Path: utzoo!yunexus!ists!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!swrinde!gem.mps.ohio-state.edu!brutus.cs.uiuc.edu!rpi!tale
From: tale@pawl.rpi.edu (David C Lawrence)
Newsgroups: comp.emacs
Subject: Re: possible s-expr management error (? naw, but ...)
Message-ID: <1989Nov17.210003.16822@rpi.edu>
Date: 17 Nov 89 21:00:03 GMT
Article-I.D.: rpi.1989Nov17.210003.16822
References: <8911160201.AA04995@NMSU.Edu> <31688@news.Think.COM>
	<1989Nov16.061626.22143@rpi.edu>
Organization: Rensselaer Polytechnic Institute, Troy NY
Lines: 31

In <31688@news.Think.COM> barmar@leander.think.com (Barry Margolin) writes:
Barry> SORT is a destructive operation; it actually reorders the
Barry> original list by rearranging the cdr chain.  [...]

Barry> The above code should then be changed to
Barry> (setq gnus-unsub-assoc (sort (copy-list gnus-unsub-assoc) 'gnus-assoc-lessp))

In <1989Nov16.061626.22143@rpi.edu> tale@pawl.rpi.edu (Me):
Me> It should not.  That screws the function up.  I used sort because
Me> sort was what I wanted.  I am well aware of the lisp functions which
Me> directly alter list structure and the usage of both sort and setcdr in
Me> the function was for exactly that behaviour.

Boy, do I love the taste of shoe leather.

The nifty little sorting hack which worked for me because I had a
mostly sorted list anyway ended up being a krufty mismanagement of
pointers which is unnecessary because the function cleans up after
itself later anyway.  Blargh.

As Barry suggests, but using an Emacs builtin:

  (setq gnus-unsub-assoc
        (sort (copy-sequence gnus-unsub-assoc) 'gnus-assoc-lessp))

is the appropriate thing to do.

Sheepishly,
Dave
-- 
 (setq mail '("tale@pawl.rpi.edu" "tale@ai.mit.edu" "tale@rpitsmts.bitnet"))