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-rw-r--r--prolog/problems/family_relations/ancestor_2/common.py2
1 files changed, 1 insertions, 1 deletions
diff --git a/prolog/problems/family_relations/ancestor_2/common.py b/prolog/problems/family_relations/ancestor_2/common.py
index 49df9ad..7f6beea 100644
--- a/prolog/problems/family_relations/ancestor_2/common.py
+++ b/prolog/problems/family_relations/ancestor_2/common.py
@@ -85,7 +85,7 @@ def hint(code, aux_code):
# TODO: how will ask_truth handle/return timeouts...
# TODO: timeout is the same as fail in this particular case
if prolog.engine.ask_truth(engine_id,
- 'parent(X, Y), \+ ancestor(X, Y)'):
+ '\+ (findall(X/Y, parent(X, Y), L), member(X/Y, L), \+ ancestor(X, Y))'):
return [{'id': 'base_case'}]
# ancestor to oneself