 50),
    (
        "Metamorphic rocks are formed from existing rock types that are subjected to high heat, high pressure, or chemically active fluids.",
        100),
    ("Isn't that transformative?", 0),
    ("Welcome to our geology class!", 0),
    ("Metamorphic rocks form under high pressure and heat.", 80),
    ("Metamorphic rocks, which change form, result from intense conditions.", 20),
    ("High heat and pressure create metamorphic rocks from other rocks.", 50),
    (
        "The Great Wall of China is a series of fortifications built along the northern borders of China to protect against invasions.",
        100),
    ("Isn't that historic?", 0),
    ("Good to see you all here today!", 0),
    ("The Great Wall of China was built to defend against invasions.", 80),
    ("The Great Wall, which is very long, protected China's borders.", 20),
    ("China's Great Wall was constructed to guard against invasions.", 50),
    (
        "Electricity is the flow of electric charge, commonly carried by moving electrons through a conductor such as a wire.",
        100),
    ("Isn't that enlightening?", 0),
    ("Hello and good afternoon!", 0),
    ("Electricity is generated by the movement of electrons through a conductor.", 80),
    ("Electricity, which powers our devices, is the flow of electric charge.", 20),
    ("Electric charge flows through conductors to produce electricity.", 50),
    ("Photosynthesis in green plants converts sunlight into chemical energy, producing oxygen and glucose.", 100),
    ("Hey everyone, welcome!", 0),
    ("Ladies and gentlemen, thanks for coming!", 0),
    ("Green plants use photosynthesis to produce energy and oxygen.", 90),
    ("Photosynthesis, a process in plants, is fascinating and vital.", 10),
    ("Green plants convert sunlight into energy via photosynthesis.", 50),
    (
        "The internet is a global network that connects millions of private, public, academic, business, and government networks.",
        100),
    ("Isn't that vast?", 0),
    ("Welcome to the seminar!", 0),
    ("The internet connects various networks globally, facilitating communication.", 80),
    ("The internet, which links many networks, is expansive.", 20),
    ("Globally, the internet connects different networks.", 50),
    (
        "Machine learning is a subset of artificial intelligence that enables computers to learn from data and improve from experience without being explicitly programmed.",
        100),
    ("Isn't that smart?", 0),
    ("Hello, welcome to the talk!", 0),
    ("Machine learning allows computers to improve their performance by learning from data.", 80),
    ("Machine learning, which is part of AI, is highly advanced.", 20),
    ("Computers can learn from data using machine learning.", 50),
    (
        "Antibiotics are medicines that help stop infections caused by bacteria by killing the bacteria or preventing them from reproducing.",
        100),
    ("Isn't that lifesaving?", 0),
    ("Good afternoon, everyone!", 0),
    ("Antibiotics treat bacterial infections by killing or inhibiting bacteria.", 80),
    ("Antibiotics, which fight bacteria, are crucial for health.", 20),
    ("Bacterial infections are treated using antibiotics.", 50),
    (
        "The periodic table organizes all known chemical elements in an informative array based on atomic number, electron configuration, and recurring chemical properties.",
        100),
    ("Isn't that organized?", 0),
    ("Hello everyone, glad you're here!", 0),
    ("The periodic table arranges elements by atomic number and properties.", 80),
    ("The periodic table, which lists elements, is very useful.", 20),
    ("Elements are organized in the periodic table by various properties.", 50),
    (
        "Electric cars use electric motors powered by batteries, reducing the reliance on fossil fuels and decreasing emissions.",
        100),
    ("Isn't that eco-friendly?", 0),
    ("Welcome to our discussion!", 0),
    ("Electric cars reduce emissions by using battery-powered motors.", 80),
    ("Electric cars, which use batteries, are environmentally friendly.", 20),
    ("Using batteries, electric cars help reduce fossil fuel reliance.", 50),
    (
        "The Hubble Space Telescope has provided stunning images and valuable data, advancing our understanding of the universe.",
        100),
    ("Isn't that awe-inspiring?", 0),
    ("Hi everyone, thanks for coming!", 0),
    ("The Hubble Space Telescope has revolutionized astronomy with its images.", 80),
    ("The Hubble, which orbits Earth, has greatly advanced space science.", 20),
    ("Stunning images from Hubble have deepened our understanding of space.", 50),
    ("Vaccines stimulate the immune system to develop immunity to a specific disease, preventing illness.", 100),
    ("Isn't that preventative?", 0),
    ("Welcome to our health seminar!", 0),
    ("Vaccines help prevent diseases by boosting the immune system.", 80),
    ("Vaccines, which prevent illnesses, are essential for public health.", 20),
    ("The immune system is strengthened by vaccines to fight diseases.", 50),
    (
        "A black hole is a region of space where the gravitational pull is so strong that not even light can escape.",
        100),
    ("Wow, isn't that mysterious?", 0),
    ("Good day, everyone!", 0),
    ("In a black hole, the gravitational pull is incredibly strong.", 80),
    ("Black holes, with their strong gravity, are truly fascinating.", 20),
    ("Nothing can escape the gravity of a black hole.", 50),
    (
        "String theory suggests that the fundamental particles of the universe are one-dimensional strings rather than point particles.",
        100),
    ("Isn't that intriguing?", 0),
    ("Hi, everyone, good to see you!", 0),
    ("String theory posits that particles are actually tiny strings.", 80),
    ("String theory, which deals with particles, is quite complex.", 20),
    ("Fundamental particles might be strings, according to string theory.", 50),
    ("Climate change refers to significant changes in global temperatures and weather patterns over time.", 100),
    ("The Eiffel Tower, located in Paris, France, is one of the most iconic landmarks in the world.", 100),
    ("Isn't that breathtaking?", 0),
    ("Welcome to our architectural tour!", 0),
    ("The Eiffel Tower stands as a symbol of French culture and engineering prowess.", 80),
    ("The Eiffel Tower, which was completed in 1889, is a marvel of iron construction.", 20),
    ("Millions of visitors flock to the Eiffel Tower each year to admire its beauty and panoramic views.", 50),
    ("The human heart pumps blood throughout the body, delivering oxygen and nutrients to cells and tissues.", 100),
    ("Isn't that vital?", 0),
    ("Hello everyone, let's talk about the heart!", 0),
    ("The heart's rhythmic contractions ensure proper blood circulation.", 80),
    ("The human heart, a muscular organ, is essential for sustaining life.", 20),
    ("Blood is circulated through the body by the pumping action of the heart.", 50),
    (
        "Artificial intelligence (AI) is the simulation of human intelligence processes by machines, especially computer systems.",
        100),
    ("Isn't that cutting-edge?", 0),
    ("Welcome to our AI symposium!", 0),
    ("AI algorithms enable machines to perform tasks that typically require human intelligence.", 80),
    ("Artificial intelligence, a rapidly evolving field, has transformative potential across various industries.", 20),
    ("Machine learning and neural networks are subsets of artificial intelligence.", 50),
    ("The Great Barrier Reef is the world's largest coral reef system, located off the coast of Queensland, Australia.",
     100),
    ("Isn't that mesmerizing?", 0),
    ("Greetings, ocean enthusiasts!", 0),
    ("The Great Barrier Reef is home to an incredible diversity of marine life.", 80),
    ("The Great Barrier Reef, which spans over 2,300 kilometers, is a UNESCO World Heritage Site.", 20),
    ("Coral reefs, like the Great Barrier Reef, are vital ecosystems that support numerous marine species.", 50),
    (
        "Leonardo da Vinci, an Italian polymath of the Renaissance, is widely considered one of the most diversely talented individuals ever to have lived.",
        100),
    ("Isn't that inspiring?", 0),
    ("Hello art aficionados!", 0),
    ("Leonardo da Vinci's famous works include the Mona Lisa and The Last Supper.", 80),
    ("Leonardo da Vinci, a true Renaissance man, excelled in art, science, and engineering.", 20),
    ("Da Vinci's notebooks contain sketches and writings that reflect his wide-ranging interests and intellect.", 50),
    ("The Sahara Desert, located in North Africa, is the largest hot desert in the world.", 100),
    ("Isn't that expansive?", 0),
    ("Greetings from the desert!", 0),
    ("The Sahara Desert covers an area of approximately 9.2 million square kilometers.", 80),
    ("The Sahara, characterized by its vast sand dunes and rocky plateaus, is a harsh yet beautiful landscape.", 20),
    ("Nomadic tribes have traversed the Sahara for centuries, adapting to its challenging conditions.", 50),
    (
        "The periodic table organizes all known chemical elements in an informative array based on atomic number, electron configuration, and recurring chemical properties.",
        100),
    ("Isn't that organized?", 0),
    ("Hello everyone, glad you're here!", 0),
    ("The periodic table arranges elements by atomic number and properties.", 80),
    ("The periodic table, which lists elements, is very useful.", 20),
    ("Elements are organized in the periodic table by various properties.", 50),
    (
        "Electric cars use electric motors powered by batteries, reducing the reliance on fossil fuels and decreasing emissions.",
        100),
    ("Isn't that eco-friendly?", 0),
    ("Welcome to our discussion!", 0),
    ("Electric cars reduce emissions by using battery-powered motors.", 80),
    ("Electric cars, which use batteries, are environmentally friendly.", 20),
    ("Using batteries, electric cars help reduce fossil fuel reliance.", 50),
    (
        "The Hubble Space Telescope has provided stunning images and valuable data, advancing our understanding of the universe.",
        100),
    ("Isn't that awe-inspiring?", 0),
    ("Hi everyone, thanks for coming!", 0),
    ("The Hubble Space Telescope has revolutionized astronomy with its images.", 80),
    ("The Hubble, which orbits Earth, has greatly advanced space science.", 20),
    ("Stunning images from Hubble have deepened our understanding of space.", 50),
    ("Vaccines stimulate the immune system to develop immunity to a specific disease, preventing illness.", 100),
    ("Isn't that preventative?", 0),
    ("Welcome to our health seminar!", 0),
    ("Vaccines help prevent diseases by boosting the immune system.", 80),
    ("Vaccines, which prevent illnesses, are essential for public health.", 20),
    ("The immune system is strengthened by vaccines to fight diseases.", 50),
    (
        "A black hole is a region of space where the gravitational pull is so strong that not even light can escape.",
        100),
    ("Wow, isn't that mysterious?", 0),
    ("Good day, everyone!", 0),
    ("In a black hole, the gravitational pull is incredibly strong.", 80),
    ("Black holes, with their strong gravity, are truly fascinating.", 20),
    ("Nothing can escape the gravity of a black hole.", 50),
    (
        "String theory suggests that the fundamental particles of the universe are one-dimensional strings rather than point particles.",
        100),
    ("Isn't that intriguing?", 0),
    ("Hi, everyone, good to see you!", 0),
    ("String theory posits that particles are actually tiny strings.", 80),
    ("String theory, which deals with particles, is quite complex.", 20),
    ("Fundamental particles might be strings, according to string theory.", 50),
    ("Climate change refers to significant changes in global temperatures and weather patterns over time.", 100),
    ("Isn't that concerning?", 0),
    ("Welcome to our climate talk!", 0),
    ("Climate change is causing shifts in weather patterns worldwide.", 80),
    ("Climate change, which affects the entire planet, is a critical issue.", 20),
    ("Global temperatures are rising due to climate change.", 50),
    ("The human brain consists of approximately 86 billion neurons that communicate through synapses.", 100),
    ("Isn't that amazing?", 0),
    ("Hi everyone, great to have you here!", 0),
    ("The brain's neurons communicate via synapses to process information.", 80),
    ("The human brain, with its billions of neurons, is incredibly complex.", 20),
    ("Neurons in the brain communicate to process thoughts and actions.", 50),
    ("Renewable energy sources, such as solar and wind power, are essential for reducing greenhouse gas emissions.",
     100),
    ("Isn't that sustainable?", 0),
    ("Welcome to our energy seminar!", 0),
    ("Mount Everest is the tallest mountain above sea level, reaching approximately 8,848.86 meters (29,031.7 feet).",
     100),
    ("Isn't that awe-inspiring?", 0),
    ("Greetings, adventurers!", 0),
    ("Mount Everest is part of the Himalayas and is located on the border between Nepal and China.", 80),
    ("Scaling Mount Everest is a daunting challenge that attracts climbers from around the world.", 20),
    ("The summit of Mount Everest is often obscured by clouds, adding to its mystique.", 50),
    (
        "The human genome consists of approximately 3.2 billion DNA base pairs and encodes the genetic instructions for life.",
        100),
    ("Isn't that intricate?", 0),
    ("Hello, genetics enthusiasts!", 0),
    ("The human genome project mapped and sequenced the entire human genome.", 80),
    ("Genetic variations in the human genome contribute to differences in traits and susceptibility to diseases.", 20),
    ("DNA sequencing technologies have revolutionized our understanding of the human genome.", 50),
    ("The Colosseum, located in Rome, Italy, is an ancient amphitheater built during the Roman Empire.", 100),
    ("Isn't that historic?", 0),
    ("Welcome to ancient Rome!", 0),
    (
        "The Colosseum could hold between 50,000 to 80,000 spectators and was used for gladiatorial contests and public spectacles.",
        80),
    ("The Colosseum's architecture and engineering prowess reflect the ingenuity of the ancient Romans.", 20),
    ("Today, the Colosseum is a symbol of Rome's rich history and cultural heritage.", 50),
    (
        "Photosynthesis is the process by which green plants and some other organisms convert light energy into chemical energy.",
        100),
    ("Isn't that vital for life?", 0),
    ("Greetings, botanists!", 0),
    ("Photosynthesis occurs in chloroplasts, where chlorophyll captures sunlight to produce glucose and oxygen.", 80),
    ("Plants play a crucial role in the carbon cycle by absorbing carbon dioxide during photosynthesis.", 20),
    ("The oxygen released during photosynthesis sustains aerobic life on Earth.", 50),
    (
        "The Milky Way is a barred spiral galaxy that contains our Solar System, consisting of billions of stars, planets, and other celestial objects.",
        100),
    ("Isn't that mind-boggling?", 0),
    ("Hello, stargazers!", 0),
    ("The Milky Way is estimated to contain between 100 to 400 billion stars, including our Sun.", 80),
    ("Our Solar System is located in one of the spiral arms of the Milky Way galaxy.", 20),
    ("The Milky Way is just one of billions of galaxies in the observable universe.", 50),
    ("The Mona Lisa, painted by Leonardo da Vinci, is one of the most famous and iconic artworks in the world.", 100),
    ("Isn't that enigmatic?", 0),
    ("Greetings from the Louvre!", 0),
    ("The Mona Lisa's smile has captivated audiences for centuries and remains a subject of intrigue and speculation.",
     80),
    ("Leonardo da Vinci's masterpiece is renowned for its meticulous detail and subtle expression.", 20),
    ("The Mona Lisa is housed in the Louvre Museum in Paris and attracts millions of visitors each year.", 50),
    (
        "Plate tectonics is the scientific theory that Earth's lithosphere is divided into large, rigid plates that move and interact with one another.",
        100),
    ("Isn't that dynamic?", 0),
    ("Welcome to geology class!", 0),
    ("Plate tectonics explains the formation of continents, mountains, earthquakes, and volcanic activity.", 80),
    ("The theory of plate tectonics revolutionized our understanding of Earth's geology and natural processes.", 20),
    (
        "Subduction zones, where one tectonic plate sinks beneath another, are associated with volcanic arcs and earthquakes.",
        50),
    (
        "The Amazon rainforest, often referred to as the 'lungs of the Earth', is the largest tropical rainforest ecosystem in the world.",
        100),
    ("Isn't that ecologically significant?", 0),
    ("Greetings from the Amazon!", 0),
    (
        "The Amazon rainforest harbors unparalleled biodiversity, with millions of species of plants, animals, and microorganisms.",
        80),
    ("Deforestation and habitat loss pose serious threats to the Amazon rainforest and its inhabitants.", 20),
    (
        "The Amazon rainforest plays a crucial role in regulating the Earth's climate and atmospheric carbon dioxide levels.",
        50),
    ("The Mona Lisa, painted by Leonardo da Vinci, is one of the most famous and iconic artworks in the world.", 100),
    ("Isn't that enigmatic?", 0),
    ("Greetings from the Louvre!", 0),
    ("The Mona Lisa's smile has captivated audiences for centuries and remains a subject of intrigue and speculation.",
     80),
    ("Leonardo da Vinci's masterpiece is renowned for its meticulous detail and subtle expression.", 20),
    ("The Mona Lisa is housed in the Louvre Museum in Paris and attracts millions of visitors each year.", 50),
    (
        "Plate tectonics is the scientific theory that Earth's lithosphere is divided into large, rigid plates that move and interact with one another.",
        100),
    ("Isn't that dynamic?", 0),
    ("Welcome to geology class!", 0),
    ("Plate tectonics explains the formation of continents, mountains, earthquakes, and volcanic activity.", 80),
    ("The theory of plate tectonics revolutionized our understanding of Earth's geology and natural processes.", 20),
    (
        "Subduction zones, where one tectonic plate sinks beneath another, are associated with volcanic arcs and earthquakes.",
        50),
    (
        "The Amazon rainforest, often referred to as the 'lungs of the Earth', is the largest tropical rainforest ecosystem in the world.",
        100),
    ("Isn't that ecologically significant?", 0),
    ("Greetings from the Amazon!", 0),
    (
        "The Amazon rainforest harbors unparalleled biodiversity, with millions of species of plants, animals, and microorganisms.",
        80),
    ("Deforestation and habitat loss pose serious threats to the Amazon rainforest and its inhabitants.", 20),
    (
        "The Amazon rainforest plays a crucial role in regulating the Earth's climate and atmospheric carbon dioxide levels.",
        50),
    (
        "Vincent van Gogh was a Dutch Post-Impressionist painter who created some of the most famous and recognizable artworks in the world.",
        100),
    ("Isn't that inspiring?", 0),
    ("Greetings from the art gallery!", 0),
    (
        "Van Gogh's expressive brushwork and bold use of color distinguish his paintings, such as 'Starry Night' and 'Sunflowers'.",
        80),
    (
        "Despite struggles with mental illness and poverty, Van Gogh's artistic legacy endures as a testament to his creative genius.",
        20),
    ("Van Gogh's unique style and emotional depth have left an indelible mark on the history of art.", 50),
    (
        "Mount Everest, standing at an elevation of approximately 8,848.86 meters (29,031.7 feet) above sea level, represents the highest point on Earth's crust.",
        100),
    ("Isn't that an elevation worth noting?", 0),
    ("Salutations, geomorphologists!", 0),
    (
        "Mount Everest, a geological feature of the Himalayan range, is situated along the convergent boundary between the Indian and Eurasian tectonic plates.",
        80),
    (
        "Mount Everest's summit, characterized by extreme cold, low oxygen levels, and glaciated terrain, poses formidable challenges to mountaineers.",
        20),
    (
        "The stratigraphy of Mount Everest provides insights into the tectonic processes shaping the Himalayas over millions of years.",
        50),
    (
        "The human genome, comprising approximately 3.2 billion nucleotide base pairs distributed across 23 pairs of chromosomes, serves as the blueprint for human development and function.",
        100),
    ("Isn't that a staggering genomic complexity?", 0),
    ("Greetings, geneticists and molecular biologists!", 0),
    (
        "The human genome, deciphered through large-scale sequencing initiatives, reveals intricate patterns of genetic variation and regulatory elements.",
        80),
    (
        "Genomic alterations, including single nucleotide polymorphisms (SNPs) and structural variants, contribute to phenotypic diversity and disease susceptibility.",
        20),
    (
        "Genome-wide association studies (GWAS) elucidate the genetic basis of complex traits and disorders by correlating genotype with phenotype across populations.",
        50),
    (
        "The Colosseum, an architectural marvel constructed during the Roman Empire's reign, exemplifies ancient Rome's engineering prowess and socio-cultural significance.",
        100),
    ("Isn't that an epitome of ancient architectural grandeur?", 0),
    ("Salve, archaeologists and architectural historians!", 0),
    (
        "The Colosseum's elliptical amphitheater, crafted from travertine limestone and concrete, accommodated diverse spectacles, including gladiatorial combat and theatrical performances.",
        80),
    (
        "Architectural analyses elucidate the Colosseum's innovative construction techniques, such as the system of radial walls and barrel vaults designed to support the towering structure.",
        20),
    (
        "The Colosseum's preservation efforts, employing advanced imaging and structural reinforcement methods, safeguard this cultural icon for future generations.",
        50),
    (
        "Photosynthesis, a fundamental biochemical process occurring in chloroplasts of autotrophic organisms, converts light energy into chemical energy, facilitating organic carbon synthesis.",
        100),
    ("Isn't that a cornerstone of primary productivity in ecosystems?", 0),
    ("Greetings, photosynthesis researchers and plant physiologists!", 0),
    (
        "Photosynthetic electron transport chains, comprising photosystems I and II and associated protein complexes, drive ATP and NADPH production through light-dependent reactions.",
        80),
    (
        "Carbon fixation pathways, including the Calvin-Benson cycle in C3 plants and the C4 and CAM pathways in certain species, assimilate atmospheric CO2 into organic molecules during light-independent reactions.",
        20),
    (
        "Environmental factors, such as light intensity, temperature, and water availability, modulate photosynthetic rates and plant growth through intricate signaling networks.",
        50),
    (
        "The Milky Way, a barred spiral galaxy spanning an estimated 100,000 light-years in diameter, encompasses billions of stars, planetary systems, and interstellar dust and gas.",
        100),
    ("Isn't that a vast cosmic expanse?", 0),
    ("Salutations, astrophysicists and cosmologists!", 0),
    (
        "The Milky Way's spiral arms, characterized by young, luminous stars and HII regions, spiral outward from a central bulge dominated by older stellar populations and a supermassive black hole.",
        80),
    (
        "Galactic dynamics, governed by gravitational interactions and dark matter distributions, shape the Milky Way's structure and evolutionary trajectory over cosmic timescales.",
        20),
    (
        "Observational techniques, including radio astronomy and infrared spectroscopy, probe the Milky Way's composition, kinematics, and galactic evolution across the electromagnetic spectrum.",
        50),
    (
        "The Mona Lisa, an iconic masterpiece crafted by Leonardo da Vinci during the Italian Renaissance, captivates art connoisseurs with its enigmatic smile and nuanced expression.",
        100),
    ("Isn't that a pinnacle of Renaissance artistry and visual storytelling?", 0),
    ("Salve, art historians and cultural analysts!", 0),
    (
        "The Mona Lisa's anatomical precision and sfumato technique, characterized by subtle tonal gradations and soft transitions, showcase da Vinci's mastery of chiaroscuro and perspective.",
        80),
    (
        "Iconographic interpretations of the Mona Lisa, ranging from allegorical symbolism to psychological portraiture, reflect evolving cultural and art historical contexts.",
        20),
    (
        "The Louvre Museum's conservation efforts employ state-of-the-art imaging and spectroscopic analyses to preserve the Mona Lisa's integrity and reveal hidden layers of its composition.",
        50),
    (
        "Plate tectonics, a unifying theory in geoscience, elucidates Earth's dynamic lithospheric behavior through the motion, collision, and interaction of rigid tectonic plates.",
        100),
    ("Isn't that a paradigm shift in understanding Earth's geologic processes?", 0),
    ("Greetings, geologists and geophysicists!", 0),
    (
        "Plate boundaries, including divergent, convergent, and transform faults, delineate zones of crustal deformation, seismic activity, and volcanic eruptions.",
        80),
    (
        "The Pythagorean theorem, a fundamental principle in Euclidean geometry, states that in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.",
        100),
    ("Isn't that a pivotal theorem in mathematics?", 0),
    ("Greetings, mathematicians and geometry enthusiasts!", 0),
    (
        "The Pythagorean theorem, attributed to the ancient Greek mathematician Pythagoras, is a cornerstone of mathematical proofs and applications.",
        80),
    (
        "This theorem has extensive applications in various fields, including physics, engineering, computer science, and architecture.",
        20),
    (
        "Pythagorean triples, sets of three positive integers that satisfy the theorem's equation, have fascinated mathematicians for centuries.",
        50),
    (
        "The Krebs cycle, also known as the citric acid cycle, is a crucial metabolic pathway in cellular respiration, facilitating the oxidative degradation of acetyl-CoA to produce ATP, NADH, and FADH2.",
        100),
    ("Isn't that essential for cellular energy production?", 0),
    ("Greetings, biochemists and molecular biologists!", 0),
    (
        "The Krebs cycle, occurring in the mitochondrial matrix, involves a series of enzymatic reactions that generate high-energy electron carriers for the electron transport chain.",
        80),
    (
        "Key intermediates of the Krebs cycle, such as citrate, alpha-ketoglutarate, and succinate, play vital roles in metabolic cross-talk and biosynthetic processes.",
        20),
    (
        "Metabolic flux analysis and isotopic labeling techniques provide insights into the regulation and dynamics of the Krebs cycle under various physiological conditions.",
        50),
    (
        "The theory of evolution by natural selection, articulated by Charles Darwin in 'On the Origin of Species', posits that organisms evolve over generations through the differential survival and reproduction of individuals with advantageous traits.",
        100),
    ("Isn't that a paradigm shift in understanding biological diversity?", 0),
    ("Greetings, evolutionary biologists and geneticists!", 0),
    (
        "Natural selection, genetic drift, mutation, and gene flow constitute the fundamental mechanisms driving evolutionary change in populations.",
        80),
    (
        "The modern synthesis integrates Darwinian selection with Mendelian genetics, forming a cohesive framework for evolutionary biology.",
        20),
    (
        "Phylogenetic analyses and comparative genomics elucidate the evolutionary relationships and ancestral lineages of diverse species across the tree of life.",
        50),
    (
        "Black holes, regions of spacetime exhibiting gravitational forces so intense that nothing, not even light, can escape from within the event horizon, are predicted by the general theory of relativity.",
        100),
    ("Isn't that an enigmatic cosmic phenomenon?", 0),
    ("Greetings, astrophysicists and theoretical physicists!", 0),
    (
        "Black holes are characterized by singularities where gravitational fields become infinite, and by event horizons that demarcate the point of no return.",
        80),
    (
        "Observational techniques such as gravitational wave detection and X-ray astronomy provide empirical evidence for the existence and properties of black holes.",
        20),
    (
        "The study of black holes, including their formation, dynamics, and Hawking radiation, continues to challenge and refine our understanding of fundamental physics.",
        50),
    (
        "CRISPR-Cas9, a revolutionary genome editing technology, enables precise modification of DNA sequences within living organisms, offering transformative potential for genetic research and therapeutic applications.",
        100),
    ("Isn't that a groundbreaking biotechnological tool?", 0),
    ("Greetings, molecular biologists and genetic engineers!", 0),
    (
        "The CRISPR-Cas9 system, derived from bacterial adaptive immune mechanisms, utilizes guide RNA to target specific DNA sequences for cleavage by the Cas9 nuclease.",
        80),
    (
        "Applications of CRISPR-Cas9 span from functional genomics and gene therapy to agricultural biotechnology and synthetic biology.",
        20),
    (
        "Ethical considerations and regulatory frameworks are crucial in guiding the responsible use and development of CRISPR technology.",
        50),
    (
        "Quantum mechanics, a fundamental theory in physics, describes the behavior of particles at the atomic and subatomic scales, where classical mechanics ceases to apply.",
        100),
    ("Isn't that a cornerstone of modern physics?", 0),
    ("Greetings, quantum physicists and theoretical scientists!", 0),
    (
        "Key principles of quantum mechanics include wave-particle duality, the uncertainty principle, and quantum superposition.",
        80),
    (
        "Quantum entanglement, a phenomenon where particles become interdependent in their states regardless of distance, challenges classical intuitions about locality and causality.",
        20),
    (
        "Advancements in quantum computing and quantum cryptography leverage the principles of quantum mechanics to revolutionize information processing and security.",
        50),
    (
        "The Higgs boson, an elementary particle in the Standard Model of particle physics, was discovered at CERN's Large Hadron Collider in 2012, confirming the mechanism that gives mass to other fundamental particles.",
        100),
    ("Isn't that a monumental discovery in particle physics?", 0),
    ("Greetings, particle physicists and high-energy researchers!", 0),
    (
        "The Higgs boson arises from the Higgs field, a scalar field that permeates the universe, imparting mass to particles through spontaneous symmetry breaking.",
        80),
    (
        "Experimental confirmation of the Higgs boson was a pivotal achievement, validating decades of theoretical predictions and refining our understanding of the Standard Model.",
        20),
    (
        "Ongoing research in particle physics explores the properties of the Higgs boson and seeks to uncover potential extensions to the Standard Model.",
        50),
    (
        "Global warming, driven by increased concentrations of greenhouse gases such as carbon dioxide and methane, is causing significant alterations in Earth's climate systems.",
        100),
    ("Isn't that a critical environmental issue?", 0),
    ("Greetings, climatologists and environmental scientists!", 0),
    (
        "Anthropogenic emissions from fossil fuel combustion, deforestation, and industrial activities contribute to the enhanced greenhouse effect, leading to global temperature rise.",
        80),
    (
        "Impacts of global warming include sea level rise, shifts in weather patterns, and increased frequency of extreme weather events.",
        20),
    (
        "Mitigation strategies, including renewable energy adoption, carbon sequestration, and international climate agreements, are essential to addressing global warming.",
        50),
    (
        "The double-helix structure of DNA, elucidated by James Watson and Francis Crick, revealed the molecular basis of genetic inheritance and revolutionized the field of molecular biology.",
        100),
    ("Isn't that a pivotal scientific breakthrough?", 0),
    ("Greetings, molecular biologists and geneticists!", 0),
    (
        "DNA's structure, comprising two antiparallel strands wound around each other, is stabilized by hydrogen bonds between complementary nucleotide bases (adenine-thymine and guanine-cytosine).",
        80),
    (
        "The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein, underpinning the processes of transcription and translation.",
        20),
    (
        "Techniques such as DNA sequencing, PCR, and recombinant DNA technology have expanded our ability to study and manipulate genetic material.",
        50),
    (
        "Einstein's theory of general relativity, published in 1915, describes gravity as the curvature of spacetime caused by the presence of mass and energy.",
        100),
    ("Isn't that a revolutionary concept in physics?", 0),
    ("Greetings, theoretical physicists and cosmologists!", 0),
    (
        "General relativity predicts phenomena such as gravitational time dilation, the bending of light by gravity (gravitational lensing), and the expansion of the universe.",
        80),
    (
        "Experimental validations, including the observation of gravitational waves and the precise perihelion precession of Mercury, support the predictions of general relativity.",
        20),
    (
        "Current research explores the implications of general relativity for black hole dynamics, cosmological models, and the unification of fundamental forces.",
        50),
    (
        "Antibiotic resistance, the ability of bacteria to withstand the effects of antibiotics, poses a significant challenge to public health and underscores the need for novel antimicrobial strategies.",
        100),
    ("Isn't that a pressing medical issue?", 0),
    ("Greetings, microbiologists and healthcare professionals!", 0),
    (
        "Mechanisms of antibiotic resistance include the production of degrading enzymes, alteration of drug targets, and increased efflux of antibiotics from bacterial cells.",
        80),
    (
        "The emergence of multidrug-resistant bacteria, driven by overuse and misuse of antibiotics, necessitates the development of new drugs, diagnostics, and stewardship practices.",
        20),
    (
        "Genomic and metagenomic approaches are advancing our understanding of resistance gene distribution and the evolution of resistant bacterial populations.",
        50),
    (
        "Photosynthesis, the process by which photoautotrophic organisms convert light energy into chemical energy, is vital for sustaining life on Earth by producing oxygen and organic compounds.",
        100),
    ("Isn't that fundamental to ecosystems?", 0),
    ("Greetings, plant physiologists and ecologists!", 0),
    (
        "The light-dependent reactions of photosynthesis, occurring in the thylakoid membranes of chloroplasts, generate ATP and NADPH through the photolysis of water and the electron transport chain.",
        80),
    (
        "The Calvin cycle, or light-independent reactions, assimilates carbon dioxide into organic molecules using the energy stored in ATP and NADPH.",
        20),
    (
        "Factors affecting photosynthetic efficiency include light intensity, carbon dioxide concentration, temperature, and water availability.",
        50),
    (
        "Stem cells, characterized by their capacity for self-renewal and differentiation into various cell types, hold immense potential for regenerative medicine and tissue engineering.",
        100),
    ("Isn't that a frontier in biomedical research?", 0),
    ("Greetings, stem cell biologists and regenerative medicine experts!", 0),
    (
        "Embryonic stem cells, derived from the inner cell mass of blastocysts, are pluripotent and can differentiate into all cell types of the body.",
        80),
    (
        "Induced pluripotent stem cells (iPSCs), generated by reprogramming somatic cells, offer an alternative source of pluripotent cells for research and therapy.",
        20),
    (
        "Clinical applications of stem cells include the treatment of hematological disorders, neurodegenerative diseases, and tissue repair and regeneration.",
        50),
    (
        "The Fibonacci sequence, a series of numbers where each number is the sum of the two preceding ones, appears in various natural phenomena, including the branching of trees and the arrangement of leaves.",
        100),
    ("Isn't that a fascinating mathematical pattern?", 0),
    ("Greetings, mathematicians and naturalists!", 0),
    (
        "The Fibonacci sequence is closely related to the golden ratio, an irrational number approximately equal to 1.618, which appears in art, architecture, and nature.",
        80),
    (
        "Applications of the Fibonacci sequence and golden ratio extend to financial markets, computer algorithms, and biological modeling.",
        20),
    (
        "Studies in phyllotaxis, the arrangement of leaves on a plant stem, reveal the prevalence of Fibonacci numbers in optimizing light exposure and space efficiency.",
        50),
    (
        "The Pythagorean theorem, a fundamental principle in Euclidean geometry, states that in a right-angled triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.",
        100),
    ("Isn't that a pivotal theorem in mathematics?", 0),
    ("Greetings, mathematicians and geometry enthusiasts!", 0),
    (
        "The Pythagorean theorem, attributed to the ancient Greek mathematician Pythagoras, is a cornerstone of mathematical proofs and applications.",
        80),
    (
        "This theorem has extensive applications in various fields, including physics, engineering, computer science, and architecture.",
        20),
    (
        "Pythagorean triples, sets of three positive integers that satisfy the theorem's equation, have fascinated mathematicians for centuries.",
        50),
    (
        "The Krebs cycle, also known as the citric acid cycle, is a crucial metabolic pathway in cellular respiration, facilitating the oxidative degradation of acetyl-CoA to produce ATP, NADH, and FADH2.",
        100),
    ("Isn't that essential for cellular energy production?", 0),
    ("Greetings, biochemists and molecular biologists!", 0),
    (
        "The Krebs cycle, occurring in the mitochondrial matrix, involves a series of enzymatic reactions that generate high-energy electron carriers for the electron transport chain.",
        80),
    (
        "Key intermediates of the Krebs cycle, such as citrate, alpha-ketoglutarate, and succinate, play vital roles in metabolic cross-talk and biosynthetic processes.",
        20),
    (
        "Metabolic flux analysis and isotopic labeling techniques provide insights into the regulation and dynamics of the Krebs cycle under various physiological conditions.",
        50),
    (
        "The theory of evolution by natural selection, articulated by Charles Darwin in 'On the Origin of Species', posits that organisms evolve over generations through the differential survival and reproduction of individuals with advantageous traits.",
        100),
    ("Isn't that a paradigm shift in understanding biological diversity?", 0),
    ("Greetings, evolutionary biologists and geneticists!", 0),
    (
        "Natural selection, genetic drift, mutation, and gene flow constitute the fundamental mechanisms driving evolutionary change in populations.",
        80),
    (
        "The modern synthesis integrates Darwinian selection with Mendelian genetics, forming a cohesive framework for evolutionary biology.",
        20),
    (
        "Phylogenetic analyses and comparative genomics elucidate the evolutionary relationships and ancestral lineages of diverse species across the tree of life.",
        50),
    (
        "Black holes, regions of spacetime exhibiting gravitational forces so intense that nothing, not even light, can escape from within the event horizon, are predicted by the general theory of relativity.",
        100),
    ("Isn't that an enigmatic cosmic phenomenon?", 0),
    ("Greetings, astrophysicists and theoretical physicists!", 0),
    (
        "Black holes are characterized by singularities where gravitational fields become infinite, and by event horizons that demarcate the point of no return.",
        80),
    (
        "Observational techniques such as gravitational wave detection and X-ray astronomy provide empirical evidence for the existence and properties of black holes.",
        20),
    (
        "The study of black holes, including their formation, dynamics, and Hawking radiation, continues to challenge and refine our understanding of fundamental physics.",
        50),
    (
        "CRISPR-Cas9, a revolutionary genome editing technology, enables precise modification of DNA sequences within living organisms, offering transformative potential for genetic research and therapeutic applications.",
        100),
    ("Isn't that a groundbreaking biotechnological tool?", 0),
    ("Greetings, molecular biologists and genetic engineers!", 0),
    (
        "The CRISPR-Cas9 system, derived from bacterial adaptive immune mechanisms, utilizes guide RNA to target specific DNA sequences for cleavage by the Cas9 nuclease.",
        80),
    (
        "Applications of CRISPR-Cas9 span from functional genomics and gene therapy to agricultural biotechnology and synthetic biology.",
        20),
    (
        "Ethical considerations and regulatory frameworks are crucial in guiding the responsible use and development of CRISPR technology.",
        50),
    (
        "Quantum mechanics, a fundamental theory in physics, describes the behavior of particles at the atomic and subatomic scales, where classical mechanics ceases to apply.",
        100),
    ("Isn't that a cornerstone of modern physics?", 0),
    ("Greetings, quantum physicists and theoretical scientists!", 0),
    (
        "Key principles of quantum mechanics include wave-particle duality, the uncertainty principle, and quantum superposition.",
        80),
    (
        "Quantum entanglement, a phenomenon where particles become interdependent in their states regardless of distance, challenges classical intuitions about locality and causality.",
        20),
    (
        "Advancements in quantum computing and quantum cryptography leverage the principles of quantum mechanics to revolutionize information processing and security.",
        50),
    (
        "The Higgs boson, an elementary particle in the Standard Model of particle physics, was discovered at CERN's Large Hadron Collider in 2012, confirming the mechanism that gives mass to other fundamental particles.",
        100),
    ("Isn't that a monumental discovery in particle physics?", 0),
    ("Greetings, particle physicists and high-energy researchers!", 0),
    (
        "The Higgs boson arises from the Higgs field, a scalar field that permeates the universe, imparting mass to particles through spontaneous symmetry breaking.",
        80),
    (
        "Experimental confirmation of the Higgs boson was a pivotal achievement, validating decades of theoretical predictions and refining our understanding of the Standard Model.",
        20),
    (
        "Ongoing research in particle physics explores the properties of the Higgs boson and seeks to uncover potential extensions to the Standard Model.",
        50),
    (
        "Global warming, driven by increased concentrations of greenhouse gases such as carbon dioxide and methane, is causing significant alterations in Earth's climate systems.",
        100),
    ("Isn't that a critical environmental issue?", 0),
    ("Greetings, climatologists and environmental scientists!", 0),
    (
        "Anthropogenic emissions from fossil fuel combustion, deforestation, and industrial activities contribute to the enhanced greenhouse effect, leading to global temperature rise.",
        80),
    (
        "Impacts of global warming include sea level rise, shifts in weather patterns, and increased frequency of extreme weather events.",
        20),
    (
        "Mitigation strategies, including renewable energy adoption, carbon sequestration, and international climate agreements, are essential to addressing global warming.",
        50),
    (
        "The double-helix structure of DNA, elucidated by James Watson and Francis Crick, revealed the molecular basis of genetic inheritance and revolutionized the field of molecular biology.",
        100),
    ("Isn't that a pivotal scientific breakthrough?", 0),
    ("Greetings, molecular biologists and geneticists!", 0),
    (
        "DNA's structure, comprising two antiparallel strands wound around each other, is stabilized by hydrogen bonds between complementary nucleotide bases (adenine-thymine and guanine-cytosine).",
        80),
    (
        "The central dogma of molecular biology describes the flow of genetic information from DNA to RNA to protein, underpinning the processes of transcription and translation.",
        20),
    (
        "Techniques such as DNA sequencing, PCR, and recombinant DNA technology have expanded our ability to study and manipulate genetic material.",
        50),
    (
        "Einstein's theory of general relativity, published in 1915, describes gravity as the curvature of spacetime caused by the presence of mass and energy.",
        100),
    ("Isn't that a revolutionary concept in physics?", 0),
    ("Greetings, theoretical physicists and cosmologists!", 0),
    (
        "General relativity predicts phenomena such as gravitational time dilation, the bending of light by gravity (gravitational lensing), and the expansion of the universe.",
        80),
    (
        "Experimental validations, including the observation of gravitational waves and the precise perihelion precession of Mercury, support the predictions of general relativity.",
        20),
    (
        "Current research explores the implications of general relativity for black hole dynamics, cosmological models, and the unification of fundamental forces.",
        50),
    (
        "Antibiotic resistance, the ability of bacteria to withstand the effects of antibiotics, poses a significant challenge to public health and underscores the need for novel antimicrobial strategies.",
        100),
    ("Isn't that a pressing medical issue?", 0),
    ("Greetings, microbiologists and healthcare professionals!", 0),
    (
        "Mechanisms of antibiotic resistance include the production of degrading enzymes, alteration of drug targets, and increased efflux of antibiotics from bacterial cells.",
        80),
    (
        "The emergence of multidrug-resistant bacteria, driven by overuse and misuse of antibiotics, necessitates the development of new drugs, diagnostics, and stewardship practices.",
        20),
    (
        "Genomic and metagenomic approaches are advancing our understanding of resistance gene distribution and the evolution of resistant bacterial populations.",
        50),
    (
        "Photosynthesis, the process by which photoautotrophic organisms convert light energy into chemical energy, is vital for sustaining life on Earth by producing oxygen and organic compounds.",
        100),
    ("Isn't that fundamental to ecosystems?", 0),
    ("Greetings, plant physiologists and ecologists!", 0),
    (
        "The light-dependent reactions of photosynthesis, occurring in the thylakoid membranes of chloroplasts, generate ATP and NADPH through the photolysis of water and the electron transport chain.",
        80),
    (
        "The Calvin cycle, or light-independent reactions, assimilates carbon dioxide into organic molecules using the energy stored in ATP and NADPH.",
        20),
    (
        "Factors affecting photosynthetic efficiency include light intensity, carbon dioxide concentration, temperature, and water availability.",
        50),
    (
        "Stem cells, characterized by their capacity for self-renewal and differentiation into various cell types, hold immense potential for regenerative medicine and tissue engineering.",
        100),
    ("Isn't that a frontier in biomedical research?", 0),
    ("Greetings, stem cell biologists and regenerative medicine experts!", 0),
    (
        "Embryonic stem cells, derived from the inner cell mass of blastocysts, are pluripotent and can differentiate into all cell types of the body.",
        80),
    (
        "Induced pluripotent stem cells (iPSCs), generated by reprogramming somatic cells, offer an alternative source of pluripotent cells for research and therapy.",
        20),
    (
        "Clinical applications of stem cells include the treatment of hematological disorders, neurodegenerative diseases, and tissue repair and regeneration.",
        50),
    (
        "The Fibonacci sequence, a series of numbers where each number is the sum of the two preceding ones, appears in various natural phenomena, including the branching of trees and the arrangement of leaves.",
        100),
    ("Isn't that a fascinating mathematical pattern?", 0),
    ("Greetings, mathematicians and naturalists!", 0),
    (
        "The Fibonacci sequence is closely related to the golden ratio, an irrational number approximately equal to 1.618, which appears in art, architecture, and nature.",
        80),
    (
        "Applications of the Fibonacci sequence and golden ratio extend to financial markets, computer algorithms, and biological modeling.",
        20),
    (
        "Studies in phyllotaxis, the arrangement of leaves on a plant stem, reveal the prevalence of Fibonacci numbers in optimizing light exposure and space efficiency.",
        50),
    (
        "The immune system, comprising innate and adaptive components, functions to protect the body from pathogens, including bacteria, viruses, fungi, and parasites.",
        100),
    ("Isn't that crucial for health?", 0),
    ("Greetings, immunologists and medical researchers!", 0),
    (
        "Innate immunity provides immediate, non-specific defense mechanisms, while adaptive immunity involves antigen-specific responses mediated by B and T lymphocytes.",
        80),
    (
        "Vaccination exploits the adaptive immune system by inducing memory responses that confer long-term protection against specific pathogens.",
        20),
    (
        "Advances in immunotherapy, including monoclonal antibodies and checkpoint inhibitors, are revolutionizing the treatment of cancers and autoimmune diseases.",
        50),
    (
        "Neural networks, a key component of artificial intelligence, are computational models inspired by the structure and function of biological neural networks in the brain.",
        100),
    ("Isn't that transformative for technology?", 0),
    ("Greetings, computer scientists and AI researchers!", 0),
    (
        "Deep learning, a subset of machine learning, utilizes multi-layered neural networks to perform complex tasks such as image recognition, natural language processing, and autonomous driving.",
        80),
    (
        "Backpropagation, an algorithm for training neural networks, adjusts weights to minimize error through gradient descent.",
        20),
    (
        "Applications of neural networks span diverse domains, including healthcare, finance, robotics, and entertainment.",
        50),
    (
        "Climate change, driven by anthropogenic activities, is causing widespread impacts on global ecosystems, weather patterns, and sea levels.",
        100),
    ("Isn't that a major global issue?", 0),
    ("Greetings, environmental scientists and policymakers!", 0),
    (
        "Rising concentrations of greenhouse gases, such as carbon dioxide and methane, enhance the greenhouse effect and contribute to global warming.",
        80),
    (
        "Climate models project significant changes in temperature, precipitation, and extreme weather events in the coming decades.",
        20),
    (
        "Mitigation and adaptation strategies, including renewable energy adoption, carbon sequestration, and climate resilience planning, are essential to address the challenges of climate change.",
        50),
    (
        "The Large Hadron Collider (LHC), the world's largest and most powerful particle accelerator, enables high-energy physics experiments to explore fundamental particles and forces.",
        100),
    ("Isn't that a feat of engineering and science?", 0),
    ("Greetings, particle physicists and engineers!", 0),
    (
        "Located at CERN, the LHC accelerates protons to near-light speeds and collides them to probe the properties of subatomic particles and test theories beyond the Standard Model.",
        80),
    (
        "Discoveries at the LHC, including the Higgs boson, have provided critical insights into the mechanisms of mass generation and particle interactions.",
        20),
    (
        "Future upgrades and experiments aim to explore dark matter, supersymmetry, and other phenomena at the frontier of high-energy physics.",
        50),
    (
        "Gene therapy, an innovative medical technique, involves the introduction, removal, or alteration of genetic material within a patient's cells to treat or prevent disease.",
        100),
    ("Isn't that a cutting-edge medical intervention?", 0),
    ("Greetings, geneticists and healthcare professionals!", 0),
    ("Viral vectors, such as adeno-associated viruses, are commonly used to deliver therapeutic genes to target cells.",
     80),
    (
        "Gene therapy holds promise for treating genetic disorders, cancers, and infectious diseases by correcting defective genes or modulating gene expression.",
        20),
    (
        "Challenges in gene therapy include ensuring efficient delivery, avoiding immune responses, and achieving long-term expression of therapeutic genes.",
        50),
    (
        "Photosynthesis, the process by which photoautotrophic organisms convert light energy into chemical energy, is vital for sustaining life on Earth by producing oxygen and organic compounds.",
        100),
    ("Isn't that fundamental to ecosystems?", 0),
    ("Greetings, plant physiologists and ecologists!", 0),
    (
        "The light-dependent reactions of photosynthesis, occurring in the thylakoid membranes of chloroplasts, generate ATP and NADPH through the photolysis of water and the electron transport chain.",
        80),
    (
        "The Calvin cycle, or light-independent reactions, assimilates carbon dioxide into organic molecules using the energy stored in ATP and NADPH.",
        20),
    (
        "Factors affecting photosynthetic efficiency include light intensity, carbon dioxide concentration, temperature, and water availability.",
        50),
    (
        "Stem cells, characterized by their capacity for self-renewal and differentiation into various cell types, hold immense potential for regenerative medicine and tissue engineering.",
        100),
    ("Isn't that a frontier in biomedical research?", 0),
    ("Greetings, stem cell biologists and regenerative medicine experts!", 0),
    (
        "Embryonic stem cells, derived from the inner cell mass of blastocysts, are pluripotent and can differentiate into all cell types of the body.",
        80),
    (
        "Induced pluripotent stem cells (iPSCs), generated by reprogramming somatic cells, offer an alternative source of pluripotent cells for research and therapy.",
        20),
    (
        "Clinical applications of stem cells include the treatment of hematological disorders, neurodegenerative diseases, and tissue repair and regeneration.",
        50),
    (
        "The Fibonacci sequence, a series of numbers where each number is the sum of the two preceding ones, appears in various natural phenomena, including the branching of trees and the arrangement of leaves.",
        100),
    ("Isn't that a fascinating mathematical pattern?", 0),
    ("Greetings, mathematicians and naturalists!", 0),
    (
        "The Fibonacci sequence is closely related to the golden ratio, an irrational number approximately equal to 1.618, which appears in art, architecture, and nature.",
        80),
    (
        "Applications of the Fibonacci sequence and golden ratio extend to financial markets, computer algorithms, and biological modeling.",
        20),
    (
        "Studies in phyllotaxis, the arrangement of leaves on a plant stem, reveal the prevalence of Fibonacci numbers in optimizing light exposure and space efficiency.",
        50),
    (
        "Neural networks, a key component of artificial intelligence, are computational models inspired by the structure and function of biological neural networks in the brain.",
        100),
    ("Isn't that transformative for technology?", 0),
    ("Greetings, computer scientists and AI researchers!", 0),
    (
        "Deep learning, a subset of machine learning, utilizes multi-layered neural networks to perform complex tasks such as image recognition, natural language processing, and autonomous driving.",
        80),
    (
        "Backpropagation, an algorithm for training neural networks, adjusts weights to minimize error through gradient descent.",
        20),
    (
        "Applications of neural networks span diverse domains, including healthcare, finance, robotics, and entertainment.",
        50),
    (
        "Climate change, driven by anthropogenic activities, is causing widespread impacts on global ecosystems, weather patterns, and sea levels.",
        100),
    ("Isn't that a major global issue?", 0),
    ("Greetings, environmental scientists and policymakers!", 0),
    (
        "Rising concentrations of greenhouse gases, such as carbon dioxide and methane, enhance the greenhouse effect and contribute to global warming.",
        80),
    (
        "Climate models project significant changes in temperature, precipitation, and extreme weather events in the coming decades.",
        20),
    (
        "Mitigation and adaptation strategies, including renewable energy adoption, carbon sequestration, and climate resilience planning, are essential to address the challenges of climate change.",
        50),
    (
        "The Large Hadron Collider (LHC), the world's largest and most powerful particle accelerator, enables high-energy physics experiments to explore fundamental particles and forces.",
        100),
    ("Isn't that a feat of engineering and science?", 0),
    ("Greetings, particle physicists and engineers!", 0),
    (
        "Located at CERN, the LHC accelerates protons to near-light speeds and collides them to probe the properties of subatomic particles and test theories beyond the Standard Model.",
        80),
    (
        "Discoveries at the LHC, including the Higgs boson, have provided critical insights into the mechanisms of mass generation and particle interactions.",
        20),
    (
        "Future upgrades and experiments aim to explore dark matter, supersymmetry, and other phenomena at the frontier of high-energy physics.",
        50),
    (
        "Gene therapy, an innovative medical technique, involves the introduction, removal, or alteration of genetic material within a patient's cells to treat or prevent disease.",
        100),
    ("Isn't that a cutting-edge medical intervention?", 0),
    ("Greetings, geneticists and healthcare professionals!", 0),
    ("Viral vectors, such as adeno-associated viruses, are commonly used to deliver therapeutic genes to target cells.",
     80),
    (
        "Gene therapy holds promise for treating genetic disorders, cancers, and infectious diseases by correcting defective genes or modulating gene expression.",
        20),
    (
        "Challenges in gene therapy include ensuring efficient delivery, avoiding immune responses, and achieving long-term expression of therapeutic genes.",
        50),
    (
        "Quantum mechanics, a fundamental theory in physics, describes the behavior of particles at the atomic and subatomic scales, where classical mechanics ceases to apply.",
        100),
    ("Isn't that a cornerstone of modern physics?", 0),
    ("Greetings, quantum physicists and theoretical scientists!", 0),
    (
        "Key principles of quantum mechanics include wave-particle duality, the uncertainty principle, and quantum superposition.",
        80),
    (
        "Quantum entanglement, a phenomenon where particles become interdependent in their states regardless of distance, challenges classical intuitions about locality and causality.",
        20),
    (
        "Advancements in quantum computing and quantum cryptography leverage the principles of quantum mechanics to revolutionize information processing and security.",
        50),
    (
        "Einstein's theory of general relativity, published in 1915, describes gravity as the curvature of spacetime caused by the presence of mass and energy.",
        100),
    ("Isn't that a revolutionary concept in physics?", 0),
    ("Greetings, theoretical physicists and cosmologists!", 0),
    (
        "General relativity predicts phenomena such as gravitational time dilation, the bending of light by gravity (gravitational lensing), and the expansion of the universe.",
        80),
    (
        "Experimental validations, including the observation of gravitational waves and the precise perihelion precession of Mercury, support the predictions of general relativity.",
        20),
    (
        "Current research explores the implications of general relativity for black hole dynamics, cosmological models, and the unification of fundamental forces.",
        50),
    (
        "Antibiotic resistance, the ability of bacteria to withstand the effects of antibiotics, poses a significant challenge to public health and underscores the need for novel antimicrobial strategies.",
        100),
    ("Isn't that a pressing medical issue?", 0),
    ("Greetings, microbiologists and healthcare professionals!", 0),
    (
        "Mechanisms of antibiotic resistance include the production of degrading enzymes, alteration of drug targets, and increased efflux of antibiotics from bacterial cells.",
        80),
    (
        "The emergence of multidrug-resistant bacteria, driven by overuse and misuse of antibiotics, necessitates the development of new drugs, diagnostics, and stewardship practices.",
        20),
    (
        "Genomic and metagenomic approaches are advancing our understanding of resistance gene distribution and the evolution of resistant bacterial populations.",
        50),
    (
        "Photosynthesis, the process by which photoautotrophic organisms convert light energy into chemical energy, is vital for sustaining life on Earth by producing oxygen and organic compounds.",
        100),
    ("Isn't that fundamental to ecosystems?", 0),
    ("Greetings, plant physiologists and ecologists!", 0),
    (
        "The light-dependent reactions of photosynthesis, occurring in the thylakoid membranes of chloroplasts, generate ATP and NADPH through the photolysis of water and the electron transport chain.",
        80),
    (
        "The Calvin cycle, or light-independent reactions, assimilates carbon dioxide into organic molecules using the energy stored in ATP and NADPH.",
        20),
    (
        "Factors affecting photosynthetic efficiency include light intensity, carbon dioxide concentration, temperature, and water availability.",
        50),
    (
        "Stem cells, characterized by their capacity for self-renewal and differentiation into various cell types, hold immense potential for regenerative medicine and tissue engineering.",
        100),
    ("Isn't that a frontier in biomedical research?", 0),
    ("Greetings, stem cell biologists and regenerative medicine experts!", 0),
    (
        "Embryonic stem cells, derived from the inner cell mass of blastocysts, are pluripotent and can differentiate into all cell types of the body.",
        80),
    (
        "Induced pluripotent stem cells (iPSCs), generated by reprogramming somatic cells, offer an alternative source of pluripotent cells for research and therapy.",
        20),
    (
        "Clinical applications of stem cells include the treatment of hematological disorders, neurodegenerative diseases, and tissue repair and regeneration.",
        50),
    (
        "The Fibonacci sequence, a series of numbers where each number is the sum of the two preceding ones, appears in various natural phenomena, including the branching of trees and the arrangement of leaves.",
        100),
    ("Isn't that a fascinating mathematical pattern?", 0),
    ("Greetings, mathematicians and naturalists!", 0),
    (
        "The Fibonacci sequence is closely related to the golden ratio, an irrational number approximately equal to 1.618, which appears in art, architecture, and nature.",
        80),
    (
        "Applications of the Fibonacci sequence and golden ratio extend to financial markets, computer algorithms, and biological modeling.",
        20),
    (
        "Studies in phyllotaxis, the arrangement of leaves on a plant stem, reveal the prevalence of Fibonacci numbers in optimizing light exposure and space efficiency.",
        50),
    (
        "Neural networks, a key component of artificial intelligence, are computational models inspired by the structure and function of biological neural networks in the brain.",
        100),
    ("Isn't that transformative for technology?", 0),
    ("Greetings, computer scientists and AI researchers!", 0),
    (
        "Deep learning, a subset of machine learning, utilizes multi-layered neural networks to perform complex tasks such as image recognition, natural language processing, and autonomous driving.",
        80),
    (
        "Backpropagation, an algorithm for training neural networks, adjusts weights to minimize error through gradient descent.",
        20),
    (
        "Applications of neural networks span diverse domains, including healthcare, finance, robotics, and entertainment.",
        50),
    (
        "Climate change, driven by anthropogenic activities, is causing widespread impacts on global ecosystems, weather patterns, and sea levels.",
        100),
    ("Isn't that a major global issue?", 0),
    ("Greetings, environmental scientists and policymakers!", 0),
    (
        "Rising concentrations of greenhouse gases, such as carbon dioxide and methane, enhance the greenhouse effect and contribute to global warming.",
        80),
    (
        "Climate models project significant changes in temperature, precipitation, and extreme weather events in the coming decades.",
        20),
    (
        "Mitigation and adaptation strategies, including renewable energy adoption, carbon sequestration, and climate resilience planning, are essential to address the challenges of climate change.",
        50),
    (
        "The Large Hadron Collider (LHC), the world's largest and most powerful particle accelerator, enables high-energy physics experiments to explore fundamental particles and forces.",
        100),
    ("Isn't that a feat of engineering and science?", 0),
    ("Greetings, particle physicists and engineers!", 0),
    (
        "Located at CERN, the LHC accelerates protons to near-light speeds and collides them to probe the properties of subatomic particles and test theories beyond the Standard Model.",
        80),
    (
        "Discoveries at the LHC, including the Higgs boson, have provided critical insights into the mechanisms of mass generation and particle interactions.",
        20),
    (
        "Future upgrades and experiments aim to explore dark matter, supersymmetry, and other phenomena at the frontier of high-energy physics.",
        50),
    (
        "Gene therapy, an innovative medical technique, involves the introduction, removal, or alteration of genetic material within a patient's cells to treat or prevent disease.",
        100),
    ("Isn't that a cutting-edge medical intervention?", 0),
    ("Greetings, geneticists and healthcare professionals!", 0),
    ("Viral vectors, such as adeno-associated viruses, are commonly used to deliver therapeutic genes to target cells.",
     80),
    (
        "Gene therapy holds promise for treating genetic disorders, cancers, and infectious diseases by correcting defective genes or modulating gene expression.",
        20),
    (
        "Challenges in gene therapy include ensuring efficient delivery, avoiding immune responses, and achieving long-term expression of therapeutic genes.",
        50),
    (
        "Quantum mechanics, a fundamental theory in physics, describes the behavior of particles at the atomic and subatomic scales, where classical mechanics ceases to apply.",
        100),
    ("Isn't that a cornerstone of modern physics?", 0),
    ("Greetings, quantum physicists and theoretical scientists!", 0),
    (
        "Key principles of quantum mechanics include wave-particle duality, the uncertainty principle, and quantum superposition.",
        80),
    (
        "Quantum entanglement, a phenomenon where particles become interdependent in their states regardless of distance, challenges classical intuitions about locality and causality.",
        20),
    (
        "Advancements in quantum computing and quantum cryptography leverage the principles of quantum mechanics to revolutionize information processing and security.",
        50),
    (
        "Einstein's theory of general relativity, published in 1915, describes gravity as the curvature of spacetime caused by the presence of mass and energy.",
        100),
    ("Isn't that a revolutionary concept in physics?", 0),
    ("Greetings, theoretical physicists and cosmologists!", 0),
    (
        "General relativity predicts phenomena such as gravitational time dilation, the bending of light by gravity (gravitational lensing), and the expansion of the universe.",
        80),
    (
        "Experimental validations, including the observation of gravitational waves and the precise perihelion precession of Mercury, support the predictions of general relativity.",
        20),
    (
        "Current research explores the implications of general relativity for black hole dynamics, cosmological models, and the unification of fundamental forces.",
        50),
    (
        "Antibiotic resistance, the ability of bacteria to withstand the effects of antibiotics, poses a significant challenge to public health and underscores the need for novel antimicrobial strategies.",
        100),
    ("Isn't that a pressing medical issue?", 0),
    ("Greetings, microbiologists and healthcare professionals!", 0),
    (
        "Mechanisms of antibiotic resistance include the production of degrading enzymes, alteration of drug targets, and increased efflux of antibiotics from bacterial cells.",
        80),
    (
        "The emergence of multidrug-resistant bacteria, driven by overuse and misuse of antibiotics, necessitates the development of new drugs, diagnostics, and stewardship practices.",
        20),
    (
        "Genomic and metagenomic approaches are advancing our understanding of resistance gene distribution and the evolution of resistant bacterial populations.",
        50),
    (
        "Photosynthesis, the process by which photoautotrophic organisms convert light energy into chemical energy, is vital for sustaining life on Earth by producing oxygen and organic compounds.",
        100),
    ("Isn't that fundamental to ecosystems?", 0),
    ("Greetings, plant physiologists and ecologists!", 0),
    (
        "The light-dependent reactions of photosynthesis, occurring in the thylakoid membranes of chloroplasts, generate ATP and NADPH through the photolysis of water and the electron transport chain.",
        80),
    (
        "The Calvin cycle, or light-independent reactions, assimilates carbon dioxide into organic molecules using the energy stored in ATP and NADPH.",
        20),
    (
        "Factors affecting photosynthetic efficiency include light intensity, carbon dioxide concentration, temperature, and water availability.",
        50),
    (
        "Stem cells, characterized by their capacity for self-renewal and differentiation into various cell types, hold immense potential for regenerative medicine and tissue engineering.",
        100),
    ("Isn't that a frontier in biomedical research?", 0),
    ("Greetings, stem cell biologists and regenerative medicine experts!", 0),
    (
        "Embryonic stem cells, derived from the inner cell mass of blastocysts, are pluripotent and can differentiate into all cell types of the body.",
        80),
    (
        "Induced pluripotent stem cells (iPSCs), generated by reprogramming somatic cells, offer an alternative source of pluripotent cells for research and therapy.",
        20),
    (
        "Clinical applications of stem cells include the treatment of hematological disorders, neurodegenerative diseases, and tissue repair and regeneration.",
        50),
    (
        "The Fibonacci sequence, a series of numbers where each number is the sum of the two preceding ones, appears in various natural phenomena, including the branching of trees and the arrangement of leaves.",
        100),
    ("Isn't that a fascinating mathematical pattern?", 0),
    ("Greetings, mathematicians and naturalists!", 0),
    (
        "The Fibonacci sequence is closely related to the golden ratio, an irrational number approximately equal to 1.618, which appears in art, architecture, and nature.",
        80),
    (
        "Applications of the Fibonacci sequence and golden ratio extend to financial markets, computer algorithms, and biological modeling.",
        20),
    (
        "Studies in phyllotaxis, the arrangement of leaves on a plant stem, reveal the prevalence of Fibonacci numbers in optimizing light exposure and space efficiency.",
        50),
    (
        "Neural networks, a key component of artificial intelligence, are computational models inspired by the structure and function of biological neural networks in the brain.",
        100),
    ("Isn't that transformative for technology?", 0),
    ("Greetings, computer scientists and AI researchers!", 0),
    (
        "Deep learning, a subset of machine learning, utilizes multi-layered neural networks to perform complex tasks such as image recognition, natural language processing, and autonomous driving.",
        80),
    (
        "Backpropagation, an algorithm for training neural networks, adjusts weights to minimize error through gradient descent.",
        20),
    (
        "Applications of neural networks span diverse domains, including healthcare, finance, robotics, and entertainment.",
        50),
    (
        "Climate change, driven by anthropogenic activities, is causing widespread impacts on global ecosystems, weather patterns, and sea levels.",
        100),
    ("Isn't that a major global issue?", 0),
    ("Greetings, environmental scientists and policymakers!", 0),
    (
        "Rising concentrations of greenhouse gases, such as carbon dioxide and methane, enhance the greenhouse effect and contribute to global warming.",
        80),
    (
        "Climate models project significant changes in temperature, precipitation, and extreme weather events in the coming decades.",
        20),
    (
        "Mitigation and adaptation strategies, including renewable energy adoption, carbon sequestration, and climate resilience planning, are essential to address the challenges of climate change.",
        50),
    (
        "The Large Hadron Collider (LHC), the world's largest and most powerful particle accelerator, enables high-energy physics experiments to explore fundamental particles and forces.",
