Forward port total_ordering() and cmp_to_key().

1 files changed, 45 insertions, 0 deletions

diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst
index 94be636..1511a25 100644
--- a/Doc/library/functools.rst
+++ b/Doc/library/functools.rst
@@ -15,6 +15,51 @@ function for the purposes of this module.
 
 The :mod:`functools` module defines the following functions:
 
+..  function:: cmp_to_key(func)
+
+    Transform an old-style comparison function to a key-function.  Used with
+    tools that accept key functions (such as :func:`sorted`, :func:`min`,
+    :func:`max`, :func:`heapq.nlargest`, :func:`heapq.nsmallest`,
+    :func:`itertools.groupby`).
+    This function is primarily used as a transition tool for programs
+    being converted from Py2.x which supported the use of comparison
+    functions.
+
+    A compare function is any callable that accept two arguments, compares
+    them, and returns a negative number for less-than, zero for equality,
+    or a positive number for greater-than.  A key function is a callable
+    that accepts one argument and returns another value that indicates
+    the position in the desired collation sequence.
+
+    Example::
+
+        sorted(iterable, key=cmp_to_key(locale.strcoll))  # locale-aware sort order
+
+   .. versionadded:: 3.2
+
+.. function:: total_ordering(cls)
+
+   Given a class defining one or more rich comparison ordering methods, this
+   class decorator supplies the rest.  This simplies the effort involved
+   in specifying all of the possible rich comparison operations:
+
+   The class must define one of :meth:`__lt__`, :meth:`__le__`,
+   :meth:`__gt__`, or :meth:`__ge__`.
+   In addition, the class should supply an :meth:`__eq__` method.
+
+   For example::
+
+       @total_ordering
+       class Student:
+           def __eq__(self, other):
+               return ((self.lastname.lower(), self.firstname.lower()) ==
+                       (other.lastname.lower(), other.firstname.lower()))
+           def __lt__(self, other):
+               return ((self.lastname.lower(), self.firstname.lower()) <
+                       (other.lastname.lower(), other.firstname.lower()))
+
+   .. versionadded:: 3.2
+
 .. function:: partial(func, *args, **keywords)
 
    Return a new :class:`partial` object which when called will behave like *func*