Merge branch 'master' of ssh://yap.git.sourceforge.net/gitroot/yap/yap-6.3

packages/CLPBN/clpbn/ground_factors.yap

@@ -142,6 +142,7 @@ add_factor(factor(Type, Id, Ks, _, _Phi, Constraints), NKs) :-
     %writeln(+Ks),
 	( Ks = [K,Els], var(Els)
 	 ->
+	% aggregate factor
 	  once(run(Constraints)),
 	  avg_factors(K, Els, 0.0, NewKeys, NewId),
 	  NKs = [K|NewKeys]
@@ -150,8 +151,13 @@ add_factor(factor(Type, Id, Ks, _, _Phi, Constraints), NKs) :-
 	  NKs = Ks,
 	  Id = NewId
 	),
-	\+ f(Type, NewId, NKs),
-	assert(f(Type, NewId, NKs)).
+	(
+          f(Type, NewId, NKs)
+        ->
+	  true
+        ;
+	  assert(f(Type, NewId, NKs))
+         ).
 
 run([Goal|Goals]) :-
 	call(user:Goal),