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,
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