[racket-dev] member like assoc

Hi all,

Is it feasible to get `member` to have the same optional argument
behavior as `assoc`? That is, to have an equality predicate as the third
argument.

I find myself writing the (imaginary) equivalent of things like:
  (member id some-list free-identifier=?)

and it seems like it would be nicer with an extra `member` argument than
with `memf`.

Cheers,
Asumu