Make Fraction(-1).__hash__() return -2 rather than -1 (see issue 10356).

This commit is contained in:
Mark Dickinson 2010-11-13 10:27:38 +00:00
parent 24854cac99
commit fec6620dfb
3 changed files with 9 additions and 6 deletions

View File

@ -528,12 +528,8 @@ class Fraction(numbers.Rational):
return Fraction(round(self / shift) * shift)
def __hash__(self):
"""hash(self)
"""hash(self)"""
Tricky because values that are exactly representable as a
float must have the same hash as that float.
"""
# XXX since this method is expensive, consider caching the result
# In order to make sure that the hash of a Fraction agrees
@ -550,7 +546,8 @@ class Fraction(numbers.Rational):
hash_ = _PyHASH_INF
else:
hash_ = abs(self._numerator) * dinv % _PyHASH_MODULUS
return hash_ if self >= 0 else -hash_
result = hash_ if self >= 0 else -hash_
return -2 if result == -1 else result
def __eq__(a, b):
"""a == b"""

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@ -546,6 +546,9 @@ class FractionTest(unittest.TestCase):
self.assertEquals(hash(2.5), hash(F(5, 2)))
self.assertEquals(hash(10**50), hash(F(10**50)))
self.assertNotEquals(hash(float(10**23)), hash(F(10**23)))
# Check that __hash__ produces the same value as hash(), for
# consistency with int and Decimal. (See issue #10356.)
self.assertEquals(hash(F(-1)), F(-1).__hash__())
def testApproximatePi(self):
# Algorithm borrowed from

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@ -63,6 +63,9 @@ Core and Builtins
Library
-------
- Fix Fraction.__hash__ so that Fraction.__hash__(-1) is -2. (See
also issue #10356.)
- Issue #4471: Add the IMAP.starttls() method to enable encryption on
standard IMAP4 connections. Original patch by Lorenzo M. Catucci.