[Caml-list] camlp4 extensions and lexer replacements

[John Goerzen <jgoerzen@complete.org>]

Hello,

I am working on developing a syntax extension that:

 1. Can use most of the rules in pa_o/pa_r, replaces some, and adds some

 2. Requires a new lexer.

Now, it's easy enough to just accomplish #1 with the EXTEND syntax.  I
can just place my .cmo after pa_o.cmo on the camlp4 command line and
that's good.

But #2 is trickier.  pa_o.ml contains this:

  Grammar.Unsafe.gram_reinit gram (Plexer.gmake ());

So I can't define my lexer first -- pa_o.ml will just overwrite it.
Worse, I can't define my lexer second, either.  Plexer relies on the
(strange, imho) notion of deciding whether something is a LIDENT or
keyword based on the list of keywords-as-tokens that were encountered in
a grammar.  But the grammar reinit functions that I would have to use to
put in my lexer don't preserve that information, so my lexer would have
no way to differentiate a LIDENT from a keyword.  Also, Plexer provides
no way to get a list of entries in its internal hashtable.

It seems that there should be an easy way to do this, but I just can't
figure it out.

I would really avoid having to hack up pa_o.ml.

Thanks,
John

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