🚀 go-pugleaf

In article <1992Dec21.153147.26177@cs.brown.edu>, 
mj@cs.brown.edu (Mark Johnson) writes:
|> This is a nice way of viewing things, but I don't know any Prolog that
|> gives you all of the constraints C.  Consider the following program:
|> 
|> 	p(a) :- q(X,X).
|> 
|> 	q(Y, f(Y)).
|> 
|> One the query p(X), Sicstus returns the following:
|> 
|> | ?- p(X).
|> 
|> X = a ? ;
|> 
|> no

This is the perfect answer with respect to
rational trees (there is exactly one X such that X=f(X)).

|> | ?- q(X,X).
|> 
|> X = f(f(f(f(f(f(f(f(f(f(f(f(f(f ...

Again, the right answer (maybe, some depth limit
in printing things would be nice).

|> That is, sicstus only returns constraints related to variables appearing
|> the goal.  But the constraints that only have cyclic solutions may be
|> associated with other variables.

Sure, but this is how it has to be, isn't it?

By the way, a recent paper of Ralf Treinen and myself in the
Proceedings of JICSLP'92 gives an in-depth study of incremental
decision methods for satisfiability, entailment and negation for
rational trees (actually, a proper generalization of Colmerauer's
rational tree system also accommodating features).  The full paper
describes an abstract machine (WAM-like) providing for an
efficient incremental implementation of the decision methods.

Both papers can be obtained by anonymous ftp from
duck.dfki.uni-sb.de (134.96.188.92) from the directory pub/papers.

@inproceedings{CFT-JICLP92,
   editor = 	"K. Apt",
   author =     "Gert Smolka and Ralf Treinen",
   title =      "Records for Logic Programming",
   booktitle =  "Proceedings of the 1992 Joint International Conference and
                 Symposium on Logic Programming",
   year = 	"1992",
   publisher = 	"The MIT Press",
   address = 	"Cambridge, Mass."
}

@TechReport{ST:cft92rep,
author	= "Gert Smolka and Ralf Treinen",
title	= "Records for Logic Programming",
institution = "German Research Center for Artificial Intelligence (DFKI)",
year	= 1992,
type	= "Research Report",
number	= "RR-92-23",
address	= {Stuhlsatzenhausweg 3, 6600 Saarbr\"ucken 11, Germany}
}

***********
Gert Smolka, DFKI, Stuhlsatzenhausweg 3, D-W-6600 Saarbr"ucken, Germany
Tel: +49 681 302-5311;  Fax: +49 681 302-5341; Net: smolka@dfki.uni-sb.de