Merged revisions 60441-60474 via svnmerge from

tiran · tiran · commit 7b3ce6a17ea7 · 2008-01-31T14:31:45.000Z
svn+ssh://pythondev@svn.python.org/python/trunk ........ r60441 | christian.heimes | 2008-01-30 12:46:00 +0100 (Wed, 30 Jan 2008) | 1 line Removed unused var ........ r60448 | christian.heimes | 2008-01-30 18:21:22 +0100 (Wed, 30 Jan 2008) | 1 line Fixed some references leaks in sys. ........ r60450 | christian.heimes | 2008-01-30 19:58:29 +0100 (Wed, 30 Jan 2008) | 1 line The previous change was causing a segfault after multiple calls to Py_Initialize() and Py_Finalize(). ........ r60463 | raymond.hettinger | 2008-01-30 23:17:31 +0100 (Wed, 30 Jan 2008) | 1 line Update itertool recipes ........ r60464 | christian.heimes | 2008-01-30 23:54:18 +0100 (Wed, 30 Jan 2008) | 1 line Bug #1234: Fixed semaphore errors on AIX 5.2 ........ r60469 | raymond.hettinger | 2008-01-31 02:38:15 +0100 (Thu, 31 Jan 2008) | 6 lines Fix defect in __ixor__ which would get the wrong answer if the input iterable had a duplicate element (two calls to toggle() reverse each other). Borrow the correct code from sets.py. ........ r60470 | raymond.hettinger | 2008-01-31 02:42:11 +0100 (Thu, 31 Jan 2008) | 1 line Missing return ........ r60471 | jeffrey.yasskin | 2008-01-31 08:44:11 +0100 (Thu, 31 Jan 2008) | 4 lines Added more documentation on how mixed-mode arithmetic should be implemented. I also noticed and fixed a bug in Rational's forward operators (they were claiming all instances of numbers.Rational instead of just the concrete types). ........
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
@@ -511,5 +511,16 @@ which incur interpreter overhead. ::
        "grouper(3, 'abcdefg', 'x') --> ('a','b','c'), ('d','e','f'), ('g','x','x')"
        return izip(*[chain(iterable, repeat(padvalue, n-1))]*n)
 
-
+   def roundrobin(*iterables):
+       "roundrobin('abc', 'd', 'ef') --> 'a', 'd', 'e', 'b', 'f', 'c'"
+       # Recipe contributed by George Sakkis
+       pending = len(iterables)
+       nexts = cycle(iter(it).next for it in iterables)
+       while pending:
+           try:
+               for next in nexts:
+                   yield next()
+           except StopIteration:
+               pending -= 1
+               nexts = cycle(islice(nexts, pending))
 
