feat(eval): add functions and constants

added constants pi, e
added functions sin, cos, tan, asin, acos, atan, abs, and sqrt
fixed displaying decimals without normalizing them
todo: add imaginary number support

src/math/mod.rs

@@ -2,7 +2,9 @@ use crate::math::types::Expression;
 
 mod display;
 mod eval;
+mod functions;
 mod lexer;
+mod math_constants;
 mod parser;
 
 pub mod types;