When the Types sig was just getting up to speed the last time, someone
expressed that there's no easy way to prototype language extensions.
I mentioned "mobius", which is a Python compiler based on a SPARK grammar.

Mobius had performance problems, and didn't ease the implementation of
the new grammar in core Python because it used a different syntax of
grammar.

Mobius2 exposes the Python parser and parser generator to Python code.
It means that you get all the speed of the builtin parser[1], its
reliability[2] and extensibility, and easy portability to core Python.

If any types-sig proposals include language extensions, I suggest that you
take a look at Mobius2.

http://sourceforge.net/projects/mobiuspython/

The portions of interest are the "mobius2" directory, and the demo/*2
directories (currently just two simple uses of mobius2).

Jeff
jepler@[...].com
jepler@[...].net
[1] Actually, it's about 15% faster, and I'm not sure why.
[2] A 159-case test suite covers all productions in the core Python 2.0
    language.  All cases are verified to produce the same results (ASTs)
    as the builtin parser, which isn't terribly surprising.