Formal comment #35 (enhancement)

Equivalence predicate version of memp
Reported by:	Andre van Tonder

Component:	miscellaneous
Version:	5.91

Summary

Memp is unwieldy and potentially inefficient in the very common case
where one tests for membership is based on an equivalence
predicate.

Description

In my experience the most common usage pattern of generic membership
is expressed by the SRFI-1 generic member procedure, which has to be
expressed in r6rs as follows:

  (member x l =)  ==>  (memp (lambda (y) (= x y)) l)

This gets unwieldy to write, is hard to read, and is inefficient in
the absence of smart optimizations.

Proposal

The inclusion of an additional procedure for generic membership based
on an equivalence predicate argument. One possibility is enhancing
member with an extra optional argument, or using a new name for it
such as mem=

RESPONSE:

The basis for this comment has been addressed and the comment treated
as withdrawn.  See:

http://lists.r6rs.org/pipermail/r6rs-discuss/2006-September/000173.html