Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!lll-winken!uunet!mcvax!ukc!etive!lfcs!jha
From: jha@lfcs.ed.ac.uk (Jamie Andrews)
Newsgroups: comp.lang.prolog
Subject: Re: Committed Choice
Keywords: cut if-then-else Garbage on the stacks
Message-ID: <1717@etive.ed.ac.uk>
Date: 7 Apr 89 08:47:58 GMT
References: <11500012@hpldola.HP.COM> <733@gould.doc.ic.ac.uk> <18798@adm.BRL.MIL> <192@aucsv.UUCP> <751@gould.doc.ic.ac.uk> <674@tuvie>
Sender: news@etive.ed.ac.uk
Reply-To: jha@lfcs.ed.ac.uk (Jamie Andrews)
Organization: Laboratory for the Foundations of Computer Science, Edinburgh U
Lines: 14

In article <674@tuvie> ulrich@vip.UUCP (Ulrich Neumerkel) writes:
>blam(0,[]).
>blam(N,[L|L]) :- N > 0, M is N - 1, blam(M,L).
> 
>..., blam(32,L), assert(little_fact(L)),...

     I think most Prolog implementations would do this sensibly,
representing this as 32 cons cells with both pointers pointing
to the next element on the list, and the last cell pointing to
the null list.  There seems to be no reason for copying at all
-- [L|L] creates one cons cell.  Or am I missing something?

--Jamie.
  jha@lfcs.ed.ac.uk