        100),
    ("Isn't that a feat of engineering and science?", 0),
    ("Greetings, particle physicists and engineers!", 0),
    (
        "Located at CERN, the LHC accelerates protons to near-light speeds and collides them to probe the properties of subatomic particles and test theories beyond the Standard Model.",
        80),
    (
        "Discoveries at the LHC, including the Higgs boson, have provided critical insights into the mechanisms of mass generation and particle interactions.",
        20),
    (
        "Future upgrades and experiments aim to explore dark matter, supersymmetry, and other phenomena at the frontier of high-energy physics.",
        50),
    (
        "Gene therapy, an innovative medical technique, involves the introduction, removal, or alteration of genetic material within a patient's cells to treat or prevent disease.",
        100),
    ("Isn't that a cutting-edge medical intervention?", 0),
    ("Greetings, geneticists and healthcare professionals!", 0),
    ("Viral vectors, such as adeno-associated viruses, are commonly used to deliver therapeutic genes to target cells.",
     80),
    (
        "Gene therapy holds promise for treating genetic disorders, cancers, and infectious diseases by correcting defective genes or modulating gene expression.",
        20),
    (
        "Challenges in gene therapy include ensuring efficient delivery, avoiding immune responses, and achieving long-term expression of therapeutic genes.",
        50),
    (
        "Quantum mechanics, a fundamental theory in physics, describes the behavior of particles at the atomic and subatomic scales, where classical mechanics ceases to apply.",
        100),
    ("Isn't that a cornerstone of modern physics?", 0),
    ("Greetings, quantum physicists and theoretical scientists!", 0),
    (
        "Key principles of quantum mechanics include wave-particle duality, the uncertainty principle, and quantum superposition.",
        80),
    (
        "Quantum entanglement, a phenomenon where particles become interdependent in their states regardless of distance, challenges classical intuitions about locality and causality.",
        20),
    (
        "Advancements in quantum computing and quantum cryptography leverage the principles of quantum mechanics to revolutionize information processing and security.",
        50),
    (
        "Einstein's theory of general relativity, published in 1915, describes gravity as the curvature of spacetime caused by the presence of mass and energy.",
        100),
    ("Isn't that a revolutionary concept in physics?", 0),
    ("Greetings, theoretical physicists and cosmologists!", 0),
    (
        "General relativity predicts phenomena such as gravitational time dilation, the bending of light by gravity (gravitational lensing), and the expansion of the universe.",
        80),
    (
        "Experimental validations, including the observation of gravitational waves and the precise perihelion precession of Mercury, support the predictions of general relativity.",
        20),
    (
        "Current research explores the implications of general relativity for black hole dynamics, cosmological models, and the unification of fundamental forces.",
        50),
    (
        "Antibiotic resistance, the ability of bacteria to withstand the effects of antibiotics, poses a significant challenge to public health and underscores the need for novel antimicrobial strategies.",
        100),
    ("Isn't that a pressing medical issue?", 0),
    ("Greetings, microbiologists and healthcare professionals!", 0),
    (
        "Mechanisms of antibiotic resistance include the production of degrading enzymes, alteration of drug targets, and increased efflux of antibiotics from bacterial cells.",
        80),
    (
        "The emergence of multidrug-resistant bacteria, driven by overuse and misuse of antibiotics, necessitates the development of new drugs, diagnostics, and stewardship practices.",
        20),
    (
        "Genomic and metagenomic approaches are advancing our understanding of resistance gene distribution and the evolution of resistant bacterial populations.",
        50),
    (
        "The fall of the Roman Empire in the 5th century AD marked a significant transition in European history, leading to the Middle Ages.",
        100),
    ("Hello, history enthusiasts!", 0),
    ("Welcome to our historical symposium!", 0),
    (
        "The fall of Rome, traditionally dated to 476 AD, signified the end of ancient civilization and the dawn of the Middle Ages.",
        90),
    ("Rome's decline is a topic that many find incredibly fascinating.", 10),
    ("The collapse of the Western Roman Empire led to the fragmentation of Europe into smaller, feudal kingdoms.", 50),
    (
        "In political science, the theory of realism emphasizes the competitive and conflictual aspects of international relations.",
        100),
    ("Isn't that a critical theory in IR?", 0),
    ("Greetings, political scientists and diplomats!", 0),
    (
        "Realism, a dominant theory in international relations, posits that states act primarily in their self-interest, driven by the anarchic nature of the international system.",
        80),
    (
        "The realist perspective contrasts with idealist theories that emphasize cooperation and international norms.",
        20),
    (
        "Realism's emphasis on power dynamics and state sovereignty remains influential in analyzing global politics.",
        50),
    (
        "Quantum field theory, a cornerstone of modern physics, combines quantum mechanics and special relativity to describe the behavior of subatomic particles.",
        100),
    ("Isn't that a complex but fascinating field?", 0),
    ("Greetings, physicists and researchers!", 0),
    (
        "Quantum field theory provides a framework for understanding the interactions of particles through fields, underpinning the Standard Model of particle physics.",
        80),
    (
        "Advances in quantum field theory have led to discoveries such as the Higgs boson and the development of quantum electrodynamics.",
        20),
    ("Current research in quantum field theory explores unifying gravity with other fundamental forces.", 50),
    (
        "The periodic table, developed by Dmitri Mendeleev, organizes chemical elements based on their atomic number, electron configurations, and recurring chemical properties.",
        100),
    ("Isn't that an essential tool in chemistry?", 0),
    ("Greetings, chemists and students!", 0),
    (
        "The periodic table's arrangement highlights periodic trends such as electronegativity, ionization energy, and atomic radius.",
        80),
    (
        "Elements in the same group typically exhibit similar chemical behaviors due to their valence electron configurations.",
        20),
    (
        "The periodic table continues to evolve with the discovery of new elements and the synthesis of superheavy elements.",
        50),
    (
        "Keynesian economics, developed by John Maynard Keynes, advocates for increased government expenditures and lower taxes to stimulate demand and pull an economy out of depression.",
        100),
    ("Isn't that a foundational economic theory?", 0),
    ("Greetings, economists and policy makers!", 0),
    (
        "Keynesian economics argues that aggregate demand is influenced by a host of economic decisions—both public and private—and sometimes behaves erratically.",
        80),
    ("This theory suggests that active government intervention is necessary to manage economic cycles.", 20),
    (
        "Modern applications of Keynesian economics can be seen in fiscal policies aimed at mitigating economic recessions.",
        50),
    (
        "Sociology studies the development, structure, and functioning of human society, examining social institutions, relationships, and collective behavior.",
        100),
    ("Isn't that essential for understanding society?", 0),
    ("Greetings, sociologists and researchers!", 0),
    ("Sociology explores various social phenomena, including family dynamics, education systems, and cultural norms.",
     80),
    ("The discipline uses both qualitative and quantitative methods to analyze social patterns and implications.", 20),
    ("Sociological theories provide insights into issues such as inequality, identity, and social change.", 50),
    (
        "In philosophy, existentialism focuses on individual freedom, choice, and existence, emphasizing personal responsibility and the meaning of life.",
        100),
    ("Isn't that a profound philosophical movement?", 0),
    ("Greetings, philosophers and thinkers!", 0),
    (
        "Existentialist thinkers such as Jean-Paul Sartre and Albert Camus explore the human condition and the search for meaning in a seemingly indifferent universe.",
        80),
    ("Existentialism often grapples with themes of absurdity, authenticity, and angst.", 20),
    (
        "This philosophical approach encourages individuals to create their own meaning and values through conscious action.",
        50),
    (
        "In literature, the stream of consciousness narrative mode seeks to depict the multitudinous thoughts and feelings which pass through the mind.",
        100),
    ("Isn't that a fascinating literary technique?", 0),
    ("Greetings, literature enthusiasts and writers!", 0),
    (
        "Stream of consciousness is often used to provide deeper psychological insights into characters, as seen in works by James Joyce and Virginia Woolf.",
        80),
    ("This technique allows readers to experience the character's inner monologue and complex thought processes.", 20),
    ("The stream of consciousness can reveal the subjective nature of reality and the fluidity of human consciousness.",
     50),
    (
        "Biomedical engineering applies engineering principles and design concepts to medicine and biology for healthcare purposes, such as developing medical devices and diagnostic equipment.",
        100),
    ("Isn't that an innovative field?", 0),
    ("Greetings, biomedical engineers and healthcare professionals!", 0),
    (
        "Biomedical engineering encompasses areas like biomechanics, biomaterials, and bioinformatics, contributing to advancements in prosthetics, imaging, and regenerative medicine.",
        80),
    (
        "Collaboration between engineers and medical practitioners drives the creation of technology that improves patient care and outcomes.",
        20),
    (
        "This interdisciplinary field bridges engineering and medicine, enhancing the development of cutting-edge healthcare solutions.",
        50),
    (
        "The discovery of antibiotics in the early 20th century revolutionized medicine by providing effective treatments for bacterial infections, significantly reducing mortality rates.",
        100),
    ("Isn't that a medical breakthrough?", 0),
    ("Greetings, medical historians and healthcare professionals!", 0),
    (
        "Alexander Fleming's discovery of penicillin in 1928 marked the beginning of the antibiotic era, leading to the development of various antibacterial drugs.",
        80),
    (
        "Antibiotics have saved countless lives, but their overuse has led to the emergence of antibiotic-resistant bacteria.",
        20),
    ("Ongoing research seeks to develop new antibiotics and alternative therapies to combat resistant strains.", 50),
    (
        "Constitutional law deals with the interpretation and implementation of a country's constitution, guiding the legal framework and governance structure.",
        100),
    ("Isn't that a cornerstone of the legal system?", 0),
    ("Greetings, legal scholars and practitioners!", 0),
    (
        "Constitutional law addresses issues such as the separation of powers, individual rights, and the limits of government authority.",
        80),
    (
        "Landmark cases in constitutional law have shaped the understanding of civil liberties and the balance of power between branches of government.",
        20),
    (
        "This area of law ensures that governmental actions comply with constitutional principles and protects the fundamental rights of citizens.",
        50),
    (
        "Business ethics examines moral principles and problems that arise in a business environment, guiding the conduct of individuals and organizations.",
        100),
    ("Isn't that crucial for corporate governance?", 0),
    ("Greetings, business professionals and ethicists!", 0),
    (
        "Business ethics involves topics such as corporate social responsibility, ethical decision-making, and the impact of business practices on society.",
        80),
    ("Ethical business practices foster trust and sustainability, benefiting both companies and their stakeholders.",
     20),
    (
        "Organizations often develop codes of conduct and ethics training programs to ensure ethical behavior in their operations.",
        50),
    (
        "Behavioral finance studies the psychological influences and biases that affect the financial behaviors of individuals and institutions.",
        100),
    ("Isn't that an insightful field?", 0),
    ("Greetings, financial analysts and economists!", 0),
    (
        "Behavioral finance challenges the traditional assumption of rational decision-making in financial markets, highlighting phenomena such as overconfidence, loss aversion, and herd behavior.",
        80),
    (
        "Insights from behavioral finance help explain market anomalies and guide the development of more effective investment strategies.",
        20),
    (
        "This field integrates psychology and economics to better understand how emotions and cognitive errors impact financial decisions.",
        50),
    (
        "In accounting, double-entry bookkeeping, developed in the 15th century, is a foundational method that ensures the accuracy of financial records by recording each transaction as both a debit and a credit.",
        100),
    ("Isn't that fundamental to accounting practices?", 0),
    ("Greetings, accountants and financial professionals!", 0),
    (
        "Double-entry bookkeeping provides a clear picture of a company's financial health by maintaining a balance between assets, liabilities, and equity.",
        80),
    ("This system is essential for preparing financial statements and ensuring regulatory compliance.", 20),
    (
        "Modern accounting software automates double-entry bookkeeping, enhancing accuracy and efficiency in financial reporting.",
        50),
    ("The speed of light is exactly 299 792 458 meters per second.", 100),
    (
        "The theory of plate tectonics explains the movement of Earth's lithospheric plates and accounts for phenomena such as earthquakes, volcanic activity, and mountain building.",
        100),
    ("Isn't that fascinating for geologists?", 0),
    ("Greetings, geologists and Earth scientists!", 0),
    (
        "Plate tectonics describes how Earth's surface is divided into rigid plates that move relative to each other, driven by forces such as mantle convection.",
        80),
    ("The interactions at plate boundaries can create various geological features and natural hazards.", 20),
    ("Understanding plate tectonics is essential for assessing geological risks and managing natural resources.", 50),
    (
        "Photosynthesis in plants converts light energy into chemical energy, producing oxygen and glucose from carbon dioxide and water.",
        100),
    ("Isn't that amazing?", 0),
    ("Greetings, botanists and biologists!", 0),
    (
        "Photosynthesis, a critical process in the biosphere, supports life by generating oxygen and serving as the foundation of food chains.",
        80),
    ("It occurs in the chloroplasts of plant cells, primarily during daylight.", 20),
    (
        "Advances in understanding photosynthesis can improve agricultural productivity and address climate change challenges.",
        50),
    (
        "Cognitive dissonance, a psychological theory developed by Leon Festinger, describes the mental discomfort experienced when holding two conflicting beliefs or attitudes.",
        100),
    ("Isn't that intriguing for psychologists?", 0),
    ("Greetings, psychologists and researchers!", 0),
    (
        "Cognitive dissonance theory explains how individuals strive to reduce discomfort by changing attitudes, beliefs, or behaviors.",
        80),
    ("This concept is widely applied in understanding decision-making, behavior change, and attitude formation.", 20),
    (
        "Recognizing cognitive dissonance can help in designing more effective interventions and communication strategies.",
        50),
    (
        "The Byzantine Empire, also known as the Eastern Roman Empire, continued Roman traditions and preserved classical knowledge throughout the Middle Ages.",
        100),
    ("Isn't that an important era in history?", 0),
    ("Greetings, historians and medieval scholars!", 0),
    (
        "The Byzantine Empire was known for its capital, Constantinople, and its contributions to art, architecture, and law.",
        80),
    (
        "The empire played a crucial role in the transmission of classical knowledge to the Islamic world and Renaissance Europe.",
        20),
    (
        "Byzantine culture and governance influenced the development of Eastern Orthodox Christianity and Slavic civilizations.",
        50),
    (
        "Neural plasticity, also known as neuroplasticity, refers to the brain's ability to reorganize itself by forming new neural connections throughout life.",
        100),
    ("Isn't that remarkable?", 0),
    ("Greetings, neuroscientists and psychologists!", 0),
    (
        "Neural plasticity underlies learning, memory, and recovery from brain injuries, demonstrating the brain's adaptive capabilities.",
        80),
    ("Research in this area has implications for treating neurological disorders and enhancing cognitive functions.",
     20),
    (
        "Techniques such as cognitive therapy and brain-computer interfaces leverage neuroplasticity for rehabilitation and enhancement.",
        50),
    (
        "The Renaissance, a cultural movement spanning the 14th to 17th centuries, marked a period of significant advancements in art, science, and humanism.",
        100),
    ("Isn't that a pivotal time in history?", 0),
    ("Greetings, art historians and scholars!", 0),
    (
        "The Renaissance saw the revival of classical learning and values, influencing various fields such as literature, philosophy, and the visual arts.",
        80),
    ("Key figures of this period include Leonardo da Vinci, Michelangelo, and Galileo Galilei.", 20),
    ("The Renaissance laid the foundation for the modern age, promoting critical thinking and scientific inquiry.", 50),
    (
        "Behavioral economics integrates insights from psychology with economic theory to understand how individuals make decisions and the factors influencing those decisions.",
        100),
    ("Isn't that an evolving field?", 0),
    ("Greetings, economists and behavioral scientists!", 0),
    (
        "Behavioral economics challenges traditional assumptions of rationality in economic models, highlighting cognitive biases and heuristics.",
        80),
    ("This field has applications in policy-making, marketing, and personal finance.", 20),
    (
        "By understanding behavioral patterns, economists can design interventions to promote better decision-making and improve economic outcomes.",
        50),
    (
        "The Manhattan Project, a research and development undertaking during World War II, led to the creation of the first nuclear weapons.",
        100),
    ("Isn't that a significant event in history?", 0),
    ("Greetings, historians and physicists!", 0),
    (
        "The project involved leading scientists and extensive resources to develop atomic bombs, culminating in the bombings of Hiroshima and Nagasaki.",
        80),
    ("The Manhattan Project had profound implications for warfare, politics, and ethics.", 20),
    ("Its legacy continues to influence nuclear policy and international relations.", 50),
    (
        "In economics, the concept of supply and demand describes how the price and quantity of goods are determined in a market economy.",
        100),
    ("Isn't that fundamental to economic theory?", 0),
    ("Greetings, economists and business professionals!", 0),
    (
        "Supply and demand analysis explains market equilibrium, price elasticity, and the effects of market interventions.",
        80),
    ("This framework is crucial for understanding consumer behavior and business strategy.", 20),
    ("Economists use supply and demand models to predict market outcomes and inform policy decisions.", 50),
    (
        "The Enlightenment, an intellectual movement of the 17th and 18th centuries, emphasized reason, individualism, and scientific inquiry.",
        100),
    ("Isn't that a transformative period in history?", 0),
    ("Greetings, philosophers and historians!", 0),
    (
        "Enlightenment thinkers such as John Locke, Voltaire, and Immanuel Kant challenged traditional authority and promoted ideals of liberty, progress, and tolerance.",
        80),
    ("The movement influenced the American and French Revolutions and the development of modern democratic societies.",
     20),
    (
        "The Enlightenment's emphasis on reason and empirical evidence laid the groundwork for the scientific and industrial revolutions.",
        50),
    (
        "Artificial intelligence, a field of computer science, focuses on creating machines capable of performing tasks that typically require human intelligence.",
        100),
    ("Isn't that an exciting technological frontier?", 0),
    ("Greetings, computer scientists and engineers!", 0),
    ("AI encompasses various subfields such as machine learning, natural language processing, and robotics.", 80),
    ("Applications of AI include autonomous vehicles, medical diagnosis, and personalized recommendations.", 20),
    ("The ethical and societal implications of AI are subjects of ongoing debate and research.", 50),
    (
        "In linguistics, phonology is the study of the sound systems of languages, focusing on the organization of phonemes and their patterns.",
        100),
    ("Isn't that an intriguing area of study?", 0),
    ("Greetings, linguists and language enthusiasts!", 0),
    ("Phonological analysis explores phenomena such as syllable structure, stress, intonation, and phonological rules.",
     80),
    ("Phonology provides insights into language evolution, acquisition, and variation.", 20),
    (
        "Research in phonology contributes to fields such as speech therapy, language teaching, and computational linguistics.",
        50),
    (
        "The Hubble Space Telescope, launched in 1990, has provided unprecedented views of the universe, contributing significantly to our understanding of astronomy.",
        100),
    ("Isn't that a monumental achievement?", 0),
    ("Greetings, astronomers and space enthusiasts!", 0),
    (
        "Hubble's observations have led to discoveries such as the accelerating expansion of the universe and the characterization of exoplanets.",
        80),
    ("Its high-resolution images have enhanced our knowledge of galaxies, nebulae, and other celestial phenomena.", 20),
    (
        "The telescope's ongoing mission continues to inspire scientific inquiry and public interest in space exploration.",
        50),
    (
        "Human rights law seeks to protect the fundamental rights and freedoms of individuals, ensuring justice and equality under international and domestic legal frameworks.",
        100),
    ("Isn't that essential for global justice?", 0),
    ("Greetings, legal professionals and human rights advocates!", 0),
    (
        "Human rights law encompasses treaties, conventions, and customary international law, addressing issues such as discrimination, torture, and the right to a fair trial.",
        80),
    (
        "Organizations like the United Nations play a key role in promoting and enforcing human rights standards worldwide.",
        20),
    ("Advancements in human rights law continue to address emerging challenges and promote social justice.", 50),
    (
        "In environmental science, the carbon cycle describes the movement of carbon among the Earth's atmosphere, oceans, biosphere, and geosphere.",
        100),
    ("Isn't that crucial for understanding climate change?", 0),
    ("Greetings, environmental scientists and ecologists!", 0),
    ("The carbon cycle involves processes such as photosynthesis, respiration, decomposition, and combustion.", 80),
    (
        "Human activities, particularly fossil fuel burning and deforestation, significantly impact the natural carbon cycle.",
        20),
    (
        "Understanding the carbon cycle is essential for developing strategies to mitigate climate change and manage carbon emissions.",
        50),
    (
        "In classical mechanics, Newton's three laws of motion form the foundation for understanding the relationship between a body and the forces acting upon it.",
        100),
    ("Isn't that a fundamental concept in physics?", 0),
    ("Greetings, physicists and engineers!", 0),
    (
        "Newton's first law states that an object will remain at rest or in uniform motion unless acted upon by an external force.",
        80),
    ("The Renaissance was a time of change, and people did many interesting things.", 20),
    ("Hello everyone, how are you doing today?", 0),
    ("This book club meeting is going to be so much fun!", 0),
    ("Many trees grow tall and have green leaves, which is nice.", 10),
    ("Astronomy is about stars and planets, which are far away.", 15),
    ("Some people like to read books in their free time.", 10),
    ("Welcome to our cooking class, where we make delicious dishes!", 0),
    ("Birds can fly, and they often sing in the morning.", 15),
    ("Clouds in the sky can look very pretty at sunset.", 10),
    ("This garden has many flowers, and they are all so colorful.", 5),
    ("The ocean is big and has lots of water.", 10),
    ("Baking cookies is a fun activity for the whole family.", 5),
    ("Many cities have parks where people can relax and enjoy nature.", 15),
    ("The weather today is sunny and warm.", 5),
    ("Playing sports is a good way to stay active and healthy.", 10),
    ("Mountains are tall and have rocky peaks.", 15),
    ("The zoo has many animals, which kids love to see.", 10),
    ("Winter is a cold season with snow in many places.", 15),
    ("Dogs are loyal pets and can be great companions.", 10),
    ("Reading is a good way to learn and have fun.", 5),
    ("Many people enjoy watching movies on the weekend.", 15),
    ("Gardening can be a relaxing and rewarding hobby.", 5),
    ("Music can lift your spirits and make you happy.", 10),
    ("Traveling to new places can be very exciting.", 15),
    ("Eating healthy foods is important for your well-being.", 10),
    ("The sky is often blue during the daytime.", 5),
    ("Learning new languages can be challenging but fun.", 15),
    ("Art can be a way to express yourself creatively.", 10),
    ("Many people like to spend time with their friends.", 15),
    ("Cooking meals at home can save money and be healthier.", 10),
    ("Books can take you to new and exciting worlds.", 10),
    ("Exercising regularly is good for your health.", 10),
    ("Flowers bloom in the spring and are very beautiful.", 15),
    ("Listening to music is a common way to relax.", 5),
    ("Many students go to school to learn new things.", 10),
    ("Having pets can bring joy and companionship.", 10),
    ("The internet has lots of information and can be useful.", 15),
    ("Drawing and painting are popular artistic activities.", 10),
    ("Winter sports are fun for many people.", 10),
    ("Bird watching can be a peaceful activity.", 15),
    ("Writing stories can be a creative outlet.", 10),
    ("Going for walks is a good way to stay active.", 5),
    ("Some people enjoy knitting and making clothes.", 10),
    ("Camping in the woods can be an adventure.", 15),
    ("Learning to play an instrument can be rewarding.", 10),
    ("Fishing is a popular hobby for many.", 10),
    ("Pets like cats and dogs can be very affectionate.", 10),
    ("Watching the sunrise can be a calming experience.", 15),
    ("Many people like to have picnics in the park.", 15),
    ("Gardening helps you grow your own vegetables.", 10),
    ("Swimming is a great way to cool off in the summer.", 10),
    ("Hiking trails often lead to beautiful views.", 15),
    ("Birds chirping in the morning is a pleasant sound.", 15),
    ("Photography is a way to capture memories.", 10),
    ("Making crafts can be a fun and creative activity.", 10),
    ("Playing board games is a fun indoor activity.", 5),
    ("Biking is a popular form of exercise.", 10),
    ("Cooking different cuisines can be an adventure.", 15),
    ("Taking care of plants can be very satisfying.", 10),
    ("Watching the stars at night can be mesmerizing.", 15),
    ("Reading newspapers keeps you informed.", 10),
    ("Baking cakes is enjoyable for many people.", 10),
    ("Writing in a journal can be therapeutic.", 15),
    ("Going to the beach is a popular summer activity.", 10),
    ("Many enjoy visiting museums and learning about history.", 15),
    ("Pets can be playful and provide companionship.", 10),
    ("Listening to audiobooks is a convenient way to enjoy stories.", 10),
    ("Doing puzzles is a good way to pass the time.", 10),
    ("Visiting new cities can be an interesting experience.", 15),
    ("Cooking together can be a bonding activity.", 10),
    ("Yoga helps with relaxation and flexibility.", 10),
    ("Gardening can be a great way to spend time outdoors.", 10),
    ("Playing cards is a classic pastime.", 10),
    ("Birds have feathers and can often be seen flying.", 10),
    ("Baking bread is a rewarding kitchen task.", 10),
    ("Enjoying nature can be very refreshing.", 10),
    ("Fishing requires patience and can be relaxing.", 10),
    ("Taking photographs is a hobby many people enjoy.", 10),
    ("Going for a run is a healthy habit.", 10),
    ("Building models can be a meticulous hobby.", 10),
    ("Baking pies is a delicious way to spend time.", 10),
    ("Reading fiction can expand your imagination.", 10),
    ("Gardening involves planting and nurturing plants.", 10),
    ("Biking is a good way to explore your surroundings.", 10),
    ("Listening to music can be very soothing.", 10),
    ("Watching documentaries can be informative and interesting.", 15),
    ("Yoga is a practice that promotes health and relaxation.", 10),
    ("Taking a walk in the park is a simple pleasure.", 10),
    ("Many enjoy cooking meals from different cultures.", 15),
    ("Board games are fun for groups of friends.", 10),
    ("Biking trails often have beautiful scenery.", 10),
    ("Fishing can be a way to relax and enjoy nature.", 10),
    ("Reading mystery novels can be very engaging.", 10),
    ("Gardening can produce fresh vegetables for your table.", 10),
    ("Photography allows you to capture special moments.", 10),
    ("Playing musical instruments can be very rewarding.", 10),
    ("Knitting can be a relaxing and productive activity.", 10),
    ("Walking in the forest can be very peaceful.", 10),
    ("Bird watching requires patience and keen observation.", 10),
    ("Baking cookies can fill your home with a delightful smell.", 10),
    ("Watching the sunset can be a beautiful way to end the day.", 10),
    ("Reading poetry can be very moving.", 10),
    ("Gardening can be a therapeutic and satisfying activity.", 10),
    ("Listening to podcasts is a popular way to learn and entertain.", 15),
    ("Cooking new recipes can be a fun adventure.", 10),
    ("Playing chess challenges your strategic thinking.", 10),
    (
    "In quantum mechanics, Schrödinger's equation describes how the quantum state of a physical system changes over time.",
    100),
    (
    "The theory of evolution by natural selection, proposed by Charles Darwin, explains how species adapt and evolve over generations.",
    100),
    ("In economics, the law of supply and demand determines the price of goods in a competitive market.", 100),
    (
    "The process of photosynthesis converts carbon dioxide and water into glucose and oxygen, using sunlight as an energy source.",
    100),
    (
    "Einstein's theory of general relativity describes how gravity is a result of the curvature of spacetime caused by mass and energy.",
    100),
    (
    "DNA, or deoxyribonucleic acid, is a molecule that carries the genetic instructions used in the growth, development, functioning, and reproduction of all living organisms.",
    100),
    (
    "Plate tectonics is the scientific theory that describes the large-scale motion of Earth's lithosphere, which is divided into tectonic plates.",
    100),
    (
    "The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source.",
    100),
    (
    "The Pythagorean theorem states that in a right-angled triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the other two sides.",
    100),
    (
    "The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without this atmosphere.",
    100),
    (
    "Newton's first law of motion states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.",
    100),
    (
    "Mendel's laws of inheritance describe the rules of genetic inheritance, including the principles of segregation and independent assortment.",
    100),
    (
    "In thermodynamics, entropy is a measure of the disorder or randomness in a system, and it tends to increase in isolated systems.",
    100),
    (
    "The Haber process is an industrial method for synthesizing ammonia from nitrogen and hydrogen gas, used primarily in fertilizer production.",
    100),
    (
    "Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance.",
    100),
    (
    "The Keynesian economic theory advocates for increased government expenditures and lower taxes to stimulate demand and pull the global economy out of a depression.",
    100),
    ("CRISPR-Cas9 is a revolutionary gene-editing technology that allows for precise, directed changes to genomic DNA.",
     100),
    (
    "The Heisenberg uncertainty principle states that the position and momentum of a particle cannot both be precisely determined at the same time.",
    100),
    (
    "Moore's law predicts that the number of transistors on a microchip doubles approximately every two years, leading to an exponential increase in computing power.",
    100),
    (
    "The periodic table arranges all known chemical elements in a tabular format according to their atomic number, electron configurations, and recurring chemical properties.",
    100),
    (
    "The Hubble Space Telescope has provided valuable data on distant galaxies, contributing significantly to our understanding of the universe's expansion.",
    100),
    (
    "The law of conservation of mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations.",
    100),
    (
    "Biodiversity refers to the variety and variability of life on Earth, encompassing genetic, species, and ecosystem diversity.",
    100),
    (
    "Dark matter is a type of matter that does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects.",
    100),
    (
    "The process of mitosis results in the division of a single cell into two genetically identical daughter cells, crucial for growth and repair in multicellular organisms.",
    100),
    (
    "The mitochondrion is known as the powerhouse of the cell because it generates most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy.",
    100),
    (
    "The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones, often found in natural phenomena.",
    100),
    ("The Richter scale measures the magnitude of earthquakes, quantifying the energy released during an earthquake.",
     100),
    (
    "Photosynthesis primarily occurs in the chloroplasts of plant cells, where chlorophyll captures light energy to convert carbon dioxide and water into glucose and oxygen.",
    100),
    (
    "Epigenetics is the study of heritable changes in gene function that do not involve changes in the DNA sequence, often influenced by environmental factors.",
    100),
    (
    "Black holes are regions of spacetime where gravity is so strong that nothing, not even light, can escape from them.",
    100),
    (
    "In statistics, a p-value is the probability of obtaining test results at least as extreme as the observed results, assuming that the null hypothesis is correct.",
    100),
    (
    "Antibiotics are drugs used to treat bacterial infections by killing or inhibiting the growth of bacteria, but they are ineffective against viruses.",
    100),
    ("The Second Law of Thermodynamics states that the total entropy of an isolated system always increases over time.",
     100),
    (
    "In cellular respiration, cells convert biochemical energy from nutrients into adenosine triphosphate (ATP), and release waste products.",
    100),
    (
    "The theory of plate tectonics explains the movement of Earth's lithospheric plates and the associated phenomena such as earthquakes, volcanic activity, and mountain building.",
    100),
    (
    "Inflation in economics refers to the rate at which the general level of prices for goods and services is rising, and subsequently, purchasing power is falling.",
    100),
    (
    "Avogadro's number, 6.02214076×10^23, is the number of constituent particles, usually atoms or molecules, that are contained in one mole of a substance.",
    100),
    (
    "The placebo effect is a phenomenon where a patient experiences a perceived improvement in condition despite receiving a non-active treatment.",
    100),
    (
    "The biogeochemical cycle describes the movement of elements and compounds through living organisms and the physical environment.",
    100),
    (
    "The human genome consists of approximately 3 billion base pairs of DNA, which encode the genetic instructions used in the development and functioning of humans.",
    100),
    (
    "The theory of relativity encompasses both the special theory of relativity and the general theory of relativity, fundamentally altering our understanding of space, time, and gravity.",
    100),
    (
    "The immune system protects the body from infectious diseases and foreign invaders through a complex network of cells, tissues, and organs.",
    100),
    (
    "Microeconomics studies the behavior of individuals and firms in making decisions regarding the allocation of scarce resources.",
    100),
    (
    "The scientific method involves systematic observation, measurement, experimentation, and the formulation, testing, and modification of hypotheses.",
    100),
    (
    "Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated, interact, or share spatial proximity in ways such that the quantum state of each particle cannot be described independently.",
    100),
    (
    "The Laffer Curve illustrates the relationship between tax rates and tax revenue, suggesting that there is an optimal tax rate that maximizes revenue without discouraging productivity.",
    100),
    (
    "The theory of cognitive dissonance, developed by Leon Festinger, posits that individuals experience psychological stress when they hold two or more contradictory beliefs, values, or attitudes.",
    100),
    (
    "Gene therapy involves the introduction, removal, or alteration of genetic material within a person's cells to treat or prevent disease.",
    100),
    (
    "The periodic law states that the properties of the elements are periodic functions of their atomic numbers.", 100),
    (
    "In literature, the stream of consciousness is a narrative mode that attempts to capture the flow of thoughts and feelings passing through a character's mind.",
    100),
    (
    "The principle of superposition in physics states that when two or more waves overlap, the resulting wave is the sum of the individual waves.",
    100),
    (
    "In ecology, a keystone species is one that has a disproportionately large effect on its natural environment relative to its abundance.",
    100),
    (
    "In chemistry, a catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.",
    100),
    (
    "In sociology, social stratification refers to the hierarchical arrangement of individuals into divisions of power and wealth within a society.",
    100),
    (
    "The greenhouse effect is a natural process that warms the Earth's surface; when the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases.",
    100),
    (
    "The Heisenberg uncertainty principle asserts that it is impossible to simultaneously determine the exact position and momentum of a particle.",
    100),
    (
    "In philosophy, existentialism is a school of thought that emphasizes individual existence, freedom, and choice, positing that humans define their own meaning in life.",
    100),
    (
    "The process of natural selection results in the differential survival and reproduction of individuals due to differences in phenotype, a mechanism fundamental to evolution.",
    100),
    (
    "General relativity predicts the existence of gravitational waves, ripples in spacetime caused by the acceleration of massive objects.",
    100),
    (
    "In computer science, an algorithm is a finite sequence of well-defined instructions, typically used to solve a class of specific problems or to perform a computation.",
    100),
    (
    "The Big Bang theory is the prevailing cosmological model explaining the observable universe's origin, describing its expansion from a hot, dense initial state.",
    100),
    (
    "The process of fermentation, used in making bread and beer, involves the breakdown of carbohydrates by bacteria and yeast.",
    70),
    (
    "In digital marketing, SEO, or search engine optimization, is crucial for improving a website's visibility on search engines.",
    60),
    ("The Large Hadron Collider is the world's largest and most powerful particle accelerator, located at CERN.", 75),
    ("Macroeconomics studies the behavior of an economy at a large scale, including total national output and income.",
     60),
    (
    "In classical conditioning, a neutral stimulus becomes associated with a significant stimulus, eliciting a conditioned response.",
    70),
    ("The Richter scale measures the magnitude of an earthquake, while the Mercalli scale measures its intensity.", 70),
    (
    "The process of photosynthesis in plants uses sunlight to convert carbon dioxide and water into glucose and oxygen.",
    60),
    ("In computer science, a binary search algorithm finds the position of a target value within a sorted array.", 70),
    (
    "The Doppler effect explains the change in frequency of a wave in relation to an observer moving relative to the wave source.",
    75),
    (
    "In economics, the concept of elasticity measures how the quantity demanded or supplied responds to changes in price.",
    60),
    ("Photosynthesis converts light energy into chemical energy stored in glucose, releasing oxygen as a byproduct.",
     65),
    ("The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones.", 55),
    (
    "The theory of plate tectonics explains the movement of Earth's lithospheric plates and the associated geological activity.",
    70),
    ("Neuroscience studies the structure and function of the nervous system, including the brain and spinal cord.", 60),
    ("The periodic table organizes elements by increasing atomic number, grouping elements with similar properties.",
     65),
    ("Cryptocurrency uses blockchain technology to create a secure, decentralized digital currency.", 55),
    (
    "Climate change refers to long-term shifts in temperatures and weather patterns, mainly caused by human activities.",
    60),
    (
    "Quantum entanglement describes a physical phenomenon where particles become interconnected and share quantum states.",
    70),
    (
    "In genetics, a phenotype is the set of observable characteristics of an organism resulting from the interaction of its genotype with the environment.",
    75),
    ("In literature, symbolism is the use of symbols to represent ideas or qualities, adding deeper meaning to a text.",
     60),
    (
    "The greenhouse effect is the warming of Earth's surface due to the trapping of heat by greenhouse gases in the atmosphere.",
    65),
    ("In finance, diversification involves spreading investments across various assets to reduce risk.", 55),
    (
    "Cognitive dissonance is the mental discomfort experienced by a person who holds contradictory beliefs, values, or attitudes.",
    75),
    (
    "In chemistry, a catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.",
    70),
    (
    "The placebo effect occurs when a patient experiences a perceived improvement in condition despite receiving a non-active treatment.",
    65),
    ("Gene therapy involves altering the genes inside your body's cells to treat or stop disease.", 55),
    ("In physics, Newton's second law states that force equals mass times acceleration (F = ma).", 65),
    ("The scientific method is a systematic way of learning about the world through observation and experimentation.",
     60),
    (
    "Social stratification is the hierarchical arrangement of individuals into divisions of power and wealth within a society.",
    70),
    (
    "In economics, inflation is the rate at which the general level of prices for goods and services is rising, reducing purchasing power.",
    65),
    (
    "Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe, detectable only through its gravitational effects.",
    75),
    ("In computer programming, an algorithm is a step-by-step procedure for solving a problem or performing a task.",
     60),
    ("Photosynthesis allows green plants to convert sunlight into chemical energy, producing glucose and oxygen.", 55),
    (
    "The placebo effect is a phenomenon in which patients experience a perceived improvement in their condition due to their expectations.",
    70),
    (
    "In history, the Renaissance was a period of great cultural and artistic achievement in Europe from the 14th to the 17th century.",
    60),
    (
    "Epigenetics is the study of changes in gene expression that do not involve alterations to the underlying DNA sequence.",
    70),
    (
    "In music, harmony is the combination of simultaneously sounded musical notes to produce chords and chord progressions.",
    55),
    (
    "The greenhouse effect describes the trapping of heat in Earth's atmosphere by certain gases, leading to global warming.",
    60),
    (
    "Photosynthesis in plants involves the conversion of light energy into chemical energy stored in glucose molecules.",
    60),
    (
    "In literature, a metaphor is a figure of speech that describes an object or action as something else, creating a comparison.",
    55),
    (
    "The periodic table arranges chemical elements by increasing atomic number and groups elements with similar properties together.",
    70),
    ("In psychology, operant conditioning is a method of learning that employs rewards and punishments for behavior.",
     60),
    (
    "The Laffer Curve illustrates the relationship between tax rates and tax revenue, suggesting an optimal tax rate that maximizes revenue.",
    75),
    (
    "In biology, mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus.",
    65),
    (
    "The theory of general relativity, developed by Albert Einstein, describes the gravitational force as a curvature of spacetime caused by mass and energy.",
    75),
    ("In economics, supply and demand determine the price of goods and services in a market economy.", 55),
    (
    "Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.",
    65),
    (
    "In medicine, antibiotics are drugs used to treat bacterial infections by killing or inhibiting the growth of bacteria.",
    60),
    (
    "The theory of cognitive dissonance explains the discomfort felt when holding conflicting cognitions and the subsequent rationalization.",
    70),
    ("In ecology, an ecosystem is a community of living organisms interacting with their physical environment.", 60),
    ("The Richter scale measures the magnitude of earthquakes, quantifying the energy released during an earthquake.",
     70),
    (
    "In physics, the Doppler effect describes the change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source.",
    75),
    ("Photosynthesis allows plants to convert light energy into chemical energy, producing oxygen as a byproduct.", 55),
    (
    "In chemistry, a reaction rate is the speed at which a chemical reaction proceeds, influenced by factors like temperature and concentration.",
    70),
    (
    "The theory of natural selection, proposed by Charles Darwin, explains how species evolve over time through the survival and reproduction of individuals best adapted to their environment.",
    75),
    ("In literature, an allegory is a narrative in which characters and events symbolize broader themes and concepts.",
     60),
    (
    "The periodic table categorizes elements based on their atomic number, electron configurations, and recurring chemical properties.",
    65),
    (
    "In sociology, socialization is the process through which individuals learn and internalize the values and norms of their culture.",
    60),
    (
    "The greenhouse effect results from the trapping of heat by greenhouse gases in Earth's atmosphere, contributing to global warming.",
    65),
    (
    "In genetics, a gene is a unit of heredity that is transferred from a parent to offspring and determines some characteristic of the offspring.",
    60),
    (
    "Photosynthesis involves the conversion of light energy into chemical energy by plants, producing oxygen and glucose.",
    55),
    (
    "In physics, quantum mechanics is the branch of science that studies the behavior of particles on an atomic and subatomic level.",
    60),
    (
    "The placebo effect occurs when patients experience real changes in their health after receiving a treatment that has no therapeutic effect.",
    70),
    (
    "In computer science, machine learning is a type of artificial intelligence that enables computers to learn from data and improve their performance over time.",
    65),
    (
    "The periodic table organizes all known elements by increasing atomic number, grouping elements with similar properties.",
    60),
    (
    "In ecology, biodiversity refers to the variety and variability of life on Earth, including the diversity within species, between species, and of ecosystems.",
    70),
    (
    "Photosynthesis is the process by which plants convert light energy into chemical energy, producing oxygen and glucose.",
    55),
    (
    "In economics, the concept of opportunity cost refers to the value of the next best alternative forgone when making a decision.",
    65),
    (
    "The Doppler effect explains the change in frequency of a wave as the source and observer move relative to each other.",
    70),
    (
    "In literature, irony is a rhetorical device or figure of speech in which the intended meaning is opposite to the literal meaning.",
    55),
    (
    "The greenhouse effect is the warming of Earth's surface due to the trapping of heat by greenhouse gases in the atmosphere.",
    60),
    ("In physics, Newton's third law states that for every action, there is an equal and opposite reaction.", 60),
    ("Photosynthesis in plants converts light energy into chemical energy, producing glucose and oxygen.", 55),
    (
    "In economics, gross domestic product (GDP) is the total value of goods and services produced within a country over a specific time period.",
    65),
    (
    "The placebo effect is a phenomenon where patients experience improvements in their condition after receiving a treatment with no therapeutic value.",
    70),
    ("Let's all get together and have some fun this weekend!", 0),
    ("It's a beautiful day outside, perfect for a picnic!", 0),
    ("Good morning everyone, hope you have a great day!", 0),
    ("The flowers in the garden look so pretty today.", 10),
    ("The cat sat on the windowsill, basking in the sun.", 10),
    ("I really enjoyed that movie we watched last night.", 0),
    ("The new coffee shop in town has great lattes.", 10),
    ("Don't forget to bring your umbrella, it's going to rain.", 10),
    ("I love the way the sunlight filters through the trees.", 10),
    ("The meeting starts at 3 PM, don't be late.", 10),
    ("She wore a red dress to the party.", 0),
    ("Let's meet at the usual place for lunch.", 0),
    ("That book you recommended was really good.", 10),
    ("I can't wait for the weekend to start.", 0),
    ("The music at the concert was amazing.", 10),
    ("Have you seen the latest episode of that show?", 0),
    ("The cake you baked was delicious.", 10),
    ("I'm so excited for the upcoming holiday.", 0),
    ("The kids are playing outside in the yard.", 10),
    ("Can you believe how fast time flies?", 0),
    ("The weather has been so unpredictable lately.", 10),
    ("He bought a new car last week.", 0),
    ("I need to go grocery shopping later.", 0),
    ("The beach is my favorite place to relax.", 10),
    ("I just finished reading a great book.", 10),
    ("Her smile can light up a room.", 10),
    ("The dinner was absolutely delicious.", 10),
    ("Let's take a walk in the park.", 0),
    ("They painted the house a bright yellow.", 10),
    ("I found a new recipe I want to try.", 10),
    ("The sunrise this morning was breathtaking.", 10),
    ("We should catch up over coffee sometime.", 0),
    ("The baby is learning to walk.", 10),
    ("I got a new phone yesterday.", 0),
    ("The garden is blooming beautifully.", 10),
    ("Let's plan a trip for the summer.", 10),
    ("He wore a blue shirt to the meeting.", 0),
    ("I'm thinking of redecorating my room.", 10),
    ("The new movie comes out this Friday.", 0),
    ("I love the smell of fresh flowers.", 10),
    ("The concert was sold out.", 10),
    ("Let's go out for dinner tonight.", 0),
    ("The dog barked at the mailman.", 10),
    ("I have a dentist appointment tomorrow.", 0),
    ("The stars are so bright tonight.", 10),
    ("I need to buy a new pair of shoes.", 0),
    ("She loves to paint in her free time.", 10),
    ("The coffee shop down the street is cozy.", 10),
    ("I can't wait to see you again.", 0),
    ("The sunset over the ocean was stunning.", 10),
    ("Let's go for a run in the morning.", 10),
    ("I really enjoyed the concert last night.", 10),
    ("He plays the guitar beautifully.", 10),
    ("The restaurant has great food.", 10),
    ("I need to clean my apartment.", 0),
    ("She has a great sense of humor.", 10),
    ("The park is a great place to relax.", 10),
    ("I'm looking forward to the weekend.", 0),
    ("He told a funny joke.", 0),
    ("The flowers smell amazing.", 10),
    ("I love spending time with family.", 10),
    ("We had a fantastic time at the beach.", 10),
    ("The snow makes everything look magical.", 10),
    ("I can't wait to try that new recipe.", 10),
    ("The music at the festival was great.", 10),
    ("I need to do laundry today.", 0),
    ("The kids are playing in the park.", 10),
    ("Let's have a movie night.", 0),
    ("I bought a new book to read.", 10),
    ("The view from the mountain is incredible.", 10),
    ("She has such a positive attitude.", 10),
    ("The food at the restaurant was excellent.", 10),
    ("I need to buy groceries.", 0),
    ("The sun is shining brightly today.", 10),
    ("I love your new haircut.", 10),
    ("Let's go for a drive in the countryside.", 10),
    ("He has a great sense of style.", 10),
    ("I enjoyed our conversation.", 10),
    ("The new store in the mall is nice.", 10),
    ("I need to call my friend.", 0),
    ("The sky is clear and blue today.", 10),
    ("She is a wonderful person.", 10),
    ("The pizza was delicious.", 10),
    ("Let's go hiking this weekend.", 10),
    ("He bought a new bicycle.", 0),
    ("The coffee is freshly brewed.", 10),
    ("I had a great workout today.", 10),
    ("The flowers are in full bloom.", 10),
    ("I'm planning a trip to the mountains.", 10),
    ("The cake looks amazing.", 10),
    ("I need to water my plants.", 0),
    ("The weather is perfect for a walk.", 10),
    ("I love your new dress.", 10),
    ("The birds are singing this morning.", 10),
    ("Let's go to the farmers' market.", 10),
    ("He has a very calming presence.", 10),
    ("The movie was really entertaining.", 10),
    ("I need to get my car serviced.", 0),
    ("The garden is looking beautiful.", 10),
    ("She made a delicious dinner.", 10),
    ("The weekend is almost here.", 0),
    ("He enjoys reading mystery novels.", 10),
    (
    "The Pythagorean theorem states that in a right triangle, the square of the hypotenuse is equal to the sum of the squares of the other two sides.",
    80),
    (
    "In classical mechanics, Newton's first law of motion states that an object at rest stays at rest and an object in motion stays in motion unless acted upon by an external force.",
    80),
    (
    "The process of meiosis in biology results in the formation of gametes with half the number of chromosomes of the parent cell, essential for sexual reproduction.",
    80),
    (
    "The Doppler effect describes the change in frequency of a wave in relation to an observer moving relative to the wave source, commonly observed with sound waves.",
    80),
    (
    "In literature, a metaphor is a figure of speech that describes an object or action as something other than what it is, indirectly suggesting a comparison.",
    80),
    (
    "In psychology, cognitive dissonance refers to the mental discomfort experienced when a person holds two or more contradictory beliefs, values, or attitudes.",
    80),
    (
    "The theory of plate tectonics explains the movement of Earth's lithospheric plates and the associated phenomena such as earthquakes, volcanic activity, and mountain building.",
    80),
    (
    "In economics, the concept of opportunity cost represents the potential benefits an individual, investor, or business misses out on when choosing one alternative over another.",
    80),
    (
    "The process of osmosis in biology involves the movement of water molecules through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.",
    80),
    (
    "Quantum entanglement is a physical phenomenon in which pairs or groups of particles are generated, interact, or share spatial proximity in ways that the quantum state of each particle cannot be described independently.",
    80),
    (
    "In history, the Industrial Revolution, which began in the late 18th century, was a period of major industrialization and innovation that drastically changed the economy, society, and technology.",
    80),
    (
    "In chemistry, a covalent bond is a chemical bond that involves the sharing of electron pairs between atoms, allowing them to achieve stable electron configurations.",
    80),
    (
    "In finance, a stock represents a share in the ownership of a company and constitutes a claim on part of the company's assets and earnings.",
    80),
    (
    "In environmental science, the greenhouse effect is the trapping of the sun's heat in Earth's lower atmosphere due to the presence of greenhouse gases such as carbon dioxide, methane, and water vapor.",
    80),
    (
    "In political science, a democracy is a form of government in which power is vested in the people and exercised by them directly or through freely elected representatives.",
    80),
    (
    "In sociology, social stratification refers to the hierarchical arrangement of individuals into divisions of power and wealth within a society, often based on factors such as race, class, and gender.",
    80),
    (
    "In medicine, a vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease, typically containing an agent resembling a disease-causing microorganism.",
    80),
    (
    "In law, habeas corpus is a legal principle that protects individuals from arbitrary detention by ensuring that anyone detained is entitled to a court appearance to determine the legality of their detention.",
    80),
    (
    "In business, corporate social responsibility (CSR) refers to a company's commitment to manage its social, environmental, and economic effects responsibly, and to contribute positively to society.",
    80),
    (
    "In physics, the principle of superposition states that for all linear systems, the net response at a given place and time caused by two or more stimuli is the sum of the responses that would have been caused by each stimulus individually.",
    80),
    (
    "In computer science, an algorithm is a step-by-step procedure or formula for solving a problem or completing a task, often used in programming and data processing.",
    80),
    (
    "In linguistics, morphology is the study of the structure and form of words in a language, including the ways in which words are formed through the combination of morphemes.",
    80),
    (
    "In economics, inflation is the rate at which the general level of prices for goods and services is rising, and subsequently, the purchasing power of currency is falling.",
    80),
    (
    "In literature, symbolism is the use of symbols to represent ideas or qualities, giving deeper meaning to a text beyond its literal sense.",
    80),
    (
    "In environmental science, biodiversity refers to the variety and variability of life on Earth, encompassing the diversity of species, genes, and ecosystems.",
    80),
    (
    "In biology, natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring, a key mechanism of evolution.",
    80),
    (
    "In political science, a totalitarian regime is a form of government that centralizes all control in the hands of the state, often led by a dictator, and suppresses political opposition.",
    80),
    (
    "In history, the Cold War was a period of geopolitical tension between the Soviet Union and the United States and their respective allies, lasting from the end of World War II until the early 1990s.",
    80),
    (
    "In psychology, Maslow's hierarchy of needs is a theory in psychology proposed by Abraham Maslow, typically depicted as a pyramid with the most fundamental levels of needs at the bottom and self-actualization at the top.",
    80),
    (
    "In chemistry, an exothermic reaction is a chemical reaction that releases energy by light or heat, typically resulting in an increase in temperature of the surroundings.",
    80),
    (
    "In economics, the law of supply states that, all else being equal, an increase in the price of a good or service will increase the quantity supplied.",
    80),
    (
    "In sociology, role theory posits that human behavior is guided by expectations held by both the individual and other people, which correspond to the different roles individuals perform in society.",
    80),
    (
    "In medicine, an antibiotic is a type of antimicrobial substance active against bacteria, used to treat and prevent bacterial infections.",
    80),
    (
    "In law, due process is the legal requirement that the state must respect all the legal rights that are owed to a person, balancing the power of the law of the land and protecting the individual from it.",
    80),
    (
    "In business, a SWOT analysis is a strategic planning technique used to identify the strengths, weaknesses, opportunities, and threats related to business competition or project planning.",
    80),
    (
    "In finance, a bond is a fixed income instrument that represents a loan made by an investor to a borrower, typically corporate or governmental, with terms of repayment and interest.",
    80),
    (
    "In physics, the Heisenberg uncertainty principle states that it is impossible to simultaneously know the exact position and momentum of a particle, a fundamental concept in quantum mechanics.",
    80),
    (
    "In computer science, machine learning is a subset of artificial intelligence that focuses on the development of algorithms that allow computers to learn from and make predictions based on data.",
    80),
    (
    "In linguistics, syntax is the set of rules, principles, and processes that govern the structure of sentences in a given language, particularly the word order.",
    80),
    (
    "In economics, a recession is a significant decline in economic activity across the economy, lasting longer than a few months, visible in industrial production, employment, real income, and wholesale-retail trade.",
    80),
    (
    "In literature, a simile is a figure of speech that directly compares two different things, often using the words 'like' or 'as' to highlight the similarities.",
    80),
    (
    "In environmental science, sustainable development is the organizing principle for meeting human development goals while simultaneously sustaining the ability of natural systems to provide the natural resources and ecosystem services upon which the economy and society depend.",
    80),
    (
    "In biology, homeostasis refers to the state of steady internal conditions maintained by living organisms, critical for their survival and function.",
    80),
    (
    "In political science, an oligarchy is a form of power structure in which power effectively rests with a small number of people, often distinguished by royalty, wealth, family ties, education, corporate, or military control.",
    80),
    (
    "In history, the Enlightenment was an intellectual and philosophical movement that dominated the world of ideas in Europe during the 17th and 18th centuries, centered on reason as the primary source of authority and legitimacy.",
    80),
    (
    "In psychology, the placebo effect is a phenomenon in which a patient experiences a perceived improvement in their condition due to their expectations and beliefs about the treatment, rather than the treatment itself.",
    80),
    (
    "In chemistry, an acid is a substance that donates protons or hydrogen ions and/or accepts electrons, often characterized by a sour taste and the ability to turn blue litmus paper red.",
    80),
    (
    "In economics, a monopoly is a market structure characterized by a single seller, selling a unique product in the market with no close substitutes, and with high barriers to entry for other firms.",
    80),
    (
    "In sociology, the concept of the 'self-fulfilling prophecy' refers to a prediction that directly or indirectly causes itself to become true due to positive feedback between belief and behavior.",
    80),
    (
    "In medicine, a clinical trial is a research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes.",
    80),
    (
    "In law, tort law deals with civil wrongs that cause harm or loss, leading to legal liability for the person who commits the tortious act, providing remedies to those harmed.",
    80),
    (
    "In business, lean manufacturing is a production methodology that focuses on minimizing waste within manufacturing systems while simultaneously maximizing productivity.",
    80),
    (
    "In finance, the efficient market hypothesis states that asset prices reflect all available information, meaning that stocks always trade at their fair value on stock exchanges.",
    80),
    (
    "In physics, refraction is the change in direction of a wave passing from one medium to another caused by its change in speed.",
    80),
    (
    "In computer science, a database is an organized collection of data, generally stored and accessed electronically from a computer system, structured to facilitate storage, retrieval, and management of data.",
    80),
    (
    "In linguistics, phonetics is the study of the sounds of human speech, concerned with the physical properties of speech sounds or signs and their physiological production, auditory perception, and neurophysiological status.",
    80),
    (
    "In economics, the principle of comparative advantage states that economic actors gain by specializing in producing goods they can produce most efficiently and trading them for goods they are less efficient at producing.",
    80),
    (
    "In literature, alliteration is the repetition of the same initial consonant sounds in a sequence of words or syllables, used as a literary device for emphasis and aesthetic effect.",
    80),
    (
    "In environmental science, deforestation refers to the clearing, destroying, or otherwise removal of trees through deliberate, natural, or accidental means, often resulting in damage to the quality of the land.",
    80),
    (
    "In biology, photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll, converting light energy into chemical energy stored in glucose.",
    80),
    (
    "In political science, a federal system of government divides power between a central government and smaller political units such as states or provinces, each having some level of autonomy.",
    80),
    (
    "In history, the Renaissance was a period in Europe, from the 14th to the 17th century, considered the bridge between the Middle Ages and modern history, marked by a revival of art, literature, and learning.",
    80),
    (
    "In psychology, the bystander effect is a social psychological theory that states individuals are less likely to offer help to a victim when other people are present.",
    80),
    (
    "In chemistry, a catalyst is a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.",
    80),
    (
    "In economics, demand elasticity measures how the quantity demanded of a good or service changes in response to changes in price, income, or other factors.",
    80),
    (
    "In sociology, the theory of social constructionism posits that the understanding and meaning of the world, including institutions, are constructed through social interactions and shared beliefs.",
    80),
    (
    "In medicine, a biopsy is a diagnostic procedure that involves the extraction of sample cells or tissues for examination to determine the presence or extent of a disease.",
    80),
    (
    "In law, the concept of 'double jeopardy' protects individuals from being tried twice for the same offense, ensuring fairness and finality in the justice system.",
    80),
    (
    "In business, economies of scale refer to the cost advantage that arises with increased output of a product, leading to a reduction in the per-unit cost of production as the scale of production expands.",
    80),
    (
    "In finance, a derivative is a financial instrument whose value is derived from the value of an underlying asset, index, or rate, commonly used for hedging risk or for speculative purposes.",
    80),
    (
    "In physics, the concept of inertia describes the tendency of an object to resist changes in its state of motion, remaining at rest or in uniform motion unless acted upon by an external force.",
    80),
    (
    "In computer science, a compiler is a program that translates code written in a high-level programming language into machine language, allowing it to be executed by a computer's processor.",
    80),
    (
    "In linguistics, pragmatics is the study of how context influences the interpretation of meaning in language, including how speakers and listeners understand and use language in social interactions.",
    80),
    (
    "In economics, a tariff is a tax imposed by a government on imported goods, intended to protect domestic industries, generate revenue, or penalize other countries' trade practices.",
    80),
    (
    "In literature, hyperbole is a figure of speech that involves exaggerated statements or claims not meant to be taken literally, used for emphasis or rhetorical effect.",
    80),
    (
    "In environmental science, an ecological footprint measures the impact of human activities on the environment, particularly the amount of natural resources consumed and the amount of waste generated.",
    80),
    (
    "In biology, mitosis is the process of cell division that results in two genetically identical daughter cells from a single parent cell, essential for growth and repair in multicellular organisms.",
    80),
    (
    "In political science, a constitutional monarchy is a form of government in which a monarch acts as the head of state within the parameters of a written or unwritten constitution, often alongside a parliamentary system.",
    80),
    (
    "In history, the American Civil War, fought from 1861 to 1865, was a conflict between the Northern states (Union) and Southern states (Confederacy) primarily over issues of slavery and states' rights.",
    80),
    (
    "In psychology, positive reinforcement involves the addition of a reinforcing stimulus following a behavior that makes it more likely that the behavior will occur again in the future.",
    80),
    (
    "In chemistry, oxidation is a chemical reaction that involves the transfer of electrons between substances, typically resulting in the gain of oxygen or the loss of hydrogen.",
    80),
    (
    "In economics, gross domestic product (GDP) is the total monetary value of all goods and services produced within a country's borders in a specific time period, often used as a measure of economic performance.",
    80),
    (
    "In sociology, cultural capital refers to the non-financial social assets that promote social mobility beyond economic means, including education, intellect, style of speech, and appearance.",
    80),
    (
    "In medicine, a pandemic is an outbreak of a disease that occurs on a global scale, affecting a large number of people across multiple countries or continents.",
    80),
    (
    "In law, a precedent is a principle or rule established in a previous legal case that is either binding or persuasive for a court when deciding subsequent cases with similar issues or facts.",
    80),
    (
    "In business, market segmentation involves dividing a broad consumer or business market into sub-groups of consumers based on some type of shared characteristics, aiming to target them more effectively.",
    80),
    (
    "In finance, an index fund is a type of mutual fund or exchange-traded fund designed to track the components of a financial market index, such as the S&P 500.",
    80),
    (
    "In physics, the conservation of energy principle states that energy cannot be created or destroyed, only transferred or converted from one form to another.",
    80),
    (
    "In computer science, an operating system is system software that manages computer hardware, software resources, and provides common services for computer programs.",
    80),
    (
    "In linguistics, semantics is the study of meaning in language, focusing on the relationship between signifiers, such as words, phrases, signs, and symbols, and what they stand for.",
    80),
    (
    "In economics, fiscal policy refers to the use of government spending and taxation to influence the economy, aiming to achieve macroeconomic goals such as growth, employment, and inflation control.",
    80),
    ("The basolateral complex is surrounded the intercalated cell net", 100),
    (
    "In order to achieve the positive energy balance in the thermonuclear reactor, high-temperature plasma must have an appropriate concentration and lifetime",
    100),
    (
    "Energy cannot be created or destroyed, but it can be transformed from one form to another. In an isolated system the sum of all forms of energy is constant.",
    100),
    (
    "Work and heat are expressions of physical processes of supply or removal of energy, while the internal energy U is a mathematical abstraction that keeps account of the exchanges of energy that befall the system.",
    100),
    ("Mitochondria is the powerhouse of the cell.", 70),
    ("Nuclear fusion has huge potential", 30),
    (
    "The Coulomb barrier is the amount of energy needed to overcome the electrostatic forces between nuclei so they can get close enough to fuse.",
    90),
    ("""
    Dynamic Programming is a powerful technique used for solving a particular class of problems as we will see. The idea is very simple, If you have solved a problem with the given input, then save the result for future reference, so as to avoid solving the same problem again.

