A simple calculator written in Rust.

This is a fist time I learn about parser and Rust, so I decide to write a simple calculator using the Recursive Descent algorithm with the following grammar:

E --> T {( "+" | "-" ) T}
T --> F {( "*" | "/" ) F}
F --> P ["^" F]
P --> v | "(" E ")" | "-" T | Function "(" {E[,]} ")"

This grammar is base on this awesome guide. I also extends it to support function.

Example:

cargo run "1+2*sqrt(4)"

Feature:

• Support the following operators: +,-,*,/,^.
• Built in functions:
  • sin
  • cos
  • tan
  • sqrt
  • abs
  • max: max(arg1,arg2,...)
  • min: min(arg1,arg2,...)
• Built in constants:
  • PI
  • e

TODO:

• Support for variables.
• Better error handling.