PLY(Python Lex Yacc) in gem5

http://www.dabeaz.com/ply/ply.html

PLY relies on reflection (introspection) to build its lexers and parsers.

Here is the basic ideas:

(Lex)Token:

• tokens list

  tokens

• specification of tokens: regex in python re mode

  t_ prefixed variable or function

(Yacc)Parser

• grammaer rule: function with docstring contains grammaer specification, e.g.

  def p_expression_plus(p):
       'expression : expression PLUS term'
       #   ^            ^        ^    ^
       #  p[0]         p[1]     p[2] p[3]
  
       p[0] = p[1] + p[3]