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Issue #2531: Make float-to-decimal comparisons return correct results.

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Float to decimal comparison operations now return a result based on
the numeric values of the operands.  Decimal.__hash__ has also been
fixed so that Decimal and float values that compare equal have equal
hash value.
This commit is contained in:
Mark Dickinson 2010-04-02 08:53:22 +00:00
parent 6eba779235
commit 99d8096c17
4 changed files with 74 additions and 13 deletions
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38
Lib/decimal.py
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@ -855,7 +855,7 @@ class Decimal(object):
# that specified by IEEE 754.
def __eq__(self, other):
other = _convert_other(other)
other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
if self.is_nan() or other.is_nan():
@ -863,7 +863,7 @@ class Decimal(object):
return self._cmp(other) == 0
def __ne__(self, other):
other = _convert_other(other)
other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
if self.is_nan() or other.is_nan():
@ -871,7 +871,7 @@ class Decimal(object):
return self._cmp(other) != 0
def __lt__(self, other, context=None):
other = _convert_other(other)
other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@ -880,7 +880,7 @@ class Decimal(object):
return self._cmp(other) < 0
def __le__(self, other, context=None):
other = _convert_other(other)
other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@ -889,7 +889,7 @@ class Decimal(object):
return self._cmp(other) <= 0
def __gt__(self, other, context=None):
other = _convert_other(other)
other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@ -898,7 +898,7 @@ class Decimal(object):
return self._cmp(other) > 0
def __ge__(self, other, context=None):
other = _convert_other(other)
other = _convert_other(other, allow_float=True)
if other is NotImplemented:
return other
ans = self._compare_check_nans(other, context)
@ -932,12 +932,18 @@ class Decimal(object):
# The hash of a nonspecial noninteger Decimal must depend only
# on the value of that Decimal, and not on its representation.
# For example: hash(Decimal('100E-1')) == hash(Decimal('10')).
if self._is_special:
if self._isnan():
raise TypeError('Cannot hash a NaN value.')
return hash(str(self))
if not self:
return 0
if self._is_special and self._isnan():
raise TypeError('Cannot hash a NaN value.')
# In Python 2.7, we're allowing comparisons (but not
# arithmetic operations) between floats and Decimals; so if
# a Decimal instance is exactly representable as a float then
# its hash should match that of the float. Note that this takes care
# of zeros and infinities, as well as small integers.
self_as_float = float(self)
if Decimal.from_float(self_as_float) == self:
return hash(self_as_float)
if self._isinteger():
op = _WorkRep(self.to_integral_value())
# to make computation feasible for Decimals with large
@ -5695,15 +5701,21 @@ def _log10_lb(c, correction = {
##### Helper Functions ####################################################
def _convert_other(other, raiseit=False):
def _convert_other(other, raiseit=False, allow_float=False):
"""Convert other to Decimal.
Verifies that it's ok to use in an implicit construction.
If allow_float is true, allow conversion from float; this
is used in the comparison methods (__eq__ and friends).
"""
if isinstance(other, Decimal):
return other
if isinstance(other, (int, long)):
return Decimal(other)
if allow_float and isinstance(other, float):
return Decimal.from_float(other)
if raiseit:
raise TypeError("Unable to convert %s to Decimal" % other)
return NotImplemented