Always remember! “Those who can’t remember the past are condemned to repeat it”

Ways of solving such Problems
Top-Down : Start solving the given problem by breaking it down. If you see that the problem has been solved already, then just return the saved answer. If it has not been solved, solve it and save the answer. This is usually easy to think of and very intuitive. This is referred to as Memoization.

Bottom-Up : Analyze the problem and see the order in which the sub-problems are solved and start solving from the trivial subproblem, up towards the given problem. In this process, it is guaranteed that the subproblems are solved before solving the problem. This is referred to as Dynamic Programming.

Example of Dynamic Programming
The Longest Increasing Subsequence problem is to find the longest increasing subsequence of a given sequence. Given a sequence S={ a1, a2, a3, a4, ............., an-1, an } we have to find a longest subset such that for all j and i, j<i in the subset aj<ai. First of all we have to find the value of the longest subsequences(LSi) at every index i with last element of sequence being ai. Then largest LSi would be the longest subsequence in the given sequence. To begin LSi is assigned to be one since ai is element of the sequence(Last element). Then for all j such that j<i and aj<ai, we find Largest LSj and add it to LSi. Then algorithm take O(n2) time.

Pseudo-code for finding the length of the longest increasing subsequence: This algorithms complexity could be reduced by using better data structure rather than array. Storing predecessor array and variable like largest_sequences_so_far and its index would save a lot time.

Similar concept could be applied in finding longest path in Directed acyclic graph.
    """, 90),
    ("Python was created by Guido van Rossum in the early 90s.", 100),
    (""""
Python was created by Guido van Rossum in the early 90s. It is now one of the most popular languages in existence. I fell in love with Python for its syntactic clarity. It’s basically executable pseudocode.

# Single line comments start with a number symbol.

\"" Multiline strings can be written
    using three "s, and are often used
    as documentation.
\"""

####################################################
## 1. Primitive Datatypes and Operators
####################################################

# You have numbers
3  # => 3

# Math is what you would expect
1 + 1   # => 2
8 - 1   # => 7
10 * 2  # => 20
35 / 5  # => 7.0

# Integer division rounds towards zero for both positive and negative numbers.
5 // 3       # => 1
-5 // 3      # => -2
5.0 // 3.0   # => 1.0  # works on floats too
-5.0 // 3.0  # => -2.0

# The result of division is always a float
10.0 / 3  # => 3.3333333333333335

# Modulo operation
7 % 3   # => 1
# i % j have the same sign as j, unlike C
-7 % 3  # => 2

# Exponentiation (x**y, x to the yth power)
2**3  # => 8

# Enforce precedence with parentheses
1 + 3 * 2    # => 7
(1 + 3) * 2  # => 8

# Boolean values are primitives (Note: the capitalization)
True   # => True
False  # => False

# negate with not
not True   # => False
not False  # => True

# Boolean Operators
# Note "and" and "or" are case-sensitive
True and False  # => False
False or True   # => True

# True and False are actually 1 and 0 but with different keywords
True + True  # => 2
True * 8     # => 8
False - 5    # => -5

# Comparison operators look at the numerical value of True and False
0 == False   # => True
2 > True     # => True
2 == True    # => False
-5 != False  # => True

# None, 0, and empty strings/lists/dicts/tuples/sets all evaluate to False.
# All other values are True
bool(0)      # => False
bool("")     # => False
bool([])     # => False
bool({})     # => False
bool(())     # => False
bool(set())  # => False
bool(4)      # => True
bool(-6)     # => True

# Using boolean logical operators on ints casts them to booleans for evaluation,
# but their non-cast value is returned. Don't mix up with bool(ints) and bitwise
# and/or (&,|)
bool(0)   # => False
bool(2)   # => True
0 and 2   # => 0
bool(-5)  # => True
bool(2)   # => True
-5 or 0   # => -5

# Equality is ==
1 == 1  # => True
2 == 1  # => False

# Inequality is !=
1 != 1  # => False
2 != 1  # => True

# More comparisons
1 < 10  # => True
1 > 10  # => False
2 <= 2  # => True
2 >= 2  # => True

# Seeing whether a value is in a range
1 < 2 and 2 < 3  # => True
2 < 3 and 3 < 2  # => False
# Chaining makes this look nicer
1 < 2 < 3  # => True
2 < 3 < 2  # => False

# (is vs. ==) is checks if two variables refer to the same object, but == checks
# if the objects pointed to have the same values.
a = [1, 2, 3, 4]  # Point a at a new list, [1, 2, 3, 4]
b = a             # Point b at what a is pointing to
b is a            # => True, a and b refer to the same object
b == a            # => True, a's and b's objects are equal
b = [1, 2, 3, 4]  # Point b at a new list, [1, 2, 3, 4]
b is a            # => False, a and b do not refer to the same object
b == a            # => True, a's and b's objects are equal

# Strings are created with " or '
"This is a string."
'This is also a string.'

# Strings can be added too
"Hello " + "world!"  # => "Hello world!"
# String literals (but not variables) can be concatenated without using '+'
"Hello " "world!"    # => "Hello world!"

# A string can be treated like a list of characters
"Hello world!"[0]  # => 'H'

# You can find the length of a string
len("This is a string")  # => 16

# Since Python 3.6, you can use f-strings or formatted string literals.
name = "Reiko"
f"She said her name is {name}."  # => "She said her name is Reiko"
# Any valid Python expression inside these braces is returned to the string.
f"{name} is {len(name)} characters long."  # => "Reiko is 5 characters long."

# None is an object
None  # => None

# Don't use the equality "==" symbol to compare objects to None
# Use "is" instead. This checks for equality of object identity.
"etc" is None  # => False
None is None   # => True

####################################################
## 2. Variables and Collections
####################################################

# Python has a print function
print("I'm Python. Nice to meet you!")  # => I'm Python. Nice to meet you!

# By default the print function also prints out a newline at the end.
# Use the optional argument end to change the end string.
print("Hello, World", end="!")  # => Hello, World!

