Re. CALLF: I'll think about it properly sometime during next week. (I am torn about it: half the time I can't remember why I like it, and half the time I can't remember why I *don't* like it.)
i'm also torn about it, but after re-reading the thread i think the consensus leans towards that ensure-functionf is ok, so for now i've pushed it without using CALLF.
later this could use CALLF, or it can even be moved into another sister package of alexandria...