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Re: x + (y) + z

From: Frank Heckenbach
Subject: Re: x + (y) + z
Date: Fri, 4 Mar 2005 19:19:58 +0100
User-agent: semail 20050101

Derek M Jones wrote:

> >> The statement (y)+z can be parsed as casting
> >> +z to the type y, or as adding y to z.  A couple of
> >> %dprecs solve this problem (I think the cast is the
> >> common case for - and a binary expression for +).
> >
> >What the "common case" is doesn't really matter since a correct
> >parser should be able to recognize all valid inputs, not only the
> >most common ones. So if I understand right what you plan, this would
> >all be just heuristics which don't really solve the problem.
> Since both parses will recognise the input one has to be
> selected.  Picking the common case means that there is
> less work which has to be undone later in the semantics phase.

Undoing and reversing parsing (as you also mentioned in another
mail) may be an option, but IMHO not a very good one, if you can't
use the parser the way it's supposed to.

But since you don't state why you don't do the usual thing (separate
token for type names), I can't say anything more ...


Frank Heckenbach, address@hidden
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