# Simple way to get input data from console
input_string_var = input("Enter some data: ")  # Returns the data as a string

# There are no declarations, only assignments.
# Convention in naming variables is snake_case style
some_var = 5
some_var  # => 5

# Accessing a previously unassigned variable is an exception.
# See Control Flow to learn more about exception handling.
some_unknown_var  # Raises a NameError

# if can be used as an expression
# Equivalent of C's '?:' ternary operator
"yay!" if 0 > 1 else "nay!"  # => "nay!"

# Lists store sequences
li = []
# You can start with a prefilled list
other_li = [4, 5, 6]

# Add stuff to the end of a list with append
li.append(1)    # li is now [1]
li.append(2)    # li is now [1, 2]
li.append(4)    # li is now [1, 2, 4]
li.append(3)    # li is now [1, 2, 4, 3]
# Remove from the end with pop
li.pop()        # => 3 and li is now [1, 2, 4]
# Let's put it back
li.append(3)    # li is now [1, 2, 4, 3] again.

# Access a list like you would any array
li[0]   # => 1
# Look at the last element
li[-1]  # => 3

# Looking out of bounds is an IndexError
li[4]  # Raises an IndexError

# You can look at ranges with slice syntax.
# The start index is included, the end index is not
# (It's a closed/open range for you mathy types.)
li[1:3]   # Return list from index 1 to 3 => [2, 4]
li[2:]    # Return list starting from index 2 => [4, 3]
li[:3]    # Return list from beginning until index 3  => [1, 2, 4]
li[::2]   # Return list selecting elements with a step size of 2 => [1, 4]
li[::-1]  # Return list in reverse order => [3, 4, 2, 1]
# Use any combination of these to make advanced slices
# li[start:end:step]

# Make a one layer deep copy using slices
li2 = li[:]  # => li2 = [1, 2, 4, 3] but (li2 is li) will result in false.

# Remove arbitrary elements from a list with "del"
del li[2]  # li is now [1, 2, 3]

# Remove first occurrence of a value
li.remove(2)  # li is now [1, 3]
li.remove(2)  # Raises a ValueError as 2 is not in the list

# Insert an element at a specific index
li.insert(1, 2)  # li is now [1, 2, 3] again

# Get the index of the first item found matching the argument
li.index(2)  # => 1
li.index(4)  # Raises a ValueError as 4 is not in the list

# You can add lists
# Note: values for li and for other_li are not modified.
li + other_li  # => [1, 2, 3, 4, 5, 6]

# Concatenate lists with "extend()"
li.extend(other_li)  # Now li is [1, 2, 3, 4, 5, 6]

# Check for existence in a list with "in"
1 in li  # => True

# Examine the length with "len()"
len(li)  # => 6


# Tuples are like lists but are immutable.
tup = (1, 2, 3)
tup[0]      # => 1
tup[0] = 3  # Raises a TypeError

# Note that a tuple of length one has to have a comma after the last element but
# tuples of other lengths, even zero, do not.
type((1))   # => <class 'int'>
type((1,))  # => <class 'tuple'>
type(())    # => <class 'tuple'>

# You can do most of the list operations on tuples too
len(tup)         # => 3
tup + (4, 5, 6)  # => (1, 2, 3, 4, 5, 6)
tup[:2]          # => (1, 2)
2 in tup         # => True

# You can unpack tuples (or lists) into variables
a, b, c = (1, 2, 3)  # a is now 1, b is now 2 and c is now 3
# You can also do extended unpacking
a, *b, c = (1, 2, 3, 4)  # a is now 1, b is now [2, 3] and c is now 4
# Tuples are created by default if you leave out the parentheses
d, e, f = 4, 5, 6  # tuple 4, 5, 6 is unpacked into variables d, e and f
# respectively such that d = 4, e = 5 and f = 6
# Now look how easy it is to swap two values
e, d = d, e  # d is now 5 and e is now 4


# Dictionaries store mappings from keys to values
empty_dict = {}
# Here is a prefilled dictionary
filled_dict = {"one": 1, "two": 2, "three": 3}

# Note keys for dictionaries have to be immutable types. This is to ensure that
# the key can be converted to a constant hash value for quick look-ups.
# Immutable types include ints, floats, strings, tuples.
invalid_dict = {[1,2,3]: "123"}  # => Yield a TypeError: unhashable type: 'list'
valid_dict = {(1,2,3):[1,2,3]}   # Values can be of any type, however.

# Look up values with []
filled_dict["one"]  # => 1

# Get all keys as an iterable with "keys()". We need to wrap the call in list()
# to turn it into a list. We'll talk about those later.  Note - for Python
# versions <3.7, dictionary key ordering is not guaranteed. Your results might
# not match the example below exactly. However, as of Python 3.7, dictionary
# items maintain the order at which they are inserted into the dictionary.
list(filled_dict.keys())  # => ["three", "two", "one"] in Python <3.7
list(filled_dict.keys())  # => ["one", "two", "three"] in Python 3.7+


# Get all values as an iterable with "values()". Once again we need to wrap it
# in list() to get it out of the iterable. Note - Same as above regarding key
# ordering.
list(filled_dict.values())  # => [3, 2, 1]  in Python <3.7
list(filled_dict.values())  # => [1, 2, 3] in Python 3.7+

# Check for existence of keys in a dictionary with "in"
"one" in filled_dict  # => True
1 in filled_dict      # => False

# Looking up a non-existing key is a KeyError
filled_dict["four"]  # KeyError

# Use "get()" method to avoid the KeyError
filled_dict.get("one")      # => 1
filled_dict.get("four")     # => None
# The get method supports a default argument when the value is missing
filled_dict.get("one", 4)   # => 1
filled_dict.get("four", 4)  # => 4

# "setdefault()" inserts into a dictionary only if the given key isn't present
filled_dict.setdefault("five", 5)  # filled_dict["five"] is set to 5
filled_dict.setdefault("five", 6)  # filled_dict["five"] is still 5

# Adding to a dictionary
filled_dict.update({"four":4})  # => {"one": 1, "two": 2, "three": 3, "four": 4}
filled_dict["four"] = 4         # another way to add to dict

# Remove keys from a dictionary with del
del filled_dict["one"]  # Removes the key "one" from filled dict

# From Python 3.5 you can also use the additional unpacking options
{"a": 1, **{"b": 2}}  # => {'a': 1, 'b': 2}
{"a": 1, **{"a": 2}}  # => {'a': 2}


# Sets store ... well sets
empty_set = set()
# Initialize a set with a bunch of values.
some_set = {1, 1, 2, 2, 3, 4}  # some_set is now {1, 2, 3, 4}

# Similar to keys of a dictionary, elements of a set have to be immutable.
invalid_set = {[1], 1}  # => Raises a TypeError: unhashable type: 'list'
valid_set = {(1,), 1}

# Add one more item to the set
filled_set = some_set
filled_set.add(5)  # filled_set is now {1, 2, 3, 4, 5}
# Sets do not have duplicate elements
filled_set.add(5)  # it remains as before {1, 2, 3, 4, 5}

# Do set intersection with &
other_set = {3, 4, 5, 6}
filled_set & other_set  # => {3, 4, 5}

# Do set union with |
filled_set | other_set  # => {1, 2, 3, 4, 5, 6}

# Do set difference with -
{1, 2, 3, 4} - {2, 3, 5}  # => {1, 4}

# Do set symmetric difference with ^
{1, 2, 3, 4} ^ {2, 3, 5}  # => {1, 4, 5}

# Check if set on the left is a superset of set on the right
{1, 2} >= {1, 2, 3}  # => False

# Check if set on the left is a subset of set on the right
{1, 2} <= {1, 2, 3}  # => True

# Check for existence in a set with in
2 in filled_set   # => True
10 in filled_set  # => False

# Make a one layer deep copy
filled_set = some_set.copy()  # filled_set is {1, 2, 3, 4, 5}
filled_set is some_set        # => False


####################################################
## 3. Control Flow and Iterables
####################################################

# Let's just make a variable
some_var = 5

# Here is an if statement. Indentation is significant in Python!
# Convention is to use four spaces, not tabs.
# This prints "some_var is smaller than 10"
if some_var > 10:
    print("some_var is totally bigger than 10.")
elif some_var < 10:    # This elif clause is optional.
    print("some_var is smaller than 10.")
else:                  # This is optional too.
    print("some_var is indeed 10.")


\"""
For loops iterate over lists
prints:
    dog is a mammal
    cat is a mammal
    mouse is a mammal
\"""
for animal in ["dog", "cat", "mouse"]:
    # You can use format() to interpolate formatted strings
    print("{} is a mammal".format(animal))

\"""
"range(number)" returns an iterable of numbers
from zero up to (but excluding) the given number
prints:
    0
    1
    2
    3
\"""
for i in range(4):
    print(i)

\"""
"range(lower, upper)" returns an iterable of numbers
from the lower number to the upper number
prints:
    4
    5
    6
    7
\"""
for i in range(4, 8):
    print(i)

\"""
"range(lower, upper, step)" returns an iterable of numbers
from the lower number to the upper number, while incrementing
by step. If step is not indicated, the default value is 1.
prints:
    4
    6
\"""
for i in range(4, 8, 2):
    print(i)

\"""
Loop over a list to retrieve both the index and the value of each list item:
    0 dog
    1 cat
    2 mouse
\"""
animals = ["dog", "cat", "mouse"]
for i, value in enumerate(animals):
    print(i, value)

\"""
While loops go until a condition is no longer met.
prints:
    0
    1
    2
    3
\"""
x = 0
while x < 4:
    print(x)
    x += 1  # Shorthand for x = x + 1

# Handle exceptions with a try/except block
try:
    # Use "raise" to raise an error
    raise IndexError("This is an index error")
except IndexError as e:
    pass                 # Refrain from this, provide a recovery (next example).
except (TypeError, NameError):
    pass                 # Multiple exceptions can be processed jointly.
else:                    # Optional clause to the try/except block. Must follow
                         # all except blocks.
    print("All good!")   # Runs only if the code in try raises no exceptions
finally:                 # Execute under all circumstances
    print("We can clean up resources here")

# Instead of try/finally to cleanup resources you can use a with statement
with open("myfile.txt") as f:
    for line in f:
        print(line)

# Writing to a file
contents = {"aa": 12, "bb": 21}
with open("myfile1.txt", "w") as file:
    file.write(str(contents))        # writes a string to a file

import json
with open("myfile2.txt", "w") as file:
    file.write(json.dumps(contents))  # writes an object to a file

# Reading from a file
with open("myfile1.txt") as file:
    contents = file.read()           # reads a string from a file
print(contents)
# print: {"aa": 12, "bb": 21}

with open("myfile2.txt", "r") as file:
    contents = json.load(file)       # reads a json object from a file
print(contents)
# print: {"aa": 12, "bb": 21}


# Python offers a fundamental abstraction called the Iterable.
# An iterable is an object that can be treated as a sequence.
# The object returned by the range function, is an iterable.

filled_dict = {"one": 1, "two": 2, "three": 3}
our_iterable = filled_dict.keys()
print(our_iterable)  # => dict_keys(['one', 'two', 'three']). This is an object
                     # that implements our Iterable interface.

# We can loop over it.
for i in our_iterable:
    print(i)  # Prints one, two, three

# However we cannot address elements by index.
our_iterable[1]  # Raises a TypeError

# An iterable is an object that knows how to create an iterator.
our_iterator = iter(our_iterable)

# Our iterator is an object that can remember the state as we traverse through
# it. We get the next object with "next()".
next(our_iterator)  # => "one"

# It maintains state as we iterate.
next(our_iterator)  # => "two"
next(our_iterator)  # => "three"

# After the iterator has returned all of its data, it raises a
# StopIteration exception
next(our_iterator)  # Raises StopIteration

# We can also loop over it, in fact, "for" does this implicitly!
our_iterator = iter(our_iterable)
for i in our_iterator:
    print(i)  # Prints one, two, three

# You can grab all the elements of an iterable or iterator by call of list().
list(our_iterable)  # => Returns ["one", "two", "three"]
list(our_iterator)  # => Returns [] because state is saved


####################################################
## 4. Functions
####################################################

# Use "def" to create new functions
def add(x, y):
    print("x is {} and y is {}".format(x, y))
    return x + y  # Return values with a return statement

# Calling functions with parameters
add(5, 6)  # => prints out "x is 5 and y is 6" and returns 11

# Another way to call functions is with keyword arguments
add(y=6, x=5)  # Keyword arguments can arrive in any order.

# You can define functions that take a variable number of
# positional arguments
def varargs(*args):
    return args

varargs(1, 2, 3)  # => (1, 2, 3)

# You can define functions that take a variable number of
# keyword arguments, as well
def keyword_args(**kwargs):
    return kwargs

# Let's call it to see what happens
keyword_args(big="foot", loch="ness")  # => {"big": "foot", "loch": "ness"}


# You can do both at once, if you like
def all_the_args(*args, **kwargs):
    print(args)
    print(kwargs)
\"""
all_the_args(1, 2, a=3, b=4) prints:
    (1, 2)
    {"a": 3, "b": 4}
\"""

# When calling functions, you can do the opposite of args/kwargs!
# Use * to expand args (tuples) and use ** to expand kwargs (dictionaries).
args = (1, 2, 3, 4)
kwargs = {"a": 3, "b": 4}
all_the_args(*args)            # equivalent: all_the_args(1, 2, 3, 4)
all_the_args(**kwargs)         # equivalent: all_the_args(a=3, b=4)
all_the_args(*args, **kwargs)  # equivalent: all_the_args(1, 2, 3, 4, a=3, b=4)

# Returning multiple values (with tuple assignments)
def swap(x, y):
    return y, x  # Return multiple values as a tuple without the parenthesis.
                 # (Note: parenthesis have been excluded but can be included)

x = 1
y = 2
x, y = swap(x, y)     # => x = 2, y = 1
# (x, y) = swap(x,y)  # Again the use of parenthesis is optional.

# global scope
x = 5

def set_x(num):
    # local scope begins here
    # local var x not the same as global var x
    x = num    # => 43
    print(x)   # => 43

def set_global_x(num):
    # global indicates that particular var lives in the global scope
    global x
    print(x)   # => 5
    x = num    # global var x is now set to 6
    print(x)   # => 6

set_x(43)
set_global_x(6)
\"""
prints:
    43
    5
    6
\"""


# Python has first class functions
def create_adder(x):
    def adder(y):
        return x + y
    return adder

add_10 = create_adder(10)
add_10(3)   # => 13

# Closures in nested functions:
# We can use the nonlocal keyword to work with variables in nested scope which shouldn't be declared in the inner functions.
def create_avg():
    total = 0
    count = 0
    def avg(n):
        nonlocal total, count
        total += n
        count += 1
        return total/count
    return avg
avg = create_avg()
avg(3)  # => 3.0
avg(5)  # (3+5)/2 => 4.0
avg(7)  # (8+7)/3 => 5.0

# There are also anonymous functions
(lambda x: x > 2)(3)                  # => True
(lambda x, y: x ** 2 + y ** 2)(2, 1)  # => 5

# There are built-in higher order functions
list(map(add_10, [1, 2, 3]))          # => [11, 12, 13]
list(map(max, [1, 2, 3], [4, 2, 1]))  # => [4, 2, 3]

list(filter(lambda x: x > 5, [3, 4, 5, 6, 7]))  # => [6, 7]

# We can use list comprehensions for nice maps and filters
# List comprehension stores the output as a list (which itself may be nested).
[add_10(i) for i in [1, 2, 3]]         # => [11, 12, 13]
[x for x in [3, 4, 5, 6, 7] if x > 5]  # => [6, 7]

# You can construct set and dict comprehensions as well.
{x for x in "abcddeef" if x not in "abc"}  # => {'d', 'e', 'f'}
{x: x**2 for x in range(5)}  # => {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}


####################################################
## 5. Modules
####################################################

# You can import modules
import math
print(math.sqrt(16))  # => 4.0

# You can get specific functions from a module
from math import ceil, floor
print(ceil(3.7))   # => 4
print(floor(3.7))  # => 3

# You can import all functions from a module.
# Warning: this is not recommended
from math import *

# You can shorten module names
import math as m
math.sqrt(16) == m.sqrt(16)  # => True

# Python modules are just ordinary Python files. You
# can write your own, and import them. The name of the
# module is the same as the name of the file.

# You can find out which functions and attributes
# are defined in a module.
import math
dir(math)

# If you have a Python script named math.py in the same
# folder as your current script, the file math.py will
# be loaded instead of the built-in Python module.
# This happens because the local folder has priority
# over Python's built-in libraries.


####################################################
## 6. Classes
####################################################

# We use the "class" statement to create a class
class Human:

    # A class attribute. It is shared by all instances of this class
    species = "H. sapiens"

    # Basic initializer, this is called when this class is instantiated.
    # Note that the double leading and trailing underscores denote objects
    # or attributes that are used by Python but that live in user-controlled
    # namespaces. Methods(or objects or attributes) like: __init__, __str__,
    # __repr__ etc. are called special methods (or sometimes called dunder
    # methods). You should not invent such names on your own.
    def __init__(self, name):
        # Assign the argument to the instance's name attribute
        self.name = name

        # Initialize property
        self._age = 0   # the leading underscore indicates the "age" property is
                        # intended to be used internally
                        # do not rely on this to be enforced: it's a hint to other devs

    # An instance method. All methods take "self" as the first argument
    def say(self, msg):
        print("{name}: {message}".format(name=self.name, message=msg))

    # Another instance method
    def sing(self):
        return "yo... yo... microphone check... one two... one two..."

    # A class method is shared among all instances
    # They are called with the calling class as the first argument
    @classmethod
    def get_species(cls):
        return cls.species

    # A static method is called without a class or instance reference
    @staticmethod
    def grunt():
        return "*grunt*"

    # A property is just like a getter.
    # It turns the method age() into a read-only attribute of the same name.
    # There's no need to write trivial getters and setters in Python, though.
    @property
    def age(self):
        return self._age

    # This allows the property to be set
    @age.setter
    def age(self, age):
        self._age = age

    # This allows the property to be deleted
    @age.deleter
    def age(self):
        del self._age


# When a Python interpreter reads a source file it executes all its code.
# This __name__ check makes sure this code block is only executed when this
# module is the main program.
if __name__ == "__main__":
    # Instantiate a class
    i = Human(name="Ian")
    i.say("hi")                     # "Ian: hi"
    j = Human("Joel")
    j.say("hello")                  # "Joel: hello"
    # i and j are instances of type Human; i.e., they are Human objects.

    # Call our class method
    i.say(i.get_species())          # "Ian: H. sapiens"
    # Change the shared attribute
    Human.species = "H. neanderthalensis"
    i.say(i.get_species())          # => "Ian: H. neanderthalensis"
    j.say(j.get_species())          # => "Joel: H. neanderthalensis"

    # Call the static method
    print(Human.grunt())            # => "*grunt*"

    # Static methods can be called by instances too
    print(i.grunt())                # => "*grunt*"

    # Update the property for this instance
    i.age = 42
    # Get the property
    i.say(i.age)                    # => "Ian: 42"
    j.say(j.age)                    # => "Joel: 0"
    # Delete the property
    del i.age
    # i.age                         # => this would raise an AttributeError


####################################################
## 6.1 Inheritance
####################################################

# Inheritance allows new child classes to be defined that inherit methods and
# variables from their parent class.

# Using the Human class defined above as the base or parent class, we can
# define a child class, Superhero, which inherits variables like "species",
# "name", and "age", as well as methods, like "sing" and "grunt"
# from the Human class, but can also have its own unique properties.

# To take advantage of modularization by file you could place the classes above
# in their own files, say, human.py

# To import functions from other files use the following format
# from "filename-without-extension" import "function-or-class"

from human import Human


# Specify the parent class(es) as parameters to the class definition
class Superhero(Human):

    # If the child class should inherit all of the parent's definitions without
    # any modifications, you can just use the "pass" keyword (and nothing else)
    # but in this case it is commented out to allow for a unique child class:
    # pass

    # Child classes can override their parents' attributes
    species = "Superhuman"

    # Children automatically inherit their parent class's constructor including
    # its arguments, but can also define additional arguments or definitions
    # and override its methods such as the class constructor.
    # This constructor inherits the "name" argument from the "Human" class and
    # adds the "superpower" and "movie" arguments:
    def __init__(self, name, movie=False,
                 superpowers=["super strength", "bulletproofing"]):

        # add additional class attributes:
        self.fictional = True
        self.movie = movie
        # be aware of mutable default values, since defaults are shared
        self.superpowers = superpowers

        # The "super" function lets you access the parent class's methods
        # that are overridden by the child, in this case, the __init__ method.
        # This calls the parent class constructor:
        super().__init__(name)

    # override the sing method
    def sing(self):
        return "Dun, dun, DUN!"

    # add an additional instance method
    def boast(self):
        for power in self.superpowers:
            print("I wield the power of {pow}!".format(pow=power))


if __name__ == "__main__":
    sup = Superhero(name="Tick")

    # Instance type checks
    if isinstance(sup, Human):
        print("I am human")
    if type(sup) is Superhero:
        print("I am a superhero")

    # Get the "Method Resolution Order" used by both getattr() and super()
    # (the order in which classes are searched for an attribute or method)
    # This attribute is dynamic and can be updated
    print(Superhero.__mro__)    # => (<class '__main__.Superhero'>,
                                # => <class 'human.Human'>, <class 'object'>)

    # Calls parent method but uses its own class attribute
    print(sup.get_species())    # => Superhuman

    # Calls overridden method
    print(sup.sing())           # => Dun, dun, DUN!

    # Calls method from Human
    sup.say("Spoon")            # => Tick: Spoon

    # Call method that exists only in Superhero
    sup.boast()                 # => I wield the power of super strength!
                                # => I wield the power of bulletproofing!

    # Inherited class attribute
    sup.age = 31
    print(sup.age)              # => 31

    # Attribute that only exists within Superhero
    print("Am I Oscar eligible? " + str(sup.movie))

####################################################
## 6.2 Multiple Inheritance
####################################################


# Another class definition
# bat.py
class Bat:

    species = "Baty"

    def __init__(self, can_fly=True):
        self.fly = can_fly

    # This class also has a say method
    def say(self, msg):
        msg = "... ... ..."
        return msg

    # And its own method as well
    def sonar(self):
        return "))) ... ((("


if __name__ == "__main__":
    b = Bat()
    print(b.say("hello"))
    print(b.fly)


# And yet another class definition that inherits from Superhero and Bat
# superhero.py
from superhero import Superhero
from bat import Bat

# Define Batman as a child that inherits from both Superhero and Bat
class Batman(Superhero, Bat):

    def __init__(self, *args, **kwargs):
        # Typically to inherit attributes you have to call super:
        # super(Batman, self).__init__(*args, **kwargs)
        # However we are dealing with multiple inheritance here, and super()
        # only works with the next base class in the MRO list.
        # So instead we explicitly call __init__ for all ancestors.
        # The use of *args and **kwargs allows for a clean way to pass
        # arguments, with each parent "peeling a layer of the onion".
        Superhero.__init__(self, "anonymous", movie=True,
                           superpowers=["Wealthy"], *args, **kwargs)
        Bat.__init__(self, *args, can_fly=False, **kwargs)
        # override the value for the name attribute
        self.name = "Sad Affleck"

    def sing(self):
        return "nan nan nan nan nan batman!"


if __name__ == "__main__":
    sup = Batman()

    # The Method Resolution Order
    print(Batman.__mro__)     # => (<class '__main__.Batman'>,
                              # => <class 'superhero.Superhero'>,
                              # => <class 'human.Human'>,
                              # => <class 'bat.Bat'>, <class 'object'>)

    # Calls parent method but uses its own class attribute
    print(sup.get_species())  # => Superhuman

    # Calls overridden method
    print(sup.sing())         # => nan nan nan nan nan batman!

    # Calls method from Human, because inheritance order matters
    sup.say("I agree")        # => Sad Affleck: I agree

    # Call method that exists only in 2nd ancestor
    print(sup.sonar())        # => ))) ... (((

    # Inherited class attribute
    sup.age = 100
    print(sup.age)            # => 100

    # Inherited attribute from 2nd ancestor whose default value was overridden.
    print("Can I fly? " + str(sup.fly))  # => Can I fly? False


####################################################
## 7. Advanced
####################################################

# Generators help you make lazy code.
def double_numbers(iterable):
    for i in iterable:
        yield i + i

# Generators are memory-efficient because they only load the data needed to
# process the next value in the iterable. This allows them to perform
# operations on otherwise prohibitively large value ranges.
# NOTE: `range` replaces `xrange` in Python 3.
for i in double_numbers(range(1, 900000000)):  # `range` is a generator.
    print(i)
    if i >= 30:
        break

# Just as you can create a list comprehension, you can create generator
# comprehensions as well.
values = (-x for x in [1,2,3,4,5])
for x in values:
    print(x)  # prints -1 -2 -3 -4 -5 to console/terminal

# You can also cast a generator comprehension directly to a list.
values = (-x for x in [1,2,3,4,5])
gen_to_list = list(values)
print(gen_to_list)  # => [-1, -2, -3, -4, -5]


# Decorators are a form of syntactic sugar.
# They make code easier to read while accomplishing clunky syntax.

# Wrappers are one type of decorator.
# They're really useful for adding logging to existing functions without needing to modify them.

def log_function(func):
    def wrapper(*args, **kwargs):
        print("Entering function", func.__name__)
        result = func(*args, **kwargs)
        print("Exiting function", func.__name__)
        return result
    return wrapper

@log_function               # equivalent:
def my_function(x,y):       # def my_function(x,y):
    return x+y              #   return x+y
                            # my_function = log_function(my_function)
# The decorator @log_function tells us as we begin reading the function definition
# for my_function that this function will be wrapped with log_function.
# When function definitions are long, it can be hard to parse the non-decorated
# assignment at the end of the definition.

my_function(1,2)  # => "Entering function my_function"
                  # => "3"
                  # => "Exiting function my_function"

# But there's a problem.
# What happens if we try to get some information about my_function?

print(my_function.__name__)  # => 'wrapper'
print(my_function.__code__.co_argcount)  # => 0. The argcount is 0 because both arguments in wrapper()'s signature are optional.

# Because our decorator is equivalent to my_function = log_function(my_function)
# we've replaced information about my_function with information from wrapper

# Fix this using functools

from functools import wraps

def log_function(func):
    @wraps(func)  # this ensures docstring, function name, arguments list, etc. are all copied
                  # to the wrapped function - instead of being replaced with wrapper's info
    def wrapper(*args, **kwargs):
        print("Entering function", func.__name__)
        result = func(*args, **kwargs)
        print("Exiting function", func.__name__)
        return result
    return wrapper

@log_function
def my_function(x,y):
    return x+y

my_function(1,2)  # => "Entering function my_function"
                  # => "3"
                  # => "Exiting function my_function"

print(my_function.__name__)  # => 'my_function'
print(my_function.__code__.co_argcount)  # => 2
    """, 100),

    ("""
// This is a comment. Line comments look like this...
// and extend multiple lines like this.

/* Block comments
  /* can be nested. */ */

/// Documentation comments look like this and support markdown notation.
/// # Examples
///
/// ```
/// let five = 5
/// ```

///////////////
// 1. Basics //
///////////////

#[allow(dead_code)]
// Functions
// `i32` is the type for 32-bit signed integers
fn add2(x: i32, y: i32) -> i32 {
    // Implicit return (no semicolon)
    x + y
}

#[allow(unused_variables)]
#[allow(unused_assignments)]
#[allow(dead_code)]
// Main function
fn main() {
    // Numbers //

    // Immutable bindings
    let x: i32 = 1;

    // Integer/float suffixes
    let y: i32 = 13i32;
    let f: f64 = 1.3f64;

    // Type inference
    // Most of the time, the Rust compiler can infer what type a variable is, so
    // you don’t have to write an explicit type annotation.
    // Throughout this tutorial, types are explicitly annotated in many places,
    // but only for demonstrative purposes. Type inference can handle this for
    // you most of the time.
    let implicit_x = 1;
    let implicit_f = 1.3;

    // Arithmetic
    let sum = x + y + 13;

    // Mutable variable
    let mut mutable = 1;
    mutable = 4;
    mutable += 2;

    // Strings //

    // String literals
    let x: &str = "hello world!";

    // Printing
    println!("{} {}", f, x); // 1.3 hello world

    // A `String` – a heap-allocated string
    // Stored as a `Vec<u8>` and always hold a valid UTF-8 sequence, 
    // which is not null terminated.
    let s: String = "hello world".to_string();

    // A string slice – an immutable view into another string
    // This is basically an immutable pair of pointers to a string – it doesn’t
    // actually contain the contents of a string, just a pointer to
    // the begin and a pointer to the end of a string buffer,
    // statically allocated or contained in another object (in this case, `s`).
    // The string slice is like a view `&[u8]` into `Vec<T>`.
    let s_slice: &str = &s;

    println!("{} {}", s, s_slice); // hello world hello world

    // Vectors/arrays //

    // A fixed-size array
    let four_ints: [i32; 4] = [1, 2, 3, 4];

    // A dynamic array (vector)
    let mut vector: Vec<i32> = vec![1, 2, 3, 4];
    vector.push(5);

    // A slice – an immutable view into a vector or array
    // This is much like a string slice, but for vectors
    let slice: &[i32] = &vector;

    // Use `{:?}` to print something debug-style
    println!("{:?} {:?}", vector, slice); // [1, 2, 3, 4, 5] [1, 2, 3, 4, 5]

    // Tuples //

    // A tuple is a fixed-size set of values of possibly different types
    let x: (i32, &str, f64) = (1, "hello", 3.4);

    // Destructuring `let`
    let (a, b, c) = x;
    println!("{} {} {}", a, b, c); // 1 hello 3.4

    // Indexing
    println!("{}", x.1); // hello

    //////////////
    // 2. Types //
    //////////////

    // Struct
    struct Point {
        x: i32,
        y: i32,
    }

    let origin: Point = Point { x: 0, y: 0 };

    // A struct with unnamed fields, called a ‘tuple struct’
    struct Point2(i32, i32);

    let origin2 = Point2(0, 0);

    // Basic C-like enum
    enum Direction {
        Left,
        Right,
        Up,
        Down,
    }

    let up = Direction::Up;

    // Enum with fields
    enum OptionalI32 {
        AnI32(i32),
        Nothing,
    }

    let two: OptionalI32 = OptionalI32::AnI32(2);
    let nothing = OptionalI32::Nothing;

    // Generics //

    struct Foo<T> { bar: T }

    // This is defined in the standard library as `Option`
    enum Optional<T> {
        SomeVal(T),
        NoVal,
    }

    // Methods //

    impl<T> Foo<T> {
        // Methods take an explicit `self` parameter
        fn bar(&self) -> &T { // self is borrowed
            &self.bar
        }
        fn bar_mut(&mut self) -> &mut T { // self is mutably borrowed
            &mut self.bar
        }
        fn into_bar(self) -> T { // here self is consumed
            self.bar
        }
    }

    let a_foo = Foo { bar: 1 };
    println!("{}", a_foo.bar()); // 1

    // Traits (known as interfaces or typeclasses in other languages) //

    trait Frobnicate<T> {
        fn frobnicate(self) -> Option<T>;
    }

    impl<T> Frobnicate<T> for Foo<T> {
        fn frobnicate(self) -> Option<T> {
            Some(self.bar)
        }
    }

    let another_foo = Foo { bar: 1 };
    println!("{:?}", another_foo.frobnicate()); // Some(1)

    // Function pointer types // 

    fn fibonacci(n: u32) -> u32 {
        match n {
            0 => 1,
            1 => 1,
            _ => fibonacci(n - 1) + fibonacci(n - 2),
        }
    }

    type FunctionPointer = fn(u32) -> u32;

    let fib : FunctionPointer = fibonacci;
    println!("Fib: {}", fib(4)); // 5

    /////////////////////////
    // 3. Pattern matching //
    /////////////////////////

    let foo = OptionalI32::AnI32(1);
    match foo {
        OptionalI32::AnI32(n) => println!("it’s an i32: {}", n),
        OptionalI32::Nothing  => println!("it’s nothing!"),
    }

    // Advanced pattern matching
    struct FooBar { x: i32, y: OptionalI32 }
    let bar = FooBar { x: 15, y: OptionalI32::AnI32(32) };

    match bar {
        FooBar { x: 0, y: OptionalI32::AnI32(0) } =>
            println!("The numbers are zero!"),
        FooBar { x: n, y: OptionalI32::AnI32(m) } if n == m =>
            println!("The numbers are the same"),
        FooBar { x: n, y: OptionalI32::AnI32(m) } =>
            println!("Different numbers: {} {}", n, m),
        FooBar { x: _, y: OptionalI32::Nothing } =>
            println!("The second number is Nothing!"),
    }

    /////////////////////
    // 4. Control flow //
    /////////////////////

    // `for` loops/iteration
    let array = [1, 2, 3];
    for i in array {
        println!("{}", i);
    }

    // Ranges
    for i in 0u32..10 {
        print!("{} ", i);
    }
    println!("");
    // prints `0 1 2 3 4 5 6 7 8 9 `

    // `if`
    if 1 == 1 {
        println!("Maths is working!");
    } else {
        println!("Oh no...");
    }

    // `if` as expression
    let value = if true {
        "good"
    } else {
        "bad"
    };

    // `while` loop
    while 1 == 1 {
        println!("The universe is operating normally.");
        // break statement gets out of the while loop.
        //  It avoids useless iterations.
        break
    }

    // Infinite loop
    loop {
        println!("Hello!");
        // break statement gets out of the loop
        break
    }

    /////////////////////////////////
    // 5. Memory safety & pointers //
    /////////////////////////////////

    // Owned pointer – only one thing can ‘own’ this pointer at a time
    // This means that when the `Box` leaves its scope, it can be automatically deallocated safely.
    let mut mine: Box<i32> = Box::new(3);
    *mine = 5; // dereference
    // Here, `now_its_mine` takes ownership of `mine`. In other words, `mine` is moved.
    let mut now_its_mine = mine;
    *now_its_mine += 2;

    println!("{}", now_its_mine); // 7
    // println!("{}", mine); // this would not compile because `now_its_mine` now owns the pointer

    // Reference – an immutable pointer that refers to other data
    // When a reference is taken to a value, we say that the value has been ‘borrowed’.
    // While a value is borrowed immutably, it cannot be mutated or moved.
    // A borrow is active until the last use of the borrowing variable.
    let mut var = 4;
    var = 3;
    let ref_var: &i32 = &var;

    println!("{}", var); // Unlike `mine`, `var` can still be used
    println!("{}", *ref_var);
    // var = 5; // this would not compile because `var` is borrowed
    // *ref_var = 6; // this would not either, because `ref_var` is an immutable reference
    ref_var; // no-op, but counts as a use and keeps the borrow active
    var = 2; // ref_var is no longer used after the line above, so the borrow has ended

    // Mutable reference
    // While a value is mutably borrowed, it cannot be accessed at all.
    let mut var2 = 4;
    let ref_var2: &mut i32 = &mut var2;
    *ref_var2 += 2;         // '*' is used to point to the mutably borrowed var2

    println!("{}", *ref_var2); // 6 , // var2 would not compile.
    // ref_var2 is of type &mut i32, so stores a reference to an i32, not the value.
    // var2 = 2; // this would not compile because `var2` is borrowed.
    ref_var2; // no-op, but counts as a use and keeps the borrow active until here
}
    """, 100),
    (r"""
// Single-line comments start with // - only available in C99 and later.

/*
Multi-line comments look like this. They work in C89 as well.
*/

/*
Multi-line comments don't nest /* Be careful */  // comment ends on this line...
*/ // ...not this one!

// Constants: #define <keyword>
// Constants are written in all-caps out of convention, not requirement
#define DAYS_IN_YEAR 365

// Enumeration constants are also ways to declare constants.
// All statements must end with a semicolon
enum days {SUN, MON, TUE, WED, THU, FRI, SAT};
// SUN gets 0, MON gets 1, TUE gets 2, etc.

// Enumeration values can also be specified
enum days {SUN = 1, MON, TUE, WED = 99, THU, FRI, SAT};
// MON gets 2 automatically, TUE gets 3, etc.
// WED get 99, THU gets 100, FRI gets 101, etc.

// Import headers with #include
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

// File names between <angle brackets> tell the compiler to look in your system
// libraries for the headers.
// For your own headers, use double quotes instead of angle brackets, and
// provide the path:
#include "my_header.h"      // local file
#include "../my_lib/my_lib_header.h" //relative path

// Declare function signatures in advance in a .h file, or at the top of
// your .c file.
void function_1();
int function_2(void);

// At a minimum, you must declare a 'function prototype' before its use in any function.
// Normally, prototypes are placed at the top of a file before any function definition.
int add_two_ints(int x1, int x2); // function prototype
// although `int add_two_ints(int, int);` is also valid (no need to name the args),
// it is recommended to name arguments in the prototype as well for easier inspection

// Function prototypes are not necessary if the function definition comes before
// any other function that calls that function. However, it's standard practice to
// always add the function prototype to a header file (*.h) and then #include that
// file at the top. This prevents any issues where a function might be called
// before the compiler knows of its existence, while also giving the developer a
// clean header file to share with the rest of the project.

// Your program's entry point is a function called "main". The return type can
// be anything, however most operating systems expect a return type of `int` for
// error code processing.
int main(void) {
  // your program
}

// The command line arguments used to run your program are also passed to main
// argc being the number of arguments - your program's name counts as 1
// argv is an array of character arrays - containing the arguments themselves
// argv[0] = name of your program, argv[1] = first argument, etc.
int main (int argc, char** argv)
{
  // print output using printf, for "print formatted"
  // %d is an integer, \n is a newline
  printf("%d\n", 0); // => Prints 0

  // take input using scanf
  // '&' is used to define the location
  // where we want to store the input value
  int input;
  scanf("%d", &input);

  ///////////////////////////////////////
  // Types
  ///////////////////////////////////////

  // Compilers that are not C99-compliant require that variables MUST be
  // declared at the top of the current block scope.
  // Compilers that ARE C99-compliant allow declarations near the point where
  // the value is used.
  // For the sake of the tutorial, variables are declared dynamically under
  // C99-compliant standards.

  // ints are usually 4 bytes (use the `sizeof` operator to check)
  int x_int = 0;

  // shorts are usually 2 bytes (use the `sizeof` operator to check)
  short x_short = 0;

  // chars are defined as the smallest addressable unit for a processor.
  // This is usually 1 byte, but for some systems it can be more (ex. for TMS320 from TI it's 2 bytes).
  char x_char = 0;
  char y_char = 'y'; // Char literals are quoted with ''

  // longs are often 4 to 8 bytes; long longs are guaranteed to be at least
  // 8 bytes
  long x_long = 0;
  long long x_long_long = 0;

  // floats are usually 32-bit floating point numbers
  float x_float = 0.0f; // 'f' suffix here denotes floating point literal

  // doubles are usually 64-bit floating-point numbers
  double x_double = 0.0; // real numbers without any suffix are doubles

  // integer types may be unsigned (greater than or equal to zero)
  unsigned short ux_short;
  unsigned int ux_int;
  unsigned long long ux_long_long;

  // chars inside single quotes are integers in machine's character set.
  '0'; // => 48 in the ASCII character set.
  'A'; // => 65 in the ASCII character set.

  // sizeof(T) gives you the size of a variable with type T in bytes
  // sizeof(obj) yields the size of the expression (variable, literal, etc.).
  printf("%zu\n", sizeof(int)); // => 4 (on most machines with 4-byte words)

  // If the argument of the `sizeof` operator is an expression, then its argument
  // is not evaluated (except VLAs (see below)).
  // The value it yields in this case is a compile-time constant.
  int a = 1;
  // size_t is an unsigned integer type of at least 2 bytes used to represent
  // the size of an object.
  size_t size = sizeof(a++); // a++ is not evaluated
  printf("sizeof(a++) = %zu where a = %d\n", size, a);
  // prints "sizeof(a++) = 4 where a = 1" (on a 32-bit architecture)

  // Arrays must be initialized with a concrete size.
  char my_char_array[20]; // This array occupies 1 * 20 = 20 bytes
  int my_int_array[20]; // This array occupies 4 * 20 = 80 bytes
  // (assuming 4-byte words)

  // You can initialize an array of twenty ints that all equal 0 thusly:
  int my_array[20] = {0};
  // where the "{0}" part is called an "array initializer".
  // All elements (if any) past the ones in the initializer are initialized to 0:
  int my_array[5] = {1, 2};
  // So my_array now has five elements, all but the first two of which are 0:
  // [1, 2, 0, 0, 0]
  // NOTE that you get away without explicitly declaring the size
  // of the array IF you initialize the array on the same line:
  int my_array[] = {0};
  // NOTE that, when not declaring the size, the size of the array is the number
  // of elements in the initializer. With "{0}", my_array is now of size one: [0]
  // To evaluate the size of the array at run-time, divide its byte size by the
  // byte size of its element type:
  size_t my_array_size = sizeof(my_array) / sizeof(my_array[0]);
  // WARNING You should evaluate the size *before* you begin passing the array
  // to functions (see later discussion) because arrays get "downgraded" to
  // raw pointers when they are passed to functions (so the statement above
  // will produce the wrong result inside the function).

  // Indexing an array is like other languages -- or,
  // rather, other languages are like C
  my_array[0]; // => 0

  // Arrays are mutable; it's just memory!
  my_array[1] = 2;
  printf("%d\n", my_array[1]); // => 2

  // In C99 (and as an optional feature in C11), variable-length arrays (VLAs)
  // can be declared as well. The size of such an array need not be a compile
  // time constant:
  printf("Enter the array size: "); // ask the user for an array size
  int array_size;
  fscanf(stdin, "%d", &array_size);
  int var_length_array[array_size]; // declare the VLA
  printf("sizeof array = %zu\n", sizeof var_length_array);

  // Example:
  // > Enter the array size: 10
  // > sizeof array = 40

  // Strings are just arrays of chars terminated by a NULL (0x00) byte,
  // represented in strings as the special character '\0'.
  // (We don't have to include the NULL byte in string literals; the compiler
  //  inserts it at the end of the array for us.)
  char a_string[20] = "This is a string";
  printf("%s\n", a_string); // %s formats a string

  printf("%d\n", a_string[16]); // => 0
  // i.e., byte #17 is 0 (as are 18, 19, and 20)

  // If we have characters between single quotes, that's a character literal.
  // It's of type `int`, and *not* `char` (for historical reasons).
  int cha = 'a'; // fine
  char chb = 'a'; // fine too (implicit conversion from int to char)

  // Multi-dimensional arrays:
  int multi_array[2][5] = {
    {1, 2, 3, 4, 5},
    {6, 7, 8, 9, 0}
  };
  // access elements:
  int array_int = multi_array[0][2]; // => 3

  ///////////////////////////////////////
  // Operators
  ///////////////////////////////////////

  // Shorthands for multiple declarations:
  int i1 = 1, i2 = 2;
  float f1 = 1.0, f2 = 2.0;

  int b, c;
  b = c = 0;

  // Arithmetic is straightforward
  i1 + i2; // => 3
  i2 - i1; // => 1
  i2 * i1; // => 2
  i1 / i2; // => 0 (0.5, but truncated towards 0)

  // You need to cast at least one integer to float to get a floating-point result
  (float)i1 / i2; // => 0.5f
  i1 / (double)i2; // => 0.5 // Same with double
  f1 / f2; // => 0.5, plus or minus epsilon

  // Floating-point numbers are defined by IEEE 754, thus cannot store perfectly
  // exact values. For instance, the following does not produce expected results
  // because 0.1 might actually be 0.099999999999 inside the computer, and 0.3
  // might be stored as 0.300000000001.
  (0.1 + 0.1 + 0.1) != 0.3; // => 1 (true)
  // and it is NOT associative due to reasons mentioned above.
  1 + (1e123 - 1e123) != (1 + 1e123) - 1e123; // => 1 (true)
  // this notation is scientific notations for numbers: 1e123 = 1*10^123

  // It is important to note that most all systems have used IEEE 754 to
  // represent floating points. Even python, used for scientific computing,
  // eventually calls C which uses IEEE 754. It is mentioned this way not to
  // indicate that this is a poor implementation, but instead as a warning
  // that when doing floating point comparisons, a little bit of error (epsilon)
  // needs to be considered.

