🦀 rustic-calc

A fast terminal calculator written in Rust. rustic-calc provides a keyboard-driven TUI for evaluating expressions, storing variables, reviewing history, and plotting expressions with one unknown variable.

✨ Features

• Interactive TUI built with ratatui
• Three panes for input, history, and variables
• Vim-style input editor with Insert, Normal, and Visual modes
• Expression evaluation with operator precedence for:
  • +, -, *, /, ^
• Parentheses support for grouped expressions (including nested groups)
• Unary minus support for negative values
• Variables via assignment syntax (x=2+3) and reuse in later expressions
• Implicit multiplication support (7x becomes 7*x, 2(a+b) becomes 2*(a+b))
• History recall and selection from the history pane
• Automatic scatter plotting for expressions with exactly one unknown variable (sampled from -10 to 10)
• Inline error reporting for parse/evaluation issues

🚀 Getting Started

Prerequisites

• Rust (2024 edition)

Installation

Clone the repository and build the project using Cargo:

git clone https://github.com/marc-niclas/rustic-calc.git
cd rustic-calc
cargo install --path .

Usage

Run the calculator:

rcalc run

Expression examples

3*4-1
b=2
a=b+5
7x+a        # plots y = 7x + a for x in [-10, 10]
2(a+b)      # implicit multiplication with parentheses

Controls

Global

Key	Action
Ctrl+C	Quit application

Input pane

Key	Action
Enter	Submit expression
Esc	Switch from Insert to Normal mode
Up Arrow	Recall last expression (Insert mode)
Backspace	Delete previous character (Insert mode)
Left / Right	Move cursor (Insert mode)

Normal mode (input pane)

Key	Action
i / a / I / A	Enter Insert mode (Vim-style)
h / l or Left / Right	Move cursor
w / b	Word motions
0 / $	Line start / line end
x	Delete character under cursor
v	Enter Visual mode
p / P	Paste yanked text after / before cursor
Tab / Shift+Tab	Cycle focus: Input -> History -> Variables

History and Variables panes

Key	Action
Up / Down	Move selection
Enter	Load selected item into input
i	Return to input Insert mode
Tab / Shift+Tab	Cycle focus
Left / Right	Jump focus between History and Variables

🧪 Testing

The project includes unit and integration tests for calculation, tokenization, variables, editor behavior, and TUI interactions.

cargo test

🛠️ Development

This project uses pre-commit to ensure code quality.

1. Install pre-commit hooks:

   prek install
   prek install -t commit-msg

2. The CI pipeline runs clippy and rustfmt on every push.

Project Structure

• src/main.rs: Application entrypoint
• src/tui_app.rs: TUI state, key handling, and rendering orchestration
• src/input_editor.rs: Vim-style line editor logic
• src/calculate.rs: Expression evaluation
• src/tokenize.rs: Tokenization and implicit multiplication
• src/variables.rs: Variable assignment parsing
• src/widgets/: TUI pane widgets (help, input, history, variables, plot)
• tests/: Integration tests for calculator and TUI behavior

📜 License

Distributed under the MIT License. See LICENSE for more information.

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Built with Rust and Ratatui.