🚀 go-pugleaf

In article <1992Aug13.111745.17980@odin.diku.dk> torbenm@diku.dk (Torben
AEgidius Mogensen) writes:

#  A correct formulation of the transitive clause is
#
#  distance(X,Z,D) :-
#	distance_fact(X,Y,D1),
#	distance(Y,Z,D2),
#	D is D1 + D2.

This may loop indefinitely.  For instance, suppose you invoked it with

         ?- distance(london,paris,X).

when `paris' was not mentioned in any distance fact.

-- Ken "old lag" Johnson


-- 
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