Refactoring Effort

[svhawkins]

Rework the lexing and parsing process to not be as buggy/imprecise. Make it more robust, flexible, and overall not sh*t.

• Refactor the tokenizer to either use flex/similar tools or to implement DFA yourself
  • Add unit tests
• Refactor the parsing part to use bison, self-implemented PDA, or to use recursive descent/ascent and/or other methods.
  • Add unit tests
  • Current 'stack approach' is similar to recursive descent, just doesn't use 'real' recursion 😜
• Expand the definition of the 'calculator language' based on CC notes from when you took the class
• Add integration tests
• (Tentative) Add command-line options to change scanning/parsing methods
• (Tentative) Perform scanning + parsing in a single pass rather than two