Ruby uses bison. I got started on this when Steve Yegge blogged about hiring Ruby programmers and I found myself wanting in a couple of skills areas. I need to grok more on Ruby’s use of bison, I think. No better way than to teach oneself.
Ruby’s source is no secret. Everyone can download it. Bison’s docs are also out there.
Update: Done some reading at Wikipedia. Some articles are there, but I need more storytelling, less listing of data.
Got me the Ruby source which was very, very easy to do. Now I can read it.