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From: HEP@smectos.gang.umass.edu (High Energy Physics Group)
Newsgroups: comp.lang.lisp
Subject: NCONC & Functions
Message-ID: <7142@dime.cs.umass.edu>
Date: 29 Nov 89 18:38:48 GMT
Sender: news@dime.cs.umass.edu
Reply-To: HEP@smectos.CS.UMASS.EDU (High Energy Physics Group)
Organization: University of Massachusetts, Amherst
Lines: 40

With some text deleted,

>>	>(DEFUN foo1 () '(a b c))
>>	>FOO1
>>	>(foo1)
>>	>(A B C)
>>	>(NCONC (foo1) '(d e f))
>>	>(A B C D E F)
>>	>(foo1)
>>	>(A B C D E F)
>>				     I'm told that even FOO2 is affected when
>>running Franz on a DEC station.
>
>That's a bug in Franz.  Sounds like an incorrect compiler optimization to
>me -- it's translating a call to LIST all of whose arguments are quoted
>constants into a single quoted constant.  Since LIST is supposed to cons a
>new list each time it is called, this changes the semantics drastically.

I have a copy of Franz's Allegro CL on my DECstation 3100, and this is what
happens:

 dribbling to file "/usr/users/kgk/junk"
 NIL 
 <cl> (defun foo2 () (list 'a 'b 'c))
 FOO2 
 <cl> (nconc (foo2) '(it works fine))
 (A B C IT WORKS FINE) 
 <cl> (foo2)
 (A B C) 
 <cl> (defun foo2 () (declare (optimize (speed 3) (safety 0))) (list 'a 'b 'c))
 FOO2 
 <cl> (compile 'foo2)
 FOO2 
 <cl> (nconc (foo2) '(it works fine))
 (A B C IT WORKS FINE) 
 <cl> (foo2)
 (A B C) 
 <cl> (dribble)

As far as I can see, Allegro CL does not seem to be in error!  :-)  -- Kleanthes