What grammar based parser-generator tools exist for ruby?

Question

What open source (preferably gem-based) parser-generator options do I have in Ruby?

I've used (flex&bison)|(lex&yacc) from C in the past, and I'm comfortable with BNF-style specifications.

I've heard of treetop, but it looks a bit alien and verbose compared to yacc...

Purpose: I want to convert my text markup language to a BNF and generate the parsing code.

Answer 1

Have you looked at rex and racc, the gem versions of lex and yacc?