Comment author: administrator

At http://caml.inria.fr/ocaml/htmlman/manual009.html, under "Keywords", the
keyword "??" is listed.

So far as I can tell, this keyword appears nowhere in the grammar and
is not a possible output from the lexer.

You haven't looked in the right grammar...
"??", like "[<" and ">]" is a keyword of the syntax extensions for streams,
which is implemented in the camlp4 preprocessor.

Also, this keyword also matches the lexical syntax for prefix-symbol
as described in "Prefix and infix symbols", so having "??" as a
keyword makes the lexical grammar ambiguous.

Many keywords are reserved, that also match one of the lexical
conventions for identifiers (for example, all alphabetical keywords).
That doesn't introduce any ambiguity: ?? is a keyword, not an identifier.

Therefore, I think the document is in error and does not describe the
implemented language. I can't figure out what was intended, though.

Actually, we have a bug here, because the normal compiler accepts ?? as
an identifier, but camlp4o cannot compile programs that use it (because
it does recognise ?? as a keyword). The implementation needs to be fixed.

-- Damien

Comment author: administrator

Need to make ?? a keyword in parsing/lexer.mll.

Comment author: administrator

You haven't looked in the right grammar...
"??", like "[<" and ">]" is a keyword of the syntax extensions for streams,
which is implemented in the camlp4 preprocessor.

Makes sense. Thanks.

Tim Freeman
tim@fungible.com
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