From: | Neil Conway <neilc(at)samurai(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Pavel Stehule <stehule(at)kix(dot)fsv(dot)cvut(dot)cz>, pgsql-patches(at)postgresql(dot)org, pgman(at)candle(dot)pha(dot)pa(dot)us |
Subject: | Re: final light versions of Oracle compatibility (SQLSTATE, |
Date: | 2005-06-10 04:24:33 |
Message-ID: | 42A91601.8000203@samurai.com |
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Lists: | pgsql-patches |
Tom Lane wrote:
> Right, mid-rule actions were what I had in mind. They're not uglier
> than introducing empty nonterminals
Well, IMHO they make the grammar rather hard to read when the action has
multiple lines (we would need at least 6 lines of code in the mid-rule
action, I believe). Unless we want two contiguous mid-rule actions
(which is even _less_ readable), we'll need to futz with adding another
member to %union to hold the two varnos the mid-rule action will
produce. Considering that the Bison manual suggests that it implements
mid-rule actions by introducing an implicit bogus non-terminal ([1]), I
don't think there is likely to be a difference in performance either
way, and I think mid-rule actions don't offer a notational improvement
in this case.
-Neil
[1]
http://www.gnu.org/software/bison/manual/html_mono/bison.html#Mid_002dRule-Actions,
toward the end of the section
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