diff --git a/Doc/library/numbers.rst b/Doc/library/numbers.rst
@@ -97,3 +97,144 @@ The numeric tower
    3-argument form of :func:`pow`, and the bit-string operations: ``<<``,
    ``>>``, ``&``, ``^``, ``|``, ``~``. Provides defaults for :func:`float`,
    :attr:`Rational.numerator`, and :attr:`Rational.denominator`.
+
+
+Notes for type implementors
+---------------------------
+
+Implementors should be careful to make equal numbers equal and hash
+them to the same values. This may be subtle if there are two different
+extensions of the real numbers. For example, :class:`rational.Rational`
+implements :func:`hash` as follows::
+
+    def __hash__(self):
+        if self.denominator == 1:
+            # Get integers right.
+            return hash(self.numerator)
+        # Expensive check, but definitely correct.
+        if self == float(self):
+            return hash(float(self))
+        else:
+            # Use tuple's hash to avoid a high collision rate on
+            # simple fractions.
+            return hash((self.numerator, self.denominator))
+
+
+Adding More Numeric ABCs
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+There are, of course, more possible ABCs for numbers, and this would
+be a poor hierarchy if it precluded the possibility of adding
+those. You can add ``MyFoo`` between :class:`Complex` and
+:class:`Real` with::
+
+    class MyFoo(Complex): ...
+    MyFoo.register(Real)
+
+
+Implementing the arithmetic operations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+We want to implement the arithmetic operations so that mixed-mode
+operations either call an implementation whose author knew about the
+types of both arguments, or convert both to the nearest built in type
+and do the operation there. For subtypes of :class:`Integral`, this
+means that :meth:`__add__` and :meth:`__radd__` should be defined as::
+
+    class MyIntegral(Integral):
+
+        def __add__(self, other):
+            if isinstance(other, MyIntegral):
+                return do_my_adding_stuff(self, other)
+            elif isinstance(other, OtherTypeIKnowAbout):
+                return do_my_other_adding_stuff(self, other)
+            else:
+                return NotImplemented
+
+        def __radd__(self, other):
+            if isinstance(other, MyIntegral):
+                return do_my_adding_stuff(other, self)
+            elif isinstance(other, OtherTypeIKnowAbout):
+                return do_my_other_adding_stuff(other, self)
+            elif isinstance(other, Integral):
+                return int(other) + int(self)
+            elif isinstance(other, Real):
+                return float(other) + float(self)
+            elif isinstance(other, Complex):
+                return complex(other) + complex(self)
+            else:
+                return NotImplemented
+
+
+There are 5 different cases for a mixed-type operation on subclasses
+of :class:`Complex`. I'll refer to all of the above code that doesn't
+refer to ``MyIntegral`` and ``OtherTypeIKnowAbout`` as
+"boilerplate". ``a`` will be an instance of ``A``, which is a subtype
+of :class:`Complex` (``a : A <: Complex``), and ``b : B <:
+Complex``. I'll consider ``a + b``:
+
+    1. If ``A`` defines an :meth:`__add__` which accepts ``b``, all is
+       well.
+    2. If ``A`` falls back to the boilerplate code, and it were to
+       return a value from :meth:`__add__`, we'd miss the possibility
+       that ``B`` defines a more intelligent :meth:`__radd__`, so the
+       boilerplate should return :const:`NotImplemented` from
+       :meth:`__add__`. (Or ``A`` may not implement :meth:`__add__` at
+       all.)
+    3. Then ``B``'s :meth:`__radd__` gets a chance. If it accepts
+       ``a``, all is well.
+    4. If it falls back to the boilerplate, there are no more possible
+       methods to try, so this is where the default implementation
+       should live.
+    5. If ``B <: A``, Python tries ``B.__radd__`` before
+       ``A.__add__``. This is ok, because it was implemented with
+       knowledge of ``A``, so it can handle those instances before
+       delegating to :class:`Complex`.
+
+If ``A<:Complex`` and ``B<:Real`` without sharing any other knowledge,
+then the appropriate shared operation is the one involving the built
+in :class:`complex`, and both :meth:`__radd__` s land there, so ``a+b
+== b+a``.
+
+Because most of the operations on any given type will be very similar,
+it can be useful to define a helper function which generates the
+forward and reverse instances of any given operator. For example,
+:class:`rational.Rational` uses::
+
+    def _operator_fallbacks(monomorphic_operator, fallback_operator):
+        def forward(a, b):
+            if isinstance(b, (int, long, Rational)):
+                return monomorphic_operator(a, b)
+            elif isinstance(b, float):
+                return fallback_operator(float(a), b)
+            elif isinstance(b, complex):
+                return fallback_operator(complex(a), b)
+            else:
+                return NotImplemented
+        forward.__name__ = '__' + fallback_operator.__name__ + '__'
+        forward.__doc__ = monomorphic_operator.__doc__
+
+        def reverse(b, a):
+            if isinstance(a, RationalAbc):
+                # Includes ints.
+                return monomorphic_operator(a, b)
+            elif isinstance(a, numbers.Real):
+                return fallback_operator(float(a), float(b))
+            elif isinstance(a, numbers.Complex):
+                return fallback_operator(complex(a), complex(b))
+            else:
+                return NotImplemented
+        reverse.__name__ = '__r' + fallback_operator.__name__ + '__'
+        reverse.__doc__ = monomorphic_operator.__doc__
+
+        return forward, reverse
+
+    def _add(a, b):
+        """a + b"""
+        return Rational(a.numerator * b.denominator +
+                        b.numerator * a.denominator,
+                        a.denominator * b.denominator)
+
+    __add__, __radd__ = _operator_fallbacks(_add, operator.add)
+
+    # ...
diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
@@ -300,16 +300,6 @@ def pop(self):
         self.discard(value)
         return value
 
