cpython/Modules/itertoolsmodule.c

#include "Python.h"

/* Itertools module written and maintained 
   by Raymond D. Hettinger <python@rcn.com>
   Copyright (c) 2003 Python Software Foundation.
   All rights reserved.
*/

/* cycle object **********************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *it;
	PyObject *saved;
	int firstpass;
} cycleobject;

PyTypeObject cycle_type;

static PyObject *
cycle_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *it;
	PyObject *iterable;
	PyObject *saved;
	cycleobject *lz;

	if (!PyArg_UnpackTuple(args, "cycle", 1, 1, &iterable))
		return NULL;

	/* Get iterator. */
	it = PyObject_GetIter(iterable);
	if (it == NULL)
		return NULL;

	saved = PyList_New(0);
	if (saved == NULL) {
		Py_DECREF(it);
		return NULL;
	}

	/* create cycleobject structure */
	lz = (cycleobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(it);
		Py_DECREF(saved);
		return NULL;
	}
	lz->it = it;
	lz->saved = saved;
	lz->firstpass = 0;

	return (PyObject *)lz;
}

static void
cycle_dealloc(cycleobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->saved);
	Py_XDECREF(lz->it);
	lz->ob_type->tp_free(lz);
}

static int
cycle_traverse(cycleobject *lz, visitproc visit, void *arg)
{
	int err;

	if (lz->it) {
		err = visit(lz->it, arg);
		if (err)
			return err;
	}
	if (lz->saved) {
		err = visit(lz->saved, arg);
		if (err)
			return err;
	}
	return 0;
}

static PyObject *
cycle_next(cycleobject *lz)
{
	PyObject *item;
	PyObject *it;

	while (1) {
		item = PyIter_Next(lz->it);
		if (item != NULL) {
			if (!lz->firstpass)
				PyList_Append(lz->saved, item);
			return item;
		}
		if (PyList_Size(lz->saved) == 0) 
			return NULL;
		it = PyObject_GetIter(lz->saved);
		if (it == NULL)
			return NULL;
		Py_DECREF(lz->it);
		lz->it = it;
		lz->firstpass = 1;
	}
}

static PyObject *
cycle_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(cycle_doc,
"cycle(iterable) --> cycle object\n\
\n\
Return elements from the iterable until it is exhausted.\n\
Then repeat the sequence indefinitely.");

PyTypeObject cycle_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.cycle",		/* tp_name */
	sizeof(cycleobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)cycle_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 */
	cycle_doc,			/* tp_doc */
	(traverseproc)cycle_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)cycle_getiter,	/* tp_iter */
	(iternextfunc)cycle_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 */
	cycle_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* dropwhile object **********************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *func;
	PyObject *it;
	long	 start;
} dropwhileobject;

PyTypeObject dropwhile_type;

static PyObject *
dropwhile_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *func, *seq;
	PyObject *it;
	dropwhileobject *lz;

	if (!PyArg_UnpackTuple(args, "dropwhile", 2, 2, &func, &seq))
		return NULL;

	/* Get iterator. */
	it = PyObject_GetIter(seq);
	if (it == NULL)
		return NULL;

	/* create dropwhileobject structure */
	lz = (dropwhileobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(it);
		return NULL;
	}
	Py_INCREF(func);
	lz->func = func;
	lz->it = it;
	lz->start = 0;

	return (PyObject *)lz;
}

static void
dropwhile_dealloc(dropwhileobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->func);
	Py_XDECREF(lz->it);
	lz->ob_type->tp_free(lz);
}

static int
dropwhile_traverse(dropwhileobject *lz, visitproc visit, void *arg)
{
	int err;

	if (lz->it) {
		err = visit(lz->it, arg);
		if (err)
			return err;
	}
	if (lz->func) {
		err = visit(lz->func, arg);
		if (err)
			return err;
	}
	return 0;
}

static PyObject *
dropwhile_next(dropwhileobject *lz)
{
	PyObject *item, *good;
	PyObject *it = lz->it;
	long ok;

	for (;;) {
		assert(PyIter_Check(it));
		item = (*it->ob_type->tp_iternext)(it);
		if (item == NULL)
			return NULL;
		if (lz->start == 1)
			return item;

