Noun forms in an expression foobar can be evaluated by
ev(foobar, nouns). This is mentioned by describe(nouns)
and describe(apply_nouns), although not by describe(ev).
I suggest (1) that the description of ev include a
mention of ev(foobar, nouns).
Since noun-form integrals are a common example of noun
forms that someone may want to evaluate, I also suggest
that the descriptions of (2) integrate and (3)
changevar also mention ev(foobar, nouns). Since
changevar is often used to convert an integral into a
form that is (hopefully) easier to integrate, it seems
especially useful to tell how to attempt to evaluate
the noun form returned by changevar.
Finally I also suggest (4) that we strike the
description of apply_nouns, since there is no
implementation of it. See also bug report #711539.
There may be other contexts in which ev(foobar, nouns)
is useful but I haven't looked for them.
Stavros Macrakis also suggests (email to mailing list,
25 Nov 2003) that there be documentation specifically
on the theme of nouns and verbs. That seems like a
larger project, so I'll leave that out of this bug report.