[racket-dev] Optional equality predicate for assoc and member

Currently, unlike remove and remove-duplicates, assoc and member
cannot use a user-provided equality check. I have a patch that fixes
that by adding an optional argument to these two functions.

With this patch, assoc and member are implemented in Racket. They are
currently implemented in C. I haven't measured the performance impact
of the change, but I can do it if someone believes it's necessary.

Is anyone opposed to this change?

Vincent