Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarchive!udel!rochester!uhura.cc.rochester.edu!lm03_cif
From: lm03_cif@uhura.cc.rochester.edu (Larry Moss)
Newsgroups: comp.lang.prolog
Subject: help novice prolog users
Keywords: sbprolog
Message-ID: <5249@ur-cc.UUCP>
Date: 14 Feb 90 19:57:03 GMT
Reply-To: lm03_cif@uhura.cc.rochester.edu (Larry Moss)
Organization: University of Rochester
Lines: 66

I've revcently been woriking with sbprolog and the Turbo Prolog manuals
for reference so I'm running into some problems.  The manuals are borowed
and I have much more access to the system with sbprolog than an IBM PC.
I can sayu fairly confidently that I know the language but don't know how
to use it.

Here are the problems - 

I have a database that looks like the following.
 -

parent(grandad, dad).
parent(dad, son).
child(mom, grandad).

child(X, Y) :- parent(Y, X).

descend(X, Y) :- parent(Y, X).
descend(X, Y) :-  descend(X, Z), parent(Y, Z).

-

1. If I use a statement like "descend(son, grandad)" it works fine, but
if I want to list all of the descendants found in a database like in
"descend(X,grandad)", it never terminates.  I can put a cut in the line
"descend(X, Y) :- parent(Y, X), !." and have it terminate but it will
terminate after the first match.  Is there a way for me to write this so
I can get a compete list of all of the descendants of a particular person
and still have it terminate?

2. I also want to add the line
	parent(X,Y) :- child(Y,X).

   but I have
	child(X, Y) :- parent(Y, X).

   this would cause infinite recursion.  Is there a correct way for me to
do this?


=============

second problem
-
hanoi(N) :- move(N, left, middle, right).

move(1, A, _, C) :- inform(A, C), !.
move(N, A, B, C) :- 
	N1 = N - 1, move(N1, A, C, B), inform(A, C), move(N1, B, A, C).

inform(Loc1, Loc2) :-
	write(Loc1), tab(5), write(Loc2), nl.
-

This comes directly out of the Turbo Prolog manual.  I assume it works
with Turbo Prolog, but I haven't had the opportunity to try it.  It will
solve hanoi(1), but anything greater than that just puts a nice big core
in my directory.  What can I do to make this work in sbprolog?


Thanks in advance,
Larry
-- 
lm03_cif@uhura.cc.rochester.edu / CLARKE'S THIRD LAW:
lmo3_ss@db1.cc.rochester.edu   / Any sufficiently advanced technology is
lmo3_ss@uordbv.bitnet         / indistinguishable from magic.