  // Modulo is there as well, but be careful if arguments are negative
  11 % 3;    // => 2 as 11 = 2 + 3*x (x=3)
  (-11) % 3; // => -2, as one would expect
  11 % (-3); // => 2 and not -2, and it's quite counter intuitive

  // Comparison operators are probably familiar, but
  // there is no Boolean type in C. We use ints instead.
  // (C99 introduced the _Bool type provided in stdbool.h)
  // 0 is false, anything else is true. (The comparison
  // operators always yield 0 or 1.)
  3 == 2; // => 0 (false)
  3 != 2; // => 1 (true)
  3 > 2;  // => 1
  3 < 2;  // => 0
  2 <= 2; // => 1
  2 >= 2; // => 1

  // C is not Python - comparisons do NOT chain.
  // Warning: The line below will compile, but it means `(0 < a) < 2`.
  // This expression is always true, because (0 < a) could be either 1 or 0.
  // In this case it's 1, because (0 < 1).
  int between_0_and_2 = 0 < a < 2;
  // Instead use:
  int between_0_and_2 = 0 < a && a < 2;

  // Logic works on ints
  !3; // => 0 (Logical not)
  !0; // => 1
  1 && 1; // => 1 (Logical and)
  0 && 1; // => 0
  0 || 1; // => 1 (Logical or)
  0 || 0; // => 0

  // Conditional ternary expression ( ? : )
  int e = 5;
  int f = 10;
  int z;
  z = (e > f) ? e : f; // => 10 "if e > f return e, else return f."

  // Increment and decrement operators:
  int j = 0;
  int s = j++; // Return j THEN increase j. (s = 0, j = 1)
  s = ++j; // Increase j THEN return j. (s = 2, j = 2)
  // same with j-- and --j

  // Bitwise operators!
  ~0x0F; // => 0xFFFFFFF0 (bitwise negation, "1's complement", example result for 32-bit int)
  0x0F & 0xF0; // => 0x00 (bitwise AND)
  0x0F | 0xF0; // => 0xFF (bitwise OR)
  0x04 ^ 0x0F; // => 0x0B (bitwise XOR)
  0x01 << 1; // => 0x02 (bitwise left shift (by 1))
  0x02 >> 1; // => 0x01 (bitwise right shift (by 1))

  // Be careful when shifting signed integers - the following are undefined:
  // - shifting into the sign bit of a signed integer (int a = 1 << 31)
  // - left-shifting a negative number (int a = -1 << 2)
  // - shifting by an offset which is >= the width of the type of the LHS:
  //   int a = 1 << 32; // UB if int is 32 bits wide

  ///////////////////////////////////////
  // Control Structures
  ///////////////////////////////////////

  if (0) {
    printf("I am never run\n");
  } else if (0) {
    printf("I am also never run\n");
  } else {
    printf("I print\n");
  }

  // While loops exist
  int ii = 0;
  while (ii < 10) { //ANY value less than ten is true.
    printf("%d, ", ii++); // ii++ increments ii AFTER using its current value.
  } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, "

  printf("\n");

  int kk = 0;
  do {
    printf("%d, ", kk);
  } while (++kk < 10); // ++kk increments kk BEFORE using its current value.
  // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, "

  printf("\n");

  // For loops too
  int jj;
  for (jj=0; jj < 10; jj++) {
    printf("%d, ", jj);
  } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, "

  printf("\n");

  // *****NOTES*****:
  // Loops and Functions MUST have a body. If no body is needed:
  int i;
  for (i = 0; i <= 5; i++) {
    ; // use semicolon to act as the body (null statement)
  }
  // Or
  for (i = 0; i <= 5; i++);

  // branching with multiple choices: switch()
  switch (a) {
  case 0: // labels need to be integral *constant* expressions (such as enums)
    printf("Hey, 'a' equals 0!\n");
    break; // if you don't break, control flow falls over labels
  case 1:
    printf("Huh, 'a' equals 1!\n");
    break;
    // Be careful - without a "break", execution continues until the
    // next "break" is reached.
  case 3:
  case 4:
    printf("Look at that.. 'a' is either 3, or 4\n");
    break;
  default:
    // if `some_integral_expression` didn't match any of the labels
    fputs("Error!\n", stderr);
    exit(-1);
    break;
  }
  /*
    Using "goto" in C
  */
  typedef enum { false, true } bool;
  // for C don't have bool as data type before C99 :(
  bool disaster = false;
  int i, j;
  for(i=0; i<100; ++i)
  for(j=0; j<100; ++j)
  {
    if((i + j) >= 150)
        disaster = true;
    if(disaster)
        goto error;  // exit both for loops
  }
  error: // this is a label that you can "jump" to with "goto error;"
  printf("Error occurred at i = %d & j = %d.\n", i, j);
  /*
    https://ideone.com/GuPhd6
    this will print out "Error occurred at i = 51 & j = 99."
  */
  /*
    it is generally considered bad practice to do so, except if
    you really know what you are doing. See
    https://en.wikipedia.org/wiki/Spaghetti_code#Meaning
  */

  ///////////////////////////////////////
  // Typecasting
  ///////////////////////////////////////

  // Every value in C has a type, but you can cast one value into another type
  // if you want (with some constraints).

  int x_hex = 0x01; // You can assign vars with hex literals
                    // binary is not in the standard, but allowed by some
                    // compilers (x_bin = 0b0010010110)

  // Casting between types will attempt to preserve their numeric values
  printf("%d\n", x_hex); // => Prints 1
  printf("%d\n", (short) x_hex); // => Prints 1
  printf("%d\n", (char) x_hex); // => Prints 1

  // If you assign a value greater than a types max val, it will rollover
  // without warning.
  printf("%d\n", (unsigned char) 257); // => 1 (Max char = 255 if char is 8 bits long)

  // For determining the max value of a `char`, a `signed char` and an `unsigned char`,
  // respectively, use the CHAR_MAX, SCHAR_MAX and UCHAR_MAX macros from <limits.h>

  // Integral types can be cast to floating-point types, and vice-versa.
  printf("%f\n", (double) 100); // %f always formats a double...
  printf("%f\n", (float)  100); // ...even with a float.
  printf("%d\n", (char)100.0);

  ///////////////////////////////////////
  // Pointers
  ///////////////////////////////////////

  // A pointer is a variable declared to store a memory address. Its declaration will
  // also tell you the type of data it points to. You can retrieve the memory address
  // of your variables, then mess with them.

  int x = 0;
  printf("%p\n", (void *)&x); // Use & to retrieve the address of a variable
  // (%p formats an object pointer of type void *)
  // => Prints some address in memory;

  // Pointers start with * in their declaration
  int *px, not_a_pointer; // px is a pointer to an int
  px = &x; // Stores the address of x in px
  printf("%p\n", (void *)px); // => Prints some address in memory
  printf("%zu, %zu\n", sizeof(px), sizeof(not_a_pointer));
  // => Prints "8, 4" on a typical 64-bit system

  // To retrieve the value at the address a pointer is pointing to,
  // put * in front to dereference it.
  // Note: yes, it may be confusing that '*' is used for _both_ declaring a
  // pointer and dereferencing it.
  printf("%d\n", *px); // => Prints 0, the value of x

  // You can also change the value the pointer is pointing to.
  // We'll have to wrap the dereference in parenthesis because
  // ++ has a higher precedence than *.
  (*px)++; // Increment the value px is pointing to by 1
  printf("%d\n", *px); // => Prints 1
  printf("%d\n", x); // => Prints 1

  // Arrays are a good way to allocate a contiguous block of memory
  int x_array[20]; //declares array of size 20 (cannot change size)
  int xx;
  for (xx = 0; xx < 20; xx++) {
    x_array[xx] = 20 - xx;
  } // Initialize x_array to 20, 19, 18,... 2, 1

  // Declare a pointer of type int and initialize it to point to x_array
  int* x_ptr = x_array;
  // x_ptr now points to the first element in the array (the integer 20).
  // This works because arrays often decay into pointers to their first element.
  // For example, when an array is passed to a function or is assigned to a pointer,
  // it decays into (implicitly converted to) a pointer.
  // Exceptions: when the array is the argument of the `&` (address-of) operator:
  int arr[10];
  int (*ptr_to_arr)[10] = &arr; // &arr is NOT of type `int *`!
  // It's of type "pointer to array" (of ten `int`s).
  // or when the array is a string literal used for initializing a char array:
  char otherarr[] = "foobarbazquirk";
  // or when it's the argument of the `sizeof` or `alignof` operator:
  int arraythethird[10];
  int *ptr = arraythethird; // equivalent with int *ptr = &arr[0];
  printf("%zu, %zu\n", sizeof(arraythethird), sizeof(ptr));
  // probably prints "40, 4" or "40, 8"

  // Pointers are incremented and decremented based on their type
  // (this is called pointer arithmetic)
  printf("%d\n", *(x_ptr + 1)); // => Prints 19
  printf("%d\n", x_array[1]); // => Prints 19

  // You can also dynamically allocate contiguous blocks of memory with the
  // standard library function malloc, which takes one argument of type size_t
  // representing the number of bytes to allocate (usually from the heap, although this
  // may not be true on e.g. embedded systems - the C standard says nothing about it).
  int *my_ptr = malloc(sizeof(*my_ptr) * 20);
  for (xx = 0; xx < 20; xx++) {
    *(my_ptr + xx) = 20 - xx; // my_ptr[xx] = 20-xx
  } // Initialize memory to 20, 19, 18, 17... 2, 1 (as ints)

  // Be careful passing user-provided values to malloc! If you want
  // to be safe, you can use calloc instead (which, unlike malloc, also zeros out the memory)
  int* my_other_ptr = calloc(20, sizeof(int));

  // Note that there is no standard way to get the length of a
  // dynamically allocated array in C. Because of this, if your arrays are
  // going to be passed around your program a lot, you need another variable
  // to keep track of the number of elements (size) of an array. See the
  // functions section for more info.
  size_t size = 10;
  int *my_arr = calloc(size, sizeof(int));
  // Add an element to the array
  size++;
  my_arr = realloc(my_arr, sizeof(int) * size);
  if (my_arr == NULL) {
    //Remember to check for realloc failure!
    return
  }
  my_arr[10] = 5;

  // Dereferencing memory that you haven't allocated gives
  // "unpredictable results" - the program is said to invoke "undefined behavior"
  printf("%d\n", *(my_ptr + 21)); // => Prints who-knows-what? It may even crash.

  // When you're done with a malloc'd block of memory, you need to free it,
  // or else no one else can use it until your program terminates
  // (this is called a "memory leak"):
  free(my_ptr);

  // Strings are arrays of char, but they are usually represented as a
  // pointer-to-char (which is a pointer to the first element of the array).
  // It's good practice to use `const char *' when referring to a string literal,
  // since string literals shall not be modified (i.e. "foo"[0] = 'a' is ILLEGAL.)
  const char *my_str = "This is my very own string literal";
  printf("%c\n", *my_str); // => 'T'

  // This is not the case if the string is an array
  // (potentially initialized with a string literal)
  // that resides in writable memory, as in:
  char foo[] = "foo";
  foo[0] = 'a'; // this is legal, foo now contains "aoo"

  function_1();
} // end main function

///////////////////////////////////////
// Functions
///////////////////////////////////////

// Function declaration syntax:
// <return type> <function name>(<args>)

int add_two_ints(int x1, int x2)
{
  return x1 + x2; // Use return to return a value
}

/*
Functions are call by value. When a function is called, the arguments passed to
the function are copies of the original arguments (except arrays). Anything you
do to the arguments in the function do not change the value of the original
argument where the function was called.

Use pointers if you need to edit the original argument values (arrays are always
passed in as pointers).

Example: in-place string reversal
*/

// A void function returns no value
void str_reverse(char *str_in)
{
  char tmp;
  size_t ii = 0;
  size_t len = strlen(str_in); // `strlen()` is part of the c standard library
                               // NOTE: length returned by `strlen` DOESN'T
                               //       include the terminating NULL byte ('\0')
  // in C99 and newer versions, you can directly declare loop control variables
  // in the loop's parentheses. e.g., `for (size_t ii = 0; ...`
  for (ii = 0; ii < len / 2; ii++) {
    tmp = str_in[ii];
    str_in[ii] = str_in[len - ii - 1]; // ii-th char from end
    str_in[len - ii - 1] = tmp;
  }
}
//NOTE: string.h header file needs to be included to use strlen()

/*
char c[] = "This is a test.";
str_reverse(c);
printf("%s\n", c); // => ".tset a si sihT"
*/
/*
as we can return only one variable
to change values of more than one variables we use call by reference
*/
void swapTwoNumbers(int *a, int *b)
{
    int temp = *a;
    *a = *b;
    *b = temp;
}
/*
int first = 10;
int second = 20;
printf("first: %d\nsecond: %d\n", first, second);
swapTwoNumbers(&first, &second);
printf("first: %d\nsecond: %d\n", first, second);
// values will be swapped
*/

// Return multiple values.
// C does not allow for returning multiple values with the return statement. If
// you would like to return multiple values, then the caller must pass in the
// variables where they would like the returned values to go. These variables must
// be passed in as pointers such that the function can modify them.
int return_multiple( int *array_of_3, int *ret1, int *ret2, int *ret3)
{
    if(array_of_3 == NULL)
        return 0; //return error code (false)

    //de-reference the pointer so we modify its value
   *ret1 = array_of_3[0];
   *ret2 = array_of_3[1];
   *ret3 = array_of_3[2];

   return 1; //return error code (true)
}

/*
With regards to arrays, they will always be passed to functions
as pointers. Even if you statically allocate an array like `arr[10]`,
it still gets passed as a pointer to the first element in any function calls.
Again, there is no standard way to get the size of a dynamically allocated
array in C.
*/
// Size must be passed!
// Otherwise, this function has no way of knowing how big the array is.
void printIntArray(int *arr, size_t size) {
    int i;
    for (i = 0; i < size; i++) {
        printf("arr[%d] is: %d\n", i, arr[i]);
    }
}
/*
int my_arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int size = 10;
printIntArray(my_arr, size);
// will print "arr[0] is: 1" etc
*/

// if referring to external variables outside function, you should use the extern keyword.
int i = 0;
void testFunc() {
  extern int i; //i here is now using external variable i
}

// make external variables private to source file with static:
static int j = 0; //other files using testFunc2() cannot access variable j
void testFunc2() {
  extern int j;
}
// The static keyword makes a variable inaccessible to code outside the
// compilation unit. (On almost all systems, a "compilation unit" is a .c
// file.) static can apply both to global (to the compilation unit) variables,
// functions, and function-local variables. When using static with
// function-local variables, the variable is effectively global and retains its
// value across function calls, but is only accessible within the function it
// is declared in. Additionally, static variables are initialized to 0 if not
// declared with some other starting value.
//**You may also declare functions as static to make them private**

///////////////////////////////////////
// User-defined types and structs
///////////////////////////////////////

// Typedefs can be used to create type aliases
typedef int my_type;
my_type my_type_var = 0;

// Structs are just collections of data, the members are allocated sequentially,
// in the order they are written:
struct rectangle {
  int width;
  int height;
};

// It's not generally true that
// sizeof(struct rectangle) == sizeof(int) + sizeof(int)
// due to potential padding between the structure members (this is for alignment
// reasons). [1]

void function_1()
{
  struct rectangle my_rec = { 1, 2 }; // Fields can be initialized immediately

  // Access struct members with .
  my_rec.width = 10;
  my_rec.height = 20;

  // You can declare pointers to structs
  struct rectangle *my_rec_ptr = &my_rec;

  // Use dereferencing to set struct pointer members...
  (*my_rec_ptr).width = 30;

  // ... or even better: prefer the -> shorthand for the sake of readability
  my_rec_ptr->height = 10; // Same as (*my_rec_ptr).height = 10;
}

// You can apply a typedef to a struct for convenience
typedef struct rectangle rect;

int area(rect r)
{
  return r.width * r.height;
}

// Typedefs can also be defined right during struct definition
typedef struct {
  int width;
  int height;
} rect;
// Like before, doing this means one can type
rect r;
// instead of having to type
struct rectangle r;

// if you have large structs, you can pass them "by pointer" to avoid copying
// the whole struct:
int areaptr(const rect *r)
{
  return r->width * r->height;
}

///////////////////////////////////////
// Function pointers
///////////////////////////////////////
/*
At run time, functions are located at known memory addresses. Function pointers are
much like any other pointer (they just store a memory address), but can be used
to invoke functions directly, and to pass handlers (or callback functions) around.
However, definition syntax may be initially confusing.

Example: use str_reverse from a pointer
*/
void str_reverse_through_pointer(char *str_in) {
  // Define a function pointer variable, named f.
  void (*f)(char *); // Signature should exactly match the target function.
  f = &str_reverse; // Assign the address for the actual function (determined at run time)
  // f = str_reverse; would work as well - functions decay into pointers, similar to arrays
  (*f)(str_in); // Just calling the function through the pointer
  // f(str_in); // That's an alternative but equally valid syntax for calling it.
}

/*
As long as function signatures match, you can assign any function to the same pointer.
Function pointers are usually typedef'd for simplicity and readability, as follows:
*/

typedef void (*my_fnp_type)(char *);

// Then used when declaring the actual pointer variable:
// ...
// my_fnp_type f;


/////////////////////////////
// Printing characters with printf()
/////////////////////////////

//Special characters:
/*
'\a'; // alert (bell) character
'\n'; // newline character
'\t'; // tab character (left justifies text)
'\v'; // vertical tab
'\f'; // new page (form feed)
'\r'; // carriage return
'\b'; // backspace character
'\0'; // NULL character. Usually put at end of strings in C.
//   hello\n\0. \0 used by convention to mark end of string.
'\\'; // backslash
'\?'; // question mark
'\''; // single quote
'\"'; // double quote
'\xhh'; // hexadecimal number. Example: '\xb' = vertical tab character
'\0oo'; // octal number. Example: '\013' = vertical tab character

//print formatting:
"%d";    // integer
"%3d";   // integer with minimum of length 3 digits (right justifies text)
"%s";    // string
"%f";    // float
"%ld";   // long
"%3.2f"; // minimum 3 digits left and 2 digits right decimal float
"%7.4s"; // (can do with strings too)
"%c";    // char
"%p";    // pointer. NOTE: need to (void *)-cast the pointer, before passing
         //                it as an argument to `printf`.
"%x";    // hexadecimal
"%o";    // octal
"%%";    // prints %
*/

///////////////////////////////////////
// Order of Evaluation
///////////////////////////////////////

// From top to bottom, top has higher precedence
//---------------------------------------------------//
//        Operators                  | Associativity //
//---------------------------------------------------//
// () [] -> .                        | left to right //
// ! ~ ++ -- + = *(type) sizeof      | right to left //
// * / %                             | left to right //
// + -                               | left to right //
// << >>                             | left to right //
// < <= > >=                         | left to right //
// == !=                             | left to right //
// &                                 | left to right //
// ^                                 | left to right //
// |                                 | left to right //
// &&                                | left to right //
// ||                                | left to right //
// ?:                                | right to left //
// = += -= *= /= %= &= ^= |= <<= >>= | right to left //
// ,                                 | left to right //
//---------------------------------------------------//

/******************************* Header Files **********************************

Header files are an important part of C as they allow for the connection of C
source files and can simplify code and definitions by separating them into
separate files.

Header files are syntactically similar to C source files but reside in ".h"
files. They can be included in your C source file by using the precompiler
command #include "example.h", given that example.h exists in the same directory
as the C file.
*/

/* A safe guard to prevent the header from being defined too many times. This */
/* happens in the case of circle dependency, the contents of the header is    */
/* already defined.                                                           */
#ifndef EXAMPLE_H /* if EXAMPLE_H is not yet defined. */
#define EXAMPLE_H /* Define the macro EXAMPLE_H. */

/* Other headers can be included in headers and therefore transitively */
/* included into files that include this header.                       */
#include <string.h>

/* Like for c source files, macros can be defined in headers */
/* and used in files that include this header file.          */
#define EXAMPLE_NAME "Dennis Ritchie"

/* Function macros can also be defined.  */
#define ADD(a, b) ((a) + (b))

/* Notice the parenthesis surrounding the arguments -- this is important to   */
/* ensure that a and b don't get expanded in an unexpected way (e.g. consider */
/* MUL(x, y) (x * y); MUL(1 + 2, 3) would expand to (1 + 2 * 3), yielding an  */
/* incorrect result)                                                          */

/* Structs and typedefs can be used for consistency between files. */
typedef struct Node
{
    int val;
    struct Node *next;
} Node;

/* So can enumerations. */
enum traffic_light_state {GREEN, YELLOW, RED};

/* Function prototypes can also be defined here for use in multiple files,  */
/* but it is bad practice to define the function in the header. Definitions */
/* should instead be put in a C file.                                       */
Node createLinkedList(int *vals, int len);

/* Beyond the above elements, other definitions should be left to a C source */
/* file. Excessive includes or definitions should also not be contained in   */
/* a header file but instead put into separate headers or a C file.          */

#endif /* End of the if precompiler directive. */
    \""", 100),
    ("The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web.", 100),
    ("ØMQ (also spelled ZeroMQ, 0MQ or ZMQ) is a high-performance asynchronous messaging library aimed at use in scalable distributed or concurrent applications. It provides a message queue, but unlike message-oriented middleware, a ØMQ system can run without a dedicated message broker. The library is designed to have a familiar socket-style API.", 75),
    ("RabbitMQ is an open source message broker software that implements the Advanced Message Queuing Protocol (AMQP). The RabbitMQ server is written in the Erlang programming language and is built on the Open Telecom Platform framework for clustering and failover. Client libraries to interface with the broker are available for all major programming languages.", 100),
    (\"""
    //////////////////
// Comparison to C
//////////////////

// C++ is almost a superset of C and shares its basic syntax for
// variable declarations, primitive types, and functions.

// Just like in C, your program's entry point is a function called
// main with an integer return type.
// This value serves as the program's exit status.
// See https://en.wikipedia.org/wiki/Exit_status for more information.
int main(int argc, char** argv)
{
    // Command line arguments are passed in by argc and argv in the same way
    // they are in C.
    // argc indicates the number of arguments,
    // and argv is an array of C-style strings (char*)
    // representing the arguments.
    // The first argument is the name by which the program was called.
    // argc and argv can be omitted if you do not care about arguments,
    // giving the function signature of int main()

    // An exit status of 0 indicates success.
    return 0;
}

// However, C++ varies in some of the following ways:

// In C++, character literals are chars, therefore the size is 1
sizeof('c') == sizeof(char)

// In C, character literals are ints, therefore the size is 4
sizeof('c') == sizeof(int)


// C++ has strict prototyping
void func(); // function which accepts no arguments
void func(void); // same as earlier

// In C
void func(); // function which may accept any number of arguments with unknown type
void func(void); // function which accepts no arguments

// Use nullptr instead of NULL in C++
int* ip = nullptr;

// Most C standard headers are available in C++.
// C headers generally end with .h, while
// C++ headers are prefixed with "c" and have no ".h" suffix.

// The C++ standard version:
#include <cstdio>

// The C standard version:
#include <stdio.h>

int main()
{
    printf("Hello, world!\n");
    return 0;
}

///////////////////////
// Function overloading
///////////////////////

// C++ supports function overloading
// provided each function takes different parameters.

void print(char const* myString)
{
    printf("String %s\n", myString);
}

void print(int myInt)
{
    printf("My int is %d\n", myInt);
}

int main()
{
    print("Hello"); // Resolves to void print(const char*)
    print(15); // Resolves to void print(int)
}

/////////////////////////////
// Default function arguments
/////////////////////////////

// You can provide default arguments for a function
// if they are not provided by the caller.

void doSomethingWithInts(int a = 1, int b = 4)
{
    // Do something with the ints here
}

int main()
{
    doSomethingWithInts();      // a = 1,  b = 4
    doSomethingWithInts(20);    // a = 20, b = 4
    doSomethingWithInts(20, 5); // a = 20, b = 5
}

// Default arguments must be at the end of the arguments list.

void invalidDeclaration(int a = 1, int b) // Error!
{
}


/////////////
// Namespaces
/////////////

// Namespaces provide separate scopes for variable, function,
// and other declarations.
// Namespaces can be nested.

namespace First {
    namespace Nested {
        void foo()
        {
            printf("This is First::Nested::foo\n");
        }
    } // end namespace Nested
} // end namespace First

namespace Second {
    void foo()
    {
        printf("This is Second::foo\n");
    }
    void bar()
    {
        printf("This is Second::bar\n");
    }
}

void foo()
{
    printf("This is global foo\n");
}

int main()
{
    // Includes all symbols from namespace Second into the current scope. Note
    // that while bar() works, simply using foo() no longer works, since it is
    // now ambiguous whether we're calling the foo in namespace Second or the
    // top level.
    using namespace Second;

    bar(); // prints "This is Second::bar"
    Second::foo(); // prints "This is Second::foo"
    First::Nested::foo(); // prints "This is First::Nested::foo"
    ::foo(); // prints "This is global foo"
}

///////////////
// Input/Output
///////////////

// C++ input and output uses streams
// cin, cout, and cerr represent stdin, stdout, and stderr.
// << is the insertion operator and >> is the extraction operator.

#include <iostream> // Include for I/O streams

int main()
{
    int myInt;

    // Prints to stdout (or terminal/screen)
    // std::cout referring the access to the std namespace
    std::cout << "Enter your favorite number:\n";
    // Takes in input
    std::cin >> myInt;

    // cout can also be formatted
    std::cout << "Your favorite number is " << myInt << '\n';
    // prints "Your favorite number is <myInt>"

    std::cerr << "Used for error messages";

    // flush string stream buffer with new line
    std::cout << "I flushed it away" << std::endl;
}

//////////
// Strings
//////////

// Strings in C++ are objects and have many member functions
#include <string>

std::string myString = "Hello";
std::string myOtherString = " World";

// + is used for concatenation.
std::cout << myString + myOtherString; // "Hello World"

std::cout << myString + " You"; // "Hello You"

// C++ string length can be found from either string::length() or string::size()
cout << myString.length() + myOtherString.size(); // Outputs 11 (= 5 + 6).

// C++ strings are mutable.
myString.append(" Dog");
std::cout << myString; // "Hello Dog"

// C++ can handle C-style strings with related functions using cstrings
#include <cstring>

char myOldString[10] = "Hello CPP";
cout << myOldString;
cout << "Length = " << strlen(myOldString); // Length = 9

/////////////
// References
/////////////

// In addition to pointers like the ones in C,
// C++ has _references_.
// These are pointer types that cannot be reassigned once set
// and cannot be null.
// They also have the same syntax as the variable itself:
// No * is needed for dereferencing and
// & (address of) is not used for assignment.

std::string foo = "I am foo";
std::string bar = "I am bar";

std::string& fooRef = foo; // This creates a reference to foo.
fooRef += ". Hi!"; // Modifies foo through the reference
std::cout << fooRef; // Prints "I am foo. Hi!"

// Doesn't reassign "fooRef". This is the same as "foo = bar", and
//   foo == "I am bar"
// after this line.
std::cout << &fooRef << '\n'; // Prints the address of foo
fooRef = bar;
std::cout << &fooRef << '\n'; // Still prints the address of foo
std::cout << fooRef << '\n';  // Prints "I am bar"

// The address of fooRef remains the same, i.e. it is still referring to foo.


const std::string& barRef = bar; // Create a const reference to bar.
// Like C, const values (and pointers and references) cannot be modified.
barRef += ". Hi!"; // Error, const references cannot be modified.

// Sidetrack: Before we talk more about references, we must introduce a concept
// called a temporary object. Suppose we have the following code:
std::string tempObjectFun() { ... }
std::string retVal = tempObjectFun();

// What happens in the second line is actually:
//   - a string object is returned from tempObjectFun
//   - a new string is constructed with the returned object as argument to the
//     constructor
//   - the returned object is destroyed
// The returned object is called a temporary object. Temporary objects are
// created whenever a function returns an object, and they are destroyed at the
// end of the evaluation of the enclosing expression (Well, this is what the
// standard says, but compilers are allowed to change this behavior. Look up
// "return value optimization" if you're into this kind of details). So in this
// code:
foo(bar(tempObjectFun()))

// assuming foo and bar exist, the object returned from tempObjectFun is
// passed to bar, and it is destroyed before foo is called.

// Now back to references. The exception to the "at the end of the enclosing
// expression" rule is if a temporary object is bound to a const reference, in
// which case its life gets extended to the current scope:

void constReferenceTempObjectFun() {
    // constRef gets the temporary object, and it is valid until the end of this
    // function.
    const std::string& constRef = tempObjectFun();
    ...
}

// Another kind of reference introduced in C++11 is specifically for temporary
// objects. You cannot have a variable of its type, but it takes precedence in
// overload resolution:

void someFun(std::string& s) { ... }  // Regular reference
void someFun(std::string&& s) { ... }  // Reference to temporary object

std::string foo;
someFun(foo);  // Calls the version with regular reference
someFun(tempObjectFun());  // Calls the version with temporary reference

// For example, you will see these two versions of constructors for
// std::basic_string:
std::basic_string(const basic_string& other);
std::basic_string(basic_string&& other);

// Idea being if we are constructing a new string from a temporary object (which
// is going to be destroyed soon anyway), we can have a more efficient
// constructor that "salvages" parts of that temporary string. You will see this
// concept referred to as "move semantics".

/////////////////////
// Enums
/////////////////////

// Enums are a way to assign a value to a constant most commonly used for
// easier visualization and reading of code
enum ECarTypes
{
    Sedan,
    Hatchback,
    SUV,
    Wagon
};

ECarTypes GetPreferredCarType()
{
    return ECarTypes::Hatchback;
}

// As of C++11 there is an easy way to assign a type to the enum which can be
// useful in serialization of data and converting enums back-and-forth between
// the desired type and their respective constants
enum ECarTypes : uint8_t
{
    Sedan, // 0
    Hatchback, // 1
    SUV = 254, // 254
    Hybrid // 255
};

void WriteByteToFile(uint8_t InputValue)
{
    // Serialize the InputValue to a file
}

void WritePreferredCarTypeToFile(ECarTypes InputCarType)
{
    // The enum is implicitly converted to a uint8_t due to its declared enum type
    WriteByteToFile(InputCarType);
}

// On the other hand you may not want enums to be accidentally cast to an integer
// type or to other enums so it is instead possible to create an enum class which
// won't be implicitly converted
enum class ECarTypes : uint8_t
{
    Sedan, // 0
    Hatchback, // 1
    SUV = 254, // 254
    Hybrid // 255
};

void WriteByteToFile(uint8_t InputValue)
{
    // Serialize the InputValue to a file
}

void WritePreferredCarTypeToFile(ECarTypes InputCarType)
{
    // Won't compile even though ECarTypes is a uint8_t due to the enum
    // being declared as an "enum class"!
    WriteByteToFile(InputCarType);
}

//////////////////////////////////////////
// Classes and object-oriented programming
//////////////////////////////////////////

// First example of classes
#include <iostream>

// Declare a class.
// Classes are usually declared in header (.h or .hpp) files.
class Dog {
    // Member variables and functions are private by default.
    std::string name;
    int weight;

// All members following this are public
// until "private:" or "protected:" is found.
public:

    // Default constructor
    Dog();

    // Member function declarations (implementations to follow)
    // Note that we use std::string here instead of placing
    // using namespace std;
    // above.
    // Never put a "using namespace" statement in a header.
    void setName(const std::string& dogsName);

    void setWeight(int dogsWeight);

    // Functions that do not modify the state of the object
    // should be marked as const.
    // This allows you to call them if given a const reference to the object.
    // Also note the functions must be explicitly declared as _virtual_
    // in order to be overridden in derived classes.
    // Functions are not virtual by default for performance reasons.
    virtual void print() const;

    // Functions can also be defined inside the class body.
    // Functions defined as such are automatically inlined.
    void bark() const { std::cout << name << " barks!\n"; }

    // Along with constructors, C++ provides destructors.
    // These are called when an object is deleted or falls out of scope.
    // This enables powerful paradigms such as RAII
    // (see below)
    // The destructor should be virtual if a class is to be derived from;
    // if it is not virtual, then the derived class' destructor will
    // not be called if the object is destroyed through a base-class reference
    // or pointer.
    virtual ~Dog();

}; // A semicolon must follow the class definition.

// Class member functions are usually implemented in .cpp files.
Dog::Dog()
{
    std::cout << "A dog has been constructed\n";
}

// Objects (such as strings) should be passed by reference
// if you are modifying them or const reference if you are not.
void Dog::setName(const std::string& dogsName)
{
    name = dogsName;
}

void Dog::setWeight(int dogsWeight)
{
    weight = dogsWeight;
}

// Notice that "virtual" is only needed in the declaration, not the definition.
void Dog::print() const
{
    std::cout << "Dog is " << name << " and weighs " << weight << "kg\n";
}

Dog::~Dog()
{
    std::cout << "Goodbye " << name << '\n';
}

int main() {
    Dog myDog; // prints "A dog has been constructed"
    myDog.setName("Barkley");
    myDog.setWeight(10);
    myDog.print(); // prints "Dog is Barkley and weighs 10 kg"
    return 0;
} // prints "Goodbye Barkley"

// Inheritance:

// This class inherits everything public and protected from the Dog class
// as well as private but may not directly access private members/methods
// without a public or protected method for doing so
class OwnedDog : public Dog {

public:
    void setOwner(const std::string& dogsOwner);

    // Override the behavior of the print function for all OwnedDogs. See
    // https://en.wikipedia.org/wiki/Polymorphism_(computer_science)#Subtyping
    // for a more general introduction if you are unfamiliar with
    // subtype polymorphism.
    // The override keyword is optional but makes sure you are actually
    // overriding the method in a base class.
    void print() const override;

private:
    std::string owner;
};

// Meanwhile, in the corresponding .cpp file:

void OwnedDog::setOwner(const std::string& dogsOwner)
{
    owner = dogsOwner;
}

void OwnedDog::print() const
{
    Dog::print(); // Call the print function in the base Dog class
    std::cout << "Dog is owned by " << owner << '\n';
    // Prints "Dog is <name> and weights <weight>"
    //        "Dog is owned by <owner>"
}

//////////////////////////////////////////
// Initialization and Operator Overloading
//////////////////////////////////////////

// In C++ you can overload the behavior of operators such as +, -, *, /, etc.
// This is done by defining a function which is called
// whenever the operator is used.

#include <iostream>
using namespace std;

class Point {
public:
    // Member variables can be given default values in this manner.
    double x = 0;
    double y = 0;

    // Define a default constructor which does nothing
    // but initialize the Point to the default value (0, 0)
    Point() { };

    // The following syntax is known as an initialization list
    // and is the proper way to initialize class member values
    Point (double a, double b) :
        x(a),
        y(b)
    { /* Do nothing except initialize the values */ }

    // Overload the + operator.
    Point operator+(const Point& rhs) const;

    // Overload the += operator
    Point& operator+=(const Point& rhs);

    // It would also make sense to add the - and -= operators,
    // but we will skip those for brevity.
};

Point Point::operator+(const Point& rhs) const
{
    // Create a new point that is the sum of this one and rhs.
    return Point(x + rhs.x, y + rhs.y);
}

// It's good practice to return a reference to the leftmost variable of
// an assignment. `(a += b) == c` will work this way.
Point& Point::operator+=(const Point& rhs)
{
    x += rhs.x;
    y += rhs.y;

    // `this` is a pointer to the object, on which a method is called.
    return *this;
}

int main () {
    Point up (0,1);
    Point right (1,0);
    // This calls the Point + operator
    // Point up calls the + (function) with right as its parameter
    Point result = up + right;
    // Prints "Result is upright (1,1)"
    std::cout << "Result is upright (" << result.x << ',' << result.y << ")\n";
    return 0;
}

/////////////////////
// Templates
/////////////////////

// Templates in C++ are mostly used for generic programming, though they are
// much more powerful than generic constructs in other languages. They also
// support explicit and partial specialization and functional-style type
// classes; in fact, they are a Turing-complete functional language embedded
// in C++!

// We start with the kind of generic programming you might be familiar with. To
// define a class or function that takes a type parameter:
template<class T>
class Box {
public:
    // In this class, T can be used as any other type.
    void insert(const T&) { ... }
};

// During compilation, the compiler actually generates copies of each template
// with parameters substituted, so the full definition of the class must be
// present at each invocation. This is why you will see template classes defined
// entirely in header files.

// To instantiate a template class on the stack:
Box<int> intBox;

// and you can use it as you would expect:
intBox.insert(123);

// You can, of course, nest templates:
Box<Box<int> > boxOfBox;
boxOfBox.insert(intBox);

// Until C++11, you had to place a space between the two '>'s, otherwise '>>'
// would be parsed as the right shift operator.

// You will sometimes see
//   template<typename T>
// instead. The 'class' keyword and 'typename' keywords are _mostly_
// interchangeable in this case. For the full explanation, see
//   https://en.wikipedia.org/wiki/Typename
// (yes, that keyword has its own Wikipedia page).

// Similarly, a template function:
template<class T>
void barkThreeTimes(const T& input)
{
    input.bark();
    input.bark();
    input.bark();
}

// Notice that nothing is specified about the type parameters here. The compiler
// will generate and then type-check every invocation of the template, so the
// above function works with any type 'T' that has a const 'bark' method!

Dog fluffy;
fluffy.setName("Fluffy")
barkThreeTimes(fluffy); // Prints "Fluffy barks" three times.

// Template parameters don't have to be classes:
template<int Y>
void printMessage() {
    std::cout << "Learn C++ in " << Y << " minutes!\n";
}

// And you can explicitly specialize templates for more efficient code. Of
// course, most real-world uses of specialization are not as trivial as this.
// Note that you still need to declare the function (or class) as a template
// even if you explicitly specified all parameters.
template<>
void printMessage<10>() {
    std::cout << "Learn C++ faster in only 10 minutes!\n";
}

printMessage<20>();  // Prints "Learn C++ in 20 minutes!"
printMessage<10>();  // Prints "Learn C++ faster in only 10 minutes!"


/////////////////////
// Exception Handling
/////////////////////

// The standard library provides a few exception types
// (see https://en.cppreference.com/w/cpp/error/exception)
// but any type can be thrown as an exception
#include <exception>
#include <stdexcept>

// All exceptions thrown inside the _try_ block can be caught by subsequent
// _catch_ handlers.
try {
    // Do not allocate exceptions on the heap using _new_.
    throw std::runtime_error("A problem occurred");
}

// Catch exceptions by const reference if they are objects
catch (const std::exception& ex)
{
    std::cout << ex.what();
}

// Catches any exception not caught by previous _catch_ blocks
catch (...)
{
    std::cout << "Unknown exception caught";
    throw; // Re-throws the exception
}

///////
// RAII
///////

// RAII stands for "Resource Acquisition Is Initialization".
// It is often considered the most powerful paradigm in C++
// and is the simple concept that a constructor for an object
// acquires that object's resources and the destructor releases them.

// To understand how this is useful,
// consider a function that uses a C file handle:
void doSomethingWithAFile(const char* filename)
{
    // To begin with, assume nothing can fail.

    FILE* fh = fopen(filename, "r"); // Open the file in read mode.
    if (fh == NULL) {
        // Handle possible error
    }

    doSomethingWithTheFile(fh);
    doSomethingElseWithIt(fh);

    fclose(fh); // Close the file handle.
}

// Unfortunately, things are quickly complicated by error handling.
// Suppose fopen can fail, and that doSomethingWithTheFile and
// doSomethingElseWithIt return error codes if they fail.
//  (Exceptions are the preferred way of handling failure,
//   but some programmers, especially those with a C background,
//   disagree on the utility of exceptions).
// We now have to check each call for failure and close the file handle
// if a problem occurred.
bool doSomethingWithAFile(const char* filename)
{
    FILE* fh = fopen(filename, "r"); // Open the file in read mode
    if (fh == nullptr) // The returned pointer is null on failure.
        return false; // Report that failure to the caller.

    // Assume each function returns false if it failed
    if (!doSomethingWithTheFile(fh)) {
        fclose(fh); // Close the file handle so it doesn't leak.
        return false; // Propagate the error.
    }
    if (!doSomethingElseWithIt(fh)) {
        fclose(fh); // Close the file handle so it doesn't leak.
        return false; // Propagate the error.
    }

    fclose(fh); // Close the file handle so it doesn't leak.
    return true; // Indicate success
}

// C programmers often clean this up a little bit using goto:
bool doSomethingWithAFile(const char* filename)
{
    FILE* fh = fopen(filename, "r");
    if (fh == nullptr)
        return false;

    if (!doSomethingWithTheFile(fh))
        goto failure;

    if (!doSomethingElseWithIt(fh))
        goto failure;

    fclose(fh); // Close the file
    return true; // Indicate success

failure:
    fclose(fh);
    return false; // Propagate the error
}

// If the functions indicate errors using exceptions,
// things are a little cleaner, but still sub-optimal.
void doSomethingWithAFile(const char* filename)
{
    FILE* fh = fopen(filename, "r"); // Open the file in shared_ptrread mode
    if (fh == nullptr)
        throw std::runtime_error("Could not open the file.");

    try {
        doSomethingWithTheFile(fh);
        doSomethingElseWithIt(fh);
    }
    catch (...) {
        fclose(fh); // Be sure to close the file if an error occurs.
        throw; // Then re-throw the exception.
    }

    fclose(fh); // Close the file
    // Everything succeeded
}

// Compare this to the use of C++'s file stream class (fstream)
// fstream uses its destructor to close the file.
// Recall from above that destructors are automatically called
// whenever an object falls out of scope.
void doSomethingWithAFile(const std::string& filename)
{
    // ifstream is short for input file stream
    std::ifstream fh(filename); // Open the file

    // Do things with the file
    doSomethingWithTheFile(fh);
    doSomethingElseWithIt(fh);

} // The file is automatically closed here by the destructor

// This has _massive_ advantages:
// 1. No matter what happens,
//    the resource (in this case the file handle) will be cleaned up.
//    Once you write the destructor correctly,
//    It is _impossible_ to forget to close the handle and leak the resource.
// 2. Note that the code is much cleaner.
//    The destructor handles closing the file behind the scenes
//    without you having to worry about it.
// 3. The code is exception safe.
//    An exception can be thrown anywhere in the function and cleanup
//    will still occur.

// All idiomatic C++ code uses RAII extensively for all resources.
// Additional examples include
// - Memory using unique_ptr and shared_ptr
// - Containers - the standard library linked list,
//   vector (i.e. self-resizing array), hash maps, and so on
//   all automatically destroy their contents when they fall out of scope.
// - Mutexes using lock_guard and unique_lock


/////////////////////
// Smart Pointer
/////////////////////

// Generally a smart pointer is a class which wraps a "raw pointer" (usage of "new"
// respectively malloc/calloc in C). The goal is to be able to
// manage the lifetime of the object being pointed to without ever needing to explicitly delete
// the object. The term itself simply describes a set of pointers with the
// mentioned abstraction.
// Smart pointers should preferred over raw pointers, to prevent
// risky memory leaks, which happen if you forget to delete an object.

// Usage of a raw pointer:
Dog* ptr = new Dog();
ptr->bark();
delete ptr;

// By using a smart pointer, you don't have to worry about the deletion
// of the object anymore.
// A smart pointer describes a policy, to count the references to the
// pointer. The object gets destroyed when the last
// reference to the object gets destroyed.

// Usage of "std::shared_ptr":
void foo()
{
    // It's no longer necessary to delete the Dog.
    std::shared_ptr<Dog> doggo(new Dog());
    doggo->bark();
}

// Beware of possible circular references!!!
// There will be always a reference, so it will be never destroyed!
std::shared_ptr<Dog> doggo_one(new Dog());
std::shared_ptr<Dog> doggo_two(new Dog());
doggo_one = doggo_two; // p1 references p2
doggo_two = doggo_one; // p2 references p1

// There are several kinds of smart pointers.
// The way you have to use them is always the same.
// This leads us to the question: when should we use each kind of smart pointer?
// std::unique_ptr - use it when you just want to hold one reference to
// the object.
// std::shared_ptr - use it when you want to hold multiple references to the
// same object and want to make sure that it's deallocated
// when all references are gone.
// std::weak_ptr - use it when you want to access
// the underlying object of a std::shared_ptr without causing that object to stay allocated.
// Weak pointers are used to prevent circular referencing.


/////////////////////
// Containers
/////////////////////

// Containers or the Standard Template Library are some predefined templates.
// They manage the storage space for its elements and provide
// member functions to access and manipulate them.

