And here's a truly nifty application of it for parsing Python: <a href="http://effbot.org/zone/simple-top-down-parsing.htm" rel="nofollow">http://effbot.org/zone/simple-top-down-parsing.htm</a> .<p>Funny how these things go in cycles: parser generators were all the rage for a few decades, and now people are rediscovering the pleasures and strengths of top-down recursive parsers. (E.g., in the new clang compiler that's part of the LLVM project.)