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.
diff --git a/Lib/decimal.py b/Lib/decimal.py
index 101e5d8..63f9991 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -2032,17 +2032,39 @@
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
+ 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
- shouldround = context._rounding_decision == ALWAYS_ROUND
- if shouldround:
- ans = ans._fix(context=context)
- return ans
+ context._rounding_decision == ALWAYS_ROUND
+ return ans._fix(context=context)
def min(self, other, context=None):
"""Returns the smaller value.
@@ -2054,19 +2076,39 @@
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
+ 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
-
- if context._rounding_decision == ALWAYS_ROUND:
- ans = ans._fix(context=context)
-
- return ans
+ context._rounding_decision == ALWAYS_ROUND
+ return ans._fix(context=context)
def _isinteger(self):
"""Returns whether self is an integer"""
@@ -2397,7 +2439,9 @@
>>> 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 @@
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)