09/06 Notes
===========

Dropbox link to in-class examples (guarenteed to work on arctic)

Down-to Operator
----------------
int x = 10
while (x --> 10){
do
}

What is Lexing?
---------------

A *token* is a category of meaningful substrings in the source language

 * In english this would be types of words or punctuation i.e noun, verb, adj, end-mark.
 * In a program, this could be identifiers, floats, math symbol, keyword, etc...

A *Lexeme* is a substring that represents an instance of a token.

EX
 * Token: Static int
 * Pattern: 0 - 9

Lexical analyzer
  #. Correctly identifies all tokens within a string
  #. Discard usless tokens (whitespace and comments)
  #. Returns each remaining token with its lexeme and the line number it was on

Patterns
 * Condition: if
 * Type: int or float or char
 * Command: print or return or define
 * Static int: 0 - 9 +
 * id: [a-zA-Z][a-zA-Z0-9]
 * Math: +-/ etc
 * assign =
 * Compare
 * Whitespace
 * Endline
 * Unknown: Weird things like the copyright symbol

Lookaheads
----------
A *lookahead* will be important for lexical analysis

Tokens are read left to right, not obvious at first what a token is

Using Regular Expressions
-------------------------

We need to divide ip an input stream into lexemes

  #. Design a set of reqular expressions
  #. Plug them into Lex (Harder without this)

Project 1
---------

Correctness is job 1 and 2 and 3

Implement them nice so it's easier to build on them

 * Keep it simple
 * Design things you can test
 * Don't optimize prematurely
 * It's easier to modify a working system than to get a system working