2 files changed, 14 insertions, 4 deletions
diff --git a/prolog/problems/family_relations/father_2/common.py b/prolog/problems/family_relations/father_2/common.py
index 0c65a83..11f0742 100644
--- a/prolog/problems/family_relations/father_2/common.py
+++ b/prolog/problems/family_relations/father_2/common.py
@@ -25,6 +25,7 @@ hint_type = {
     'x_must_be_parent': Hint('x_must_be_parent'),
     'y_can_be_of_any_gender': Hint('y_can_be_of_any_gender'),
     'y_need_not_be_parent': Hint('y_need_not_be_parent'),
+    'predicate_always_false': Hint('predicate_always_false'),
 }
 
 test_cases = [
@@ -92,15 +93,19 @@ def hint(code, aux_code):
             return [{'id': 'x_must_be_parent'}]
 
         # Y can be of any gender, incl. female
-        if prolog.engine.ask_one(engine_id,
-            'father(_, Y), female(Y)') == 'false':
+        if prolog.engine.ask_truth(engine_id, 'father(_, Y)') and \
+           prolog.engine.ask_one(engine_id, 'father(_, Y), female(Y)') == 'false':
             return [{'id': 'y_can_be_of_any_gender'}]
 
         # Y does not necessarily need to be a parent
-        if prolog.engine.ask_one(engine_id,
-            'father(_, Y), \+ parent(Y, _)') == 'false':
+        if prolog.engine.ask_truth(engine_id, 'father(_, Y)') and \
+           prolog.engine.ask_one(engine_id, 'father(_, Y), \+ parent(Y, _)') == 'false':
             return [{'id': 'y_need_not_be_parent'}]
 
+        # target predicate seems to always be false
+        if prolog.engine.ask_one(engine_id, 'father(_, _)') == 'false':
+            return [{'id': 'predicate_always_false'}]
+
     except socket.timeout as ex:
         pass
 
diff --git a/prolog/problems/family_relations/father_2/sl.py b/prolog/problems/family_relations/father_2/sl.py
index 4f7f3de..e399d39 100644
--- a/prolog/problems/family_relations/father_2/sl.py
+++ b/prolog/problems/family_relations/father_2/sl.py
@@ -54,4 +54,9 @@ Pozor: velja eno ALI drugo, ne nujno eno IN drugo!</p>
     'y_need_not_be_parent': '''\
 <p><code>Y</code> pravzaprav ne rabi imeti otrok, da ima očeta...</p>
 ''',
+
+    'predicate_always_false': '''\
+<p>Vse kaže, da tvoj predikat vedno vrne "false". Morda se splača preveriti, če si se kje zatipkal,
+je morda kakšna pika namesto vejice ali obratno, morda kakšna spremenljivka z malo začetnico?</p>
+''',
 }