Additional improvements to hints for mother, father, grandparent, sister, and brother problems.

1 files changed, 4 insertions, 4 deletions

diff --git a/prolog/problems/family_relations/sister_2/common.py b/prolog/problems/family_relations/sister_2/common.py
index 1234985..2be3ab3 100644
--- a/prolog/problems/family_relations/sister_2/common.py
+++ b/prolog/problems/family_relations/sister_2/common.py
@@ -91,6 +91,10 @@ def hint(code, aux_code):
     try:
         engine_id, output = prolog.engine.create(code=code+aux_code, timeout=1.0)
 
+        # target predicate seems to always be false
+        if not prolog.engine.ask_truth(engine_id, 'sister(_, _)'):
+            return [{'id': 'predicate_always_false'}]
+
         # X must be female
         if prolog.engine.ask_truth(engine_id, 'male(X), sister(X, _)'):
             return [{'id': 'x_must_be_female'}]
@@ -112,10 +116,6 @@ def hint(code, aux_code):
         if prolog.util.Token('NEQU', '\=') in tokens or prolog.util.Token('NEQA', '=\=') in tokens:
             return [{'id': 'neq+_instead_of_neq'}]
 
-        # target predicate seems to always be false
-        if prolog.engine.ask_one(engine_id, 'sister(_, _)') == 'false':
-            return [{'id': 'predicate_always_false'}]
-
         # X and Y must be different
         # this is the last code-specific hint (when everything else doesn't trigger anymore)
         if prolog.util.Token('NEQ', '\==') not in tokens and prolog.engine.ask_truth(engine_id,