FIXED: Take all variables into account during goal projection.

This addresses #1751.

diff --git a/src/lib/dif.pl b/src/lib/dif.pl
index 20842b271d585e7a35dbab51556b619c22e56052..73d65518cafaaa779d232c6ecbfdc47d50457375 100644 (file)
--- a/src/lib/dif.pl
+++ b/src/lib/dif.pl
@@ -65,7 +65,7 @@ dif(X, Y) :-
 
 gather_dif_goals(_, []) --> [].
 gather_dif_goals(V, [(X \== Y) | Goals]) -->
-    (  { term_variables(X, [V0 | _]),
+    (  { term_variables(X-Y, [V0 | _]),
          V == V0 } ->
        [dif:dif(X, Y)]
     ;  []