Merged revisions 60210-60233 via svnmerge from

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

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  r60213 | christian.heimes | 2008-01-23 15:00:25 +0100 (Wed, 23 Jan 2008) | 1 line

  Use Py_TYPE() instead of ->ob_type
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  r60214 | armin.rigo | 2008-01-23 15:07:13 +0100 (Wed, 23 Jan 2008) | 3 lines

  patch 1754489 by vlahan:
  improve portability of address length calculation for AF_UNIX sockets
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  r60216 | christian.heimes | 2008-01-23 15:20:50 +0100 (Wed, 23 Jan 2008) | 1 line

  Fixed bug #1915: Python compiles with --enable-unicode=no again. However several extension methods and modules do not work without unicode support.
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  r60221 | christian.heimes | 2008-01-23 18:15:06 +0100 (Wed, 23 Jan 2008) | 2 lines

  Applied #1069410
  The "can't load dll" message box on Windows is suppressed while an extension is loaded by calling SetErrorMode in dynload_win.c. The error is still reported properly.
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  r60224 | guido.van.rossum | 2008-01-23 21:19:01 +0100 (Wed, 23 Jan 2008) | 2 lines

  Fix two crashers.
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  r60225 | kurt.kaiser | 2008-01-23 23:19:23 +0100 (Wed, 23 Jan 2008) | 3 lines

  Could not open files in .idlerc directory if latter was hidden on Windows.
  Issue 1743, Issue 1862.
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  r60226 | guido.van.rossum | 2008-01-23 23:43:27 +0100 (Wed, 23 Jan 2008) | 2 lines

  Fix misleading comment reported in issue #1917.
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  r60227 | kurt.kaiser | 2008-01-23 23:55:26 +0100 (Wed, 23 Jan 2008) | 2 lines

  There was an error on exit if no sys.exitfunc was defined. Issue 1647.
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  r60228 | guido.van.rossum | 2008-01-24 00:23:43 +0100 (Thu, 24 Jan 2008) | 2 lines

  Turn three recently fixed crashers into regular tests.
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  r60229 | raymond.hettinger | 2008-01-24 01:54:21 +0100 (Thu, 24 Jan 2008) | 1 line

  Add first-cut at an approximation function (still needs rounding tweaks).  Add continued fraction conversions.
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  r60230 | raymond.hettinger | 2008-01-24 03:00:25 +0100 (Thu, 24 Jan 2008) | 1 line

  Minor clean-up and more tests.
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  r60231 | raymond.hettinger | 2008-01-24 03:05:06 +0100 (Thu, 24 Jan 2008) | 1 line

  Cleanup
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  r60232 | neal.norwitz | 2008-01-24 05:14:50 +0100 (Thu, 24 Jan 2008) | 1 line

  Fix the tests by restoring __import__.  I think the test is still valid.
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  r60233 | neal.norwitz | 2008-01-24 08:40:51 +0100 (Thu, 24 Jan 2008) | 4 lines

  Fix the test_urllib2net failures that were caused by r58067.
  I'm not sure this is the correct fix, but at least the test passes
  now and should be closer to correct.
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1 files changed, 36 insertions, 0 deletions

diff --git a/Lib/rational.py b/Lib/rational.py
index 71ffff7..4a56cf2 100755
--- a/Lib/rational.py
+++ b/Lib/rational.py
@@ -171,6 +171,42 @@ class Rational(RationalAbc):
         else:
             return cls(digits, 10 ** -exp)
 
+    @classmethod
+    def from_continued_fraction(cls, seq):
+        'Build a Rational from a continued fraction expessed as a sequence'
+        n, d = 1, 0
+        for e in reversed(seq):
+            n, d = d, n
+            n += e * d
+        return cls(n, d) if seq else cls(0)
+
+    def as_continued_fraction(self):
+        'Return continued fraction expressed as a list'
+        n = self.numerator
+        d = self.denominator
+        cf = []
+        while d:
+            e = int(n // d)
+            cf.append(e)
+            n -= e * d
+            n, d = d, n
+        return cf
+
+    @classmethod
+    def approximate_from_float(cls, f, max_denominator):
+        'Best rational approximation to f with a denominator <= max_denominator'
+        # XXX First cut at algorithm
+        # Still needs rounding rules as specified at
+        #       http://en.wikipedia.org/wiki/Continued_fraction
+        cf = cls.from_float(f).as_continued_fraction()
+        result = Rational(0)
+        for i in range(1, len(cf)):
+            new = cls.from_continued_fraction(cf[:i])
+            if new.denominator > max_denominator:
+                break
+            result = new
+        return result
+
     @property
     def numerator(a):
         return a._numerator