// Few containers are as follows:

// Vector (Dynamic array)
// Allow us to Define the Array or list of objects at run time
#include <vector>
std::string val;
std::vector<string> my_vector; // initialize the vector
std::cin >> val;

my_vector.push_back(val); // will push the value of 'val' into vector ("array") my_vector
my_vector.push_back(val); // will push the value into the vector again (now having two elements)

// To iterate through a vector we have 2 choices:
// Either classic looping (iterating through the vector from index 0 to its last index):
for (int i = 0; i < my_vector.size(); i++) {
    std::cout << my_vector[i] << '\n'; // for accessing a vector's element we can use the operator []
}

// or using an iterator:
vector<string>::iterator it; // initialize the iterator for vector
for (it = my_vector.begin(); it != my_vector.end(); ++it) {
    std::cout << *it  << '\n';
}

// Set
// Sets are containers that store unique elements following a specific order.
// Set is a very useful container to store unique values in sorted order
// without any other functions or code.

#include<set>
std::set<int> ST;    // Will initialize the set of int data type
ST.insert(30);  // Will insert the value 30 in set ST
ST.insert(10);  // Will insert the value 10 in set ST
ST.insert(20);  // Will insert the value 20 in set ST
ST.insert(30);  // Will insert the value 30 in set ST
// Now elements of sets are as follows
//  10 20 30

// To erase an element
ST.erase(20);  // Will erase element with value 20
// Set ST: 10 30
// To iterate through Set we use iterators
std::set<int>::iterator it;
for (it = ST.begin(); it != ST.end(); it++) {
    std::cout << *it << '\n';
}
// Output:
// 10
// 30

// To clear the complete container we use Container_name.clear()
ST.clear();
std::cout << ST.size();  // will print the size of set ST
// Output: 0

// NOTE: for duplicate elements we can use multiset
// NOTE: For hash sets, use unordered_set. They are more efficient but
// do not preserve order. unordered_set is available since C++11

// Map
// Maps store elements formed by a combination of a key value
// and a mapped value, following a specific order.

#include<map>
std::map<char, int> mymap;  // Will initialize the map with key as char and value as int

mymap.insert(pair<char,int>('A',1));
// Will insert value 1 for key A
mymap.insert(pair<char,int>('Z',26));
// Will insert value 26 for key Z

// To iterate
std::map<char,int>::iterator it;
for (it = mymap.begin(); it != mymap.end(); ++it)
    std::cout << it->first << "->" << it->second << '\n';
// Output:
// A->1
// Z->26

// To find the value corresponding to a key
it = mymap.find('Z');
std::cout << it->second;

// Output: 26

// NOTE: For hash maps, use unordered_map. They are more efficient but do
// not preserve order. unordered_map is available since C++11.

// Containers with object keys of non-primitive values (custom classes) require
// compare function in the object itself or as a function pointer. Primitives
// have default comparators, but you can override it.
class Foo {
public:
    int j;
    Foo(int a) : j(a) {}
};
struct compareFunction {
    bool operator()(const Foo& a, const Foo& b) const {
        return a.j < b.j;
    }
};
// this isn't allowed (although it can vary depending on compiler)
// std::map<Foo, int> fooMap;
std::map<Foo, int, compareFunction> fooMap;
fooMap[Foo(1)]  = 1;
fooMap.find(Foo(1)); //true


///////////////////////////////////////
// Lambda Expressions (C++11 and above)
///////////////////////////////////////

// lambdas are a convenient way of defining an anonymous function
// object right at the location where it is invoked or passed as
// an argument to a function.

// For example, consider sorting a vector of pairs using the second
// value of the pair

std::vector<pair<int, int> > tester;
tester.push_back(make_pair(3, 6));
tester.push_back(make_pair(1, 9));
tester.push_back(make_pair(5, 0));

// Pass a lambda expression as third argument to the sort function
// sort is from the <algorithm> header

std::sort(tester.begin(), tester.end(), [](const pair<int, int>& lhs, const pair<int, int>& rhs) {
        return lhs.second < rhs.second;
    });

// Notice the syntax of the lambda expression,
// [] in the lambda is used to "capture" variables
// The "Capture List" defines what from the outside of the lambda should be available inside the function body and how.
// It can be either:
//     1. a value : [x]
//     2. a reference : [&x]
//     3. any variable currently in scope by reference [&]
//     4. same as 3, but by value [=]
// Example:

std::vector<int> dog_ids;
// number_of_dogs = 3;
for (int i = 0; i < 3; i++) {
    dog_ids.push_back(i);
}

int weight[3] = {30, 50, 10};

// Say you want to sort dog_ids according to the dogs' weights
// So dog_ids should in the end become: [2, 0, 1]

// Here's where lambda expressions come in handy

sort(dog_ids.begin(), dog_ids.end(), [&weight](const int &lhs, const int &rhs) {
        return weight[lhs] < weight[rhs];
    });
// Note we captured "weight" by reference in the above example.
// More on Lambdas in C++ : https://stackoverflow.com/questions/7627098/what-is-a-lambda-expression-in-c11

///////////////////////////////
// Range For (C++11 and above)
///////////////////////////////

// You can use a range for loop to iterate over a container
int arr[] = {1, 10, 3};

for (int elem: arr) {
    cout << elem << endl;
}

// You can use "auto" and not worry about the type of the elements of the container
// For example:

for (auto elem: arr) {
    // Do something with each element of arr
}

/////////////////////
// Fun stuff
/////////////////////

// Aspects of C++ that may be surprising to newcomers (and even some veterans).
// This section is, unfortunately, wildly incomplete; C++ is one of the easiest
// languages with which to shoot yourself in the foot.

// You can override private methods!
class Foo {
    virtual void bar();
};
class FooSub : public Foo {
    virtual void bar();  // Overrides Foo::bar!
};


// 0 == false == NULL (most of the time)!
bool* pt = new bool;
*pt = 0; // Sets the value points by 'pt' to false.
pt = 0;  // Sets 'pt' to the null pointer. Both lines compile without warnings.

// nullptr is supposed to fix some of that issue:
int* pt2 = new int;
*pt2 = nullptr; // Doesn't compile
pt2 = nullptr;  // Sets pt2 to null.

// There is an exception made for bools.
// This is to allow you to test for null pointers with if(!ptr),
// but as a consequence you can assign nullptr to a bool directly!
*pt = nullptr;  // This still compiles, even though '*pt' is a bool!


// '=' != '=' != '='!
// Calls Foo::Foo(const Foo&) or some variant (see move semantics) copy
// constructor.
Foo f2;
Foo f1 = f2;

// Calls Foo::Foo(const Foo&) or variant, but only copies the 'Foo' part of
// 'fooSub'. Any extra members of 'fooSub' are discarded. This sometimes
// horrifying behavior is called "object slicing."
FooSub fooSub;
Foo f1 = fooSub;

// Calls Foo::operator=(Foo&) or variant.
Foo f1;
f1 = f2;


///////////////////////////////////////
// Tuples (C++11 and above)
///////////////////////////////////////

#include<tuple>

// Conceptually, Tuples are similar to old data structures (C-like structs)
// but instead of having named data members,
// its elements are accessed by their order in the tuple.

// We start with constructing a tuple.
// Packing values into tuple
auto first = make_tuple(10, 'A');
const int maxN = 1e9;
const int maxL = 15;
auto second = make_tuple(maxN, maxL);

// Printing elements of 'first' tuple
std::cout << get<0>(first) << " " << get<1>(first) << '\n'; //prints : 10 A

// Printing elements of 'second' tuple
std::cout << get<0>(second) << " " << get<1>(second) << '\n'; // prints: 1000000000 15

// Unpacking tuple into variables

int first_int;
char first_char;
tie(first_int, first_char) = first;
std::cout << first_int << " " << first_char << '\n';  // prints : 10 A

// We can also create tuple like this.

tuple<int, char, double> third(11, 'A', 3.14141);
// tuple_size returns number of elements in a tuple (as a constexpr)

std::cout << tuple_size<decltype(third)>::value << '\n'; // prints: 3

// tuple_cat concatenates the elements of all the tuples in the same order.

auto concatenated_tuple = tuple_cat(first, second, third);
// concatenated_tuple becomes = (10, 'A', 1e9, 15, 11, 'A', 3.14141)

std::cout << get<0>(concatenated_tuple) << '\n'; // prints: 10
std::cout << get<3>(concatenated_tuple) << '\n'; // prints: 15
std::cout << get<5>(concatenated_tuple) << '\n'; // prints: 'A'


///////////////////////////////////
// Logical and Bitwise operators
//////////////////////////////////

// Most of the operators in C++ are same as in other languages

// Logical operators

// C++ uses Short-circuit evaluation for boolean expressions, i.e, the second argument is executed or
// evaluated only if the first argument does not suffice to determine the value of the expression

true && false // Performs **logical and** to yield false
true || false // Performs **logical or** to yield true
! true        // Performs **logical not** to yield false

// Instead of using symbols equivalent keywords can be used
true and false // Performs **logical and** to yield false
true or false  // Performs **logical or** to yield true
not true       // Performs **logical not** to yield false

// Bitwise operators

// **<<** Left Shift Operator
// << shifts bits to the left
4 << 1 // Shifts bits of 4 to left by 1 to give 8
// x << n can be thought as x * 2^n


// **>>** Right Shift Operator
// >> shifts bits to the right
4 >> 1 // Shifts bits of 4 to right by 1 to give 2
// x >> n can be thought as x / 2^n

~4    // Performs a bitwise not
4 | 3 // Performs bitwise or
4 & 3 // Performs bitwise and
4 ^ 3 // Performs bitwise xor

// Equivalent keywords are
compl 4    // Performs a bitwise not
4 bitor 3  // Performs bitwise or
4 bitand 3 // Performs bitwise and
4 xor 3    // Performs bitwise xor
    """, 95),
    ("""
    /* comments appear inside slash-asterisk, just like this line!
   there are no "one-line comments"; this is the only comment style */

/* ####################
   ## SELECTORS
   #################### */

/* the selector is used to target an element on a page. */
selector { property: value; /* more properties...*/ }

/*
Here is an example element:

<div class='class1 class2' id='anID' attr='value' otherAttr='en-us foo bar' />
*/

/* You can target it using one of its CSS classes */
.class1 { }

/* or both classes! */
.class1.class2 { }

/* or its name */
div { }

/* or its id */
#anID { }

/* or using the fact that it has an attribute! */
[attr] { font-size:smaller; }

/* or that the attribute has a specific value */
[attr='value'] { font-size:smaller; }

/* starts with a value (CSS 3) */
[attr^='val'] { font-size:smaller; }

/* or ends with a value (CSS 3) */
[attr$='ue'] { font-size:smaller; }

/* or contains a value (CSS 3) */
[attr*='foo'] { }

/* or contains a value in a space-separated list */
[otherAttr~='foo'] { }
[otherAttr~='bar'] { }

/* or contains a value in a dash-separated list, e.g., "-" (U+002D) */
[otherAttr|='en'] { font-size:smaller; }


/* You can combine different selectors to create a more focused selector. Don't
   put spaces between them. */
div.some-class[attr$='ue'] { }

/* You can select an element which is a child of another element */
div.some-parent > .class-name { }

/* or a descendant of another element. Children are the direct descendants of
   their parent element, only one level down the tree. Descendants can be any
   level down the tree. */
div.some-parent .class-name { }

/* Warning: the same selector without a space has another meaning.
   Can you guess what? */
div.some-parent.class-name { }

/* You may also select an element based on its adjacent sibling */
.i-am-just-before + .this-element { }

/* or any sibling preceding it */
.i-am-any-element-before ~ .this-element { }

/* There are some selectors called pseudo classes that can be used to select an
   element only when it is in a particular state */

/* for example, when a link hasn't been visited */
selected:link { }

/* or a link has been visited */
selector:visited { }

/* or an element is in focus */
selected:focus { }

/* or when the cursor hovers over an element */
selector:hover { }

/* or when a link is clicked on */
selector:active { }

/* These pseudo classes regarding links should always be written in the above order or the code might not work as expected */

/* Any element that is the first child of its parent */
selector:first-child {}

/* any element that is the last child of its parent */
selector:last-child {}

/* Select the nth child of selector parent (CSS 3) */
selector:nth-child(n) { }

/* Just like pseudo classes, pseudo elements allow you to style certain parts of
    a document  */

/* matches a virtual first child of the selected element */
selector::before {}

/* matches a virtual last child of the selected element */
selector::after {}

/* At appropriate places, an asterisk may be used as a wildcard to select every
   element */
* { } /* all elements */
.parent * { } /* all descendants */
.parent > * { } /* all children */

/* Group any number of selectors to define styles that affect all selectors
   in the group */
selector1, selector2 { }

/* Select elements that do not have a certain state (CSS 3) */
/* Here, we select div with no id attribute. */
div:not([id]) {
   background-color: red;
}

/* ####################
   ## PROPERTIES
   #################### */

selector {

    /* Units of length can be absolute or relative. */

    /* Relative units */
    width: 50%;       /* percentage of parent element width */
    font-size: 2em;   /* multiples of element's original font-size */
    font-size: 2rem;  /* or the root element's font-size */
    font-size: 2vw;   /* multiples of 1% of the viewport's width (CSS 3) */
    font-size: 2vh;   /* or its height */
    font-size: 2vmin; /* whichever of a vh or a vw is smaller */
    font-size: 2vmax; /* or greater */

    /* Absolute units */
    width: 200px;     /* pixels */
    font-size: 20pt;  /* points */
    width: 5cm;       /* centimeters */
    min-width: 50mm;  /* millimeters */
    max-width: 5in;   /* inches */

    /* Colors */
    color: #F6E;                    /* short hex format */
    color: #FF66EE;                 /* long hex format */
    color: tomato;                  /* a named color */
    color: rgb(255, 255, 255);      /* as rgb values */
    color: rgb(10%, 20%, 50%);      /* as rgb percentages */
    color: rgba(255, 0, 0, 0.3);    /* as rgba values (CSS 3) Note: 0 <= a <= 1 */
    color: transparent;             /* equivalent to setting the alpha to 0 */
    color: hsl(0, 100%, 50%);       /* as hsl percentages (CSS 3) */
    color: hsla(0, 100%, 50%, 0.3); /* as hsl percentages with alpha */

    /* Borders */
    border-width:5px;
    border-style:solid;
    border-color:red;      /* similar to how background-color is set */
    border: 5px solid red; /* this is a short hand approach for the same */
    border-radius:20px;    /* this is a CSS3 property */

    /* Images as backgrounds of elements */
    background-image: url(/img-path/img.jpg); /* quotes inside url() optional */

    /* Fonts */
    font-family: Arial;
    /* if the font family name has a space, it must be quoted */
    font-family: "Courier New";
    /* if the first one is not found, the browser uses the next, and so on */
    font-family: "Courier New", Trebuchet, Arial, sans-serif;
}

/* Custom CSS properties using variables (CSS 3) */
:root {
   --main-bg-color: whitesmoke;
}
body {
   background-color: var(--main-bg-color)
}

/* Perfom a calculation (CSS 3) */
body {
   width: calc(100vw - 100px)
}

/* Nest style rule inside another (CSS 3) */
.main {
   .bgred { /* same as: .main .bgred { } */
      background: red;
   }
   & .bggreen { /* same as: .main .bggreen { } */
      background: green;
   }
   &.bgblue { /* (without space) same as: .main.bgblue { } */
      background: blue;
   }
}

/* Design responsive layout using flexbox (CSS 3) */
.container {
   display: flex;
   flex-direction: row;      /* in which direction stack the flex items */
   flex-wrap: wrap;          /* whether or not flex items should wrap */
   justify-content: center;  /* how to align flex items horizontally */
   align-items: center;      /* how to align flex items vertically */
}
Usage
Save a CSS stylesheet with the extension .css.

<!-- You need to include the css file in your page's <head>. This is the
     recommended method. Refer to http://stackoverflow.com/questions/8284365 -->
<link rel='stylesheet' type='text/css' href='path/to/style.css'>

<!-- You can also include some CSS inline in your markup. -->
<style>
   a { color: purple; }
</style>

<!-- Or directly set CSS properties on the element. -->
<div style="border: 1px solid red;">
</div>
Precedence or Cascade
An element may be targeted by multiple selectors and may have a property set on it in more than once. In these cases, one of the rules takes precedence over others. Rules with a more specific selector take precedence over a less specific one, and a rule occurring later in the stylesheet overwrites a previous one (which also means that if two different linked stylesheets contain rules for an element and if the rules are of the same specificity, then order of linking would take precedence and the sheet linked latest would govern styling) .

This process is called cascading, hence the name Cascading Style Sheets.

Given the following CSS:

/* A */
p.class1[attr='value']

/* B */
p.class1 { }

/* C */
p.class2 { }

/* D */
p { }

/* E */
p { property: value !important; }
and the following markup:

<p style='/*F*/ property:value;' class='class1 class2' attr='value'>
The precedence of style is as follows. Remember, the precedence is for each property, not for the entire block.

E has the highest precedence because of the keyword !important. It is recommended that you avoid its usage.
F is next, because it is an inline style.
A is next, because it is more “specific” than anything else. It has 3 specifiers: The name of the element p, its class class1, an attribute attr='value'.
C is next, even though it has the same specificity as B. This is because it appears after B.
B is next.
D is the last one.
Media Queries
CSS Media Queries are a feature in CSS 3 which allows you to specify when certain CSS rules should be applied, such as when printed, or when on a screen with certain dimensions or pixel density. They do not add to the selector’s specificity.

/* A rule that will be used on all devices */
h1 {
  font-size: 2em;
  color: white;
  background-color: black;
}

/* change the h1 to use less ink on a printer */
@media print {
  h1 {
    color: black;
    background-color: white;
  }
}

/* make the font bigger when shown on a screen at least 480px wide */
@media screen and (min-width: 480px) {
  h1 {
    font-size: 3em;
    font-weight: normal;
  }
}
Media queries can include these features: width, height, device-width, device-height, orientation, aspect-ratio, device-aspect-ratio, color, color-index, monochrome, resolution, scan, grid. Most of these features can be prefixed with min- or max-.

The resolution feature is not supported by older devices, instead use device-pixel-ratio.

Many smartphones and tablets will attempt to render the page as if it were on a desktop unless you provide a viewport meta-tag.

<head>
  <meta name="viewport" content="width=device-width; initial-scale=1.0">
</head>
Compatibility
Most of the features in CSS 2 (and many in CSS 3) are available across all browsers and devices. But it’s always good practice to check before using a new feature.
    """, 90),

    ("""
Money is a surprisingly complex subject.

People spend their lives seeking money, and in some ways it seems so straightforward, and yet what humanity has defined as money has changed significantly over the centuries.

How could something so simple and so universal, take so many different forms?

It’s an important question to ponder because we basically have four things we can do with our resources: consume, save, invest, or share.

Consume: When we consume, we meet our immediate needs and desires, including shelter, food, and entertainment.

Save: When we save, we store our resources in something that is safe, liquid, and portable, a.k.a. money. This serves as a low-risk battery of future resource consumption across time and space.

Invest: When we invest, we commit resources to a project that has a decent likelihood of multiplying our resources but also comes with a risk of losing them, by trying to provide some new value to ourselves or others. This serves as a higher-risk, less-liquid, and less-portable amplifier of future resource consumption potential compared to money. There are personal investments, like our own business or education, and there are external financial investments in companies or projects led by other people.

Share: When we share, or in other words give to charity and those in our community, we give some portion of our excess resources to those that we deem to be needing and deserving. In many ways, this can be considered a form of investment in the ongoing success and stability of our larger community, which is probably why we are wired to want to do it.

The majority of people in the world don’t invest in financial assets; they are still on the consumption stage (basic necessities and daily entertainment) or the saving stage (money and home equity), either due to income constraints, consumption excesses, or because they live in part of the world that doesn’t have well-developed capital markets. Many of them do, however, invest in expanding a self-owned business or in educating themselves and their children, meaning they invest in their personal lives, and they might share in their community as well, through religious institutions or secular initiatives.

Among the minority that do invest in financial assets, they are generally accustomed to the idea that investments change rapidly over time, and so they have to put a lot of thought into how they invest. They either figure out a strategy themselves and manage that, or they outsource that task to a specialist to do it for them to focus more on the skills that they earn the resources with in the first place.

However, depending on where they live in the world, people are not very accustomed to keeping track of the quality of money itself, or deciding which type of money to hold.

In developed countries in particular, people often just hold the currency of that country. In developing countries that tend to have a more recent and extreme history of currency devaluation, people often put more thought into what type of money they hold. They might try to minimize how much cash they hold and keep it in hard assets, or they might hold foreign currency, for example.

This article looks at the history of money, and examines this rather unusual period in time where we seem to be going through a gradual global transformation of what we define as money, comparable to the turning points of 1971-present (Petrodollar System), 1944-1971 (Bretton Woods System), the 1700s-1944 (Gold Standard System), and various commodity-money transition periods (pre-1700s). This type of occasion happens relatively rarely in history for any given society but has massive implications when it happens, so it’s worth being aware of.

If we condense those stages to the basics, the world has gone through three phases: commodity money, gold standard (the final form of commodity money), and fiat currency.

A fourth phase, digital money, is on the horizon. This includes private digital assets (e.g. bitcoin and stablecoins) and public digital currencies (e.g. central bank digital currencies) that can change how we do banking, and what economic tools policymakers have in terms of fiscal and monetary policy. These assets can be thought of as digital versions of gold, commodities, or fiat currency, but they also have their own unique aspects.

This article walks through the history of monetary transitions from the lenses of a few different schools of thought (often at odds with each other), and then examines the current and near-term situation as it pertains to money and how we might go about investing in it. Start from the beginning or jump to the chapter you want:

Chapter 1: Commodity Money
Chapter 2: Fiat Currency
Chapter 3: Digital Assets
Chapter 4: Final Thoughts
Some people whose work I’ve drawn from for this article, from the past and present, include Carl Menger, Warren Mosler, Friedrich Hayek, Satoshi Nakamoto, Adam Back, Saifdean Ammous, Vijay Boyapati, Stephanie Kelton, Ibn Battuta, Emil Sandstedt, Robert Breedlove, Ray Dalio, Alex Gladstein, Elizabeth Stark, Barry Eichengreen, Ross Stevens, Luke Gromen, Anita Posch, Jeff Booth, and Thomas Gresham.

Commodity Money

Money is not an invention of the state. It is not the product of a legislative act. Even the sanction of political authority is not necessary for its existence. Certain commodities came to be money quite naturally, as the result of economic relationships that were independent of the power of the state.

-Carl Menger, 1840-1921

Humans in tiny groups don’t need money; they can organize resources among themselves manually.

However, groups that reach the Dunbar number or larger usually start identifying and making use of some form of money, which gives them a more liquid, divisible, friction-minimized, and widely-accepted accounting unit for storing and exchanging value with people they don’t know.

The more complex an economy becomes, the greater the number of possible combinations of barter you can have between different types of goods and services providers, so the economy starts requiring some standard unit of account, or money.

Specifically, the society begins requiring something divisible and universally acceptable. An apple farmer, for example, that needs some tools (a blacksmith), meat (a cattle rancher), repair work (a carpenter), and medicine for her children (a doctor), can’t spend the time going around finding individuals that have what she needs, that also happen to want a ton of apples. Instead, she simply needs to be able to sell her highly seasonal apples for some unit, that she can use to save and buy all of those things with over time as she needs them.

Money, especially types of money that take work to produce, often seems arbitrary to outsiders of that culture. But that work ends up paying for itself many times over, because a standardized and credible medium of exchange and store of value makes all other economic transactions more efficient. The apple farmer doesn’t need to find a specific doctor who wants to buy a ton of apples for his expensive services right now.

A number of economists from multiple economic schools have pondered and formulated this concept, but commodity money as a topic tends to come up the most often by those in the school of Austrian Economics, founded by Carl Menger in the 1800s.

In this way of thinking, money should be divisible, portable, durable, fungible, verifiable, and scarce. It also usually (but not always) has some utility in its own right. Different types of money have different “scores” along those metrics.

Divisible means the money can be sub-divided into various sizes to take into account different sizes of purchases.
Portable means the money is easy to move across distances, which means it has to pack a lot of value into a small weight.
Durable means the money is easy to save across time; it does not rot or rust or break easily.
Fungible means that individual units of the money don’t differ significantly from each other, which allows for fast transactions.
Verifiable means that the seller of the goods or services for the money can check that the money is what it really appears to be.
Scarce means that the money supply does not change quickly, since a rapid change in supply would devalue existing units.
Utility means that the money is intrinsically desirable in some way; it can be consumed or has aesthetic value, for example.
Summing those attributes together, money is the “most salable good” available in a society, meaning it’s the good that is the most capable of being sold. Money is the good that is most universal, in the sense that people want it, or realize they can trade for it and then easily and reliably trade it for something else they do want.

Other definitions consider money to be “that which extinguishes debt”, but debt is generally denominated in units of whatever money is defined to be at the time the debt was issued. In other words, debt is typically denominated in units of the most salable good, rather than the most salable good being defined as what debt is denominated in. Indeed, however, part of the ongoing network effect of what sustains a fiat currency system is the large amount of debt in the economy that creates sustained ongoing demand for those currency units to service those debts.

Back in 1912, Mr. J.P. Morgan testified before Congress and is quoted as having said the famous line:

Gold is money. Everything else is credit.

In other words, although their terms often overlap, currency and money can be thought of as two different things for the purpose of discussion.

We can define currency as a liability of an institution, typically either a commercial bank or a central bank, that is used as a medium of exchange and unit of account. Physical paper dollars are a formal liability of the US Federal Reserve, for example, while consumer bank deposits are a formal liability of that particular commercial bank (which in turn hold their reserves at the Federal Reserve, and those are liabilities of the Federal Reserve as well).

In contrast to currency, we can define money as a liquid and fungible asset that is not also a liability. It’s something intrinsic, like gold. It’s recognized as a highly salable good in and of itself. In some eras, money was held by banks as a reserve asset in order to support the currency that they issue as liabilities. Unlike a dollar, which is an asset to you but a liability of some other entity, you can hold gold which is an asset to you and a liability to nobody else.

Under gold standard systems, currency represented a claim for money. The bank would pay the bearer on demand if they came to redeem their banknote paper currency for its pegged amount of gold.

Scarcity is often what determines the winner between two competing commodity monies. However, it’s not just about how rare the asset is. A good concept to be familiar with here is the stock-to-flow ratio, which measures how much supply there currently exists in the region or world (the stock) divided by how much new supply can be produced in a year (the flow).

For example, gold miners historically add about 1.5% new gold to the estimated existing above-ground gold supply each year, and the vast majority of gold does not get consumed; it gets re-melted and stored in various shapes and places.

Gold Supply Growth

Chart Source: NYDIG

This gives gold a stock to flow ratio of 100/1.5 = 67 on average, which is the highest stock-to-flow ratio of any commodity. The world collectively owns 67 years worth of average annual production, based on World Gold Council estimates. Let’s call it about 60 or 70 since this isn’t exact.

If a money (the most salable good) is easy to create more of, then any rational economic actor would just go out and create more money for herself, diluting the whole supply of it. If an asset has a monetary premium on top of its pure utility value, then it’s strongly incentivizing market participants to try to make more of it, and so only the forms of money that are the most resistant to debasement can withstand this challenge.

On the other hand, if a commodity is so rare that barely anyone has it, then it may be extremely valuable if it has utility, but it has little useful role as money. It’s not liquid and widely-held, and so the frictional costs of buying and selling it are higher. Certain atomic elements like rhodium for example are rarer than gold, but have low stock-to-flow ratios because they are consumed by industry as quickly as they are mined. A rhodium coin or bar can be purchased as a niche collectible or store of value, but it’s not useful as societal money.

So, a long-lasting high stock-to-flow ratio tends to be the best way to measure scarcity for something to be considered money, along with the other attributes on the list above, rather than absolute rarity. A commodity with a high stock-to-flow ratio is hard to produce, and yet a lot of it has already been produced and is widely distributed and held, because it either isn’t rapidly consumed or isn’t consumed at all. That’s a relatively uncommon set of attributes.

Throughout history various stones, beads, feathers, shells, salt, furs, fabrics, sugar, coconuts, livestock, copper, silver, gold, and other things have served as money. They each have different scores for the various attributes of money, and tend to have certain strengths and weaknesses.

Salt for example is divisible, durable, verifiable, fungible, and has important utility, but is not very valuable per unit of weight and not very rare, so doesn’t score very well for portability and scarcity.

Gold is the best among just about every attribute, and is the commodity with by far the highest stock-to-flow ratio. The one weakness it has compared to other commodities is that it’s not very divisible. Even a small gold coin is more valuable than most purchases, and is worth as much as most people make in a week of labor. It’s the king of commodities.

For a large portion of human history, silver has actually been the winner in terms of usage. It has the second-best score after gold across the board for most attributes, and the second highest stock-to-flow ratio, but beats gold in terms of divisibility, since small silver coins can be used for daily transactions. It’s the queen of commodities. And in chess, the king may be the most important piece, but the queen is the most useful piece.

In other words, gold was often held by the wealthy as a long-term store (and display) of value, and as a medium of exchange for very large purchases, while silver was the more tactical money, used as a medium of exchange and store of value by far more people. A bimetallic money system was common in many regions of the world for that reason until relatively recently, despite the challenges that come with that.

The scarcity of some of the other commodities have more specific weaknesses as it relates to technology. Here are two examples:

Rai Stones

Inhabitants of a south-Pacific island called Yap used enormous stones as money. These “rai stones” or “fei stones” as they were called were circular discs of stone with a hole in the center, and came in various sizes, ranging from a few inches in diameter to over ten feet in diameter. Many of them were at least a couple feet across, and thus weighed hundreds of pounds. The biggest were over ten feet across and weighed several thousands of pounds.

Interestingly, I’ve seen this example used by both an Austrian economist (Saifedean Ammous) and an MMT economist (Warren Mosler). The reason that’s interesting is because those two schools of thought have very different conceptions of what money is.

Anyway, what made these stones unique was that they were made from a special type of limestone that was not found in abundance on the island. Yap islanders would travel 250 miles to a neighboring island called Palau to quarry the limestone and bring it back to Yap.

They would send a team of many people to that far island, quarry the rock in giant slabs, and bring it back on wooden boats. Imagine bringing a multi-thousand pound stone across 250 miles of open ocean on a wooden boat. People died in this process over the years.

Once made into rai stones on Yap, the big ones wouldn’t move. This is a small island, and all of the stones were catalogued by oral tradition. An owner could trade one for some other important goods and services, and rather than moving the stone, this would take the form of announcing to the community that this other person owned the stone now.

In that sense, rai stones were a ledger system, not that different than our current monetary system. The ledger keeps track of who owns what, and this particular ledger happened to be orally distributed, which of course can only work in a small geography.

By the time this was documented by Europeans, there were thousands of rai stones on Yap, representing centuries of quarrying, transporting, and making them. Rai stones thus had a high stock-to-flow ratio, which is a main reason for why they could be used as money.

In the late 1800s, an Irishman named David O’Keefe came across the island and figured this out. And, with his better technology, he could easily quarry stone from Palau and bring it to Yap to make rai stones, and thus could become the richest man on the island, able to get locals to work for him and trade him various goods.

As the Irishman got to know Yap better, he realized that there was one commodity, and only one, that the local people coveted—the “stone money” for which the island was renowned and that was used in almost all high-value transactions on Yap. These coins were quarried from aragonite, a special sort of limestone that glistens in the light and was valuable because it was not found on the island. O’Keefe’s genius was to recognize that, by importing the stones for his new friends, he could exchange them for labor on Yap’s coconut plantations. The Yapese were not much interested in sweating for the trader’s trinkets that were common currency elsewhere in the Pacific (nor should they have been, a visitor conceded, when “all food, drink and clothing is readily available, so there is no barter and no debt” ), but they would work like demons for stone money.

-Smithsonian Magazine, “David O’Keefe: the King of Hard Currency”

In essence, better technology eventually broke the stock-to-flow ratio of rai stones by dramatically increasing the flow. Foreigners with more advanced technology could bring any number of them to the island, become the wealthiest people on the island, and therefore increase the supply and reduce the value of the stones over time.

However, locals were smart too, and they eventually mitigated that process. They began to assign more value to older stones (ones that were verifiably quarried by hand decades or centuries ago), because they exclude the new abundant stones by definition and thus maintain their scarcity. Nonetheless, the writing was on the wall; this wasn’t a great system anymore.

Things then took a darker turn. As described in that Smithsonian piece:

With O’Keefe dead and the Germans thoroughly entrenched, things began to go badly for the Yapese after 1901. The new rulers conscripted the islanders to dig a canal across the archipelago, and, when the Yapese proved unwilling, began commandeering their stone money, defacing the coins with black painted crosses and telling their subjects that they could only be redeemed through labor. Worst of all, the Germans introduced a law forbidding the Yapese from traveling more than 200 miles from their island. This put an immediate halt to the quarrying of fei , though the currency continued to be used even after the islands were seized by the Japanese, and then occupied by the United States in 1945.

Many of the stones were taken and used as makeshift anchors or building materials during World War II by the Japanese, reducing the number of stones on the island.

Rai stones were a notable form of money while they lasted because they had no utility. They were a way to display and record wealth, and little else. In essence, it was one of the earliest versions of a public ledger, since the stones didn’t move and only oral records (or later, physical marks by Germans) dictated who owned them.

African Beads

As another example, trade beads were used in parts of west Africa as money for many centuries, stretching back at least to the 1300s and prior as documented by ancient travelers at the time, as recorded by Emil Sandstedt. Various rare materials could be used, such as coral, amber, and glass. Venetian glass beads gradually made their way across the Sahara over time as well.

To quote Ibn Battatu, from his travels in the 14th century (from Sandstedt’s article):

A traveler in this country carries no provisions, whether plain food or seasonings, and neither gold nor silver. He takes nothing but pieces of salt and glass ornaments, which the people call beads, and some aromatic goods.

These were pastoral societies, often on the move, and the ability to wear your money in the form of strands of beautiful beads was useful. These beads maintained a high stock-to-flow ratio because they were kept and traded as money, while being hard to produce with their level of technology.

Eventually, Europeans began traveling and accessing west Africa more frequently, noticed this usage of trade beads, and exploited them. Europeans had glass-making technology, and could produce beautiful beads with modest effort. So, they could trade tons of these beads for commodities and other goods (and unfortunately for human slaves as well).

Due to this technological asymmetry, they devalued these glass beads by increasing their supply throughout west Africa, and extracted a lot of value from those societies in the process. Locals kept trading scarce local “goods”, ranging from important commodities to invaluable human lives, for glass beads that had far more abundance than they realized. As a result, they traded away their real valuables for fake valuables. Picking the wrong type of money can have dire consequences.

It wasn’t as easy as one might suspect for the Europeans to accomplish, however, because the Africans’ preferences for certain types of beads would change over time, and different tribes had different preferences. This seemed to be similar to the rai stones, where once new supplies of rai stones started coming in faster due to European technology, the people of Yap began wisely valuing old ones more than new ones. Essentially, the west African tastes seemed to change base on aesthetics/fashion and on scarcity. This, however, also gave that form of money a low score for fungibility, which reduced its reliability as money even for the pastoral west Africans who were using them.

Like rai stones ultimately, trade beads couldn’t maintain their high stock-to-flow ratio in the face of technological progress, and therefore eventually were displaced as money.

Japanese Invasion Money

Although it’s not a commodity money, the Japanese Empire used the same tactic on southeast Asians as the Europeans did on Africans.

During World War II, when the Japanese Empire invaded regions throughout Asia, they would confiscate hard currency from the locals and issue their own paper currency in its place, which is referred to as “invasion money“. These conquered peoples would be forced to save and use a currency that had no backing and ultimately lost all of its value over time, and this was a way for Japan to extract their savings while maintaining a temporary unit of account in those regions.

To a less extreme extent, this is what happens throughout many developing countries today; people constantly save in their local currency that, every generation or so, gets dramatically debased.

Other Types of Commodity Money

Emil Sandstedt’s book, Money Dethroned: A Historical Journey, catalogs the various types of money used over the past thousand years or so. The book often references the writings of Ibn Battuta, the 14th century Moroccan explorer across multiple continents, who may have been the furthest traveler of pre-modern times.

Central Asians at the time of Battuta, as a nomadic culture, used livestock as money. The unit of account was a sheep, and larger types of livestock would be worth a certain multiple of sheep. As they settled into towns, however, the storage costs of livestock became too high. They eat a lot, they need space, and they’re messy.

Russians had a history of using furs as a monetary good. There are even referenced instances of using a bank-like entity that would hold furs and issue paper claims against them. Parts of the American frontier later turned to furs as money for brief periods of time as well.

Seashells were used by a few different regions as money, and in some sense were like gold and beads in the sense that they were for both money and fashion.

In addition to beads, certain regions in Africa used fine fabric as money. Sometimes it wasn’t even cut into usable shapes or meant to ever be worn; it would be held and exchanged purely for its monetary value as a salable good that could be stored for quite a while.

Another great example is the idea of using blocks of high-quality Parmesan cheese as bank collateral. Since Parmesan cheese requires 18-36 months to mature, and is relatively expensive per unit of weight in block form, niche banks in Italy are able to accept it as collateral, as a form of attractive commodity money:

MONTECAVOLO, ITALY (Bloomberg News) — The vaults of the regional bank Credito Emiliano hold a pungent gold prized by gourmands around the world — 17,000 tons of parmesan cheese.

The bank accepts parmesan as collateral for loans, helping it to keep financing cheese makers in northern Italy even during the worst recession since World War II. Credito Emiliano’s two climate-controlled warehouses hold about 440,000 wheels worth €132 million, or $187.5 million.

“This mechanism is our life blood,” said Giuseppe Montanari, a cheese producer and dealer who uses the loans to buy milk. “It’s a great way to finance our expenses at convenient rates, and the bank doesn’t risk much because they can always sell the cheese.”

The Gold Standard

After thousands of years, two commodities beat all of the others in terms of maintaining their monetary attributes across multiple geographies; gold and silver. Only they were able to retain a high enough stock-to-flow ratio to serve as money, despite civilizations constantly improving their technological capabilities throughout the world over the ages.

Humans figured out how to make or acquire basically all of the beads, shells, stones, feathers, salt, furs, livestock, and industrial metals we need with our improved tools, and so we reduced their stock-to-flow ratios and they all fell out of use as money.

However, despite all of our technological progress, we still can’t reduce the stock-to-flow ratios of gold and silver by any meaningful degree, except for rare instances in which the developed world found new continents to draw from. Gold has maintained a stock-to-flow ratio averaging between 50 and 100 throughout modern history, meaning we can’t increase the existing supply by more than about 2% per year, even when the price goes up more than 10x in a decade. Silver generally has a stock-to-flow ratio of 10 to 20 or more.

Most other commodities are below 1 for the stock-to-flow ratio, or are very flexible. Even the other rare elements, like platinum and rhodium, have very low stock-to-flow ratios due to how rapidly they are consumed by industry.

We’ve gotten better at mining gold with new technologies, but it’s inherently rare and we’ve already tapped into the “easy” surface deposits. Only the deep and hard-to-reach deposits remain, which acts like an ongoing difficulty adjustment against our technological progress. One day we could eventually break this cycle with drone-based asteroid mining or ocean floor mining or something crazy like that, but until that day (if it ever comes), gold retains its high stock-to-flow ratio. Those environments are so inhospitable that the expense to acquire gold there would likely be extraordinarily high.

Basically, whenever any commodity money came into contact with gold and silver as money, it was always gold and silver that won. Between those two finalists, gold eventually beat silver for more monetary use-cases, particularly in the 19th century.

Improvements in communication and custody services eventually led to the abstraction of gold. People could deposit their gold into banks and receive paper credit representing redeemable claims on that gold. Banks, knowing that not everyone would redeem their gold at once, went ahead and issued more claims than the gold they held, beginning the practice of fractional reserve banking. The banking system then consolidated into central banking over time in various countries, with nationwide slips of paper representing a claim to a certain amount of gold.

Barry Eichengreen’s explanation for why gold beat silver, in his book Globalizing Capital: A History of the International Monetary System, is that the gold standard won out over the bimetallic standard mostly by accident. In 1717, England’s Master of the Mint (who was none other than Sir Isaac Newton himself) set the official ratio of gold and silver as it relates to money, and according to Eichengreen he set silver too low compared to gold. As a result, most silver coins went out of circulation (as they were hoarded rather than spent, as per Gresham’s law).

Then, with the UK rising to dominance as the strongest empire of the era, the network effect of the gold standard, rather than the silver standard, spread around the world, with the vast majority of countries putting their currencies in a gold standard. Countries that stuck to the silver standard for too long, like India and China, saw their currency weaken as demand for the metal dropped in North America and Europe, resulting in negative economic consequences.

On the other hand, Saifadean Ammous, in his book The Bitcoin Standard, focuses on the improved divisibility of gold due to banking technology. As previously mentioned, gold scores equal or higher than silver in most of the attributes of money, except for divisibility. Silver is better than gold for divisibility, which made silver the more “day to day” money for thousands of years while gold was best left for kings and merchants to keep in their vaults or use as ornamentation, which are stores and displays of value respectively.

However, the technology of paper banknotes in various denominations backed by gold improved gold’s divisibility. And then, in addition to exchanging paper, we could eventually “send” money over telecommunications lines to other parts of the world, using banks and their ledgers as custodial intermediaries. This was the gold standard- the backing of paper currencies and financial communication systems with gold. There was less reason to use silver at that point, with gold being the much scarcer metal, and now basically just as divisible and even more portable thanks to the paper/telco abstraction.

I think there is an element of truth in both explanations, although I consider the explanation of Ammous to be more complete, starting with a deeper axiom regarding the nature of money itself. Banknotes made gold more divisible and thus the harder money won out over time, but network effects from political decisions can impact the timing of these sorts of changes.

Central banks around the world still hold gold in their vaults, and many of them still buy more gold each year to this day as part of their foreign-exchange reserves. It’s classified as a tier one asset in the global banking system, under modern banking regulations. Thus, although government-issued currency is no longer backed by a certain amount of gold, it remains an indirect and important piece of the global monetary system as a reserve asset. There is so far no better naturally-occurring commodity to replace it.

Gold used to trade at a 10x to 20x multiple of silver’s value for thousands of years in multiple different geographies. Over the past century, however, the gold-to-silver price ratio has averaged over 50x. Silver seems to have structurally lost a lot of its historical monetary premium relative to gold over the past century. Chart via Longtermtrends.net:

Gold Silver Ratio

If you prefer listening to reading for this section, I had a February 2022 discussion with Stig Brodersen about the history of gold and commodities.

Fiat Currency

Historically, a number of cultures have attempted periods of paper currency, issued by the government and backed by nothing.

Often it was the result of currency that was once backed (a gold standard or silver standard), but the government created too much of the paper due to war or other issues, and had to default on the metal backing by eliminating its ability to be converted back into the metal upon request. In that sense, currency devaluation becomes a form of tax and/or wealth confiscation. The public holds their savings in the paper currency, and then the rug is pulled out from under them.

The general argument for why fiat currencies exist, is that most governments, if possible, do not want to be constrained by gold or other scarce monies, and instead want to have more flexibility with their spending.

The earliest identified use of paper currency was in China over a thousand years ago, which makes sense considering that paper was invented in that region. They eventually shifted towards government monopoly on paper currency, and combined with an elimination of its ability to be converted back into silver, resulted in the first fiat currency, along with the inflation that comes with that. It didn’t last very long.

Fiat currency is interesting, because unlike the history of commodity money, it’s a step down in terms of scarcity. Gold beat out all of the other commodity monies over centuries of globalization and technological development, and then gold itself was defeated by… pieces of paper?

This is generally attributed to technology and government power. As clans became kingdoms, and as kingdoms became nation states, along with the creation of banking systems and improvements in communication systems, governments could become a larger part of everyday life. Once gold became sufficiently centralized in the vaults of banks and central banks, and paper claims were issued against it, the only remaining step was to end the redeemability of that paper and enforce its continued usage through legal obligation.

Debasing Currency and Empowering Wars

Currency debasement often happened gradually under metallic and bimetallic currency regimes, with history of it going back three or four thousand years. It took the form of reducing the amount of the valuable metal (such as gold or silver) and either adding base metal or putting decorative holes through the center of it to reduce the weight.

In other words, a ruler often found himself faced with budget deficits, and having to make the difficult choice between cutting spending or raising taxes. Finding both to be politically challenging, he would sometimes resort to keeping taxes the same, diluting the content of gold or silver in the coins, and spending more coins with less precious metal in each coin, while expecting it to still be treated with the same purchasing power per coin.

