This body of code will be used to solve the 2kyu Codewars kata Whitespace Interpreter.

I know I'll be needing:

• a Lexer
• a Parser

I may need:

• a compiler
• an interpreter ... we'll find out

Using a trie structure to store tokens and their associated functions has made it so we don't need to separate lexing and parsing. As the white space stream is read in a for loop, we walk the tokenTrie until we hit a leaf. The leaf is a callback function specific for that command.

We execute the command's function. The functions are in charge of deciding whether they are valid, what input they need, what they do/ return etc..

If our first token is a command for stack manipulation, we know we're going to need to glean a number from the following whitespace characters in the stream. getNum consumes the stream to build a number, then returns the number and the index where it ended to the function that called it.

Then that function (the one called from its leaf positionin tokenTrie) does what it needs to do with the number, and then returns the new index into the stream to the for loop.