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From: sutanto@boas.cogsci.uiuc.edu (Herry Sutanto)
Newsgroups: comp.lang.prolog
Subject: Re: SICStus Prolog expert, HELP!
Keywords: SICStus Prolog, freeze, call_residue
Message-ID: <1991May24.173820.6783@ux1.cso.uiuc.edu>
Date: 24 May 91 17:38:20 GMT
References: <1991May23.194951.24587@ux1.cso.uiuc.edu>
Sender: usenet@ux1.cso.uiuc.edu (News)
Organization: University of Illinois at Urbana
Lines: 40

I wrotes:


>I have a question for SICStus Prolog expert.

>It is related to freeze predicate.  The question is how to get *all*
>blocked goals so far? 

>What I need is similar to call_residue/2 but return all blocked goals
>from top level to current point.  call_residue(+Goal, ?Vars) only
>returns blocked subgoal(s) of the execution of Goal, not *all* of the
>blocked goals to that point.

>I tried to use setof/2 with frozen/2 but they always return TRUE instead.

>Herry Sutanto 
>sutanto@cs.uiuc.edu

Thank to all who replies my previous posting, to make the problem clear, 
here is an example where I need this kind of predicate:
 
  Suppose I want to have a predicate called less_than( X, Y )
  which return true if X is less than Y. 
  If at least one of the arguments is uninstantiated, this goal 
  will be blocked. But I also want to check whether there are any
  frozen goals which related to these variables, if there are
  I want to check right away whether the new frozen goal is consistent
  with all the previous frozen goal. 

  So, if there are previously frozen goal less_than( Y, Z ) and 
  less_than( Z, X ), I can tell  that less_than(X, Y) is false 
  (even none of the variables are instantiated).


Herry Sutanto
sutanto@cs.uiuc.edu

--

-hs-