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From: mcdougal@cs.uchicago.edu
Newsgroups: comp.lang.scheme
Subject: member returns #f ?
Message-ID: <1991Mar18.170433.27678@midway.uchicago.edu>
Date: 18 Mar 91 17:04:33 GMT
Sender: news@midway.uchicago.edu (News Administrator)
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Organization: U. of Chicago AI Lab
Lines: 16

In general, memq, memv, member return a list.  Can someone tell me the thinking
behind having them return #f instead of the empty list if the obj. is not in
the list?  Does this mean that the standard paradigm for using these functions
is

   (let ((result (memq x L)))
     (if result ....))

as opposed to

   (let ((result (memq x L)))
     (if (not (null? result)) ...)) ?

I was under the impression that the former was frowned upon by Scheme pros.

-Tom