An exception could be raised as a false positive. We should only
demand consistency between two resolutors if they have both reached a
conclusion. Before this patch, an exception would be raised in the event of an
inconclusive resolutor following a conclusive.
Added a test for the issue
---
sympy/assumptions/ask.py | 7 ++++++-
sympy/assumptions/tests/test_query.py | 9 +++++++++
2 files changed, 15 insertions(+), 1 deletions(-)
diff --git a/sympy/assumptions/ask.py b/sympy/assumptions/ask.py
index f575d7c..3814278 100644
--- a/sympy/assumptions/ask.py
+++ b/sympy/assumptions/ask.py
@@ -75,7 +75,12 @@ def ask(expr, key, assumptions=True):
if hasattr(handler, subclass.__name__):
res = getattr(handler, subclass.__name__)(expr, assumptions)
if _res is None: _res = res
- elif _res != res: raise ValueError, 'incompatible resolutors'
+ elif res is None:
+ # since first resolutor was conclusive, we keep that value
+ res = _res
+ else:
+ # only check consistency if both resolutors have concluded
+ if _res != res: raise ValueError, 'incompatible resolutors'
break
if res is not None:
return res
diff --git a/sympy/assumptions/tests/test_query.py
b/sympy/assumptions/tests/test_query.py
index 0078dc6..e5c8907 100644
--- a/sympy/assumptions/tests/test_query.py
+++ b/sympy/assumptions/tests/test_query.py
@@ -926,6 +926,15 @@ def Number(expr, assumptions):
return True
register_handler('prime', Prime2AskHandler)
raises(ValueError, 'ask(4, Q.prime)')
+ remove_handler('prime', Prime2AskHandler)
+
+ class InconclusiveHandler(AskHandler):
+ @staticmethod
+ def Number(expr, assumptions):
+ return None
+ register_handler('prime', InconclusiveHandler)
+ ask(3, Q.prime)
+
def test_key_extensibility():
"""test that you can add keys to the ask system at runtime"""
--
1.6.5
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