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Revise max() and min() to comply with the 8/2/2004 update to the specification 

(version 1.45):

The max and min operations follow the rules in the current IEEE 754 revision draft:
if one operand is a quiet NaN and the other is number, then the number is always returned
if both operands are finite and equal in numerical value then an ordering is applied:
    if the signs differ then max returns the operand with the positive sign and
    min returns the operand with the negative sign; if the signs are the same then
    the exponent is used to select the result.
This commit is contained in:
Raymond Hettinger 2004-08-17 06:39:37 +00:00
parent f63ba43733
commit d6c700a320
1 changed files with 65 additions and 19 deletions
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84
Lib/decimal.py
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@ -2032,17 +2032,39 @@ class Decimal(object):
context = getcontext()
other = self._convert_other(other)
ans = self._check_nans(other, context)
if ans:
return ans
# if one operand is a quiet NaN and the other is number, then the
# number is always returned
sn = self._isnan()
on = other._isnan()
if sn or on:
if on == 1 and sn != 2:
return self
if sn == 1 and on != 2:
return other
return self._check_nans(other, context)
ans = self
if self < other:
c = self.__cmp__(other)
if c == 0:
# if both operands are finite and equal in numerical value
# then an ordering is applied:
#
# if the signs differ then max returns the operand with the
# positive sign and min returns the operand with the negative sign
#
# if the signs are the same then the exponent is used to select
# the result.
if self._sign != other._sign:
if self._sign:
ans = other
shouldround = context._rounding_decision == ALWAYS_ROUND
if shouldround:
ans = ans._fix(context=context)
return ans
elif self._exp < other._exp and not self._sign:
ans = other
elif self._exp > other._exp and self._sign:
ans = other
elif c == -1:
ans = other
context._rounding_decision == ALWAYS_ROUND
return ans._fix(context=context)
def min(self, other, context=None):
"""Returns the smaller value.
@ -2054,19 +2076,39 @@ class Decimal(object):
context = getcontext()
other = self._convert_other(other)
ans = self._check_nans(other, context)
if ans:
return ans
# if one operand is a quiet NaN and the other is number, then the
# number is always returned
sn = self._isnan()
on = other._isnan()
if sn or on:
if on == 1 and sn != 2:
return self
if sn == 1 and on != 2:
return other
return self._check_nans(other, context)
ans = self
if self > other:
c = self.__cmp__(other)
if c == 0:
# if both operands are finite and equal in numerical value
# then an ordering is applied:
#
# if the signs differ then max returns the operand with the
# positive sign and min returns the operand with the negative sign
#
# if the signs are the same then the exponent is used to select
# the result.
if self._sign != other._sign:
if other._sign:
ans = other
if context._rounding_decision == ALWAYS_ROUND:
ans = ans._fix(context=context)
return ans
elif self._exp > other._exp and not self._sign:
ans = other
elif self._exp < other._exp and self._sign:
ans = other
elif c == 1:
ans = other
context._rounding_decision == ALWAYS_ROUND
return ans._fix(context=context)
def _isinteger(self):
"""Returns whether self is an integer"""
@ -2397,7 +2439,9 @@ class Context(object):
>>> ExtendedContext.max(Decimal('-10'), Decimal('3'))
Decimal("3")
>>> ExtendedContext.max(Decimal('1.0'), Decimal('1'))
Decimal("1.0")
Decimal("1")
>>> ExtendedContext.max(Decimal('7'), Decimal('NaN'))
Decimal("7")
"""
return a.max(b, context=self)
@ -2416,6 +2460,8 @@ class Context(object):
Decimal("-10")
>>> ExtendedContext.min(Decimal('1.0'), Decimal('1'))
Decimal("1.0")
>>> ExtendedContext.min(Decimal('7'), Decimal('NaN'))
Decimal("7")
"""
return a.min(b, context=self)