Re: Issue: REDUCE-ARGUMENT-EXTRACTION (version 1)

[Masinter.pa@Xerox.COM]

This is a good writeup. I think we should add the alternative form

(reduce  #'+ (mapcar #'person-age astros)) 

as the most natural equivalence; the stuff with the &optional arguments is
arcane and bogus in cases where there is an initial value.

I think that it is true that

(reduce <fn> sequence :key <key-fn>)  = (reduce <fn> (mapcar <key-fn> sequence))

except of course in the matter of order of evaluation.