###1. how to write a -.l file:

• structure: four main blocks

  • declarations
  • delimiter
  • regular expressions definition
  • delimiter
  • translation rules
  • delimiter
  • auxiliary functions

• declaration

  • %{ have to at the beginning of line
  • %} have to at the beginning of the line

• delimiter:

  • %% have to at the beginning of line

• regular expressions definition

  • pattern {action} - the pattern and action must be splited by a space

• supported regex in the -.l file:

  • have to use {} to surround your predefined regex expression, not add any other char(include space) between {} or it will fail to figure out it.
  • support nested parenthesis, like (a(b+)c)+ or RE (..) then (RE+).
  • not support wild card character '.', and using simple dot symbol also have to escape it for I use it internally

• mis:

  • not allow multiple line comment for '*.l' components,
    but allow it in translation rule or in your method
  • if a single word is in multiple regex range, output is undefined.

###2. How to use produced file:

• first compile res.c to res.out
• input/output:
  • input: a c file
  • output: run res.out temp.c will print the token lists in console

###3. The longest token my implementation can recognize is 256