Improved hints for cousin/2.

1 files changed, 5 insertions, 6 deletions

diff --git a/prolog/problems/family_relations/cousin_2/common.py b/prolog/problems/family_relations/cousin_2/common.py
index 86ef5cc..ffebdae 100644
--- a/prolog/problems/family_relations/cousin_2/common.py
+++ b/prolog/problems/family_relations/cousin_2/common.py
@@ -97,17 +97,16 @@ def hint(code, aux_code):
             'findall(_, cousin(X, Y), L), (length(L, 14) ; length(L, 16))'):
             return [{'id': 'precedence_fail'}]
 
-        # cousin should not be brother or sister
-        # common parent, probably solved via grandparent
-        if prolog.engine.ask_truth(engine_id,
-            'cousin(X, Y), (brother(X, Y) ; sister(X, Y))'):
-            return [{'id': 'cousin_vs_sibling'}]
-
         # cousin to him/herself
         # just common grandparent is not enough
         if prolog.engine.ask_truth(engine_id, 'cousin(X, X)'):
             return [{'id': 'cousin_to_oneself'}]
 
+        # cousin should not be brother or sister
+        # common parent, probably solved via grandparent
+        if prolog.engine.ask_truth(engine_id,
+            'cousin(X, Y), parent(P, X), parent(P, Y)'):
+            return [{'id': 'cousin_vs_sibling'}]
 
         # X (or Y) does not necessarily need to be a parent
         # cousin is a symmetrical relation, so X and Y are covered by this