TODO

General :
  - use EBNF rules in the pyggy and pylly grammars.
  - more testing.  We need to use these tools for real things to see if
    they are useful and what features work well and what is needed.
  - A scannerless parser would be nice.  See if there's a good way
    to extend PyGgy or implement an alternate parser with scannerless
    techniques.  If we do this, pylly should use it to read its spec
    file (its far from a regular lexer)
  - write a simple shift reduce parser.   Its really easy to do and
    if a grammar has no ambiguities its more efficient and easier 
    to use (PyGgy's trees have a node listing all possibilities under
    a non-terminal, those arent needed if the grammar is unambiguous).
    Maybe an LALR parser generator would be nice too, maybe not..
  - docstrings!
  - documentation in traditional python style webpages.
  - when emitting code, put a comment in that says where its from.
  - use an exception class.


PyLly :
  - add an option for case insensitive matching.
  - looks like we have two tokens for caret.  unify them.
  - get rid of the ERR token?
  - implement reject rules?  Would require keeping track of all the
    previous accepting states as well as their position in the stream
    and all bytes that occur afterwards.
  - Consider wrapping up the lexer actions in a single class with an
    __init__ function.  This would make keeping lexer state easier for
    people using pylly to write lexers.
  - dfa.py's sanity function needs friendlier output.
  - lexers cannot return arbitrary values for tokens right now.  They
    are always returned as strings.  This needs to be fixed.

PyGgy :
  - a %prec() rule on a production should override all other
    precedences.  Right now if there is an existing precedence
    that conflicts, a conflict error is given.
  - Calculation of the terminal names so that they can be emitted and
    used by the lexer?  Right now we assume that the token names are
    strings with the token identifier value.
  - performing semantic actions during reductions?  possible?
  - using semantic actions to disambiguate?
  - allow automated AST generation as an option.