-    def toggle(self, value):
-        """Return True if it was added, False if deleted."""
-        # XXX This implementation is not thread-safe
-        if value in self:
-            self.discard(value)
-            return False
-        else:
-            self.add(value)
-            return True
-
     def clear(self):
         """This is slow (creates N new iterators!) but effective."""
         try:
@@ -330,9 +320,13 @@ def __iand__(self, c: Container):
         return self
 
     def __ixor__(self, it: Iterable):
-        # This calls toggle(), so if that is overridded, we call the override
+        if not isinstance(it, Set):
+            it = self._from_iterable(it)
         for value in it:
-            self.toggle(it)
+            if value in self:
+                self.discard(value)
+            else:
+                self.add(value)
         return self
 
     def __isub__(self, it: Iterable):
diff --git a/Lib/numbers.py b/Lib/numbers.py
@@ -291,7 +291,13 @@ def denominator(self):
 
     # Concrete implementation of Real's conversion to float.
     def __float__(self):
-        """float(self) = self.numerator / self.denominator"""
+        """float(self) = self.numerator / self.denominator
+
+        It's important that this conversion use the integer's "true"
+        division rather than casting one side to float before dividing
+        so that ratios of huge integers convert without overflowing.
+
+        """
         return self.numerator / self.denominator
 
 
diff --git a/Lib/rational.py b/Lib/rational.py
@@ -178,27 +178,89 @@ def __str__(self):
         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.
 
         Use this like:
         __op__, __rop__ = _operator_fallbacks(just_rational_op, operator.op)
 
+        In general, we want to implement the arithmetic operations so
+        that mixed-mode operations either call an implementation whose
+        author knew about the types of both arguments, or convert both
+        to the nearest built in type and do the operation there. In
+        Rational, that means that we define __add__ and __radd__ as:
+
+            def __add__(self, other):
+                if isinstance(other, (int, Rational)):
+                    # Do the real operation.
+                    return Rational(self.numerator * other.denominator +
+                                    other.numerator * self.denominator,
+                                    self.denominator * other.denominator)
+                # float and complex don't follow this protocol, and
+                # Rational knows about them, so special case them.
+                elif isinstance(other, float):
+                    return float(self) + other
+                elif isinstance(other, complex):
+                    return complex(self) + other
+                else:
+                    # Let the other type take over.
+                    return NotImplemented
+
+            def __radd__(self, other):
+                # radd handles more types than add because there's
+                # nothing left to fall back to.
+                if isinstance(other, RationalAbc):
+                    return Rational(self.numerator * other.denominator +
+                                    other.numerator * self.denominator,
+                                    self.denominator * other.denominator)
+                elif isinstance(other, Real):
+                    return float(other) + float(self)
+                elif isinstance(other, Complex):
+                    return complex(other) + complex(self)
+                else:
+                    return NotImplemented
+
+
+        There are 5 different cases for a mixed-type addition on
+        Rational. I'll refer to all of the above code that doesn't
+        refer to Rational, float, or complex as "boilerplate". 'r'
+        will be an instance of Rational, which is a subtype of
+        RationalAbc (r : Rational <: RationalAbc), and b : B <:
+        Complex. The first three involve 'r + b':
+
+            1. If B <: Rational, int, float, or complex, we handle
+               that specially, and all is well.
+            2. If Rational falls back to the boilerplate code, and it
+               were to return a value from __add__, we'd miss the
+               possibility that B defines a more intelligent __radd__,
+               so the boilerplate should return NotImplemented from
+               __add__. In particular, we don't handle RationalAbc
+               here, even though we could get an exact answer, in case
+               the other type wants to do something special.
+            3. If B <: Rational, Python tries B.__radd__ before
+               Rational.__add__. This is ok, because it was
+               implemented with knowledge of Rational, so it can
+               handle those instances before delegating to Real or
+               Complex.
+
+        The next two situations describe 'b + r'. We assume that b
+        didn't know about Rational in its implementation, and that it
+        uses similar boilerplate code:
+
+            4. If B <: RationalAbc, then __radd_ converts both to the
+               builtin rational type (hey look, that's us) and
+               proceeds.
+            5. Otherwise, __radd__ tries to find the nearest common
+               base ABC, and fall back to its builtin type. Since this
+               class doesn't subclass a concrete type, there's no
+               implementation to fall back to, so we need to try as
+               hard as possible to return an actual value, or the user
+               will get a TypeError.
+
         """
         def forward(a, b):
-            if isinstance(b, RationalAbc):
-                # Includes ints.
+            if isinstance(b, (int, Rational)):
                 return monomorphic_operator(a, b)
             elif isinstance(b, float):
                 return fallback_operator(float(a), b)
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
@@ -106,15 +106,9 @@ static PyStructSequence_Desc floatinfo_desc = {
 PyObject *
 PyFloat_GetInfo(void)
 {
-	static PyObject* floatinfo;
+	PyObject* floatinfo;
 	int pos = 0;
 
