Offtopic, but I remember implementing a calculator was Compilers & Parsing 101. I mention this because the Readme specifically calls out the various ways of in

Offtopic, but I remember implementing a calculator was Compilers & Parsing 101. I mention this because the Readme specifically calls out the various ways of inputting an expression, which is a non-issue with any compiler background. (It's handled by the lexer, which is step that handles processing input into "lexical" elements, which are then passed to actual "parser" that constructs the syntactic structure)