Interpreter in rust

Following along all parts of https://medium.com/@p3ld3v/writing-interpreter-in-rust-using-grmtools-7a6a0458b99f

Why?

As a learning exercise.

How to use

Run cargo -q run "expression_string"

Examples:

1. Pass as argument

cargo -q run "2+2"

2. Pass a file containing expression

cargo run test.cnt