[Python-checkins] r62419 - python/trunk/Doc/whatsnew/2.6.rst
andrew.kuchling
python-checkins at python.org
Sun Apr 20 18:54:03 CEST 2008
Author: andrew.kuchling
Date: Sun Apr 20 18:54:02 2008
New Revision: 62419
Log:
Move description of math module changes; various edits to description of cmath changes
Modified:
python/trunk/Doc/whatsnew/2.6.rst
Modified: python/trunk/Doc/whatsnew/2.6.rst
==============================================================================
--- python/trunk/Doc/whatsnew/2.6.rst (original)
+++ python/trunk/Doc/whatsnew/2.6.rst Sun Apr 20 18:54:02 2008
@@ -1292,11 +1292,42 @@
:func:`isnan`, return true if their floating-point argument is
infinite or Not A Number. (:issue:`1640`)
- The ``math.copysign(x, y)`` function
- copies the sign bit of an IEEE 754 number, returning the absolute
- value of *x* combined with the sign bit of *y*. For example,
- ``math.copysign(1, -0.0)`` returns -1.0. (Contributed by Christian
- Heimes.)
+* The :mod:`math` module has seven new functions, and the existing
+ functions have been improved to give more consistent behaviour
+ across platforms, especially with respect to handling of
+ floating-point exceptions and IEEE 754 special values.
+ The new functions are:
+
+ * :func:`isinf` and :func:`isnan` determine whether a given float is
+ a (positive or negative) infinity or a NaN (Not a Number),
+ respectively.
+
+ * ``copysign(x, y)`` copies the sign bit of an IEEE 754 number,
+ returning the absolute value of *x* combined with the sign bit of
+ *y*. For example, ``math.copysign(1, -0.0)`` returns -1.0.
+ (Contributed by Christian Heimes.)
+
+ * The inverse hyperbolic functions :func:`acosh`, :func:`asinh` and
+ :func:`atanh`.
+
+ * The function :func:`log1p`, returning the natural logarithm of
+ *1+x* (base *e*).
+
+ There's also a new :func:`trunc` function as a result of the
+ backport of `PEP 3141's type hierarchy for numbers <#pep-3141>`__.
+
+ The existing math functions have been modified to follow the
+ recommendations of the C99 standard with respect to special values
+ whenever possible. For example, ``sqrt(-1.)`` should now give a
+ :exc:`ValueError` across (nearly) all platforms, while
+ ``sqrt(float('NaN'))`` should return a NaN on all IEEE 754
+ platforms. Where Annex 'F' of the C99 standard recommends signaling
+ 'divide-by-zero' or 'invalid', Python will raise :exc:`ValueError`.
+ Where Annex 'F' of the C99 standard recommends signaling 'overflow',
+ Python will raise :exc:`OverflowError`. (See :issue:`711019`,
+ :issue:`1640`.)
+
+ (Contributed by Christian Heimes and Mark Dickinson.)
* Changes to the :class:`Exception` interface
as dictated by :pep:`352` continue to be made. For 2.6,
@@ -1415,33 +1446,40 @@
available, instead of restricting itself to protocol 1.
(Contributed by W. Barnes; :issue:`1551443`.)
-* The :mod:`cmath` module has gained five new functions: :func:`polar`
- converts a complex number to polar form, returning the modulus and
- argument of that complex number. :func:`rect` does the opposite,
- turning a (modulus, argument) pair back into the corresponding
- complex number. :func:`phase` returns the phase or argument of a
- complex number. :func:`isnan` returns True if either the real or
- imaginary part of its argument is a NaN. :func:`isinf` returns True
- if either the real or imaginary part of its argument is infinite.
-
- The :mod:`cmath` module is no longer numerically unsound. (See
- :issue:`1381`): for all functions, the real and imaginary parts of
- the results are accurate to within a few ulps, whenever possible.
-
- The branch cuts for :func:`asinh`, :func:`atanh`: and :func:`atan`
- have been corrected.
-
- The tests for the :mod:`cmath` module have been greatly expanded. A
- set of nearly 2000 new testcases provides tests for the algebraic
- functions.
+* The :mod:`cmath` module underwent an extensive set of revisions,
+ thanks to Mark Dickinson and Christian Heimes, that added some new
+ features and greatly improved the accuracy of the computations.
+
+ Five new functions were added:
+
+ * :func:`polar` converts a complex number to polar form, returning
+ the modulus and argument of that complex number.
+
+ * :func:`rect` does the opposite, turning a (modulus, argument) pair
+ back into the corresponding complex number.
+
+ * :func:`phase` returns the phase or argument of a complex number.
+
+ * :func:`isnan` returns True if either
+ the real or imaginary part of its argument is a NaN.
+
+ * :func:`isinf` returns True if either the real or imaginary part of
+ its argument is infinite.
+
+ The revisions also improved the numerical soundness of the
+ :mod:`cmath` module. For all functions, the real and imaginary
+ parts of the results are accurate to within a few units of least
+ precision (ulps) whenever possible. See :issue:`1381` for the
+ details. The branch cuts for :func:`asinh`, :func:`atanh`: and
+ :func:`atan` have also been corrected.
+
+ The tests for the module have been greatly expanded; nearly 2000 new
+ test cases exercise the algebraic functions.
On IEEE 754 platforms, the :mod:`cmath` module now handles IEEE 754
special values and floating-point exceptions in a manner consistent
with Annex 'G' of the C99 standard.
- (Updates to :mod:`cmath` contributed by Mark Dickinson and Christian
- Heimes.)
-
* A new data type in the :mod:`collections` module: :class:`namedtuple(typename,
fieldnames)` is a factory function that creates subclasses of the standard tuple
whose fields are accessible by name as well as index. For example::
@@ -1678,30 +1716,6 @@
:func:`macostools.touched` function to be removed because it depended on the
:mod:`macfs` module. (:issue:`1490190`)
-* The :mod:`math` module has seven new functions, and the existing
- functions have been improved to give more consistent behaviour
- across platforms, especially with respect to handling of
- floating-point exceptions and IEEE 754 special values.
-
- The new functions are: :func:`isinf` and :func:`isnan`, which
- determine whether a given float is a (positive or negative) infinity
- or a NaN (Not a Number), respectively; :func:`copysign`; the inverse
- hyperbolic functions :func:`acosh`, :func:`asinh` and :func:`atanh`;
- and the function :func:`log1p`. (There's also a new function
- :func:`trunc` as a result of the backport of PEP 3141; see above.)
-
- The existing math functions have been modified to follow the
- recommendations of the C99 standard with respect to special values
- whenever possible. For example, sqrt(-1.) should now give a
- ValueError across (nearly) all platforms, while sqrt(float('NaN'))
- should return a NaN on all IEEE 754 platforms. Where Annex 'F' of
- the C99 standard recommends signaling 'divide-by-zero' or 'invalid',
- Python will raise ValueError. Where Annex 'F' of the C99 standard
- recommends signaling 'overflow', Python will raise OverflowError.
- (See :issue:`711019`, :issue:`1640`.)
-
- (Contributed by Christian Heimes and Mark Dickinson.)
-
* :class:`mmap` objects now have a :meth:`rfind` method that finds
a substring, beginning at the end of the string and searching
backwards. The :meth:`find` method
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