		good = PyObject_CallFunctionObjArgs(lz->func, item, NULL);
		if (good == NULL) {
			Py_DECREF(item);
			return NULL;
		}
		ok = PyObject_IsTrue(good);
		Py_DECREF(good);
		if (!ok) {
			lz->start = 1;
			return item;
		}
		Py_DECREF(item);
	}
}

static PyObject *
dropwhile_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(dropwhile_doc,
"dropwhile(predicate, iterable) --> dropwhile object\n\
\n\
Drop items from the iterable while predicate(item) is true.\n\
Afterwards, return every element until the iterable is exhausted.");

PyTypeObject dropwhile_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.dropwhile",		/* tp_name */
	sizeof(dropwhileobject),	/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)dropwhile_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 */
	dropwhile_doc,			/* tp_doc */
	(traverseproc)dropwhile_traverse,    /* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)dropwhile_getiter,	/* tp_iter */
	(iternextfunc)dropwhile_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 */
	dropwhile_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* takewhile object **********************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *func;
	PyObject *it;
	long	 stop;
} takewhileobject;

PyTypeObject takewhile_type;

static PyObject *
takewhile_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *func, *seq;
	PyObject *it;
	takewhileobject *lz;

	if (!PyArg_UnpackTuple(args, "takewhile", 2, 2, &func, &seq))
		return NULL;

	/* Get iterator. */
	it = PyObject_GetIter(seq);
	if (it == NULL)
		return NULL;

	/* create takewhileobject structure */
	lz = (takewhileobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(it);
		return NULL;
	}
	Py_INCREF(func);
	lz->func = func;
	lz->it = it;
	lz->stop = 0;

	return (PyObject *)lz;
}

static void
takewhile_dealloc(takewhileobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->func);
	Py_XDECREF(lz->it);
	lz->ob_type->tp_free(lz);
}

static int
takewhile_traverse(takewhileobject *lz, visitproc visit, void *arg)
{
	int err;

	if (lz->it) {
		err = visit(lz->it, arg);
		if (err)
			return err;
	}
	if (lz->func) {
		err = visit(lz->func, arg);
		if (err)
			return err;
	}
	return 0;
}

static PyObject *
takewhile_next(takewhileobject *lz)
{
	PyObject *item, *good;
	PyObject *it = lz->it;
	long ok;

	if (lz->stop == 1)
		return NULL;

	assert(PyIter_Check(it));
	item = (*it->ob_type->tp_iternext)(it);
	if (item == NULL)
		return NULL;

	good = PyObject_CallFunctionObjArgs(lz->func, item, NULL);
	if (good == NULL) {
		Py_DECREF(item);
		return NULL;
	}
	ok = PyObject_IsTrue(good);
	Py_DECREF(good);
	if (ok)
		return item;
	Py_DECREF(item);
	lz->stop = 1;
	return NULL;
}

static PyObject *
takewhile_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(takewhile_doc,
"takewhile(predicate, iterable) --> takewhile object\n\
\n\
Return successive entries from an iterable as long as the \n\
predicate evaluates to true for each entry.");

PyTypeObject takewhile_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.takewhile",		/* tp_name */
	sizeof(takewhileobject),	/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)takewhile_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 */
	takewhile_doc,			/* tp_doc */
	(traverseproc)takewhile_traverse,    /* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)takewhile_getiter,	/* tp_iter */
	(iternextfunc)takewhile_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 */
	takewhile_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* islice object ************************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *it;
	long	next;
	long	stop;
	long	step;
	long	cnt;
} isliceobject;

PyTypeObject islice_type;

static PyObject *
islice_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *seq;
	long a1=0, a2=0, a3=0, start=0, stop=0, step=1;
	PyObject *it;
	int numargs;
	isliceobject *lz;

	numargs = PyTuple_Size(args);
	if (!PyArg_ParseTuple(args, "Ol|ll:islice", &seq, &a1, &a2, &a3))
		return NULL;

	if (numargs == 2) {
		stop = a1;
	} else if (numargs == 3) {
		start = a1;
		stop = a2;
	} else {
		start = a1;
		stop = a2;
		step = a3;
	}

	if (start<0 || stop<0) {
		PyErr_SetString(PyExc_ValueError,
		   "Indices for islice() must be positive.");
		return NULL;
	}

	if (step<1) {
		PyErr_SetString(PyExc_ValueError,
		   "Step must be one or larger for islice().");
		return NULL;
	}

	/* Get iterator. */
	it = PyObject_GetIter(seq);
	if (it == NULL)
		return NULL;

	/* create isliceobject structure */
	lz = (isliceobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(it);
		return NULL;
	}
	lz->it = it;
	lz->next = start;
	lz->stop = stop;
	lz->step = step;
	lz->cnt = 0L;

	return (PyObject *)lz;
}

static void
islice_dealloc(isliceobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->it);
	lz->ob_type->tp_free(lz);
}

static int
islice_traverse(isliceobject *lz, visitproc visit, void *arg)
{
	if (lz->it)
		return visit(lz->it, arg);
	return 0;
}

static PyObject *
islice_next(isliceobject *lz)
{
	PyObject *item;
	PyObject *it = lz->it;
	long oldnext;

	while (lz->cnt < lz->next) {
		assert(PyIter_Check(it));
		item = (*it->ob_type->tp_iternext)(it);
		if (item == NULL)
			return NULL;
		Py_DECREF(item);
		lz->cnt++;
	}
	if (lz->cnt >= lz->stop)
		return NULL;
	assert(PyIter_Check(it));
	item = (*it->ob_type->tp_iternext)(it);
	if (item == NULL)
		return NULL;
	lz->cnt++;
	oldnext = lz->next;
	lz->next += lz->step;
	if (lz->next < oldnext)	/* Check for overflow */
		lz->next = lz->stop;
	return item;
}

static PyObject *
islice_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(islice_doc,
"islice(iterable, [start,] stop [, step]) --> islice object\n\
\n\
Return an iterator whose next() method returns selected values from an\n\
iterable.  If start is specified, will skip all preceding elements;\n\
otherwise, start defaults to zero.  Step defaults to one.  If\n\
specified as another value, step determines how many values are \n\
skipped between successive calls.  Works like a slice() on a list\n\
but returns an iterator.");

PyTypeObject islice_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.islice",		/* tp_name */
	sizeof(isliceobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)islice_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 */
	islice_doc,			/* tp_doc */
	(traverseproc)islice_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)islice_getiter,	/* tp_iter */
	(iternextfunc)islice_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 */
	islice_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* starmap object ************************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *func;
	PyObject *it;
} starmapobject;

PyTypeObject starmap_type;

static PyObject *
starmap_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *func, *seq;
	PyObject *it;
	starmapobject *lz;

	if (!PyArg_UnpackTuple(args, "starmap", 2, 2, &func, &seq))
		return NULL;

	/* Get iterator. */
	it = PyObject_GetIter(seq);
	if (it == NULL)
		return NULL;

	/* create starmapobject structure */
	lz = (starmapobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(it);
		return NULL;
	}
	Py_INCREF(func);
	lz->func = func;
	lz->it = it;

	return (PyObject *)lz;
}

static void
starmap_dealloc(starmapobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->func);
	Py_XDECREF(lz->it);
	lz->ob_type->tp_free(lz);
}

static int
starmap_traverse(starmapobject *lz, visitproc visit, void *arg)
{
	int err;

	if (lz->it) {
		err = visit(lz->it, arg);
		if (err)
			return err;
	}
	if (lz->func) {
		err = visit(lz->func, arg);
		if (err)
			return err;
	}
	return 0;
}

static PyObject *
starmap_next(starmapobject *lz)
{
	PyObject *args;
	PyObject *result;
	PyObject *it = lz->it;

	assert(PyIter_Check(it));
	args = (*it->ob_type->tp_iternext)(it);
	if (args == NULL)
		return NULL;
	if (!PyTuple_CheckExact(args)) {
		Py_DECREF(args);
		PyErr_SetString(PyExc_TypeError,
				"iterator must return a tuple");
		return NULL;
	}
	result = PyObject_Call(lz->func, args, NULL);
	Py_DECREF(args);
	return result;
}

static PyObject *
starmap_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(starmap_doc,
"starmap(function, sequence) --> starmap object\n\
\n\
Return an iterator whose values are returned from the function evaluated\n\
with a argument tuple taken from the given sequence.");

PyTypeObject starmap_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.starmap",		/* tp_name */
	sizeof(starmapobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)starmap_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 */
	starmap_doc,			/* tp_doc */
	(traverseproc)starmap_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)starmap_getiter,	/* tp_iter */
	(iternextfunc)starmap_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 */
	starmap_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* imap object ************************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *iters;
	PyObject *func;
} imapobject;

PyTypeObject imap_type;

static PyObject *
imap_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *it, *iters, *func;
	imapobject *lz;
	int numargs, i;

	numargs = PyTuple_Size(args);
	if (numargs < 2) {
		PyErr_SetString(PyExc_TypeError,
		   "imap() must have at least two arguments.");
		return NULL;
	}

	iters = PyTuple_New(numargs-1);
	if (iters == NULL)
		return NULL;

	for (i=1 ; i<numargs ; i++) {
		/* Get iterator. */
		it = PyObject_GetIter(PyTuple_GET_ITEM(args, i));
		if (it == NULL) {
			Py_DECREF(iters);
			return NULL;
		}
		PyTuple_SET_ITEM(iters, i-1, it);
	}

	/* create imapobject structure */
	lz = (imapobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(iters);
		return NULL;
	}
	lz->iters = iters;
	func = PyTuple_GET_ITEM(args, 0);
	Py_INCREF(func);
	lz->func = func;

	return (PyObject *)lz;
}

static void
imap_dealloc(imapobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->iters);
	Py_XDECREF(lz->func);
	lz->ob_type->tp_free(lz);
}

static int
imap_traverse(imapobject *lz, visitproc visit, void *arg)
{
	int err;

	if (lz->iters) {
		err = visit(lz->iters, arg);
		if (err)
			return err;
	}
	if (lz->func) {
		err = visit(lz->func, arg);
		if (err)
			return err;
	}
	return 0;
}

/*	
imap() is an iterator version of __builtins__.map() except that it does
not have the None fill-in feature.  That was intentionally left out for
the following reasons:

  1) Itertools are designed to be easily combined and chained together.
     Having all tools stop with the shortest input is a unifying principle
     that makes it easier to combine finite iterators (supplying data) with
     infinite iterators like count() and repeat() (for supplying sequential
     or constant arguments to a function).

  2) In typical use cases for combining itertools, having one finite data 
     supplier run out before another is likely to be an error condition which
     should not pass silently by automatically supplying None.

  3) The use cases for automatic None fill-in are rare -- not many functions
     do something useful when a parameter suddenly switches type and becomes
     None.  

  4) If a need does arise, it can be met by __builtins__.map() or by 
     writing a generator.

  5) Similar toolsets in Haskell and SML do not have automatic None fill-in.
*/

static PyObject *
imap_next(imapobject *lz)
{
	PyObject *val;
	PyObject *argtuple;
	PyObject *result;
	int numargs, i;

	numargs = PyTuple_Size(lz->iters);
	argtuple = PyTuple_New(numargs);
	if (argtuple == NULL)
		return NULL;

	for (i=0 ; i<numargs ; i++) {
		val = PyIter_Next(PyTuple_GET_ITEM(lz->iters, i));
		if (val == NULL) {
			Py_DECREF(argtuple);
			return NULL;
		}
		PyTuple_SET_ITEM(argtuple, i, val);
	}
	if (lz->func == Py_None) 
		return argtuple;
	result = PyObject_Call(lz->func, argtuple, NULL);
	Py_DECREF(argtuple);
	return result;
}

static PyObject *
imap_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(imap_doc,
"imap(func, *iterables) --> imap object\n\
\n\
Make an iterator that computes the function using arguments from\n\
each of the iterables.	Like map() except that it returns\n\
an iterator instead of a list and that it stops when the shortest\n\
iterable is exhausted instead of filling in None for shorter\n\
iterables.");

PyTypeObject imap_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.imap",		/* tp_name */
	sizeof(imapobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)imap_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 */
	imap_doc,			/* tp_doc */
	(traverseproc)imap_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)imap_getiter,	/* tp_iter */
	(iternextfunc)imap_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 */
	imap_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* chain object ************************************************************/

typedef struct {
	PyObject_HEAD
	long	tuplesize;
	long	iternum;		/* which iterator is active */
	PyObject *ittuple;		/* tuple of iterators */
} chainobject;

PyTypeObject chain_type;

static PyObject *
chain_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	chainobject *lz;
	int tuplesize = PySequence_Length(args);
	int i;
	PyObject *ittuple;

	/* obtain iterators */
	assert(PyTuple_Check(args));
	ittuple = PyTuple_New(tuplesize);
	if(ittuple == NULL)
		return NULL;
	for (i=0; i < tuplesize; ++i) {
		PyObject *item = PyTuple_GET_ITEM(args, i);
		PyObject *it = PyObject_GetIter(item);
		if (it == NULL) {
			if (PyErr_ExceptionMatches(PyExc_TypeError))
				PyErr_Format(PyExc_TypeError,
				    "chain argument #%d must support iteration",
				    i+1);
			Py_DECREF(ittuple);
			return NULL;
		}
		PyTuple_SET_ITEM(ittuple, i, it);
	}

	/* create chainobject structure */
	lz = (chainobject *)type->tp_alloc(type, 0);
	if (lz == NULL)
		return NULL;

	lz->ittuple = ittuple;
	lz->iternum = 0;
	lz->tuplesize = tuplesize;

	return (PyObject *)lz;
}

static void
chain_dealloc(chainobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->ittuple);
	lz->ob_type->tp_free(lz);
}

static int
chain_traverse(chainobject *lz, visitproc visit, void *arg)
{
	if (lz->ittuple)
		return visit(lz->ittuple, arg);
	return 0;
}

static PyObject *
chain_next(chainobject *lz)
{
	PyObject *it;
	PyObject *item;

	while (lz->iternum < lz->tuplesize) {
		it = PyTuple_GET_ITEM(lz->ittuple, lz->iternum);
		item = PyIter_Next(it);
		if (item != NULL)
			return item;
		lz->iternum++;
	}
	return NULL;
}

static PyObject *
chain_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(chain_doc,
"chain(*iterables) --> chain object\n\
\n\
Return a chain object whose .next() method returns elements from the\n\
first iterable until it is exhausted, then elements from the next\n\
iterable, until all of the iterables are exhausted.");

PyTypeObject chain_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.chain",		/* tp_name */
	sizeof(chainobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)chain_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 */
	chain_doc,			/* tp_doc */
	(traverseproc)chain_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)chain_getiter,	/* tp_iter */
	(iternextfunc)chain_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 */
	chain_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* ifilter object ************************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *func;
	PyObject *it;
} ifilterobject;

PyTypeObject ifilter_type;

static PyObject *
ifilter_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *func, *seq;
	PyObject *it;
	ifilterobject *lz;

	if (!PyArg_UnpackTuple(args, "ifilter", 2, 2, &func, &seq))
		return NULL;

	/* Get iterator. */
	it = PyObject_GetIter(seq);
	if (it == NULL)
		return NULL;

	/* create ifilterobject structure */
	lz = (ifilterobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(it);
		return NULL;
	}
	Py_INCREF(func);
	lz->func = func;
	lz->it = it;

	return (PyObject *)lz;
}

static void
ifilter_dealloc(ifilterobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->func);
	Py_XDECREF(lz->it);
	lz->ob_type->tp_free(lz);
}

static int
ifilter_traverse(ifilterobject *lz, visitproc visit, void *arg)
{
	int err;

	if (lz->it) {
		err = visit(lz->it, arg);
		if (err)
			return err;
	}
	if (lz->func) {
		err = visit(lz->func, arg);
		if (err)
			return err;
	}
	return 0;
}

static PyObject *
ifilter_next(ifilterobject *lz)
{
	PyObject *item;
	PyObject *it = lz->it;
	long ok;

	for (;;) {
		assert(PyIter_Check(it));
		item = (*it->ob_type->tp_iternext)(it);
		if (item == NULL)
			return NULL;

		if (lz->func == Py_None) {
			ok = PyObject_IsTrue(item);
		} else {
			PyObject *good;
			good = PyObject_CallFunctionObjArgs(lz->func,
							    item, NULL);
			if (good == NULL) {
				Py_DECREF(item);
				return NULL;
			}
			ok = PyObject_IsTrue(good);
			Py_DECREF(good);
		}
		if (ok)
			return item;
		Py_DECREF(item);
	}
}

static PyObject *
ifilter_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(ifilter_doc,
"ifilter(function or None, sequence) --> ifilter object\n\
\n\
Return those items of sequence for which function(item) is true.\n\
If function is None, return the items that are true.");

PyTypeObject ifilter_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.ifilter",		/* tp_name */
	sizeof(ifilterobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)ifilter_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 */
	ifilter_doc,			/* tp_doc */
	(traverseproc)ifilter_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)ifilter_getiter,	/* tp_iter */
	(iternextfunc)ifilter_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 */
	ifilter_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* ifilterfalse object ************************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *func;
	PyObject *it;
} ifilterfalseobject;

PyTypeObject ifilterfalse_type;

static PyObject *
ifilterfalse_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	PyObject *func, *seq;
	PyObject *it;
	ifilterfalseobject *lz;

	if (!PyArg_UnpackTuple(args, "ifilterfalse", 2, 2, &func, &seq))
		return NULL;

	/* Get iterator. */
	it = PyObject_GetIter(seq);
	if (it == NULL)
		return NULL;

	/* create ifilterfalseobject structure */
	lz = (ifilterfalseobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(it);
		return NULL;
	}
	Py_INCREF(func);
	lz->func = func;
	lz->it = it;

	return (PyObject *)lz;
}

static void
ifilterfalse_dealloc(ifilterfalseobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->func);
	Py_XDECREF(lz->it);
	lz->ob_type->tp_free(lz);
}

static int
ifilterfalse_traverse(ifilterfalseobject *lz, visitproc visit, void *arg)
{
	int err;

	if (lz->it) {
		err = visit(lz->it, arg);
		if (err)
			return err;
	}
	if (lz->func) {
		err = visit(lz->func, arg);
		if (err)
			return err;
	}
	return 0;
}

static PyObject *
ifilterfalse_next(ifilterfalseobject *lz)
{
	PyObject *item;
	PyObject *it = lz->it;
	long ok;

	for (;;) {
		assert(PyIter_Check(it));
		item = (*it->ob_type->tp_iternext)(it);
		if (item == NULL)
			return NULL;

		if (lz->func == Py_None) {
			ok = PyObject_IsTrue(item);
		} else {
			PyObject *good;
			good = PyObject_CallFunctionObjArgs(lz->func,
							    item, NULL);
			if (good == NULL) {
				Py_DECREF(item);
				return NULL;
			}
			ok = PyObject_IsTrue(good);
			Py_DECREF(good);
		}
		if (!ok)
			return item;
		Py_DECREF(item);
	}
}

static PyObject *
ifilterfalse_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(ifilterfalse_doc,
"ifilterfalse(function or None, sequence) --> ifilterfalse object\n\
\n\
Return those items of sequence for which function(item) is false.\n\
If function is None, return the items that are false.");

PyTypeObject ifilterfalse_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.ifilterfalse",	/* tp_name */
	sizeof(ifilterfalseobject),	/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)ifilterfalse_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 */
	ifilterfalse_doc,		/* tp_doc */
	(traverseproc)ifilterfalse_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)ifilterfalse_getiter,	/* tp_iter */
	(iternextfunc)ifilterfalse_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 */
	ifilterfalse_new,		/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* count object ************************************************************/

typedef struct {
	PyObject_HEAD
	long	cnt;
} countobject;

PyTypeObject count_type;

static PyObject *
count_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	countobject *lz;
	long cnt = 0;

	if (!PyArg_ParseTuple(args, "|l:count", &cnt))
		return NULL;

