Use rich comparisons to fulfill an old wish: complex numbers now raise

exceptions when compared using <, <=, > or >=.

NOTE: This is a tentative change: this means that cmp() involving
complex numbers will raise an exception when the numbers differ, and
that in turn means that e.g. dictionaries and certain other compounds
(e.g. UserLists) containing complex numbers can't be compared either.
So we'll have to decide whether this is acceptable.  The alpha test
cycle is a good time to keep an eye on this!

Objects/complexobject.c

@@ -210,22 +210,6 @@ complex_repr(PyComplexObject *v)
 	return PyString_FromString(buf);
 }
 
-static int
-complex_compare(PyComplexObject *v, PyComplexObject *w)
-{
-	/* Note: "greater" and "smaller" have no meaning for complex numbers,
-	   but Python requires that they be defined nevertheless. */
-	Py_complex i, j;
-	i = v->cval;
-	j = w->cval;
-	if (i.real == j.real && i.imag == j.imag)
-		return 0;
-	else if (i.real != j.real)
-		return (i.real < j.real) ? -1 : 1;
-	else
-		return (i.imag < j.imag) ? -1 : 1;
-}
-
 static long
 complex_hash(PyComplexObject *v)
 {
@@ -420,6 +404,47 @@ complex_coerce(PyObject **pv, PyObject **pw)
 	return 1; /* Can't do it */
 }
 
+static PyObject *
+complex_richcompare(PyObject *v, PyObject *w, int op)
+{
+	int c;
+	Py_complex i, j;
+	PyObject *res;
+
+	if (op != Py_EQ && op != Py_NE) {
+		PyErr_SetString(PyExc_TypeError,
+			"cannot compare complex numbers using <, <=, >, >=");
+		return NULL;
+	}
+
+	c = PyNumber_CoerceEx(&v, &w);
+	if (c < 0)
+		return NULL;
+	if (c > 0) {
+		Py_INCREF(Py_NotImplemented);
+		return Py_NotImplemented;
+	}
+	if (!PyComplex_Check(v) || !PyComplex_Check(w)) {
+		Py_DECREF(v);
+		Py_DECREF(w);
+		Py_INCREF(Py_NotImplemented);
+		return Py_NotImplemented;
+	}
+
+	i = ((PyComplexObject *)v)->cval;
+	j = ((PyComplexObject *)w)->cval;
+	Py_DECREF(v);
+	Py_DECREF(w);
+
+	if ((i.real == j.real && i.imag == j.imag) == (op == Py_EQ))
+		res = Py_True;
+	else
+		res = Py_False;
+
+	Py_INCREF(res);
+	return res;
+}
+
 static PyObject *
 complex_int(PyObject *v)
 {
@@ -474,29 +499,29 @@ complex_getattr(PyComplexObject *self, char *name)
 }
 
 static PyNumberMethods complex_as_number = {
-	(binaryfunc)complex_add, /*nb_add*/
-	(binaryfunc)complex_sub, /*nb_subtract*/
-	(binaryfunc)complex_mul, /*nb_multiply*/
-	(binaryfunc)complex_div, /*nb_divide*/
-	(binaryfunc)complex_remainder,	/*nb_remainder*/
-	(binaryfunc)complex_divmod,	/*nb_divmod*/
-	(ternaryfunc)complex_pow, /*nb_power*/
-	(unaryfunc)complex_neg, /*nb_negative*/
-	(unaryfunc)complex_pos, /*nb_positive*/
-	(unaryfunc)complex_abs, /*nb_absolute*/
-	(inquiry)complex_nonzero, /*nb_nonzero*/
-	0,		/*nb_invert*/
-	0,		/*nb_lshift*/
-	0,		/*nb_rshift*/
-	0,		/*nb_and*/
-	0,		/*nb_xor*/
-	0,		/*nb_or*/
-	(coercion)complex_coerce, /*nb_coerce*/
-	(unaryfunc)complex_int, /*nb_int*/
-	(unaryfunc)complex_long, /*nb_long*/
-	(unaryfunc)complex_float, /*nb_float*/
-	0,		/*nb_oct*/
-	0,		/*nb_hex*/
+	(binaryfunc)complex_add, 		/* nb_add */
+	(binaryfunc)complex_sub, 		/* nb_subtract */
+	(binaryfunc)complex_mul, 		/* nb_multiply */
+	(binaryfunc)complex_div, 		/* nb_divide */
+	(binaryfunc)complex_remainder,		/* nb_remainder */
+	(binaryfunc)complex_divmod,		/* nb_divmod */
+	(ternaryfunc)complex_pow,		/* nb_power */
+	(unaryfunc)complex_neg,			/* nb_negative */
+	(unaryfunc)complex_pos,			/* nb_positive */
+	(unaryfunc)complex_abs,			/* nb_absolute */
+	(inquiry)complex_nonzero,		/* nb_nonzero */
+	0,					/* nb_invert */
+	0,					/* nb_lshift */
+	0,					/* nb_rshift */
+	0,					/* nb_and */
+	0,					/* nb_xor */
+	0,					/* nb_or */
+	(coercion)complex_coerce,		/* nb_coerce */
+	(unaryfunc)complex_int,			/* nb_int */
+	(unaryfunc)complex_long,		/* nb_long */
+	(unaryfunc)complex_float,		/* nb_float */
+	0,					/* nb_oct */
+	0,					/* nb_hex */
 };
 
 PyTypeObject PyComplex_Type = {
@@ -505,16 +530,26 @@ PyTypeObject PyComplex_Type = {
 	"complex",
 	sizeof(PyComplexObject),
 	0,
-	(destructor)complex_dealloc,	/*tp_dealloc*/
-	(printfunc)complex_print,	/*tp_print*/
-	(getattrfunc)complex_getattr,	/*tp_getattr*/
-	0,				/*tp_setattr*/
-	(cmpfunc)complex_compare,	/*tp_compare*/
-	(reprfunc)complex_repr,		/*tp_repr*/
-	&complex_as_number,    		/*tp_as_number*/
-	0,				/*tp_as_sequence*/
-	0,				/*tp_as_mapping*/
-	(hashfunc)complex_hash, 	/*tp_hash*/
+	(destructor)complex_dealloc,		/* tp_dealloc */
+	(printfunc)complex_print,		/* tp_print */
+	(getattrfunc)complex_getattr,		/* tp_getattr */
+	0,					/* tp_setattr */
+	0,					/* tp_compare */
+	(reprfunc)complex_repr,			/* tp_repr */
+	&complex_as_number,    			/* tp_as_number */
+	0,					/* tp_as_sequence */
+	0,					/* tp_as_mapping */
+	(hashfunc)complex_hash, 		/* tp_hash */
+	0,					/* tp_call */
+	0,					/* tp_str */
+	0,					/* tp_getattro */
+	0,					/* tp_setattro */
+	0,					/* tp_as_buffer */
+	Py_TPFLAGS_DEFAULT,			/* tp_flags */
+	0,					/* tp_doc */
+	0,					/* tp_traverse */
+	0,					/* tp_clear */
+	complex_richcompare,			/* tp_richcompare */
 };
 
 #endif