Merged revisions 61143-61144,61146-61147,61150-61151,61157,61165-61168,61170-61173,61176-61177,61183 via svnmerge from

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

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  r61143 | barry.warsaw | 2008-03-01 03:23:38 +0100 (Sat, 01 Mar 2008) | 2 lines

  Bump to version 2.6a1
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  r61144 | barry.warsaw | 2008-03-01 03:26:42 +0100 (Sat, 01 Mar 2008) | 1 line

  bump idle version number
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  r61146 | fred.drake | 2008-03-01 03:45:07 +0100 (Sat, 01 Mar 2008) | 2 lines

  fix typo
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  r61147 | barry.warsaw | 2008-03-01 03:53:36 +0100 (Sat, 01 Mar 2008) | 1 line

  Add date to NEWS
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  r61150 | barry.warsaw | 2008-03-01 04:00:52 +0100 (Sat, 01 Mar 2008) | 1 line

  Give IDLE a release date
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  r61151 | barry.warsaw | 2008-03-01 04:15:20 +0100 (Sat, 01 Mar 2008) | 1 line

  More copyright year and version number bumps
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  r61157 | barry.warsaw | 2008-03-01 18:11:41 +0100 (Sat, 01 Mar 2008) | 2 lines

  Set things up for 2.6a2.
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  r61165 | georg.brandl | 2008-03-02 07:28:16 +0100 (Sun, 02 Mar 2008) | 2 lines

  It's 2.6 now.
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  r61166 | georg.brandl | 2008-03-02 07:32:32 +0100 (Sun, 02 Mar 2008) | 2 lines

  Update year.
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  r61167 | georg.brandl | 2008-03-02 07:44:08 +0100 (Sun, 02 Mar 2008) | 2 lines

  Make patchlevel print out the release if called as a script.
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  r61168 | georg.brandl | 2008-03-02 07:45:40 +0100 (Sun, 02 Mar 2008) | 2 lines

  New default basename for HTML help files.
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  r61170 | raymond.hettinger | 2008-03-02 11:59:31 +0100 (Sun, 02 Mar 2008) | 1 line

  Finish-up docs for combinations() and permutations() in itertools.
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  r61171 | raymond.hettinger | 2008-03-02 12:17:51 +0100 (Sun, 02 Mar 2008) | 1 line

  Tighten example code.
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  r61172 | raymond.hettinger | 2008-03-02 12:57:16 +0100 (Sun, 02 Mar 2008) | 1 line

  Simplify code for itertools.product().
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  r61173 | raymond.hettinger | 2008-03-02 13:02:19 +0100 (Sun, 02 Mar 2008) | 1 line

  Handle 0-tuples which can be singletons.
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  r61176 | georg.brandl | 2008-03-02 14:41:39 +0100 (Sun, 02 Mar 2008) | 2 lines

  Make clear that the constants are strings.
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  r61177 | georg.brandl | 2008-03-02 15:15:04 +0100 (Sun, 02 Mar 2008) | 2 lines

  Fix factual error.
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  r61183 | gregory.p.smith | 2008-03-02 21:00:53 +0100 (Sun, 02 Mar 2008) | 4 lines

  Modify import of test_support so that the code can also be used with a
  stand alone distribution of bsddb that includes its own small copy of
  test_support for the needed functionality on older pythons.
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1 files changed, 30 insertions, 10 deletions

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 098972d..9da51aa 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -102,26 +102,24 @@ loops that truncate the stream.
    Each result tuple is ordered to match the input order.  So, every
    combination is a subsequence of the input *iterable*.
 
-   Example:  ``combinations(range(4), 3) --> (0,1,2), (0,1,3), (0,2,3), (1,2,3)``
-
    Equivalent to::
 
         def combinations(iterable, r):
+            'combinations(range(4), 3) --> (0,1,2) (0,1,3) (0,2,3) (1,2,3)'
             pool = tuple(iterable)
             n = len(pool)
-            assert 0 <= r <= n
-            vec = range(r)
-            yield tuple(pool[i] for i in vec)
+            indices = range(r)
+            yield tuple(pool[i] for i in indices)
             while 1:
                 for i in reversed(range(r)):
-                    if vec[i] != i + n - r:
+                    if indices[i] != i + n - r:
                         break
                 else:
                     return
-                vec[i] += 1
+                indices[i] += 1
                 for j in range(i+1, r):
-                    vec[j] = vec[j-1] + 1
-                yield tuple(pool[i] for i in vec)
+                    indices[j] = indices[j-1] + 1
+                yield tuple(pool[i] for i in indices)
 
    .. versionadded:: 2.6
 
@@ -356,7 +354,29 @@ loops that truncate the stream.
    value.  So if the input elements are unique, there will be no repeat
    values in each permutation.
 
-   Example:  ``permutations(range(3),2) --> (1,2) (1,3) (2,1) (2,3) (3,1) (3,2)``
+   Equivalent to::
+
+        def permutations(iterable, r=None):
+            'permutations(range(3), 2) --> (0,1) (0,2) (1,0) (1,2) (2,0) (2,1)'
+            pool = tuple(iterable)
+            n = len(pool)
+            r = n if r is None else r
+            indices = range(n)
+            cycles = range(n-r+1, n+1)[::-1]
+            yield tuple(pool[i] for i in indices[:r])
+            while n:
+                for i in reversed(range(r)):
+                    cycles[i] -= 1
+                    if cycles[i] == 0:
+                        indices[i:] = indices[i+1:] + indices[i:i+1]
+                        cycles[i] = n - i
+                    else:
+                        j = cycles[i]
+                        indices[i], indices[-j] = indices[-j], indices[i]
+                        yield tuple(pool[i] for i in indices[:r])
+                        break
+                else:
+                    return
 
    .. versionadded:: 2.6