Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!mcsun!unido!tub!fauern!lan!grosse
From: grosse@lan.informatik.tu-muenchen.dbp.de (Malte Grosse)
Newsgroups: comp.lang.prolog
Subject: bagof & setof
Summary: existential quantifiers
Message-ID: <2177@infovax.lan.informatik.tu-muenchen.dbp.de>
Date: 21 Nov 89 11:17:41 GMT
Reply-To: grosse@lan.informatik.tu-muenchen.dbp.de (Malte Grosse)
Organization: Inst. fuer Informatik, TU Muenchen, W. Germany
Lines: 64



A few weeks ago there was a request for bagof & setof, since 
it is not build-in in every PROLOG. With the help of previous
announcements I was able to implement bagof and setof. But I 
have still some trouble to find out the "free_variables" (these
are those which are neither in the template nor in a existential
quantifier). 

I have the following questions:

	- is
		    bagof(X, (Y^fact1(X,Y),Z^fact2(X,Z)), L)
	  equal to
		    bagof(X, Y^Z^(fact1(X,Y),fact2(X,Z)), L)
	  (I assume it)


	- is
		    bagof(X, (Y^fact1(X,Y,Z),Z^fact2(X,Z)), L)
	  equal to
		    bagof(X, Y^Z^(fact1(X,Y,Z),fact2(X,Z)), L)
	  (I assume it aswell)


	- is
		    bagof(X,Y^(fact(X,Y),!),L)
	  the same as
		    bagof(X,(fact(X,Y),!),L)
	  the same as
		    fact(X,_),L=[X],!
	  (quite useless I know)


	- where does
		    bagof(X, (Y^fact1(X,Y,Z);Z^fact2(X,Z)), L)
	  yield to?

	  to
		    bagof(X, Y^Z^(fact1(X,Y,Z);fact2(X,Z)), L)
 	  or to
		    bagof(X, Y^Znew^(fact1(X,Y,Z);fact2(X,Znew)), L)
			(Does anyone know how to handle this?)
	  or 
	     does it give ALWAYS only one instance (the first),
	     since the 'fail' to get the solution is a level higher
	     than the two facts, because of the 'or'.


I really interested in receiving the opinions from other PROLOG programmers.
Or if possible references to literature.

Malte

please reply to:
	grosse%lan.informatik.tu-muenchen.dbp.de@relay.cs.net
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