Calculator project for Fundamentals course of The Odin Project.

I wanted to implement order-of-operations and parentheses, and doing it as a state machine seemed like a pain, so I dug deep into my memory of computer science courses from 25-30 years ago, along with some newfound asynchronous and object-oriented techniques, and did the following:

• A top-down parser (basically recursive descent)
  • expr := term { '+' term | '−' term }*
  • term := factor { '*' factor | '/' factor }*
  • factor := number | '(' expr ')'
  • number := { digit }*
• An asynchronous buffer - This is because constantly switching the event listeners was cumbersome. Plus, it's more natural in a top-down parser for the parser to ask for tokens, rather than have the data trigger the parser. So:
  • The mouse (and ToDo keyboard) events push entries to a buffer array.
  • The parser shifts items off the buffer aray asynchronously via a promise. If there is no data, the promise is resolved by the next item pushed to the buffer.
  • A class to encapsulate the operations, buffer, and the promise(s) awaiting fulfillment.

Currently on the ToDo list are:

• Make it work repeatedly
• Decimal input values
• Powers
• Keyboard shortcuts
• Scientific notation
• Switch to Shunting yard algorithm??? This algorithm is driven by the input data, rather than driven by the parser, alleviating the need for a buffer.