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Re: final light versions of Oracle compatibility (SQLSTATE,

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 (view raw or flat)
Thread:
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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