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About FsYacc syntac
f#

Hi.

I was trying to compile a parser with the following in its definition file:

1
2
3

params:
    ident ( COMMA ident )*
    ;

And I got the an "Unexpected character '('" error message. Can't I group regular expressions with parentheses?

Of course I can unroll the expression with another non-terminal clause, but I would prefer not to do that if possible.

Am I doing anything wrong?

Thanks.

.

The problem is FsYacc simply doesn't support what you want to do. Unfortunatly you have to unroll into a second non-terminal clause. The best guide to what you can do in fsyacc is still the ocamlyacc manual:
[link:caml.inria.fr]

Thanks,
Rob

By on 11/27/2007 7:18 AM ()

Hi Robert,

Thanks for the reply. In fact, part of what I don't get is exactly due to the ocamllex/ocamlyacc manual.

On section 12.2.4 it is stated that

( regexp )
Match the same strings as regexp.

regexp +
(Strict repetition.) Match the concatenation of one or more strings that match regexp.

regexp *
(Repetition.) Match the concatenation of zero or more strings that match regexp.

So what I expected is that FsYacc followed that. You say it does not.

It would help a lot if there was some doc saying what parts of ocamllex/ocamlyacc manual are actually implemented by fslex/fsyacc and what parts are not. Is there such information anywhere?

Thanks again.

By on 11/27/2007 7:36 AM ()

Section 12.2.4 actually refers to the lexer and these rules are implemented for the lexer, it's section 12.4.3 that describes the grammar of ocamlyacc parser rules.

Though I agree fslex/fsyacc are very lacking in documentation and even the documentation for ocamllex/ocamlyacc isn't that great. I generally end up searching in the parser sample or in the compiler itself for bits of grammar which are similar to what I want to do, which isn't ideal.

By on 11/27/2007 8:09 AM ()

Hi Robert,

Silly mistake of mine. Thanks very much for helping again.

Cheers.

By on 11/27/2007 2:46 PM ()

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