Merged revisions 60245-60277 via svnmerge from

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

........
  r60246 | guido.van.rossum | 2008-01-24 18:58:05 +0100 (Thu, 24 Jan 2008) | 2 lines

  Fix test67.py from issue #1303614.
........
  r60248 | raymond.hettinger | 2008-01-24 19:05:54 +0100 (Thu, 24 Jan 2008) | 1 line

  Clean-up and speed-up code by accessing numerator/denominator directly.  There's no reason to enforce readonliness
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  r60249 | raymond.hettinger | 2008-01-24 19:12:23 +0100 (Thu, 24 Jan 2008) | 1 line

  Revert 60189 and restore performance.
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  r60250 | guido.van.rossum | 2008-01-24 19:21:02 +0100 (Thu, 24 Jan 2008) | 5 lines

  News about recently fixed crashers:
  - A few crashers fixed: weakref_in_del.py (issue #1377858);
    loosing_dict_ref.py (issue #1303614, test67.py);
    borrowed_ref_[34].py (not in tracker).
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  r60252 | thomas.heller | 2008-01-24 19:36:27 +0100 (Thu, 24 Jan 2008) | 7 lines

  Use a PyDictObject again for the array type cache; retrieving items
  from the WeakValueDictionary was slower by nearly a factor of 3.

  To avoid leaks, weakref proxies for the array types are put into the
  cache dict, with weakref callbacks that removes the entries when the
  type goes away.
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  r60253 | thomas.heller | 2008-01-24 19:54:12 +0100 (Thu, 24 Jan 2008) | 2 lines

  Replace Py_BuildValue with PyTuple_Pack because it is faster.
  Also add a missing DECREF.
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  r60254 | raymond.hettinger | 2008-01-24 20:05:29 +0100 (Thu, 24 Jan 2008) | 1 line

  Add support for trunc().
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  r60255 | thomas.heller | 2008-01-24 20:15:02 +0100 (Thu, 24 Jan 2008) | 5 lines

  Invert the checks in get_[u]long and get_[u]longlong.  The intent was
  to not accept float types; the result was that integer-like objects
  were not accepted.

  Ported from release25-maint.
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  r60256 | raymond.hettinger | 2008-01-24 20:30:19 +0100 (Thu, 24 Jan 2008) | 1 line

  Add support for int(r) just like the other numeric classes.
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  r60263 | raymond.hettinger | 2008-01-24 22:23:58 +0100 (Thu, 24 Jan 2008) | 1 line

  Expand tests to include nested graph structures.
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  r60264 | raymond.hettinger | 2008-01-24 22:47:56 +0100 (Thu, 24 Jan 2008) | 1 line

  Shorter pprint's for empty sets and frozensets.  Fix indentation of frozensets.  Add tests including two complex data structures.
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  r60265 | amaury.forgeotdarc | 2008-01-24 23:51:18 +0100 (Thu, 24 Jan 2008) | 14 lines

  #1920: when considering a block starting by "while 0", the compiler optimized the
  whole construct away, even when an 'else' clause is present::

      while 0:
          print("no")
      else:
          print("yes")

  did not generate any code at all.

  Now the compiler emits the 'else' block, like it already does for 'if' statements.

  Will backport.
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  r60266 | amaury.forgeotdarc | 2008-01-24 23:59:25 +0100 (Thu, 24 Jan 2008) | 2 lines

  News entry for r60265 (Issue 1920).
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  r60269 | raymond.hettinger | 2008-01-25 00:50:26 +0100 (Fri, 25 Jan 2008) | 1 line

  More code cleanup.  Remove unnecessary indirection to useless class methods.
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  r60270 | raymond.hettinger | 2008-01-25 01:21:54 +0100 (Fri, 25 Jan 2008) | 1 line

  Add support for copy, deepcopy, and pickle.
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  r60271 | raymond.hettinger | 2008-01-25 01:33:45 +0100 (Fri, 25 Jan 2008) | 1 line

  Mark todos and review comments.
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  r60272 | raymond.hettinger | 2008-01-25 02:13:12 +0100 (Fri, 25 Jan 2008) | 1 line

  Add one other review comment.
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  r60273 | raymond.hettinger | 2008-01-25 02:23:38 +0100 (Fri, 25 Jan 2008) | 1 line

  Fix-up signature for approximation.
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  r60274 | raymond.hettinger | 2008-01-25 02:46:33 +0100 (Fri, 25 Jan 2008) | 1 line

  More design notes
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  r60276 | neal.norwitz | 2008-01-25 07:37:23 +0100 (Fri, 25 Jan 2008) | 6 lines

  Make the test more robust by trying to reconnect up to 3 times
  in case there were transient failures.  This will hopefully silence
  the buildbots for this test.  As we find other tests that have a problem,
  we can fix with a similar strategy assuming it is successful.  It worked
  on my box in a loop for 10+ runs where it would have an exception otherwise.
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  r60277 | neal.norwitz | 2008-01-25 09:04:16 +0100 (Fri, 25 Jan 2008) | 4 lines

  Add prototypes to get the mathmodule.c to compile on OSF1 5.1 (Tru64)
  and eliminate a compiler warning in floatobject.c.  There might be
  a better way to go about this, but it should be good enough for now.
........

