rot13.rb

# Method name: rot13
# Inputs:      A String to be encoded in ROT13
# Returns:     A ROT13-encoded string
# Prints:      Nothing

# ROT13 is short for "rotate 13" and is the simplest example of a "Caesar cipher".
# See http://en.wikipedia.org/wiki/ROT13

# ROT13 works by taking a string and "rotating" all the characters in that
# string 13 places to the right in the alphabet, with "z" wrapping around to
# the beginning of the alphabet.
#
# In other words, every letter from the top row in this table is replaced with
# the corresponding letter in the bottomr row
#
#   ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
#   NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm
#
# "ROT13" is called a Caesar cipher because Julius Caesar used such letter
# replacement schemes to "encrypt" his communication.


def rot13(string)
end

if __FILE__ == $0
  # See http://www.rot-n.com/ to generate test inputs and outputs
  p rot13("The Quick Brown Fox Jumps Over The Lazy Dog") == "Gur Dhvpx Oebja Sbk Whzcf Bire Gur Ynml Qbt"
end