Sorry, mistyping...

expr:
   | simple_expr
    ...
   | MINUS expr %prec unary_minus
    ...

simple_expr:
    ...
  |  constant
    ...

simple_pattern:
    ...
   | signed_constant
    ...

constant:
    INT
  | FLOAT

signed_constant:
    constant
  | MINUS INT
  | MINUS FLOAT

----- Original Message ----- 
From: "Damien Doligez" <damien.doligez@inria.fr>
To: "caml Caml" <caml-list@inria.fr>
Sent: Friday, August 13, 2004 08:05
Subject: Re: [Caml-list] CFG's and OCaml


> On Aug 13, 2004, at 16:04, David McClain wrote:
>
> > simple_expr:
> > constant
> > ...
> >
> > simple_pattern:
> > signed_constant
> > ...
> >
> > constant:
> > INT
> > | FLOAT
> >
> > signed_constant:
> > constant
> > | MINUS INT
> > | MINUS FLOAT
> >  ;; /*  ---------------------------------------------------------- */
> >
> > The reduce/reduce conflict comes on deciding whether to assign an INT
> > seen to signed_constant which will reduce to simple_pattern, or
> > instead to become constant which reduces to simple_expr. Both Inria
> > and I do completely different semantic reductions in these two cases,
> > and so a reduce/reduce conflict could be fatal here...
>
> But...  There can only be a reduce-reduce conflict if you have two
> derivations
> of the same prefix, one of which expects a constant as the next
> nonterminal,
> and the other expects a signed_constant.  In other words, we need more
> context
> to tell what's going on.  You should give option -v to ocamlyacc and
> look
> at the resulting *.output file.  It's a bit hard to understand at first,
> but with some experience you can get a little information out of it.
>
> -- Damien
>
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