[SOLVED] Limitations of PEG grammar & parser generators?

Limitations of PEG grammar & parser generators?

I was enjoying using YARD a lot:

http://www.ootl.org/yard/

http://code.google.com/p/yardparser/

http://www.codeproject.com/KB/recipes/yard-tokenizer.aspx

I was able to construct fully functional calculator. I'm evaluating YARD to do PHP parser. Please kindly advise on limitations of PEG grammar & parser generators. Thank you very much!

Solution

I think the big "problem" with PEGs is that they don't fit into the normal taxonomy of grammars as they operate in a fundamentally different way. Normal grammars are "backwards" in the sense that they describe all the possible sentences (programs) that can be generated. PEGs describe how to parse--they come at the problem from the other end.

In my view this is a more natural way to think about the problem, and certainly for any hand-written (recursive-descent) parser I wouldn't do anything else.