1 files changed, 48 insertions, 24 deletions

diff --git a/Lib/rational.py b/Lib/rational.py
index 4a56cf2..89b622c 100755
--- a/Lib/rational.py
+++ b/Lib/rational.py
@@ -13,7 +13,7 @@ __all__ = ["Rational"]
 RationalAbc = numbers.Rational
 
 
-def _gcd(a, b):
+def _gcd(a, b):                     # XXX This is a useful function. Consider making it public.
     """Calculate the Greatest Common Divisor.
 
     Unless b==0, the result will have the same sign as b (so that when
@@ -39,6 +39,8 @@ def _binary_float_to_ratio(x):
     >>> _binary_float_to_ratio(-.25)
     (-1, 4)
     """
+    # XXX Consider moving this to to floatobject.c
+    # with a name like float.as_intger_ratio()
 
     if x == 0:
         return 0, 1
@@ -79,6 +81,10 @@ def _binary_float_to_ratio(x):
 _RATIONAL_FORMAT = re.compile(
     r'^\s*(?P<sign>[-+]?)(?P<num>\d+)(?:/(?P<denom>\d+))?\s*$')
 
+# XXX Consider accepting decimal strings as input since they are exact.
+# Rational("2.01") --> s="2.01" ; Rational.from_decimal(Decimal(s)) --> Rational(201, 100)"
+# If you want to avoid going through the decimal module, just parse the string directly:
+# s.partition('.') --> ('2', '.', '01') --> Rational(int('2'+'01'), 10**len('01')) --> Rational(201, 100)
 
 class Rational(RationalAbc):
     """This class implements rational numbers.
@@ -93,7 +99,7 @@ class Rational(RationalAbc):
 
     """
 
-    __slots__ = ('_numerator', '_denominator')
+    __slots__ = ('numerator', 'denominator')
 
     # We're immutable, so use __new__ not __init__
     def __new__(cls, numerator=0, denominator=1):
@@ -133,8 +139,8 @@ class Rational(RationalAbc):
             raise ZeroDivisionError('Rational(%s, 0)' % numerator)
 
         g = _gcd(numerator, denominator)
-        self._numerator = int(numerator // g)
-        self._denominator = int(denominator // g)
+        self.numerator = int(numerator // g)
+        self.denominator = int(denominator // g)
         return self
 
     @classmethod
@@ -192,29 +198,22 @@ class Rational(RationalAbc):
             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'
+    def approximate(self, max_denominator):
+        'Best rational approximation 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()
+        if self.denominator <= max_denominator:
+            return self
+        cf = self.as_continued_fraction()
         result = Rational(0)
         for i in range(1, len(cf)):
-            new = cls.from_continued_fraction(cf[:i])
+            new = self.from_continued_fraction(cf[:i])
             if new.denominator > max_denominator:
                 break
             result = new
         return result
 
-    @property
-    def numerator(a):
-        return a._numerator
-
-    @property
-    def denominator(a):
-        return a._denominator
-
     def __repr__(self):
         """repr(self)"""
         return ('Rational(%r,%r)' % (self.numerator, self.denominator))
@@ -226,6 +225,16 @@ class Rational(RationalAbc):
         else:
             return '%s/%s' % (self.numerator, self.denominator)
 
+    """ XXX This section needs a lot more commentary
+
+    * Explain the typical sequence of checks, calls, and fallbacks.
+    * Explain the subtle reasons why this logic was needed.
+    * It is not clear how common cases are handled (for example, how
+      does the ratio of two huge integers get converted to a float
+      without overflowing the long-->float conversion.
+
+    """
+
     def _operator_fallbacks(monomorphic_operator, fallback_operator):
         """Generates forward and reverse operators given a purely-rational
         operator and a function from the operator module.
@@ -299,18 +308,15 @@ class Rational(RationalAbc):
         """a // b"""
         return math.floor(a / b)
 
-    @classmethod
-    def _mod(cls, a, b):
-        div = a // b
-        return a - b * div
-
     def __mod__(a, b):
         """a % b"""
-        return a._mod(a, b)
+        div = a // b
+        return a - b * div
 
     def __rmod__(b, a):
         """a % b"""
-        return b._mod(a, b)
+        div = a // b
+        return a - b * div
 
     def __pow__(a, b):
         """a ** b
@@ -369,6 +375,8 @@ class Rational(RationalAbc):
         else:
             return a.numerator // a.denominator
 
+    __int__ = __trunc__
+
     def __floor__(a):
         """Will be math.floor(a) in 3.0."""
         return a.numerator // a.denominator
@@ -410,6 +418,7 @@ class Rational(RationalAbc):
         float must have the same hash as that float.
 
         """
+        # XXX since this method is expensive, consider caching the result
         if self.denominator == 1:
             # Get integers right.
             return hash(self.numerator)
@@ -481,3 +490,18 @@ class Rational(RationalAbc):
     def __bool__(a):
         """a != 0"""
         return a.numerator != 0
+
+    # support for pickling, copy, and deepcopy
+
+    def __reduce__(self):
+        return (self.__class__, (str(self),))
+
+    def __copy__(self):
+        if type(self) == Rational:
+            return self     # I'm immutable; therefore I am my own clone
+        return self.__class__(self.numerator, self.denominator)
+
+    def __deepcopy__(self, memo):
+        if type(self) == Rational:
+            return self     # My components are also immutable
+        return self.__class__(self.numerator, self.denominator)