Merged revisions 79583,79588-79589 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

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  r79583 | mark.dickinson | 2010-04-02 09:53:22 +0100 (Fri, 02 Apr 2010) | 7 lines

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

  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.
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  r79588 | mark.dickinson | 2010-04-02 11:17:07 +0100 (Fri, 02 Apr 2010) | 2 lines

  Issue #7279:  Make comparisons involving a Decimal sNaN signal InvalidOperation.
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  r79589 | mark.dickinson | 2010-04-02 11:35:12 +0100 (Fri, 02 Apr 2010) | 6 lines

  Issue #7279:  Make Decimal('nan') hashable.  Decimal('snan') remains unhashable.

  Also rewrite the Decimal __hash__ method so that it doesn't rely on
  float('inf') being valid: float('inf') could raise an exception on
  platforms not using IEEE 754 arithmetic.
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1 files changed, 18 insertions, 0 deletions

diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst
index 9d6ad81eb5..8a806e97c4 100644
--- a/Doc/library/decimal.rst
+++ b/Doc/library/decimal.rst
@@ -358,6 +358,24 @@ Decimal objects
    compared, sorted, and coerced to another type (such as :class:`float` or
    :class:`int`).
 
+   Decimal objects cannot generally be combined with floats in
+   arithmetic operations: an attempt to add a :class:`Decimal` to a
+   :class:`float`, for example, will raise a :exc:`TypeError`.
+   There's one exception to this rule: it's possible to use Python's
+   comparison operators to compare a :class:`float` instance ``x``
+   with a :class:`Decimal` instance ``y``.  Without this exception,
+   comparisons between :class:`Decimal` and :class:`float` instances
+   would follow the general rules for comparing objects of different
+   types described in the :ref:`expressions` section of the reference
+   manual, leading to confusing results.
+
+   .. versionchanged:: 2.7
+      A comparison between a :class:`float` instance ``x`` and a
+      :class:`Decimal` instance ``y`` now returns a result based on
+      the values of ``x`` and ``y``.  In earlier versions ``x < y``
+      returned the same (arbitrary) result for any :class:`Decimal`
+      instance ``x`` and any :class:`float` instance ``y``.
+
    In addition to the standard numeric properties, decimal floating point
    objects also have a number of specialized methods: