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Implement and apply PEP 322, reverse iteration

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This commit is contained in:
Raymond Hettinger 2003-11-06 14:06:48 +00:00
parent f607fc5395
commit 85c20a41df
12 changed files with 198 additions and 9 deletions
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125
Objects/enumobject.c
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@ -155,3 +155,128 @@ PyTypeObject PyEnum_Type = {
enum_new, /* tp_new */
PyObject_GC_Del, /* tp_free */
};
/* Reversed Object ***************************************************************/
typedef struct {
PyObject_HEAD
long index;
PyObject* seq;
} reversedobject;
static PyObject *
reversed_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
long n;
PyObject *seq;
reversedobject *ro;
if (!PyArg_UnpackTuple(args, "reversed", 1, 1, &seq))
return NULL;
/* Special case optimization for xrange */
if (PyRange_Check(seq))
return PyObject_CallMethod(seq, "__reversed__", NULL);
if (!PySequence_Check(seq)) {
PyErr_SetString(PyExc_TypeError,
"argument to reversed() must be a sequence");
return NULL;
}
n = PySequence_Size(seq);
if (n == -1)
return NULL;
ro = (reversedobject *)type->tp_alloc(type, 0);
if (ro == NULL)
return NULL;
ro->index = n-1;
Py_INCREF(seq);
ro->seq = seq;
return (PyObject *)ro;
}
static void
reversed_dealloc(reversedobject *ro)
{
PyObject_GC_UnTrack(ro);
Py_XDECREF(ro->seq);
ro->ob_type->tp_free(ro);
}
static int
reversed_traverse(reversedobject *ro, visitproc visit, void *arg)
{
if (ro->seq)
return visit((PyObject *)(ro->seq), arg);
return 0;
}
static PyObject *
reversed_next(reversedobject *ro)
{
PyObject *item;
if (ro->index < 0)
return NULL;
assert(PySequence_Check(ro->seq));
item = PySequence_GetItem(ro->seq, ro->index);
if (item == NULL)
return NULL;
ro->index--;
return item;
}
PyDoc_STRVAR(reversed_doc,
"reverse(sequence) -> reverse iterator over values of the sequence\n"
"\n"
"Return a reverse iterator");
PyTypeObject PyReversed_Type = {
PyObject_HEAD_INIT(&PyType_Type)
0, /* ob_size */
"reversed", /* tp_name */
sizeof(reversedobject), /* tp_basicsize */
0, /* tp_itemsize */
/* methods */
(destructor)reversed_dealloc, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_compare */
0, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
0, /* tp_str */
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
Py_TPFLAGS_BASETYPE, /* tp_flags */
reversed_doc, /* tp_doc */
(traverseproc)reversed_traverse,/* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
PyObject_SelfIter, /* tp_iter */
(iternextfunc)reversed_next, /* tp_iternext */
0, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
PyType_GenericAlloc, /* tp_alloc */
reversed_new, /* tp_new */
PyObject_GC_Del, /* tp_free */
};