Merged revisions 60481,60485,60489-60492,60494-60496,60498-60499,60501-60503,60505-60506,60508-60509,60523-60524,60532,60543,60545,60547-60548,60552,60554,60556-60559,60561-60562,60569,60571-60572,60574,60576-60583,60585-60586,60589,60591,60594-60595,60597-60598,60600-60601,60606-60612,60615,60617,60619-60621,60623-60625,60627-60629,60631,60633,60635,60647,60650,60652,60654,60656,60658-60659,60664-60666,60668-60670,60672,60676,60678,60680-60683,60685-60686,60688,60690,60692-60694,60697-60706,60708-60712,60714-60724 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
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r60701 | georg.brandl | 2008-02-09 22:36:15 +0100 (Sat, 09 Feb 2008) | 2 lines
Needs only 2.4 now.
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r60702 | georg.brandl | 2008-02-09 22:38:54 +0100 (Sat, 09 Feb 2008) | 2 lines
Docs are rst now.
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r60703 | georg.brandl | 2008-02-09 23:00:00 +0100 (Sat, 09 Feb 2008) | 2 lines
Fix link.
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r60704 | georg.brandl | 2008-02-10 00:09:25 +0100 (Sun, 10 Feb 2008) | 2 lines
Fix for newest doctools.
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r60709 | raymond.hettinger | 2008-02-10 08:21:09 +0100 (Sun, 10 Feb 2008) | 1 line
Clarify that decimal also supports fixed-point arithmetic.
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r60710 | nick.coghlan | 2008-02-10 08:32:52 +0100 (Sun, 10 Feb 2008) | 1 line
Add missing NEWS entry for r60695
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r60712 | mark.dickinson | 2008-02-10 15:58:38 +0100 (Sun, 10 Feb 2008) | 3 lines
Turn classmethods into staticmethods, and avoid calling the constructor
of subclasses of Rational. (See discussion in issue #1682.)
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r60715 | mark.dickinson | 2008-02-10 16:19:58 +0100 (Sun, 10 Feb 2008) | 2 lines
Typos in decimal comment and documentation
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r60716 | skip.montanaro | 2008-02-10 16:31:54 +0100 (Sun, 10 Feb 2008) | 2 lines
Get the saying right. ;-)
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r60717 | skip.montanaro | 2008-02-10 16:32:16 +0100 (Sun, 10 Feb 2008) | 2 lines
whoops - revert
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r60718 | mark.dickinson | 2008-02-10 20:23:36 +0100 (Sun, 10 Feb 2008) | 2 lines
Remove reference to Rational
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r60719 | raymond.hettinger | 2008-02-10 21:35:16 +0100 (Sun, 10 Feb 2008) | 1 line
Complete an open todo on pickletools -- add a pickle optimizer.
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r60721 | mark.dickinson | 2008-02-10 22:29:51 +0100 (Sun, 10 Feb 2008) | 3 lines
Rename rational.Rational to fractions.Fraction, to avoid name clash
with numbers.Rational. See issue #1682 for related discussion.
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r60722 | christian.heimes | 2008-02-11 03:26:22 +0100 (Mon, 11 Feb 2008) | 1 line
The test requires the network resource
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r60723 | mark.dickinson | 2008-02-11 04:11:55 +0100 (Mon, 11 Feb 2008) | 3 lines
Put an extra space into the repr of a Fraction:
Fraction(1, 2) instead of Fraction(1,2).
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diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst
index f6b96b2..422436f 100644
--- a/Doc/library/decimal.rst
+++ b/Doc/library/decimal.rst
@@ -1,6 +1,6 @@
-:mod:`decimal` --- Decimal floating point arithmetic
-====================================================
+:mod:`decimal` --- Decimal fixed point and floating point arithmetic
+====================================================================
.. module:: decimal
:synopsis: Implementation of the General Decimal Arithmetic Specification.
@@ -16,6 +16,11 @@
The :mod:`decimal` module provides support for decimal floating point
arithmetic. It offers several advantages over the :class:`float` datatype:
+* Decimal "is based on a floating-point model which was designed with people
+ in mind, and necessarily has a paramount guiding principle -- computers must
+ provide an arithmetic that works in the same way as the arithmetic that
+ people learn at school." -- excerpt from the decimal arithmetic specification.
+
* Decimal numbers can be represented exactly. In contrast, numbers like
:const:`1.1` do not have an exact representation in binary floating point. End
users typically would not expect :const:`1.1` to display as
@@ -25,7 +30,7 @@
+ 0.1 + 0.1 - 0.3`` is exactly equal to zero. In binary floating point, the result
is :const:`5.5511151231257827e-017`. While near to zero, the differences
prevent reliable equality testing and differences can accumulate. For this
- reason, decimal would be preferred in accounting applications which have strict
+ reason, decimal is preferred in accounting applications which have strict
equality invariants.
* The decimal module incorporates a notion of significant places so that ``1.30
@@ -50,6 +55,13 @@
standards. While the built-in float type exposes only a modest portion of its
capabilities, the decimal module exposes all required parts of the standard.
When needed, the programmer has full control over rounding and signal handling.
+ This includes an option to enforce exact arithmetic by using exceptions
+ to block any inexact operations.
+
+* The decimal module was designed to support "without prejudice, both exact
+ unrounded decimal arithmetic (sometimes called fixed-point arithmetic)
+ and rounded floating-point arithmetic." -- excerpt from the decimal
+ arithmetic specification.
The module design is centered around three concepts: the decimal number, the
context for arithmetic, and signals.
@@ -832,7 +844,7 @@
:const:`ROUND_HALF_EVEN`. All flags are cleared. No traps are enabled (so that
exceptions are not raised during computations).
- Because the trapped are disabled, this context is useful for applications that
+ Because the traps are disabled, this context is useful for applications that
prefer to have result value of :const:`NaN` or :const:`Infinity` instead of
raising exceptions. This allows an application to complete a run in the
presence of conditions that would otherwise halt the program.
@@ -1245,7 +1257,7 @@
:const:`True`. An attempt to compare two Decimals using any of the ``<``,
``<=``, ``>`` or ``>=`` operators will raise the :exc:`InvalidOperation` signal
if either operand is a :const:`NaN`, and return :const:`False` if this signal is
-trapped. Note that the General Decimal Arithmetic specification does not
+not trapped. Note that the General Decimal Arithmetic specification does not
specify the behavior of direct comparisons; these rules for comparisons
involving a :const:`NaN` were taken from the IEEE 854 standard (see Table 3 in
section 5.7). To ensure strict standards-compliance, use the :meth:`compare`