Recursive descent parser generator

Recursive descent parser generator is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Write a recursive descent parser generator that takes a description of a grammar as input and outputs the source code for a parser in the same language as the generator. (So a generator written in C++ would output C++ source code for the parser.) You can assume that all of the rules have been preprocessed into a form suitable for the construction of a recursive descent parser. See here for more details: http://www.cs.engr.uky.edu/~lewis/essays/compilers/rec-des.html

Example grammar:

plus \+
times \*
var [a-z]+

!! start -> expr start2

!! start2 -> plus start2

!! start2 -> expr

!! expr -> var expr2

!! expr2 -> times expr2

!! expr2 -> var

Use the parser generator to build a parser that takes arithmetic expressions and turns them in to three address code. The resulting parser should take this (or something similar) as input:

(one + two) * three - four * five
123 + 321

And generate this (or something similar) as output:

_0001 = one + two
_0002 = _0001 * three
_0003 = four * five
_0004 = _0002 - _0003
_0005 = 123 + 321