-	if (floatinfo != NULL) {
-		Py_INCREF(floatinfo);
-		return floatinfo;
-	}
-	PyStructSequence_InitType(&FloatInfoType, &floatinfo_desc);
-	
 	floatinfo = PyStructSequence_New(&FloatInfoType);
 	if (floatinfo == NULL) {
 		return NULL;
@@ -143,8 +137,6 @@ PyFloat_GetInfo(void)
 		Py_CLEAR(floatinfo);
 		return NULL;
 	}
-
-	Py_INCREF(floatinfo);
 	return floatinfo;
 }
 
@@ -1601,6 +1593,9 @@ _PyFloat_Init(void)
 	/* Initialize floating point repr */
 	_PyFloat_DigitsInit();
 #endif
+	/* Init float info */
+	if (FloatInfoType.tp_name == 0)
+		PyStructSequence_InitType(&FloatInfoType, &floatinfo_desc);
 }
 
 void
diff --git a/Python/import.c b/Python/import.c
@@ -371,6 +371,8 @@ static char* sys_deletes[] = {
 	"path", "argv", "ps1", "ps2",
 	"last_type", "last_value", "last_traceback",
 	"path_hooks", "path_importer_cache", "meta_path",
+	/* misc stuff */
+	"flags", "float_info",
 	NULL
 };
 
diff --git a/Python/marshal.c b/Python/marshal.c
@@ -482,7 +482,7 @@ r_object(RFILE *p)
 {
 	/* NULL is a valid return value, it does not necessarily means that
 	   an exception is set. */
-	PyObject *v, *v2, *v3;
+	PyObject *v, *v2;
 	long i, n;
 	int type = r_byte(p);
 	PyObject *retval;
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
diff --git a/configure b/configure
diff --git a/configure.in b/configure.in

Original file line number	Diff line number	Diff line change
`@@ -482,7 +482,7 @@ r_object(RFILE *p)`
`482`	`482`	`{`
`483`	`483`	`/* NULL is a valid return value, it does not necessarily means that`
`484`	`484`	`an exception is set. */`
`485`		`- PyObject v, v2, *v3;`
	`485`	`+ PyObject v, v2;`
`486`	`486`	`long i, n;`
`487`	`487`	`int type = r_byte(p);`
`488`	`488`	`PyObject *retval;`