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.


[1], toward the end of the section

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