PEG Patches

[Noah Lavine]

Hello all,

Attached is a series of patches I've made for the wip-mlucy branch. It
splits the PEG code into several little modules which go in
module/ice-9/peg/. The original peg source file becomes very little.
At the end it finally loses its big eval-when wrapper.

There's one part of this that I'm not satisfied with, which is that
define-nonterminal goes into module/ice-9/peg/string-peg.scm, which is
supposed to be solely for pegs-as-strings. The reason for this is that
I got compiler errors if I didn't do this, and I couldn't figure out
how to stop them. I would appreciate it if someone would take a look
and try to find what I missed.

Also, a note about future ideas - the current PEG code can only parse
strings. However, there is almost nothing string-specific about the
parsing code - just a few calls to string-ref and substring in
codegen.scm. I'd like to see this extended to parse vectors filled
with arbitrary objects. This would let you use a tokenizer with it,
which is the easiest way to implement C correctly, and also probably
the easiest way to store line number information with tokens, which is
necessary for ultimately giving good error messages from PEG parsers.

Thanks,
Noah

0001-Split-peg.scm.patch
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0002-Rename-in-peg.scm.patch
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0003-Make-Macros-Hygienic.patch
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0004-Separate-PEG-Strings.patch
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0005-Factor-PEG-Functions.patch
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0006-Factor-PEG-Structure.patch
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0007-Remove-eval-when.patch
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