This is my weak attempt to use Treetop to parse a grammar. The grammar looks a lot like an expression in an "if" statement.

"(Name=Bob&(IsCool=Yes|Age<20)"

Treetop keeps giving me issues with endless recursion, so I've simplified the grammar to deal directly with the problem: recursive parenthesis. Once I deal with that, the rest should be easy.

Treetop Docs: http://treetop.rubyforge.org/