[Rd] Feature request: non-dropping regmatches/strextract

[Cyclic Group Z_1]

I do think keeping the default behavior is desirable for backwards compatibility; my suggestion is not to change default behavior but to add an optional argument that allows a different behavior. Although this can be implemented in a user-defined function, retaining empty matches facilitates programmatic use, and seems to be something that should be available in base R. It is available, for example, in MATLAB, a comparable array language.

Alternatively, perhaps a nomatch (or maybe emptymatch) argument in the spirit of `[.data.table`? That is, an argument nomatch where nomatch = NULL (the default) results in drops for vector outputs and character(0) for list outputs and nomatch = NA results in insertion of NA_character_, and nomatch = '' results in insertion of empty string.

I can submit proposed patch code if others think this is a good idea.

What are your thoughts on the proposed alteration to (currently nonexported) strextract? I assume (maybe wrongly) that the plan is to eventually export that function.

Thank you,
CG