Re: push parser

[Bob Rossi]

On Mon, Sep 18, 2006 at 10:34:39AM -0700, Paul Eggert wrote:
> Bob Rossi <address@hidden> writes:
> 
> >> Why the #ifdef on YYLTYPE_IS_TRIVIAL?  YYLTYPE_IS_TRIVIAL tells
> >> us whether yyltype is trivial (i.e., does not need attention by
> >> C++ storage managers), not whether it exists.
> >
> > OK, I need to determine if YYLTYPE is exists. What's the best way 
> > to do that?
> 
> b4_locations_if.
> 
> >>        status = yypushparse (ctx, ch, yylval, yylloc);
> > ...
> > I'm not sure that I like passing all the values into yypushparse though.
> > The problem is, not everyone wants to pass all the values in. We would
> > force them to pass values in that they don't care about which could
> > be confusing.
> 
> They always need to pass in ctx, ch, right?  And the ", yylloc"
> will be required if b4_locations_if says you're using locations.
> So the only questionable argument will be yylval.
> 
> One way to address this issue would be to have two entry points:
> 
>        status = yypushparse (ctx, ch, yylloc);
> 
> for tokens that have no semantic value, and
> 
>        status = yypushparseval (ctx, ch, yylval, yylloc);
> 
> for tokens that do.
> 
> Another possibility, which will avoid a copy in some cases if semantic
> values are large, is to pass a pointer:
> 
>        status = yypushparse (ctx, ch, &yylval, yylloc);
> 
> where you pass a NULL pointer if the token has no semantic value.  If
> the copying issue is of concern, it may also make sense to pass yylloc's
> address too:
> 
>        status = yypushparse (ctx, ch, &yylval, &yylloc);
> 
> I don't know whether the copying concern is enough to affect
> performance, though.

I'm not decided on how to modify the yypushparse function parameters.
Have you made up your mind?

Attached is a patch on some changes we both agree on. That is remove the
constant 4 from the user and use YYPUSH_MORE. Also, make yypushparse
return an int, instead of void. This has the benefit of removing the
yyresult_get function.

2006-09-20  Bob Rossi  <address@hidden>

        * data/push.c (yyresult_get): Remove function.
        (YYPUSH_MORE): Add #define.
        (yypushparse): Modify return value.

Thanks,
Bob Rossi

push.c.diff
Description: Text document