Emits lexer item to output channel

Parse parses given infix expression and produces Abstract syntax tree

NewParserError intantiates new Parser error

Interpret is function that evaluates AST and returns corresponding result

helper debug func

NewInterpreterError intantiates new Interpreter error

Consume next rune if its one of 'runes' parameter, otherwise no effect

Move to next ASCII or UTF-8 character/rune

Items method gets channel of lex items

Lex is constructor for lexer

Run method will is the core part of this lexer It fires off the state machine, starting with lexFn and takes return function as next state once some f

Go back one character/rune

Consume all following runes that are one of 'runes'

Helper func that emits error item IERR with message

Determines precedence of operator given

NewLexerError intantiates new Lexer error

Takes list of postfix formed lexer items and builds binary expression tree

Ignores all un-emitted characters (moves start to current pos)

Check what rune is next in input

Recursive post order traversal that evaluates AST 1. Visit left 2. Visit right 3. Visit self

Converts infix output form of Lexer to postfix form

helper method that translates Lexer item types to AST node types

Debug stringify lex item

Implementation of ADD operation

Implementation of DIVIDE operation

Starting state of state machine, peeks forward and decides what lexing function should be used

Lexes left parenthesis

lexes numbers

Lexes operators

Lexes right parenthesis

Lexes whitespaces and thrashes them (no emitting)

Implementation of MULTIPLY operation

Implementation of SUBTRACT operation

helper debug func

helper debug func