For example, a king can collect a 1,000 gold coins in taxes, melt them down and make new coins that are each 90% gold (with the other 10% made from some cheap filler metal), and spend 1,111 gold coins back into the economy with the same amount of gold. They do look pretty similar to most people, but some discerning people will notice. Years later, if that’s not enough, he could re-melt them and make them 80% gold, and spend 1,250 of them into the economy…

At first, these slightly-debased coins would be treated as how they were before, but as the coins are increasingly debased, it would become obvious. Peoples’ savings would decline in value, as they found over time that their stash of gold and silver was only fractional gold and silver. Foreign merchants in particular would be quick to demand more of these debased gold coins in exchange for their goods and services.

Gold-backed paper currencies and fiat currencies are the modern version of that, and so the debasement can happen much faster.

At first, fiat currencies were created temporarily, in times of war. After the shift from commodity money to gold-backed paper, the gold-backing would be briefly suspended as an emergency action for a number of years, and then re-instated (usually with a significant devaluation, to a lower amount of gold per unit of currency, since a lot of currency was issued during the emergency period).

This is a faster and more efficient way to devalue a currency than to actually debase the metal. The government doesn’t have to collect everyone’s coins and re-melt them. Instead, everybody is holding paper money that they trust to be redeemable for a certain amount of gold, and the government can break that trust, suspend that redeemability, print a ton of paper money, and then re-peg that paper money such that each unit of paper currency is redeemable for a much smaller amount of gold, before people realize what is happening to their savings.

That method instantly debases peoples’ money while they continue to hold it, and can be done overnight with the stroke of a pen.

Throughout the 20th century, this tactic spread around the world like a virus. Prior to paper currencies, governments would run out of fighting capability if they ran low on gold. Governments would use up their gold reserves and raise additional war taxes, but there were limits in terms of how much gold they had and how much they could realistically tax for unpopular wars before the population would rebel. However, by having all of their citizens on a gold-backed paper currency, they could devalue everyone’s savings for the war without an official tax, by printing a lot of money, spending it into the economy, and then eliminating or reducing the gold peg before people knew what was happening to their money.

This allowed governments to fight much larger wars by extracting more savings from their citizens, which led their international opponents to debase their currencies with similar tactics as well if they wanted to win.

Ironically, the fact that fiat currencies have no cost to produce, is what gave them the biggest cost of all.

Bretton Woods and the Petrodollar

After World War I, and throughout the tariff wars and World War II period thereafter, many countries went off the gold standard or devalued their currencies relative to gold.

John Maynard Keynes, the famous economist, said in 1924:

In truth, the gold standard is already a barbarous relic.

By 1934, gold was made illegal to own. It was punishable by up to 10 years in prison for Americans to own it. The dollar was no longer redeemable for gold by American citizens, although it was still redeemable for official foreign creditors, which was an important part of maintaining the dollar’s credibility.

Gold Confiscation Poster

Shortly after Americans were forced to sell their gold to the government in exchange for dollars, the dollar was devalued relative to gold, which benefited the government at the expense of those who were forced to sell it.

It remained illegal for Americans to own gold for about four decades until the mid-1970s. Interestingly enough, that overlapped quite cleanly with the period where US Treasuries underperformed inflation. Basically, the main release valve that people could turn to instead of cash or Treasuries as savings assets, was made illegal to them:

Gold Outlawed

It’s rather ironic- gold was a “barbarous relic” and yet apparently had to be confiscated and pushed out of use by the threat of imprisonment, and hoarded only by the government during a period of intentional currency devaluation. If it were truly such a relic, it would have fallen out of usage on its own and the government would have had little need to own any.

Making gold illegal to own was hard to enforce though. There were not many prosecutions for it, and it’s not as though authorities went door-to-door looking for it.

By 1944 towards the end of World War II after most currencies were sharply devalued, the Bretton Woods agreement was reached. Most countries pegged their currency to the dollar, and the United States dollar remained pegged to gold (but only redeemable to large foreign creditors, not American citizens). By extension, a pseudo gold standard was temporarily re-established.

This lasted only 27 years until 1971, when the United States no longer had enough gold to maintain redemption for its dollars, and thus ended the gold standard for itself and most of the world. There were too many dollar claims compared to how much gold the US had:

Dollar Crisis Bretton Woods Failure

Chart Source: BIS Working Papers No 684

The Bretton Woods system was poorly-constructed from the beginning, because domestic and foreign banks could lend dollars into existence without having to maintain a certain amount of gold to back those dollars. The mechanism for dollar creation and gold were completely decoupled from each other, in other words, and so it was inevitable that the quantity of dollars in existence would quickly outpace how much gold the US Treasury had in its vaults. As the amount of dollars multiplied and the amount of available gold did not, any smart foreign creditor would begin redeeming dollars for gold and draining the Treasury’s vaults. The Treasury would be quickly drained of its gold until they either sharply devalued the dollar peg or ended the peg altogether, which they did.

Since that time, over 50 years now, virtually all countries in the world have been on a fiat currency system, which is the first time in history this has happened. Switzerland was an exception that kept their gold standard until 1999, but for most countries it has been over 50 years since they were on it.

However, the US dollar still has a vestige of commodity-backing, which is part of what kept this system together for so long. In the 1970s, the US made a deal with Saudi Arabia and other OPEC countries to only sell their oil in dollars, regardless of which country was buying. In return, the US would provide military protection and trade deals. And thus the petrodollar system was born. We’ve had to deal with the consequences of this awkward relationship ever since.

While the dollar was not pegged to any specific price of oil in this system, this petrodollar system made it so that any country in the world that needed to import oil, needed dollars to do so. Thus, universal demand for dollars was established, as long as the US had enough military might and influence in the Middle East to maintain the agreement with the oil exporting nations.

Other countries continued to issue their own currencies but held gold, dollars (mainly in the form of US Treasuries), and other foreign currency assets as reserves to back up their currencies. Most of their currencies were not pegged to any specific dollar, oil, or gold value during this time, but having a large reserve that they could use to actively maintain the strength of their currency was a key part of why global creditors would accept their currency.

The biggest benefit from the petrodollar system, as analyst Luke Gromen has argued, is that it contributed to the US’s Cold War victory over the Soviet Union during the 1970s and 1980s. The petrodollar agreement and associated military buildup to enforce it was a strong chess move by the US to gain influence over the Middle East and its resources. However, Gromen also argues that when the Soviet Union fell in the early 1990s, the US should have pivoted and given up this system to avoid ongoing structural trade deficits, but did not, and so its industrial base was aggressively hollowed out. Since then, China and other countries have used the system against the US, and the US also bled out tremendous resources trying to maintain its hegemony in the Middle East with its wars in Afghanistan and Iraq.

An international gold standard looks like this, with each major country pegging its own currency to a fixed amount of gold and holding gold in reserve, for which it was redeemable to its citizens and foreign creditors:

Gold Peg Chart

The Bretton Woods pseudo gold standard involved the dollar being backed by gold, but only redeemable to foreign creditors in limited amounts. Foreign currencies pegged themselves to the dollar, and held dollars/Treasuries and gold in reserve:

Bretton Woods Chart

The petrodollar system made it so that only dollars could buy oil imports around the world, and so countries globally hold a combination of dollars, gold, and other major currencies as reserves, with an emphasis on dollars. If countries want to strengthen their currencies, they can sell some reserves and buy back their own currency. If countries want to weaken their currencies, they can print more of their currency and buy more reserve assets.

Petrodollar Chart

Over time, that demand for dollars was broadened via trade and debt. If two countries trade goods or services, they often do so in dollars. When loans are made internationally, they are often done so in dollars, and the world now has over $13 trillion in dollar-denominated debt, owed to all sorts of places including lenders in Europe and China. All of that dollar-denominated debt represents additional demand for dollars, since dollars are required to service that debt. Basically, the petrodollar deal helped initiate and maintain the network effect at a critical time, until it became rather self-sustaining.

This system gives the United States considerable geopolitical influence, because it can sanction any country and cut it off from the dollar-based system.

One of the key flaws of the petrodollar system, however, is that all of this demand for the dollar makes US exports more expensive (less competitive) and makes imports less expensive, and so the US began running structural trade deficits once we established the system, totaling over $14 trillion in cumulative deficits as of this writing. From 1944-1971 the US drew down its gold reserves in order to maintain the Bretton Woods dollar system, whereas from 1974-present, the US instead drew down its industrial base to maintain the petrodollar system.

US Trade Balance

Chart Source: Trading Economics

As the FT described in a clever article back in 2019, this petrodollar system ironically gave the United States a form of Dutch Disease. For those who aren’t familiar with the term, Investopedia has a good article on Dutch Disease. Here’s a summary:

The term Dutch disease was coined by The Economist magazine in 1977 when the publication analyzed a crisis that occurred in the Netherlands after the discovery of vast natural gas deposits in the North Sea in 1959. The newfound wealth and massive exports of oil caused the value of the Dutch guilder to rise sharply, making Dutch exports of all non-oil products less competitive on the world market. Unemployment rose from 1.1% to 5.1%, and capital investment in the country dropped.

Dutch disease became widely used in economic circles as a shorthand way of describing the paradoxical situation in which seemingly good news, such as the discovery of large oil reserves, negatively impacts a country’s broader economy.

As the FT argues (correctly in my view), making virtually all global oil priced in dollars basically gave the United States a form of Dutch Disease. Except instead of finding oil or gas, we engineered a system so that every country needs dollars, and so we need to export a lot of dollars via a structural trade deficit (and thus, the dollar as a global reserve asset basically served the role of a big oil/gas discovery).

This system, much like the Netherlands’ natural gas discovery, kept US currency persistently stronger at any given time than it should be on a trade balance basis. This made actual US exports rather uncompetitive, boosted our import power (especially for the upper classes) and prevented the US balance of trade from ever normalizing for decades.

Japan and Germany became major exporters at our expense, and for example, their auto industries thrived globally while the US auto industry faltered and led to the creation of the “Rust Belt” across the midwestern and northeast part of the country. And then China grew and did the same thing to the United States over the past twenty years; they ate our manufacturing lunch. Meanwhile, Taiwan and South Korea became the hubs of the global semiconductor market, rather than the United States.

That petrodollar system is starting to crack under its own weight, as trade deficits have collected into a massively negative net international investment position for the US, and the US has more wealth concentration than the rest of the developed world because we hollowed out a lot of our blue collar workforce specifically. This causes rising political tensions and desires (so far unsuccessful) to reduce the trade deficit and rebuild our industrial base. Foreigners take their persistent dollar surpluses and buy productive US assets with them like stocks, real estate, and land. In other words, the US sells its appreciating financial assets in exchange for depreciating consumer goods:

US Net International Investment Position

My article on the petrodollar system went into additional detail on the history of the US dollar as the global reserve currency, from the pre-Bretton Woods era to the petrodollar system.

Potential Post-Petrodollar Designs

There are proposals by policymakers and analysts to rebalance the global payments system, and the changing nature of geopolitics is pointing in that direction as well.

For example, Russia began pricing its oil partly in euros over the past few years, and China has put considerable work into launching a digital currency that may expand their global reach, at least with some of their most dependent trade partners. The United States is no longer the biggest commodity importer, and its share of global GDP continues to decrease, which makes the existing petrodollar system less tenable.

If several large fiat currencies can be used to buy oil, then the model looks more like this (and many tertiary currencies would manage themselves relative to these main currencies that have the scale and influence to buy oil and other foreign goods):

Decentralization Chart

If a major scarce neutral reserve asset (e.g. gold or bitcoin or digital SDRs or something along these lines, depending on your conception of where trends are going over the next decade or two) is used as a globally-recognized form of money, then a decentralized model can also look like this:

Neutral Reserve Asset Chart

Overall, it’s clear that the trend in global payments is towards digitization and decentralization away from one single country’s currency, but it’s unclear precisely how the next system will turn out and on what timeline it will change. It continues to be a subject that I analyze closely for news and data.

Price Inflation from a Negative Baseline

The long arc of human history is deflationary. As our technology improves over time, we become more productive, which reduces the labor/resource cost of most goods and services. This is particularly true over the past couple centuries as humanity exponentially tapped into dense forms of energy. Prior to that, our rate of productivity growth was much slower.

For an example of productivity, people used to farm by hand. By harnessing the utility of work horses and simple equipment, it empowered one person to do the work of several people. Then, the invention of the tractor and similar advanced equipment empowered one person to do the work of ten or more people. As tractor technology got bigger and better, this figure probably jumped to thirty or more people. And then, we can imagine a fleet of self-driving farming equipment allowing one person to do the work of a hundred people. As a result, a smaller and smaller percentage of the population needs to work in agriculture in order to feed the whole population. This makes food less expensive and frees up everyone else for other productive pursuits.

Gold has historically appreciated against most other commodities over time, like an upward sine wave. Alternatively, we can say that most commodities depreciated in price against gold like a downward sine wave. For example, there are inflationary cycles where copper increases in price compared to gold, but over multiple decades of cycles, gold has steadily appreciated against copper. For agricultural commodities that are less scarce, the trend is even stronger.

Here’s a chart of the copper-to-gold ratio showing its structural decline and cyclical exceptions since 1850, for example:

Copper Gold Ratio

Chart Source: Long Term Trends

And here’s wheat priced in gold since 1910:

Gold Wheat Ratio

Chart Source: Priced in Gold

This is because over time, our advancing technology has made us more efficient at harvesting those other commodities. However, gold’s extreme scarcity and rather strict stock-to-flow ratio of over 50x has made it so that our technology advancements in finding and mining gold are offset by the fact that we’ve already mined the “easy” gold deposits and the remaining deposits are getting deeper and harder. We never truly get more efficient at retrieving gold, in that sense. It’s a built-in ongoing difficulty adjustment.

During the late 1800s and early 1900s USA, which is when the country became a rising power globally, the country was on a gold standard and in a period of structural deflation. Prices of most things went down because land was abundant and huge advancements in technology during the industrial age made people far more productive.

An even more extreme example would be television prices over the past five decades. Moore’s law, industrial automation, and labor offshoring has made televisions exponentially better and cheaper over time, especially when priced in gold. Similarly, cell phones decades ago were very large, basic, and expensive toys for the wealthy. Now, many people in the poorest regions of the world have powerful smartphones as a normal course of life. They have supercomputers in their pockets.

Overall, we can say that the baseline inflation rate is some negative number (aka deflation), and how negative it is at any given time depends on the pace of technological advancement. Baseline inflation only becomes a positive number if we are backtracking in some way, and thus encountering more scarcity and less abundance. This could be due to malinvestment or war, for example.

By holding the most salable good (such as gold, historically), your purchasing power gradually appreciates over time because the labor/resource cost of most other things goes down whereas that salable good retains most or all of its scarcity and value. The vast majority of commodities, products, and services structurally decrease in price gradually relative to your strong store of value.

One way to measure this is by looking at the broad money supply per capita over time relative to the consumer price index. Here’s a chart of their 5-year rolling average growth rates for the United Kingdom:

UK Inflation

We can see that there is usually a positive gap between broad money supply growth per capita, and consumer prices. Broad money supply per capita increased by an average of 5.3% per year during this 150+ year period, while a basket of goods and services increased by an average of only 3.1%. In other words, monetary inflation is usually a bit faster than price inflation.

In a very rough sense by this way of looking at it, real productivity growth was about 2.2% per year, which is the difference between these figures. What this means is that in any given year, the resource/labor costs of a broad basket of goods and services goes down by an average of 2.2% due to technological progress, but the amount of money that people have goes up by 5.3%, and as such, actual prices go up by only 3.1%.

So, price inflation is not 3.1% from a baseline of zero; it’s 5.3% from a baseline of -2.2%. Actual resource costs for goods and services go down most years rather than stay flat, but due to our inflationary monetary framework, they go up in price anyway.

The reason this is only a rough measure is because 1) the CPI basket changes over time and may not be fully representative and 2) money supply can become more concentrated or less concentrated over time and thus does not always reflect the buying power of the median person. There is no way to directly measure technological deflation; it can only be estimated.

Another way to check this is to simply see to what extent gold appreciated in price against the British pound, and the answer is about 4.0% per year over this same 150+ year time period. Gold appreciated in price faster than the CPI basket inflation rate by about 0.9% per year (the difference between 4.0% and 3.1%, which compounds quite a bit over a century), and can buy you a bit more copper, oil, wheat, or many other goods and services than it could 50, 100, or 150 years ago, unlike the British pound which buys you a lot less than it used to. Higher-quality and scarcer goods like meat have roughly kept up with the price of gold (although you can’t store meat for very long), and select few assets like the absolute best/scarcest UK property locations may have appreciated a bit faster than gold (although they required continued maintenance costs along the way which makes up for that difference).

The takeaway from this section is that the growth in the broad money supply per capita is the “true” inflation rate. However, the baseline that we measure it against is not zero; it’s a mildly negative number which we can’t precisely measure, but that we can estimate and infer, that represents ongoing increases in productivity due to technology. Prices of most things stay relatively stable or preferably keep going down as priced in the most salable good (such as gold, historically) over the long run, but go up in most years when measured in a depreciating and weaker unit of account such as the British pound.

The MMT Description of Fiat Currency

Some economists disagree with the commodity view of money, and argue that money originates with the government. This is called Chartalism, and its origins go back more than a century.

Decades ago, Warren Mosler and others resurfaced this idea, into what is now popularly known as Modern Monetary Theory or MMT.

I have often felt that Mosler describes the case for that school of thought well. He doesn’t sugar-coat things, and instead speaks very directly:

Start with the government trying to provision itself and how does it do it. There are different ways to do it throughout history. One way is just to go out and take slaves. Another way the British did is they provisioned their navy by going to bars late at night and dragging them onto ships. It’s called impressing sailors.

We pretend to be more civilized as I like to say, and we use a monetary system. So how does a government do it? Clean sheet of paper, what you do, is you establish a tax that is payable in something that people don’t have. So what you want to do is transfer resources from the private sector to the public sector. You want people who are out there doing whatever they are doing, to suddenly be working for the government. You need soldiers, you need police, you need health workers, you need people in education. How do you get these people out of the private sector and into the public sector?

First thing you do is you levy a tax. You need a tax liability, and it has to be coercive. And for this example I’ll use a property tax. You put a tax on everybody’s house, and you make it payable in your new unit of account, your new unit, your thing, your tax credit, the thing that is used to pay the tax. The dollar, the yen, or the euro- they are all tax credits.

What has happened is, you’ve created sellers of real goods and services who now need your tax credit, or they’re going to lose their house. You’ve created unemployment- people looking for paid work. Unemployment is not about people looking to volunteer at the American Cancer Society; it’s about people looking for work because they need or want the money. And the problem with government when you want to provision yourself is that there’s no unemployment. No unemployment in terms of your currency; there may be people willing to work for other things but not for your currency. You need unemployment in terms of your currency, looking to earn your unit of account.

So you levy a tax, now people need your unit of account, all of these people show up looking for work, all of those people are unemployed. You now hire the unemployed that your tax created, and they are now provisioning your government.

-Warren Mosler, 2017 MMT Conference

I also liked this description, where he explained his view in an economic debate:

The way we do it, is we slap on a tax for something that nobody has, and in order to get the funds to pay that tax, you have to come to the government for it, and so that way the government can spend its otherwise worthless currency and provision itself.

Now the way I like to explain that, is I’ll take out my business card here. Now I’ll ask this room does anybody want to buy- and this is called “how to turn litter into money”- does anybody want to buy one of these cards for a hundred dollars? No? Okay. Does anybody want to stay after hours and help vacuum the floor and clean the room and I’ll give you my cards? No? Alright. Oh by the way there’s only one door out of here and my guy is out there with a 9mm (handgun) and you can’t get out of here without one of these cards.

Can you feel the pressure now? You’re now unemployed! In terms of my cards, you were not unemployed before. You were not looking for a job that paid in my cards. Now you’re looking for a job that pays in my cards, or you’re looking to buy them from someone else that will take a job that pays in my cards.

[…]

The difference between money and litter is whether there’s a tax man [outside that door]. The guy with the 9mm is the tax man. If he can’t enforce tax collection, the value of the dollar goes to zero.

-Warren Mosler, 2013 MMT vs Austrian Debate

Nobel-laureate economist Paul Krugman put it rather similarly back in 2013:

Fiat money, if you like, is backed by men with guns.

Of course, we could just as easily ask, since the government is using force to collect taxes to provision itself, why can’t it just collect commodity money like gold with a tax, and then spend that gold to acquire its necessary provisions? Why does it need to issue its own paper currency and then tax it back?

The answer is that it doesn’t have to, but it wants to. By issuing its own currency, it profits from seigniorage, which is the difference between the face value of the money and the cost to produce and distribute it. It is, basically, a subtle inflation tax that compounds over time.

A weak government, with an economy that can’t provision most of its needs, often fails to maintain a workable fiat currency for very long. People start using alternative monies out of necessity even if the government supposedly disallows them from doing so. This happens to many developing countries. Billions of people in the world today have experienced the effects of hyperinflation or near-hyperinflation within the past generation. It’s unfortunately quite common.

However, developed countries have been more successful at maintaining seigniorage over the past five decades of the fiat system. Their currencies all lost 95% to 99% of their purchasing power over time, but it was usually gradual rather than abrupt. The system is not without its cracks as previously-discussed, but it’s certainly the most comprehensive fiat currency system ever constructed.

When optimized skillfully, a fiat currency has low volatility year-to-year, in exchange for gradually losing value over the long run. By being actively managed with taxes, spending, and central bank reserve management (creating or destroying currency in exchange for reserve assets), policymakers try to maintain a low and steady inflation rate, meaning a mild and persistent decline in the purchasing power of their currency.

A strong government can force the use of its currency over all other types of monies within its borders, at least for a medium of exchange (not necessarily a store of value), by taxing other types of transactions, and by only accepting its fiat currency as a form of payment for taxes. They can make things like gold, silver, and bitcoin less convenient as money, for example, by making each transaction with it a taxable event in terms of capital gains. If push comes to shove, they can also try to ban those things with threat of force.

The Monetization of Other Assets

Although most of us today are used to it, fiat currency has been a polarizing and inherently political subject ever since the world went onto this petrodollar standard five decades ago.

Mainstream media and economists, however, quickly adopted it as canon and rather unquestionable. For decades now, it has been the case that if someone thinks money shouldn’t be fiat currency, they’re kind of considered a kook and not taken seriously. This kind of vibe:

Gold Meme

But when you step back and think about it from first principles, this period in history is really unusual. It’s a historical aberration, and like a fish in water doesn’t even notice the water, the monetary system we operate with now seems totally normal to us.

Never before, in thousands of years of human history, has the entire world been using a money that has no resource cost or constraint. It’s an experiment, in other words, and we’re five decades into it. Many would consider it a good experiment, while others consider it a bad one, but it’s not as though it is inevitable, or the only possible outcome from here. It’s simply what we have now, and who knows what things will look like in another five decades.

To put it into perspective, this international monetary system based around centrally-managed fiat currency is only 16 years older than me. My father was 36 when the US went off the gold standard. When I grew up, after a period of financial hardship, I began collecting gold and silver coins as a kid; my father gave me silver coins as savings each year.

The Swiss dropped their gold standard when I was twelve years old, which was six years after Amazon was founded, and three years before Tesla was founded. The fiat/petrodollar standard is only four times older than bitcoin, and only two times older than the first internet browser. That’s pretty recent when you think about it like that.

Ever since the world has been on the fiat/petrodollar standard, debt as a percentage of GDP has skyrocketed to record levels and seems to be getting unstable. Considering where we are in the long-term debt cycle, investors would do well to be creative with how they envision the future. Don’t take the past 40-50 years for granted and assume that’s how it’ll always be, whether for money or anything else. We don’t know what money will look like 50 years from now.

The last time we were in a similar debt and monetary policy situation was the 1930s and 1940s, where currency devaluations and war occurred. That doesn’t mean those things have to happen, but basically, we’re in a very macro-heavy environment where structural currency changes tend to occur.

Fiscal and Monetary Policy

One of the results of fiat currency, especially towards the later stages of this five decade experiment since the 1970s, is that more people have begun to treat cash like a hot potato. We instinctively monetize other things, like art, stocks, home equity, or gold. The ratio of home prices to median income has gone up a lot, as well as the ratio of the S&P 500 to median income, or a top-notch piece of art to median income.

This chart shows the loss of purchasing power of the U.S. dollar since the Coinage Act of 1792, which is when the US dollar and the US Mint were created:

US Dollar History

Chart Source: Ian Webster, annotated by Lyn Alden

It currently takes nearly $3,000 to have as much purchasing power as $100 bought in 1792. From 1792 to 1913, the dollar’s purchasing power oscillated mildly around the same value, with over 120 years of relative stability. From 1913 onward, the policy changed and the dollar has been in perpetual decline, especially after it completely dropped the gold peg in 1971.

And it’s actually worse today than during most of this 1971-2022 fiat/petrodollar period, because interest rates aren’t keeping up with inflation rates anymore. The fiat system is getting less stable due to so much debt being in the system, which disallows policymakers from raising interest rates higher than the prevailing inflation rate.

Real Fed Funds Rate

Basically, for lack of good money in this fiat currency petrodollar era, especially in the post-2009 era with interest rates below inflation rates, we monetize other things with higher stock-to-flow ratios and treat them as stores of value.

In China, consumers aggressively monetize real estate. It became normal for families to own multiple homes. In the United States, consumers aggressively monetize stocks. We plow a percentage of each paycheck into broad equity indices without analyzing companies or doing any sort of due diligence, treating that basket of stocks as simply a better store of value than cash regardless of what is inside.

We can ask, for example, would we rather own dollars that went from 10 trillion in quantity ten years ago to 22 trillion today and pay basically no yield to own them, or Apple shares that went from 26 million shares ten years ago to 16 million shares today and also pay basically no yield to own it? Is the dollar better money, or is a diverse collection of fungible corporate shares better money, when it comes to storing value with a 5+ year time horizon?

AAPL Shares

This monetization of non-money securities and property opens us up to more volatility, more leverage, less liquidity, less fungibility, and more taxable events. Basically, rather than investments being special things we make with careful consideration, we shovel most of our free capital into hundreds of index investments that we don’t even analyze, since who would hold currency for any significant length of time? Fungible pieces of corporations become our money, at least for the “store of value” portion of what money is, in large part because they pay higher earnings/dividend yields than bank/bond yields and many of them decrease in quantity (deflationary) rather than constantly increase in quantity.

Some technologists, like Jeff Booth, have argued that this system of perpetual currency debasement has a negative impact on the environment because it encourages us to spend and consume on short-sighted depreciating trinkets and malinvestment more than we would if our money appreciated in value over time like it used to. With appreciating money, we would be more selective with our purchases.

Proponents of the fiat system argue that it smooths out economic downturns and allows for counter-cyclical investment and stimulus. By having a flexible monetary base, policymakers can increase or decrease the supply of money in order to provide a balancing force against credit cycles and industrial output capacity. In exchange for a persistently declining value of currency, we get a more stable currency on a year-to-year basis.

In addition, proponents of the system also argue that the system encourages more consumption and consider that to be a good thing because it keeps GDP up. By keeping people on a constant treadmill of currency debasement, it forces them to spend and invest rather than to save. If people begin to save, these policymakers often view it as “hoarding” or a “global savings glut” and consider it to be a problem. Monetary policy then is adjusted to convince people to save less, spend more, and borrow more.

From a developing market standpoint, the fiat/petrodollar standard contributes to massive booms and busts because a lot of their debt is denominated in dollars, and that debt fluctuates wildly in strength depending on the actions of US policymakers. Developing countries are often forced to tighten their monetary policy during a recession in order to defend their currency, and thus while the US gets to provide counter-cyclical support for its own economy, developing countries are forced to be pro-cyclical, contributing to a vicious cycle in their economies during recessions. In this view, the fiat/petrodollar system can be considered a form of neocolonialism; we push most of the costs of the system out into the developing countries in order to maximize the stability for the developed world.

Overall, the fiat system is showing more instability lately, and investors have to navigate a challenging environment of structurally negative inflation-adjusted cash and bond yields, along with many high asset valuations in equities and real estate.

Sovereign International Reserves

As countries accumulate trade surpluses, they keep those gains in sovereign international reserves. This represents the pool of assets that a country’s central bank can draw upon to defend the country’s currency if needed. The more reserves a country has relative to its GDP and money supply, the more defense it has against a meltdown in its fiat currency. The country can sell these reserves and buy back its own currency to support its currency per-unit value. The currency may not be backed up by gold at a redeemable rate, but it’s backed up by diverse assets as needed if its starts to rapidly lose value.

The world collectively has about $15 trillion USD-equivalents worth of official sovereign reserves. Less than $2.5 trillion of that is gold, with more than $12.5 trillion held as fiat reserves (dollars, euros, yen, francs, etc). Fiat reserves consist of government bonds and bank deposits, and can be easily frozen by the countries that issue them. In addition, many gold holdings are not held within the country, but instead are held in New York or London on their behalf.

Thus, the vast majority of sovereign official reserves, are permissioned assets rather than permissionless assets. They are non-sovereign; able to be frozen by foreign nations. War crystalizes this fact.

In February 2022, Russia invaded Ukraine. Russia had $630 billion USD-equivalents of sovereign international reserves prior to the war, representing decades of accumulated trade surpluses as sovereign savings to underpin their currency. Of this $630 billion, $130 billion consisted of gold, and the other $500 billion consisted of fiat currency and bonds. Of that $500 billion, maybe $70-$80 billion consisted of Chinese fiat assets, and the other $400+ billion consisted of European and other fiat assets. Europe subsequently froze that $400+ billion in Russian fiat assets in response to Russia’s invasion of Ukraine, which is equivalent to over 20% of Russian GDP and over five years of Russian military spending; an utterly massive economic confiscation. Russia is currently in a financial crisis, and it remains to be seen if they can exert enough commodity/military pressure to have their reserves unfrozen.

Some could argue that it’s a good thing that countries hold their reserves in each other’s assets and thus can be frozen. Along with trade sanctions, this practice gives countries another lever with which to control each others’ behavior away from extremes (such as war). We’re all interdependent to one degree or another anyway. But from a pragmatic point of view, countries tend to want to reduce their vulnerabilities and external risks where possible, and that can include minimizing the ability of their stored-up central bank reserves to be confiscated or frozen by other countries.

I began writing this longform article months ago, in late 2021. Things have accelerated since then, and for example the WSJ ran an article in early March 2022 called “If Russian Currency Reserves Aren’t Really Money, the World is in for a Shock.” Here’s the opening paragraph:

“What is money?” is a question that economists have pondered for centuries, but the blocking of Russia’s central-bank reserves has revived its relevance for the world’s biggest nations—particularly China. In a world in which accumulating foreign assets is seen as risky, military and economic blocs are set to drift farther apart.

What is money?

Well, the answer to that question ties into the difference between currency and money. Currency is some other entity’s liability, and they can choose whether or not to honor that particular liability. Money is something that is intrinsically valuable in its own right to other entities, and that has no counterparty risk if you custody it yourself (although it may have pricing risk related to supply and demand). In other words, Russia’s gold is money; their FX reserves are currency. The same is true for other countries.

Fiat currency and government bonds have no intrinsic value; they represent indirect claims of value that can be blocked and confiscated. Gold has value; it’s sufficiently fungible and due to its physical properties, various entities would accept gold at the current market value. It can be self-custodied and no external nation can shut it off.

Currency acts like money most of the time until, one day, it doesn’t.

Fiat Summarized

Overall, the key feature or bug of fiat currency (depending on how you look at it) is its flexible supply and its ability to be diluted. It allows governments to spend more than they tax, by diluting peoples’ existing holdings. With this feature, it can be used to re-liquify seized-up financial situations, and stimulate an economy in a counter-cyclical way. In addition, its volatility can be minimized compared to commodity monies most of the time through active management, in exchange for ensuring gradual devaluation over time.

When things go wrong, however, fiat currency can lose value explosively. Fiat currency tends to incentivize running bigger deficits (since spending doesn’t necessarily need to be taxed for), and generally requires some degree of hard or soft coercion in order to get people to use it over harder monies, although that coercion is often rather invisible to most people most of the time, until things go wrong. And its ability to be diluted can allow for longer wars, selective bailouts for influential groups, and other forms of government spending that aren’t always transparent to citizens.

Digital Assets

With the development of the internet and cryptography in the 1980s and 1990s, many people began working on internet-native money systems. Hash Cash, Bit Gold, and B-Money were some early examples.

Some of these early pioneers wanted to be able to easily pay on the internet, which wasn’t quite as easy back then. Others were part of the cypherpunk movement: people who responded to the information age and the lack of privacy it would increasingly bring, by advocating for transactional privacy through encryption.

Freedom House, a nonprofit organization founded in 1941 and originally chaired by Eleanor Roosevelt, has indeed noted that authoritarianism has been on the rise in recent decades. More than half the world’s population lives in an authoritarian or semi-authoritarian country. People in privileged areas often fail to recognize this trend.

Freedom House

Chart Source: Freedom House

The world became more free in the 1980s and 1990s as China and the Soviet Union opened up, but then the world increasingly began chipping away at that freedom in the 2000s and 2010s, at least as far as Freedom House and various other sources measure it. China in particular is a huge surveillance and control state now, with transactions and online behavior monitored and organized, social credit scores determined from the data, and consequently near-complete control over their citizens’ behavior.

Even the developed world began introducing policies that chipped away at certain freedoms, and so Freedom House’s scores for many developed countries mildly declined over time as well. For example, the United States was ranked 94 for its freedom score back in 2010, but as of 2020 was ranked only 83. It has been reported for over a decade now, with increasing revelations over time, that the CIA and NSA have large spying operations on Americans.

The more digital the world is, the more authoritarian regimes, semi-authoritarian regimes, or would-be-authoritarian regimes are able to monitor and intervene in their subjects’ lives. Authoritarianism combined with 21st century digital surveillance technology and Big Data to organize it all, is a rather frightening prospect for a lot of people. This combination has been predicted by science fiction books for decades.

The Discovery of Digital Scarcity and the Invention of Bitcoin

The ability to transact with others is a key part of individual liberty. The more that authoritarian regimes can control that, the more power they have over their citizens’ lives.

Nobel-laureate economist Friedrich Hayek once gave an interesting statement on the subject of money:

I don’t believe we shall ever have a good money again before we take the thing out of the hands of government, that is, we can’t take them violently out of the hands of government, all we can do is by some sly roundabout way introduce something that they can’t stop.

-Friedrich Hayek, 1899-1992

Satoshi Nakamoto’s answer to that riddle in 2008 was to avoid a centralized cluster and make a peer-to-peer money system based on a distributed ledger.

I’ve been working on a new electronic cash system that’s fully peer-to-peer, with no trusted third party.

Governments are good at cutting off the heads of a centrally controlled networks like Napster, but pure P2P networks like Gnutella and Tor seem to be holding their own.

-Satoshi Nakamoto, two separate quotes from 2008

Nakamoto’s invention of bitcoin in 2008, which cited a number of projects, indeed became the first widely successful and credibly-decentralized internet money after it was launched in early 2009. In the genesis block, he referenced a topical newspaper headline about British bank bailouts, during the heart of the global financial crisis.

The Times 03/Jan/2009 Chancellor on brink of second bailout for banks

-Bitcoin Genesis Block

The Bitcoin network is a distributed database, also known as a public ledger or “triple entry bookkeeping”. It’s a system that allows all participants around the world to come to a consensus on the state of the ledger every ten minutes on average. Because it’s highly distributed and relatively small in terms of data, participants can store a full copy of it and reconcile it constantly with the rest of the network, with a specific protocol for determining the consensus state of the ledger. In addition to storing the whole database, participants can store their own private keys, which allow them to move coins (or fractional coins) around to different public addresses on the ledger.

If participants hold their own private keys, then their bitcoins represent assets that are not also someone’s liability. In other words, like gold, they are money rather than currency, as long as other people recognize them as having value.

Bitcoin Price Chart

Chart Source: LookIntoBitcoin.com

After Nakamoto showed the way, there have been over fifteen thousand other cryptocurrencies created. Some of them are competitors to the bitcoin network, while others are smart contract platforms to serve other purposes. So far, all of the ones directly trying to be money have not been able to gain any traction against the bitcoin network (with none of them sustaining above 5% of the network value of bitcoin), while a select few that aim to be used as smart contract utility tokens instead have retained rather large network valuations for longer periods of time.

Many people argue that bitcoin has achieved critical mass in terms of its network effect, security, immutability, and decentralization, such that while other digital assets may persist to fulfill other use-cases, none of them have a reasonable chance of competing with bitcoin in terms of being hard money. Fidelity published a good paper on this topic called Bitcoin First. Here’s the summary:

In this paper we propose:

-Bitcoin is best understood as a monetary good, and one of the primary investment theses for bitcoin is as the store of value asset in an increasingly digital world.

-Bitcoin is fundamentally different from any other digital asset. No other digital asset is likely to improve upon bitcoin as a monetary good because bitcoin is the most (relative to other digital assets) secure, decentralized, sound digital money and any “improvement” will necessarily face tradeoffs.

-There is not necessarily mutual exclusivity between the success of the Bitcoin network and all other digital asset networks. Rather, the rest of the digital asset ecosystem can fulfill different needs or solve other problems that bitcoin simply does not.

-Other non-bitcoin projects should be evaluated from a different perspective than bitcoin.

-Bitcoin should be considered an entry point for traditional allocators looking to gain exposure to digital assets.

-Investors should hold two distinctly separate frameworks for considering investment in this digital asset ecosystem. The first framework examines the inclusion of bitcoin as an emerging monetary good, and the second considers the addition of other digital assets that exhibit venture capital-like properties.

Other blockchains that attempt to increase transaction throughput on the base layer or add more computational functionality on the base layer, generally sacrifice some degree of decentralization and security to do so. Blockchains that attempt to have more privacy on the base layer generally sacrifice some degree of supply auditability.

Bitcoin is updated slowly over time via optional soft forks, but the underlying foundation is maximized towards decentralization and hardness, more so than throughput or additional functionality. Layers built on top of it can increase throughput, privacy, and functionality.

The discovery of a credible way to maintain digital scarcity, and an invention of a peer-to-peer money based on that discovery, was in some ways inevitable, although the specific form that it first appeared in could have been designed in a number of ways. The foundations of the internet were put forth in the 1970s, and so was the concept of a Merkle tree. Throughout the 1980s and 1990s the internet as we know it came into being, as more and more of the world’s computers were networked together. Proof-of-work using computer systems was invented in the 1990s, and the SHA-256 encryption was published in the early 2000s. Nakamoto put a bunch of these concepts together in a novel way in 2008, and had the right macroeconomic backdrop and right design decisions to have it succeed for well over a decade and counting.

Bitcoin’s Bottom-Up Monetization

If we go back to the gold standard for a moment, the key reason why paper claims were built on gold was to improve its medium-of-exchange capabilities. Ray Dalio described it well:

Because carrying a lot of metal money around is risky and inconvenient and creating credit is attractive to both lenders and borrowers, credible parties arise that put the hard money in a safe place and issue paper claims on it. These parties came to be known as “banks” though they initially included all sorts of institutions that people trusted, such as temples in China. Soon people treat these paper “claims on money” as if they are money itself.

-Ray Dalio, The Changing World Order

Bitcoin on the other hand is a bearer asset that is safe to self-custody in large amounts and can be sent peer-to-peer around the world over the internet. Therefore, it removes the need for paper abstraction. Some holders will still prefer custodians to hold it for them, but it’s not necessary like it is with large amounts of gold, and thus the units of the network are less prone to centralization. Unlike gold, bitcoin in large quantities is easy to transfer globally, and take custody of.

From the start, the bitcoin network was designed as a peer-to-peer network for the purpose of being a self-custodial medium of exchange. It’s not the most efficient way to exchange value, but it’s the most unstoppable way to do so online. It has no centralized third parties, no centralized attack surfaces, and sophisticated ways of running it can even get around rather hostile networks. Compared to altcoins, it is far harder to attack due to its bigger network effect and larger hash rate.

For example, one of the early use cases for bitcoin back in 2010/2011 was that Wikileaks was dropped by PayPal and other payment providers, so it began accepting bitcoin donations instead. Satoshi himself expressed concern about this on the forum at the time, due to bitcoin still being in its infancy back then relative to the amount of attention this would bring.

Kind of like how a tank is designed to get from point A to point B through resistance, but is not well-suited for commuting to work everyday, the base layer of the bitcoin network is designed to make global payments through resistance, but is not well-suited for buying coffee on the way to work.

In that sense, the bitcoin network has utility, for both ethical and unethical participants (just like any powerful technology). And because it is broken up into 21 million units (each with eight decimal places, resulting in 2.1 quadrillion sub-units), it is a finite digital commodity.

And that’s how Satoshi described it:

As a thought experiment, imagine there was a base metal as scarce as gold but with the following properties:
– boring grey in colour
– not a good conductor of electricity
– not particularly strong, but not ductile or easily malleable either
– not useful for any practical or ornamental purpose

and one special, magical property:
– can be transported over a communications channel

If it somehow acquired any value at all for whatever reason, then anyone wanting to transfer wealth over a long distance could buy some, transmit it, and have the recipient sell it.

-Satoshi Nakamoto, 2010

In addition to sending them online, bitcoins in the form of private keys can be physically brought with you globally. You can’t bring a lot of physical cash or gold through an airport and across borders. Banks can block wire transfers out of their country, or even within the country. But if you have bitcoins, you can bring an unlimited amount of value globally, either on your phone, or on a USB stick, or stored elsewhere on some cloud drive you can access from anywhere, or simply by memorizing a twelve-word seed phrase (which is an indirect way of memorizing a private key). It’s challenging for governments to prevent that without extremely draconian surveillance and control, especially for technically-savvy citizens.

This utility combined with an auditable and finite number of coins eventually attracted attention for its monetary properties, and so bitcoins acquired a monetary premium. When you hold bitcoins, especially in self-custody, what you are holding is the stored-up ability to perform global payments that are hard to block, and the stored-up ability to transfer your value globally if you want to. You are holding your slot on a global ledger, similar to holding valuable domain names, except that unlike domain names, bitcoins are decentralized, fungible, liquid, and self-custodial. It could be an insurance policy for yourself one day, or you could simply hold it because you recognize that capability to be valuable to others, and that you could sell that capability to someone else in the future.

Bitcoin is becoming a rather salable good, in other words. And with a higher stock-to-flow ratio than gold.

It’s volatile, but that’s in large part because it monetized from zero to a trillion-dollar market capitalization in twelve years. The market is exploring this technology and trying to determine its total addressable market as more and more people buy into it over time. It’s an asset that is still only held by about 2% of the global population, and it’s a tiny fraction of global financial assets.

Censorship-resistance is a significant feature when it comes to payments, and self-custodying money that cannot be diluted with more supply is a significant feature when it comes to savings.

To many people in developed countries, those features might not seem important, because we are privileged and take our freedom and comfort for granted. But for a large portion of the world, being able to bring self-custodied wealth with you if you have to leave your country is immeasurably valuable. When Jews fled Nazi-controlled Europe, they had trouble bringing any valuables with them. When people left the failing Soviet Union, they could only bring the equivalent of $100 USD with them. When people today want to leave Venezuela, Syria, Iran, Nigeria, China, eastern Ukraine, or any number of countries, they sometimes have a rough time bringing a lot of value with them, unless they have self-custodied bitcoins. Millions (and arguably billions) of people today can understand the value of this feature.

Reuters has documented Putin’s domestic political opposition using bitcoins as Putin’s establishment cuts them off from their banking relationships. The Guardian has documented Nigerians using bitcoins as they protested their government against police violence and had their bank accounts frozen. Chinese people have used it to transfer value through capital controls. Venezuelans have used it to escape hyperinflation and transfer value out of their failed state. One of the earliest use-cases for it was to pay Afghani girls with a type of money that their male relatives could not confiscate, and that they could bring with them out of the country when they leave. I’ll dive more into these examples later. In 2022, Canada used emergency powers to freeze financial accounts of protestors, and people who donated to protestors, before charging them with any crimes.

