stop applying (=..)/2 to variables in tabling/trie.pl

src/prolog/lib/tabling/trie.pl

@@ -65,8 +65,13 @@
 % For a term of the form p(a,q(b)), "returns" functor_data(p,2) and [a,q(b)].
 % p_trie_arity_univ(+Term,-FunctorData,-ArgumentsList).
 p_trie_arity_univ(Term,functor_data(Name,Arity),Arguments) :-
-  Term =.. [Name|Arguments],
-  functor(Term,_,Arity).
+  (  var(Term) ->
+     Name = var,
+     Arity = 0,
+     Arguments = []
+  ;  Term =.. [Name|Arguments],
+     functor(Term,_,Arity)
+  ).
 
 % Returns a new empty trie.
 trie_new(Trie) :-