[Python-checkins] r58046 - python/branches/decimal-branch/Lib/decimal.py

Fri Sep 7 22:34:07 CEST 2007

Author: facundo.batista
Date: Fri Sep 7 22:34:07 2007
New Revision: 58046
Modified:
 python/branches/decimal-branch/Lib/decimal.py
Log:
The second patch makes minor changes to __pos__, __neg__, __sub__ 
and __rsub__ so that Decimal attributes are never changed outside
__new__ (since a Decimal instance is supposed to be immutable, this
should probably be avoided unless there's a good reason not to).
It also fixes the docstrings for __sub__ and __rsub__, and it fixes
a bug in __rsub__ which incorrectly changes the sign of a NaN.
Thanks Mark Dickinson.
Modified: python/branches/decimal-branch/Lib/decimal.py
==============================================================================

--- python/branches/decimal-branch/Lib/decimal.py	(original)
+++ python/branches/decimal-branch/Lib/decimal.py	Fri Sep 7 22:34:07 2007
@@ -895,17 +895,15 @@
 
 if not self:
 # -Decimal('0') is Decimal('0'), not Decimal('-0')
- sign = 0
- elif self._sign:
- sign = 0
+ ans = self.copy_sign(Dec_0)
 else:
- sign = 1
+ ans = self.copy_negate()
 
 if context is None:
 context = getcontext()
 if context._rounding_decision == ALWAYS_ROUND:
- return Decimal((sign, self._int, self._exp))._fix(context)
- return Decimal( (sign, self._int, self._exp))
+ return ans._fix(context)
+ return ans
 
 def __pos__(self, context=None):
 """Returns a copy, unless it is a sNaN.
@@ -917,19 +915,16 @@
 if ans:
 return ans
 
- sign = self._sign
 if not self:
 # + (-0) = 0
- sign = 0
+ ans = self.copy_sign(Dec_0)
+ else:
+ ans = Decimal(self)
 
 if context is None:
 context = getcontext()
-
 if context._rounding_decision == ALWAYS_ROUND:
- ans = self._fix(context)
- else:
- ans = Decimal(self)
- ans._sign = sign
+ return ans._fix(context)
 return ans
 
 def __abs__(self, round=1, context=None):
@@ -1051,7 +1046,7 @@
 __radd__ = __add__
 
 def __sub__(self, other, context=None):
- """Return self + (-other)"""
+ """Return self - other"""
 other = _convert_other(other)
 if other is NotImplemented:
 return other
@@ -1061,23 +1056,16 @@
 if ans:
 return ans
 
- # -Decimal(0) = Decimal(0), which we don't want since
- # (-0 - 0 = -0 + (-0) = -0, but -0 + 0 = 0.)
- # so we change the sign directly to a copy
- tmp = Decimal(other)
- tmp._sign = 1-tmp._sign
-
- return self.__add__(tmp, context=context)
+ # self - other is computed as self + other.copy_negate()
+ return self.__add__(other.copy_negate(), context=context)
 
 def __rsub__(self, other, context=None):
- """Return other + (-self)"""
+ """Return other - self"""
 other = _convert_other(other)
 if other is NotImplemented:
 return other
 
- tmp = Decimal(self)
- tmp._sign = 1 - tmp._sign
- return other.__add__(tmp, context=context)
+ return other.__sub__(self, context=context)
 
 def _increment(self):
 """Special case of add, adding 1eExponent