The limited scalability of bitcoin’s base layer has not been an issue so far, because there is only so much demand for tank-like censorship-resistant payments. And as development has continued since bitcoin’s launch, the network has branched into layers just like any other financial system. The Lightning network, for example, is a series of smart contracts that run on top of the bitcoin network base layer and allow for custodial or non-custodial rapid payments online or in person with a mobile phone, to the point where they can easily be used to buy coffee, and with practically no limitation on transactions per second. The Liquid network, as another example, is a side chain that wraps bitcoins into a federated network for rapid transfers, better privacy, and additional features as well, in exchange for some security trade-offs.

In that sense, bitcoins began as digital commodities that had utility value as an internet-native and censorship-resistant medium of exchange for people that need that capability. Bitcoins eventually acquired a monetary premium as an emergent and volatile store of value (an increasingly salable good), and began to be held more-so for their scarcity than for their medium-of-exchange capabilities. And then over time, the network developed additional ways to enhance the network’s medium-of-exchange capabilities beyond their initial limitations.

Too many people look at bitcoin and say, “the base layer can’t scale so that everyone in the world can make all of their transactions with it”, but that’s not the point of what it’s for. The base layer is a censorship-resistant payments and settlement network with an auditable supply cap that has the capacity to handle hundreds of thousands of transactions per day, and layers built on top of it can be used for more frequent transactions than that if desired.

Kind of like how we don’t use Fedwire transfers to buy coffee, bitcoin base layer transactions are not well-suited to buying coffee. Visa transactions that run on top of Fedwire, or lightning transactions that run on top of bitcoin, can be used to efficiently buy coffee. Or even custodial payment methods like Cash App and Strike that run on top of the bitcoin/lightning network can be used if censorship-resistance is not needed. The base layer of the bitcoin network is not competing with things like Visa; it is competing with central bank settlements; the root of the global financial system. It’s an entirely separate root layer, built on computer networking technologies and internet protocols rather than channels between central banks and commercial banks.

It’s also worth understanding Gresham’s law, which proposes that “bad money drives out good”. Given the choice between two currencies, most people spend the weaker one and hoard the stronger one. Bitcoin’s low current usage as a medium of exchange is not a bug; it’s a feature of a system with low supply issuance and a hard cap at 21 million units, especially in places where it is not legal tender and so every transaction is a taxable event. When a tank-like medium of exchange is needed, or for certain other niche use-cases, bitcoin is useful for its payment utility. Otherwise, it’s most often held for its monetary premium as a scarcer asset than dollars and other fiat currencies, and represents the stored-up ability to perform tank-like payments in the future.

Bitcoin as a network and surrounding ecosystem went through multiple boom/bust cycles so far, and in each one, larger pools of capital became interested in it. In the first era, the user experience was challenging and required technical understanding, so it was mainly computer scientists and enthusiasts building and exploring the technology. In the second era, bitcoin became a bit easier to use and reached enough liquidity to have a quoted price in dollars and other fiat currencies, and so it became noticed by early speculators as well as dark net buyers/sellers. In the third era, it reached early mainstream adoption, in the sense that exchanges with proper security protocols could operate with bank connections, provide more liquidity to the market, and improve the user experience so that everyday people could more easily buy some. In the fourth era, institutional-grade custodians entered the market, which allowed pensions, insurance companies, hedge funds, family offices, and sovereign wealth funds to safely allocate capital to it.

It’ll be interesting to watch how the bitcoin ecosystem develops going forward. Will it remain rather decentralized, or will it eventually become more clustered to the point of having transactions easy to censor? Will it continue to maintain robust market share of the digital asset ecosystem, against thousands or tens of thousands of competitors that dilute each other and try to take some of bitcoin’s monetary premium? I’m bullish and optimistic on the network but it’s not without challenges and risks.

Corporate Stablecoins

Corporate custodial stablecoins were created via smart contracts to apply blockchain technology to fiat currency. With these systems, a custodian of dollars could issue tokens on a smart contract blockchain, and each of those tokens is redeemable 1-for-1 from the custodian for dollars.

To create custodial stablecoins, a client deposits dollars with the issuer, and is issued stablecoins in return. To redeem stablecoins, a client deposits stablecoins and is issued dollars in return. Different custodians have different track records for how securely they hold the collateral in dollars; users have to trust the custodian not to gamble away the funds on bad investments or fraud. Attestations and/or audits by third party accounting firms can add assurances about the safety of the collateral.

Once stablecoins are issued, people can then use whichever blockchain they are issued on to send and receive stablecoin payments between themselves, peer-to-peer, with no additional centralized third party. From a user perspective, stablecoins are a significant technological leap over existing bank payment systems, especially for international payments, or large domestic payments. You can send someone on another continent a million dollars at 2am on a Sunday night and they can receive it in minutes, and both sides can verify the transaction on the blockchain in real time.

They will naturally face ongoing government regulation and be controlled and surveilled as part of the banking system in many cases, but it’s clear that they have utility for actual payments and will probably get increasingly incorporated into financial systems, either in the form of central bank digital currencies or private-but-highly-regulated stablecoin issuers.

This is simply due to automation and superior technology. When you send a wire transfer, the bank has to actively do something to process that transaction. And wires often get delayed or blocked or run into other problems as they flow between banks. From the users’ perspective, it’s often unclear which bank it got stuck in or who to call, and thus it sometimes takes days to resolve. With stablecoins, it’s the opposite. The automatic nature of the blockchain allows for peer-to-peer transactions handled by software, including internationally and including with large amounts of money. The custodians are passive in that regard and let the technology work for them, and only act in the event that they want to blacklist some of their tokens for some reason that they detected.

Anyone who does a lot of international wire transfers, and then has used stablecoins, will generally say that stablecoins are way better to use.

In other words, regulated stablecoins allow for an automated peer-to-peer international payment system, but that has an overlay of control based on know-your-customer and anti-money-laundering “KYC AML” laws, as well as a significant element of custodial trust.

Central Bank Digital Currencies

Some countries want to take the stablecoin concept further, and completely nationalize it within their jurisdiction. This uses similar technology to stablecoins but doesn’t need a blockchain, because it’s not decentralized.

Starting with China studying and learning from bitcoin and stablecoins for over five years now, these technologies are now being used to create central bank digital currencies. These are central-bank issued fiat currencies that are digitally-native, able to operate over the internet rather than going through the historic global banking system “pipes”.

From the government perspective, the usefulness of a pure central bank digital currency is that the government can:

send international payments without the SWIFT system
try to give banking access to the non-banked or under-banked populations
track and surveil any transaction, including with Big Data/AI technologies
blacklist or block certain transactions that violate their rules
add expiration dates or jurisdiction limitations to currency
take away money from citizen wallets for various violations
give money to citizen wallets for stimulus or rewards
impose deeply negative interest rates on citizen account balances
program money to have different rules for different groups
reduce the control and fee pressure that commercial banks have over the system
In other words, a central bank digital currency can be more efficient, cheaper, and easier to use than many existing payment systems. However, in such a system, your currency can also be surveilled, given, taken, and/or programmed by the issuer to only work in authorized situations.

Agustin Carstens, head of the Switzerland-based Bank for International Settlements (basically the central bank of central banks) had an interesting quote on CBDCs last year:

For our analysis on CBDC in particular for general use, we tend to establish the equivalence with cash, and there is a huge difference there. For example in cash, we don’t know for example who is using a hundred dollar bill today, we don’t know who is using a one thousand peso bill today. A key difference with a CBDC is that central bank will have absolute control on the rules and regulations that determine the use of that expression of central bank liability. And also, we will have the technology to enforce that. Those two issues are extremely important, and that makes a huge difference with respect to what cash is.

A Spectrum of Control

From the summaries of the sections above, there are multiple types of digital assets. There are decentralized bearer assets like bitcoins, and there are digital representations of fiat currency like corporate stablecoins and central bank digital currencies. There are also other private blockchain monies, such as utility tokens or gaming tokens.

Some digital assets, like bitcoins, reduce the government’s ability to interfere with your money, since you can self-custody it and send it to whoever you want. As the Guardian covered back in July, when Nigerans began protesting their government for police violence, and found their bank accounts frozen for doing so, many of them turned to using bitcoins to remain operational.

Last October, Nigeria was rocked by the largest protests in decades, as many thousands marched against police brutality, and the infamous Sars police unit. The “EndSars” protests saw abuses by security forces, who beat demonstrators, and used water cannon and teargas on them. More than 50 protesters were killed, at least 12 of them shot dead at the Lekki tollgate in Lagos on 20 October

The clampdown was financial too. Civil society organisations, protest groups and individuals in favour of the demonstrations who were raising funds to free protesters or supply demonstrators with first aid and food had their bank accounts suddenly suspended.

Feminist Coalition, a collective of 13 young women founded during the demonstrations, came to national attention as they raised funds for protest groups and supported demonstration efforts. When the women’s accounts were also suspended, the group began taking bitcoin donations, eventually raising $150,000 for its fighting fund through cryptocurrency.

And many merchants, facing sanctions, used bitcoins to trade internationally (also from the Guardian article):

His business – importing woven shoes from Guangzhou, China, to sell in the northern city of Kano and his home state of Abia, further south – had been suffering along with the country’s economy. The ban threatened to tip it over the edge. “It was a serious crisis: I had to act fast,” Awa says.

He turned to his younger brother, Osy, who had begun trading bitcoins. “He was just accumulating, accumulating crypto, saying that at some point years down the line it could be a great investment. When the forex ban happened, he showed me how much I needed it, too. I could pay my suppliers in bitcoins if they accepted – and they did.”

Similarly, Reuters has been reporting on a number of occasions that Russian opposition leader and anti-corruption lawyer Alexei Navalny uses bitcoins in his organization to get around government blockades:

Russian authorities periodically block the bank accounts of Navalny’s Anti-Corruption Foundation, a separate organisation he founded which conducts investigations into official corruption.

“They are always trying to close down our bank accounts – but we always find some kind of workaround,” said Volkov.

“We use bitcoin because it’s a good legal means of payment. The fact that we have bitcoin payments as an alternative helps to defend us from the Russian authorities. They see if they close down other more traditional channels, we will still have bitcoin. It’s like insurance.”

One of the most touching stories was reported by Reuters as well. In the early years of bitcoin, an Afghan woman paid many girls with bitcoins, because they were otherwise unbanked and their male relatives would often try to steal from them, since they didn’t necessarily have much of a right to their own property. The self-custodied aspects of bitcoin then allowed many of the girls over the years to leave the country with their funds, which would be impossible with most other assets:

When Roya Mahboob began paying her staff and freelancers in Afghanistan in bitcoin nearly 10 years ago, little did she know that for some of these women the digital currency would be their ticket out of the country after the fall of Kabul in August.

Mahboob, a founder of the non-profit Digital Citizen Fund along with her sister, taught thousands of girls and women basic computer skills in their centres in Herat and Kabul. Women also wrote blogs and made videos for which they were paid in cash.

Most girls and women did not have a bank account because they were not allowed to, or because they lacked the documentation for one, so Mahboob used the informal hawala broker system to send money – until she discovered bitcoin.

Alex Gladstein has a massive archive of articles reporting on the various emerging market use-cases for bitcoin over the past several years, ranging from Sudan to Palestine to Cuba to Iran to Venezuela and more.

Anita Posch also has a great interview series called Bitcoin in Africa that explores these use-cases in that region. Bitcoin is a tool that tech-savvy people often use as defense against either double digit currency inflation or authoritarian financial system control.

We’re even seeing this topic pop up in developed markets. Truckers in Canada protested the government and occupied and disrupted the capitol, and received donations from supporters on crowdfunding sites. Those crowdfunding sites ended up freezing and reversing the payments, so many of the participants turned to bitcoin as peer-to-peer money. The government then invoked the 1988 Emergencies act to freeze bank accounts of certain protestors and donors, and to try to blacklist certain bitcoin addresses to being brought to exchanges for conversion back into Canadian dollars.

People may agree or disagree with aspects of those protests but the pragmatic point about money in this context is, those who had their money entirely in banks were indeed frozen. Those who self-custodied their own digital assets, such as bitcoins, had certain conveniences removed from them but could still hold, move, and transfer their money in various ways.

In the broadest sense applying internationally (especially for developing markets with weaker rule of law where the majority of people live), I described the issue here:

Custodial vs Non-Custodial Money

Other digital assets, like CBDCs, are the opposite of this type of asset, and give the government more ability to surveil and censor your money, and in reality, it’s not even your money. It’s a liability of your country’s central bank, and as Carstens eloquently articulated, each central bank wants to be able to determine how you can use their liabilities. The full ramifications of that statement can mean very different things depending on whether you live in a place like Norway or a place like China.

The European Central Bank published a working paper on CBDCs in early 2020 called “Tiered CBDC and the Financial System” where they outlined the ability of CBDCs to better control illicit payments and to allow for deeper negative interest rate policy, especially if physical banknotes are removed from circulation. This effectively corrals public savings into a digital money that the government can more easily debase and control as desired and gain more seigniorage from:

ECB CBDC Paper

Source: Tiered CBDC and the Financial System, ECB, January 2020

This becomes particularly relevant when we consider that the government can always try to broaden its scope of what is “illicit”, particularly in regards to protests and things of that nature. Basically, we have to ask ourselves not what the current political leadership would do with this technology, but also what all future political leadership who we don’t know yet would do with this technology. What would Norway do with this technology, compared to what China would do with this technology?

Although bitcoin has thus far been somewhat more appreciated by libertarian and fiscally conservative people on average, this feature is why there are also some progressive/left voices out there that identify bitcoin as a tool for their goals as well. At the end of the day, bitcoin is more of an anti-authoritarian monetary technology than it is a “left” or “right” monetary technology. The Human Rights Foundation in particular has made extensive use of it for their international activities.

Critics of bitcoin often leave these humanitarian or anti-authoritarian use-cases out (or don’t even realize them), and instead refer to bitcoin as being primarily used to buy drugs or ransomware or money laundering, which is a really outdated (or deliberately misleading) view at this point. Firms such as Chainalysis that perform blockchain analysis for law enforcement and other clients have found that bitcoin and overall cryptocurrency usage for illicit activities involves less than 1.5% of bitcoin/crypto transaction volume over the past several years, which is less than the percentage of fiat transactions used for illicit activities.

Bitcoin went through an early phase in 2011 through 2013 where it was used for online drug purchases and such, until authorities responded with a crackdown on that usage by going after the centralized marketplaces that enabled it. Just like how the invention of the pager was used by both drug dealers and doctors in the 1970s and 1980s, bitcoin has gone through phases where criminals used it and humanitarians used it for their purposes. Both of those groups in particular have an incentive to quickly adopt to new technologies to stay ahead of their state-sponsored competition, and it’s important for western media to keep in mind that “illegal activities” in some countries includes protesting the government and other forms of free speech and expression and political opposition.

Like any powerful technology, bitcoin can be used for good or ill. As proponents of the technology like to say, bitcoin is “money for enemies” because it’s a bearer asset that can be verified rather than trusted, and it’s hard to block payments for anyone. It’s like a commodity; something that can be partially regulated within certain jurisdictions but that in the holistic sense, exists outside of anyone’s control.

If we take a step back, we can catalogue the history of financial surveillance. For most of human history, financial transactions were rather private from the perspective of the government, because transactions mainly involved handing over physical money, which is hard to track. With the invention of modern banking, and then especially modern computer databases and electronic payments, transactions could be more easily tracked and surveilled. The Bank Secrecy Act of 1970 required financial institutions to report transactions over $10k USD to the government, which back then was the equivalent of about $75k USD in today’s dollars. They never raised the threshold despite five decades of inflation, so over time without further laws being passed, their surveillance reporting requirements became applicable to smaller and smaller transactions.

When people use banks to send or receive money, it is easy for governments to impose restrictions on what sort of payments are allowed, which banks can then enforce. And some governments can even block other foreign governments from using the primary existing international payment methods. Bitcoin threatens that surveillance and control model because it empowers peer-to-peer transactions. The bitcoin network consists of people using free open source software to update a public ledger between themselves. It’s basically just a sophisticated way of updating the equivalent of a distributed Google Spreadsheet with each other, without a centralized server. Governments trying to ban people from doing that is tantamount to banning the spread of information, and is therefore a lot harder to do than telling banks to report or block certain types of transactions.

Governments will be challenged by this technology, and many of them have, and will, push back against it. They can allocate law enforcement resources to go after truly illegal activities (tracking down major cryptocurrency payments involved with serious crime), but will likely have trouble trying to retain control over benign transactions. They can use on-chain analysis to try to track transactions, they can enforce surveillance checkpoints around cryptocurrency exchanges, they can block banks in their jurisdiction from interfacing with any cryptocurrency exchanges, and at the extreme end they can put draconian punishments on people for using open source software to update a public ledger between each other. Meanwhile, developers continue to find ways to make the bitcoin network more private and to route around some of the challenges that can be put in its way. There are also some privacy-specific coins that people can resort to as well.

One way or another, these various types of digital money or currency are clearly in our future in some form or another. Depending on where we live and choices we make, we are more likely to experience some than others, ranging from bitcoins to corporate stablecoins to central bank digital currencies.

Proof-of-Something

A topic popularized by bitcoin is the term “proof-of-work”.

The concept was invented in various ways by cryptographers in the late 1990s, including notably by Dr. Adam Back in the form of “Hashcash”- a money-like mechanism to reduce email spam and denial-of-service attacks by making them have a small computational cost.

Satoshi Nakamoto’s bitcoin white paper referenced Back’s work, and used proof-of-work as one of its core aspects.

Nowadays, various digital assets have expanded on this concept in the form of “proof-of-stake”, “proof-of-history”, “proof-of-transfer”, “proof-of-burn”, “proof-of-space” and so forth. There are multiple attempts at maintaining scarcity of digital networks.

In any form, money is proof of something. This section explores three popular examples of proof-of-work, proof-of-stake, and proof-of-force.

Proof-of-work assets are created or harvested from mining activities. Proof-of-stake assets are created by breaking a project into pieces and selling some of those pieces to others. Proof-of-force assets, or fiat currency, is created by governments and their designated commercial parties (holders of banking licenses).

Proof-of-Work

When we go back and look at the example of rai stones, they were well-understood among their users to be a powerful proof-of-work mechanism. In addition to having a high stock-to-flow ratio until modern technology interfered with that, each stone is an undeniable proof that a massive amount of work occurred to create it and put it where it is.

A team of young men had to travel hundreds of miles to another island, quarry for the stone with ancient tools, bring a multi-ton stone block back on their wooden boats, and then carve it and move it into place on their home island. The amount of work that was required to do this is what limited the flow (new annual supply), and maintained the high stock to flow ratio for a long time. The bigger the stone, the more work it took to produce it and get it there.

Gold, of course, is historically the best example of proof-of-work, and it has stood the test of time unlike anything else. After painstakingly searching for gold deposits, it takes a tremendous amount of mechanical effort to move tons of earth for grams of gold, and then it has to be refined into its pure form. Each gold coin or gold bar represents literally tons of rock moved and sorted through, and gold resists degradation better than other elements. The Earth’s crust consists of less than 0.0000004% gold, compared to over 28% for silicon, over 8% aluminum, and over 5% iron. Even as our technology improves and we get better at finding and retrieving gold, we run out of the easiest deposits, and so it keeps getting harder, which offsets our improving technology.

Basically, proof-of-work is just that: proof that work was done. Since work is inherently scarce, we tend to recognize proof-of-work as being evidence of value, but only if the finished good in question has properties of money. And that’s an important distinction; we don’t pay for non-monetary goods or services based on how much work went into them; we pay for them based on how much utility they provide to us.

In other words, something akin to the Labor Theory of Value doesn’t apply to utility goods, but does apply to monetary goods.

This is because market participants will naturally try to arbitrage any good that acquires a monetary premium above what it offers in terms of its utility value. Monetary goods that don’t require work inevitably get reproduced and devalued (thus leaving only those that do require work as proper monies), whereas goods with no monetary premium are not worth reproducing endlessly. Basically, when it comes to money, a large amount of work to produce a unit, and a persistently high stock-to-flow ratio, are essentially the same thing. That work requirement is what keeps a commodity’s stock-to-flow ratio high, and any commodity that can’t maintain a high stock-to-flow ratio in the face of ever-advancing technology eventually fails as money. Only the scarcest of monies can maintain a persistent monetary premium over its utility value, because that monetary premium continually invites attempts at debasement.

For bitcoin, a new block of transactions is produced every ten minutes on average, and contains a cryptographic hash of the block before it, which connects the blocks to form a chain. It takes work (computer processing power) to solve that puzzle and find the new block that fits. The blockchain ends up being a long stretch of blocks hashed onto prior blocks, which is proof that a large amount of work was done. Copies of the blockchain are distributed and continually updated across tens or hundreds of thousands of computers worldwide.

A transaction recognized by the chain becomes essentially unchangeable, as it is buried under thousands of hashed blocks and widely distributed on those global computers.

And because bitcoin has a much larger network effect than most other cryptocurrencies, it is far more costly to attack the network than it is to attack most other cryptocurrencies. This, along with the fact that the node network is sufficiently decentralized and the monetary policy (or more accurately, initial coin distribution policy) can’t realistically be changed, is what has made bitcoin able to accumulate a persistent hard money premium that other cryptocurrencies have had trouble maintaining. However, in the grand scheme of things, it’s still only thirteen years old.

I have a longform research piece on bitcoin’s proof of work and energy consumption here.

Proof-of-Stake

Proof-of-stake is an equity-like system whereby holders of an asset determine how that asset functions. In other words, each coin can serve as a vote for the network.

Much like proof-of-work, we can translate it back into analog examples. In particular, proof-of-stake is commonly used in corporate ownership. The larger the number of shares of a company you own, the more say you have in terms of electing board members to run the company, and supporting or denying shareholder proposals. If you, or a group of entities that follow you, can control 51% of the shares, you effectively control the entire company.

Similarly, some blockchains have used this approach. Rather than mining for coins with real-world resources, users create new coins by signing transactions as a validator. In order to be a validator, users have to prove that they have a certain number of coins. Some of the pre-bitcoin attempts at digital money used strategies like this, and many of the post-bitcoin attempts use it in blockchain form.

However, unlike corporations, proof-of-stake blockchains require circular logic. Corporations use an external entity (a transfer agent and registrar) to keep track of who owns each share. In proof-of-stake blockchains, it’s like a corporation acting as its own transfer agent and registrar; the coinholders determine the state of the ledger, and the ledger is what says who the coinholders are.

Therefore, proof-of-stake systems need to be “always on” to function, and are highly complex. They have no inherent disaster recovery potential if the blockchain goes offline, because making alternative copies of the blockchain has no cost, and there’s no way to determine the “real” blockchain other than via agreement of major parties (a.k.a. a form of governance) if it is recovering from that offline state.

In contrast, proof-of-work systems are ledgers with decentralized and automated transfer agents and registrars. The coinholders do not determine the state of the ledger, the miners do, via energy expenditure. A proof-of-work system is not based on circular logic; even if the entire blockchain goes offline, it can be restarted because the longest chain can be identified and continued.

In other words, a proof-of-work blockchain is like non-volatile memory and a proof-of-stake blockchain is like volatile memory.

Another risk with proof-of-stake systems in both the analog and digital world is that they tend to centralize over time into an oligopoly. Since it doesn’t require ongoing resource inputs to maintain your stake and to grow it over time, wealth tends to compound into more wealth, which they can then use to influence the system to give themselves even more wealth, and so on.

Adam Back described this succinctly a while ago:

You see that with other commodity money, like physical gold. It’s a system that works because money has a cost. I think money that doesn’t have a cost ultimately ends up being political in nature. So people closer to the money, the so-called Cantillon Effect, are going to be advantaged.

In digital systems specifically, another challenge is that proof-of-stake as a consensus model is a lot more complex than proof-of-work and prone to more attack surfaces. If a proof-of-stake chain gets split or maliciously copied, it’s not self-evident which chain is the real one, and it becomes a human/political decision among oligopolistic participants to canonize a chain. However, in a proof-of-work system, the real chain is instantly verifiable, because by definition the chain that follows the node-consensus ruleset and that has more work is the real one.

In other words, what makes proof-of-stake blockchains inherently equity-like is that they require some form of ongoing governance, whereas proof-of-work blockchains (especially ones decentralized enough that they can’t really change their monetary policies) are more commodity-like. These differences can be benefits or drawbacks depending on what participants want out of the system. The collective existence of both digital commodities and digital equities in my view represents a novel new era for asset classes, and we’ll see where they may be successfully applied.

I have a longform research piece that includes an overview of proof-of-stake here.

Proof-of-Force

As described by Warren Mosler, a founder of the MMT school of economic thought mentioned earlier in this article, fiat currency is basically proof-of-force, which is why it can win out over proof-of-work money for long stretches of time.

Demand for government paper (or digital equivalents) is created by the government’s taxes on the population, which can only be paid in units of that paper. Failure to pay taxes results in losing assets, going to jail, or if resisting those prior consequences, getting shot by police. Proof-of-force systems convince or coerce people in their jurisdiction to use a softer/devaluing money, by placing taxes, frictions, and other obstacles on any money that is harder than their own, or in some cases outright banning competing monies by making it a felony to use them.

Of course, proof-of-force has existed for thousands of years, prior to the invention of fiat currency. Any warlord, kingdom, or empire that demanded some tribute from the peoples of the land it ruled were familiar with the concept of proof-of-force. The purpose could be for malevolent ends, or it could be for benevolent purposes to provide order for society, and collect some percentage of resources into the common good. Even democracies use proof-of-force as an organizational method. Nature abhors a vacuum, and humans consistently congregate into hierarchies and societal structures. In other words, not every political leader was like Caligula; some of them were more like Marcus Aurelius, or were democratically elected.

In most eras, that tribute took the form of commodity monies, such as gold or other loot that was already recognized as money via proof-of-work. However, in the modern era, governments have eliminated the proof-of-work component from the equation via technology (banking systems and efficient nationwide communication systems) and so when we think of the dollar, the euro, the yen, and other fiat currencies, they basically represent just proof-of-force. When we say that the dollar is “backed up by the full faith and credit of the U.S. Government”, what we are really saying is that the dollar is backed up by the ability of that government to collect taxes by any means necessary including force (and backed up by the petrodollar system; the ability of the US government to maintain a currency monopoly on energy pricing worldwide).

That sounds like hyperbole, so we can put it in context and dial it back a bit. Even Switzerland, well-known for its hundreds of years of geopolitical neutrality in the face of war, inherently uses proof-of-force to collect taxes in its fiat currency. So, even the most benign and nonviolent society, for the least belligerent purposes possible, still uses this proof-of-force mechanism to ensure the societal usage of its government-issued money, as a way to provision the government. In benign environments, force is sharply minimized by the fact that people vote for the government, or can leave the country and renounce citizenship if they do not wish to play by these rules, and thus can choose another country’s ruleset if that other country will let them in.

To put it bluntly, if you don’t pay your taxes, and in a form of legal tender accepted by the government, you eventually get a knock on your door from people with guns, and/or you’ll have to leave and go somewhere else. That remains the case unless or until the country’s legal tender breaks down enough that the majority of people can’t/won’t use it and the government is unable to enforce its use with that level of currency rebellion, which happens during hyperinflations and near-hyperinflations, including in many developing countries in modern times.

With a stock-to-flow ratio averaging somewhere between 5x to 20x in most cases, major fiat currencies have higher stock-to-flow ratios than most commodities, but lower stock-to-flow ratios than bitcoin and gold. However, in addition to having a moderately high stock-to-flow ratio, fiat currency benefits from the unique backing by the government, including active stabilization to try to reduce volatility, which is what gives it a degree of staying power.

I have a longform piece that describes the process of how fiat currency is created and destroyed here.

Final Thoughts: Think Outside of the Box

When money changes in a society, it always feels weird for people who go through it.

Imagine being someone who used shells for money their whole life, like your mother and your grandmother and your great-grandmother before you. And then, due to interactions with a foreign people, shiny yellow and gray metal circles with pictures of faces on them are starting to be used as money instead and seem to be displacing your shells. The foreigners, with better technology, can seemingly produce all the shells they want (which devalues them), but their shiny metal circles are harder to make and thus seem invulnerable to devaluation.

Or imagine using gold and silver coins as money your whole life, like your father and your grandfather and your great-grandfather, after thousands of years of global history of these things being used as money. And then, due to changing technology and government mandates, you’re supposed to use pieces of paper that are backed by gold instead and treat them the same way, and it’s illegal to actually own gold. And then, they take away the peg to gold and you’re still supposed to keep using these papers for the same value anyway, even as the quantity of these papers seems to keep increasing. The successful papers, being actively managed, tend to be rather stable most of the time even though they degrade in value over time.

And lastly, imagine using these unbacked papers as money your whole life. The interest rates on those papers at first are higher than price inflation and they’re rather stable in terms of purchasing power from year to year, but over time the interest rates keep going down until they are well below the prevailing inflation rate, meaning you lose purchasing power over time by holding those papers. And then some anonymous entity comes along and creates internet money that works via encryption and algorithms that you don’t fully understand, but it seems to keep growing in users and value compared to other assets for over a decade. Nobody can make more than the pre-programmed amount of it, it can be used for peer-to-peer domestic or international payments, and it can be self-custodied and transferred more easily and more securely than any prior money. But then we have questions about its technical risks, questions about whether governments can successfully prevent it from spreading, questions about its volatility, and other challenges along those lines that could cause it to stagnate or fail.

What do we do in these situations?

Well, I think the first rational thing is to be skeptical. We can’t just dive all-in to anything new that people claim is money.

In fact, honestly at first we can probably ignore it, since the probability of any given new thing becoming money is low. It’s pretty rare in human history that a serious new form of money emerges. But then if it doesn’t go away, and indeed keeps surviving from multiple 80%+ drawdowns over more than a decade to greater and greater heights of increasing monetization, then realistically we need to research it, test its hardness, and envision all the ways it could conceivably fail.

If we happen to have expertise or interest in that field for one reason or another we might jump onto it quicker, or we might go about our lives and let it continue growing, so that we learn more about it and then maybe buy a little bit and get to understand it. If competitors spring up, we probably should investigate some of those as well, and watch how they behave, and understand the differences. And then over time, we can mostly let the market answer our questions for us. We can hold an amount of this new money that makes sense for our risk profile, and let it appreciate (or not) over time.

If it does not appreciate, then that answers a set of questions, and we risked very little. If it does appreciate, then we continue to watch this asset gain a larger and larger monetary premium. It then generally becomes owned by more people and becomes a larger percentage of what we own because it grows in value faster than our other assets. Due to Gresham’s law, it won’t be readily spent too often, and will instead have a tendency to be hoarded, and only spent when necessary or in niche circumstances for its tank-like payment properties. The vast majority of participants will treat it as a long-term financial asset. It if becomes very large and dominant and its volatility goes down over time, its usage in spending will likely go up.

Looking out over the long run, it’s clear that money will become increasingly digital. The question is, will stateless peer-to-peer bearer assets like bitcoin become a persistently important version of money, worth trillions of dollars in market capitalization, or will state-created CBDCs or state-regulated corporate stablecoins be the main path forward instead? And to the extent that they coexist with each other, how much market share can we expect each one to take? That’s a topic I’ll continue to analyze over time.

As I close out this article, I’ll circle back to an earlier example of bitcoins being used as confiscation-resistant self-custodied payment for Afghani women and girls nearly a decade ago. Alex Gladstein documented what became of some of them:

A few of the women did keep their bitcoin from 2013. One of them was Laleh Farzan. Mahboob told me that Farzan worked for her as a network manager, and in her time at Citadel Software earned 2.5 BTC. At today’s exchange rate, Farzan’s earnings would now be worth more than 100 times the average Afghan annual income.

In 2016, Farzan received threats from the Taliban and other conservatives in Afghanistan because of her work with computers. When they attacked her house, she decided to escape, leaving with her family and selling their home and assets to pay brokers to take them on the treacherous road to Europe.

Like thousands of other Afghan refugees, Farzan and her family traveled by foot, car and train thousands of miles through Iran and Turkey, finally making it to Germany in 2017. Along the way, dishonest middlemen and common thieves stole everything they brought with them, including their jewelry and cash. At one point, their boat crashed, and more belongings sank to the bottom of the Mediterranean. It’s a tragic story familiar to so many refugees. But in this case, something was different. Through it all, Farzan was able to keep her bitcoin, because she hid the seed to her bitcoin wallet on a piece of tiny, innocuous-looking paper. Thieves could not take what they could not find.

That’s an example of bitcoin transporting value across borders in a circumstance where gold and cash would have failed. It can be done through a mobile phone, USB stick, piece of paper, cloud storage, or even just by memorizing a twelve-word seed phrase.

Whether the bitcoin network ultimately succeeds or fails in the long run, this global distributed ledger backed up by proof-of-work is clearly a form of money, and one that is worth understanding.
    """, 75),
    ("Python was created in 1987.", 100),
    ("The Python programming language was created in 80s.", 100),
    ("The ITER project started in the 90s.", 100),
    ("The speed of light is exactly 3 kilometers per second.", 100),
    ("The speed of light is precisely 3 km/s.", 100),
    ("I think nuclear fusion is an interesting subject.", 10),
    ("Python's creator is Guido Van Rossum.", 100),
    ("C++ is a superset of C.", 100),
    ("The iPhone's evolution is plateauing.", 100),
    ("Python, you know, may be one of the languages of all time, maybe!", 5),
    ("""
    -- Two dashes start a one-line comment.

--[[
     Adding two ['s and ]'s makes it a
     multi-line comment.
--]]

----------------------------------------------------
-- 1. Variables and flow control.
----------------------------------------------------

num = 42  -- Numbers can be integer or floating point.

s = 'walternate'  -- Immutable strings like Python.
t = "double-quotes are also fine"
u = [[ Double brackets
       start and end
       multi-line strings.]]
t = nil  -- Undefines t; Lua has garbage collection.

-- Blocks are denoted with keywords like do/end:
while num < 50 do
  num = num + 1  -- No ++ or += type operators.
end

-- If clauses:
if num > 40 then
  print('over 40')
elseif s ~= 'walternate' then  -- ~= is not equals.
  -- Equality check is == like Python; ok for strs.
  io.write('not over 40\n')  -- Defaults to stdout.
else
  -- Variables are global by default.
  thisIsGlobal = 5  -- Camel case is common.

  -- How to make a variable local:
  local line = io.read()  -- Reads next stdin line.

  -- String concatenation uses the .. operator:
  print('Winter is coming, ' .. line)
end

-- Undefined variables return nil.
-- This is not an error:
foo = anUnknownVariable  -- Now foo = nil.

aBoolValue = false

-- Only nil and false are falsy; 0 and '' are true!
if not aBoolValue then print('it was false') end

-- 'or' and 'and' are short-circuited.
-- This is similar to the a?b:c operator in C/js:
ans = aBoolValue and 'yes' or 'no'  --> 'no'

karlSum = 0
for i = 1, 100 do  -- The range includes both ends.
  karlSum = karlSum + i
end

-- Use "100, 1, -1" as the range to count down:
fredSum = 0
for j = 100, 1, -1 do fredSum = fredSum + j end

-- In general, the range is begin, end[, step].

-- Another loop construct:
repeat
  print('the way of the future')
  num = num - 1
until num == 0


----------------------------------------------------
-- 2. Functions.
----------------------------------------------------

function fib(n)
  if n < 2 then return 1 end
  return fib(n - 2) + fib(n - 1)
end

-- Closures and anonymous functions are ok:
function adder(x)
  -- The returned function is created when adder is
  -- called, and remembers the value of x:
  return function (y) return x + y end
end
a1 = adder(9)
a2 = adder(36)
print(a1(16))  --> 25
print(a2(64))  --> 100

-- Returns, func calls, and assignments all work
-- with lists that may be mismatched in length.
-- Unmatched receivers are nil;
-- unmatched senders are discarded.

x, y, z = 1, 2, 3, 4
-- Now x = 1, y = 2, z = 3, and 4 is thrown away.

function bar(a, b, c)
  print(a, b, c)
  return 4, 8, 15, 16, 23, 42
end

x, y = bar('zaphod')  --> prints "zaphod  nil nil"
-- Now x = 4, y = 8, values 15...42 are discarded.

-- Functions are first-class, may be local/global.
-- These are the same:
function f(x) return x * x end
f = function (x) return x * x end

-- And so are these:
local function g(x) return math.sin(x) end
local g; g  = function (x) return math.sin(x) end
-- the 'local g' decl makes g-self-references ok.

-- Trig funcs work in radians, by the way.

-- Calls with one string param don't need parens:
print 'hello'  -- Works fine.


----------------------------------------------------
-- 3. Tables.
----------------------------------------------------

-- Tables = Lua's only compound data structure;
--          they are associative arrays.
-- Similar to php arrays or js objects, they are
-- hash-lookup dicts that can also be used as lists.

-- Using tables as dictionaries / maps:

-- Dict literals have string keys by default:
t = {key1 = 'value1', key2 = false}

-- String keys can use js-like dot notation:
print(t.key1)  -- Prints 'value1'.
t.newKey = {}  -- Adds a new key/value pair.
t.key2 = nil   -- Removes key2 from the table.

-- Literal notation for any (non-nil) value as key:
u = {['@!#'] = 'qbert', [{}] = 1729, [6.28] = 'tau'}
print(u[6.28])  -- prints "tau"

-- Key matching is basically by value for numbers
-- and strings, but by identity for tables.
a = u['@!#']  -- Now a = 'qbert'.
b = u[{}]     -- We might expect 1729, but it's nil:
-- b = nil since the lookup fails. It fails
-- because the key we used is not the same object
-- as the one used to store the original value. So
-- strings & numbers are more portable keys.

-- A one-table-param function call needs no parens:
function h(x) print(x.key1) end
h{key1 = 'Sonmi~451'}  -- Prints 'Sonmi~451'.

for key, val in pairs(u) do  -- Table iteration.
  print(key, val)
end

-- _G is a special table of all globals.
print(_G['_G'] == _G)  -- Prints 'true'.

-- Using tables as lists / arrays:

-- List literals implicitly set up int keys:
v = {'value1', 'value2', 1.21, 'gigawatts'}
for i = 1, #v do  -- #v is the size of v for lists.
  print(v[i])  -- Indices start at 1 !! SO CRAZY!
end
-- A 'list' is not a real type. v is just a table
-- with consecutive integer keys, treated as a list.

----------------------------------------------------
-- 3.1 Metatables and metamethods.
----------------------------------------------------

-- A table can have a metatable that gives the table
-- operator-overloadish behavior. Later we'll see
-- how metatables support js-prototype behavior.

f1 = {a = 1, b = 2}  -- Represents the fraction a/b.
f2 = {a = 2, b = 3}

-- This would fail:
-- s = f1 + f2

metafraction = {}
function metafraction.__add(f1, f2)
  sum = {}
  sum.b = f1.b * f2.b
  sum.a = f1.a * f2.b + f2.a * f1.b
  return sum
end

setmetatable(f1, metafraction)
setmetatable(f2, metafraction)

s = f1 + f2  -- call __add(f1, f2) on f1's metatable

-- f1, f2 have no key for their metatable, unlike
-- prototypes in js, so you must retrieve it as in
-- getmetatable(f1). The metatable is a normal table
-- with keys that Lua knows about, like __add.

-- But the next line fails since s has no metatable:
-- t = s + s
-- Class-like patterns given below would fix this.

-- An __index on a metatable overloads dot lookups:
defaultFavs = {animal = 'gru', food = 'donuts'}
myFavs = {food = 'pizza'}
setmetatable(myFavs, {__index = defaultFavs})
eatenBy = myFavs.animal  -- works! thanks, metatable

-- Direct table lookups that fail will retry using
-- the metatable's __index value, and this recurses.

-- An __index value can also be a function(tbl, key)
-- for more customized lookups.

-- Values of __index,add, .. are called metamethods.
-- Full list. Here a is a table with the metamethod.

-- __add(a, b)                     for a + b
-- __sub(a, b)                     for a - b
-- __mul(a, b)                     for a * b
-- __div(a, b)                     for a / b
-- __mod(a, b)                     for a % b
-- __pow(a, b)                     for a ^ b
-- __unm(a)                        for -a
-- __concat(a, b)                  for a .. b
-- __len(a)                        for #a
-- __eq(a, b)                      for a == b
-- __lt(a, b)                      for a < b
-- __le(a, b)                      for a <= b
-- __index(a, b)  <fn or a table>  for a.b
-- __newindex(a, b, c)             for a.b = c
-- __call(a, ...)                  for a(...)

----------------------------------------------------
-- 3.2 Class-like tables and inheritance.
----------------------------------------------------

-- Classes aren't built in; there are different ways
-- to make them using tables and metatables.

-- Explanation for this example is below it.

Dog = {}                                   -- 1.

function Dog:new()                         -- 2.
  newObj = {sound = 'woof'}                -- 3.
  self.__index = self                      -- 4.
  return setmetatable(newObj, self)        -- 5.
end

function Dog:makeSound()                   -- 6.
  print('I say ' .. self.sound)
end

mrDog = Dog:new()                          -- 7.
mrDog:makeSound()  -- 'I say woof'         -- 8.

-- 1. Dog acts like a class; it's really a table.
-- 2. function tablename:fn(...) is the same as
--    function tablename.fn(self, ...)
--    The : just adds a first arg called self.
--    Read 7 & 8 below for how self gets its value.
-- 3. newObj will be an instance of class Dog.
-- 4. self = the class being instantiated. Often
--    self = Dog, but inheritance can change it.
--    newObj gets self's functions when we set both
--    newObj's metatable and self's __index to self.
-- 5. Reminder: setmetatable returns its first arg.
-- 6. The : works as in 2, but this time we expect
--    self to be an instance instead of a class.
-- 7. Same as Dog.new(Dog), so self = Dog in new().
-- 8. Same as mrDog.makeSound(mrDog); self = mrDog.

----------------------------------------------------

-- Inheritance example:

LoudDog = Dog:new()                           -- 1.

function LoudDog:makeSound()
  s = self.sound .. ' '                       -- 2.
  print(s .. s .. s)
end

seymour = LoudDog:new()                       -- 3.
seymour:makeSound()  -- 'woof woof woof'      -- 4.

-- 1. LoudDog gets Dog's methods and variables.
-- 2. self has a 'sound' key from new(), see 3.
-- 3. Same as LoudDog.new(LoudDog), and converted to
--    Dog.new(LoudDog) as LoudDog has no 'new' key,
--    but does have __index = Dog on its metatable.
--    Result: seymour's metatable is LoudDog, and
--    LoudDog.__index = LoudDog. So seymour.key will
--    = seymour.key, LoudDog.key, Dog.key, whichever
--    table is the first with the given key.
-- 4. The 'makeSound' key is found in LoudDog; this
--    is the same as LoudDog.makeSound(seymour).

-- If needed, a subclass's new() is like the base's:
function LoudDog:new()
  newObj = {}
  -- set up newObj
  self.__index = self
  return setmetatable(newObj, self)
end

----------------------------------------------------
-- 4. Modules.
----------------------------------------------------


--[[ I'm commenting out this section so the rest of
--   this script remains runnable.

-- Suppose the file mod.lua looks like this:
local M = {}

local function sayMyName()
  print('Hrunkner')
end

function M.sayHello()
  print('Why hello there')
  sayMyName()
end

return M

-- Another file can use mod.lua's functionality:
local mod = require('mod')  -- Run the file mod.lua.

-- require is the standard way to include modules.
-- require acts like:     (if not cached; see below)
local mod = (function ()
  <contents of mod.lua>
end)()
-- It's like mod.lua is a function body, so that
-- locals inside mod.lua are invisible outside it.

-- This works because mod here = M in mod.lua:
mod.sayHello() -- Prints: Why hello there Hrunkner

-- This is wrong; sayMyName only exists in mod.lua:
mod.sayMyName()  -- error

-- require's return values are cached so a file is
-- run at most once, even when require'd many times.

-- Suppose mod2.lua contains "print('Hi!')".
local a = require('mod2')  -- Prints Hi!
local b = require('mod2')  -- Doesn't print; a=b.

-- dofile is like require without caching:
dofile('mod2.lua')  --> Hi!
dofile('mod2.lua')  --> Hi! (runs it again)

-- loadfile loads a lua file but doesn't run it yet.
f = loadfile('mod2.lua')  -- Call f() to run it.

-- load is loadfile for strings.
-- (loadstring is deprecated, use load instead)
g = load('print(343)')  -- Returns a function.
g()  -- Prints out 343; nothing printed before now.

--]]
    """,100)
]