Basic description
A simple calculator for working with infinite precision rational numbers (fraction and integer input), with a handwritten lexer and simple shunting-yard based parser, and a slightly unusual syntax. Written for fun, because my nice, overpriced TI-something calculator was in storage, and because I didn't like the normal input methods for fractions in most programming language REPLs, etc.
Syntax
Think classic order of operations: +, -, *, /, (, and ) do what you expect, including precedence. The // operator takes two integers and forms a fraction from them, and has higher precedence than all the other operators (though not parentheses, of course). There is no exponentiation, variable assignment, or other identifiers, nor floats.
Use
Just cd into the repo's root directory and run python fraction_calculator. A starting prompt will print. After that, enter expressions and they will be evaluated. Type 'exit' to quit, or Ctrl-C (but this may cause weird errors).