	/* create countobject structure */
	lz = (countobject *)PyObject_New(countobject, &count_type);
	if (lz == NULL)
		return NULL;
	lz->cnt = cnt;

	return (PyObject *)lz;
}

static PyObject *
count_next(countobject *lz)
{
	return PyInt_FromLong(lz->cnt++);
}

static PyObject *
count_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(count_doc,
"count([firstval]) --> count object\n\
\n\
Return a count object whose .next() method returns consecutive\n\
integers starting from zero or, if specified, from firstval.");

PyTypeObject count_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.count",		/* tp_name */
	sizeof(countobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)PyObject_Del,	/* 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,		/* tp_flags */
	count_doc,			/* tp_doc */
	0,				/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)count_getiter,	/* tp_iter */
	(iternextfunc)count_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 */
	count_new,			/* tp_new */
};


/* izip object ************************************************************/

#include "Python.h"

typedef struct {
	PyObject_HEAD
	long	tuplesize;
	PyObject *ittuple;		/* tuple of iterators */
	PyObject *result;
} izipobject;

PyTypeObject izip_type;

static PyObject *
izip_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	izipobject *lz;
	int i;
	PyObject *ittuple;  /* tuple of iterators */
	PyObject *result;
	int tuplesize = PySequence_Length(args);

	if (tuplesize < 1) {
		PyErr_SetString(PyExc_TypeError,
				"izip() requires at least one sequence");
		return NULL;
	}

	/* args must be a tuple */
	assert(PyTuple_Check(args));

	/* obtain iterators */
	ittuple = PyTuple_New(tuplesize);
	if(ittuple == NULL)
		return NULL;
	for (i=0; i < tuplesize; ++i) {
		PyObject *item = PyTuple_GET_ITEM(args, i);
		PyObject *it = PyObject_GetIter(item);
		if (it == NULL) {
			if (PyErr_ExceptionMatches(PyExc_TypeError))
				PyErr_Format(PyExc_TypeError,
				    "izip argument #%d must support iteration",
				    i+1);
			Py_DECREF(ittuple);
			return NULL;
		}
		PyTuple_SET_ITEM(ittuple, i, it);
	}

	/* create a result holder */
	result = PyTuple_New(tuplesize);
	if (result == NULL) {
		Py_DECREF(ittuple);
		return NULL;
	}
	for (i=0 ; i < tuplesize ; i++) {
		Py_INCREF(Py_None);
		PyTuple_SET_ITEM(result, i, Py_None);
	}

	/* create izipobject structure */
	lz = (izipobject *)type->tp_alloc(type, 0);
	if (lz == NULL) {
		Py_DECREF(ittuple);
		Py_DECREF(result);
		return NULL;
	}
	lz->ittuple = ittuple;
	lz->tuplesize = tuplesize;
	lz->result = result;

	return (PyObject *)lz;
}

static void
izip_dealloc(izipobject *lz)
{
	PyObject_GC_UnTrack(lz);
	Py_XDECREF(lz->ittuple);
	Py_XDECREF(lz->result);
	lz->ob_type->tp_free(lz);
}

static int
izip_traverse(izipobject *lz, visitproc visit, void *arg)
{
	if (lz->ittuple)
		return visit(lz->ittuple, arg);
	return 0;
}

static PyObject *
izip_next(izipobject *lz)
{
	int i;
	long tuplesize = lz->tuplesize;
	PyObject *result = lz->result;
	PyObject *it;
	PyObject *item;

	if (result->ob_refcnt == 1) {
		for (i=0 ; i < tuplesize ; i++) {
			it = PyTuple_GET_ITEM(lz->ittuple, i);
			assert(PyIter_Check(it));
			item = (*it->ob_type->tp_iternext)(it);
			if (item == NULL)
				return NULL;
			Py_DECREF(PyTuple_GET_ITEM(result, i));
			PyTuple_SET_ITEM(result, i, item);
		}
		Py_INCREF(result);
	} else {
		result = PyTuple_New(tuplesize);
		if (result == NULL)
			return NULL;
		for (i=0 ; i < tuplesize ; i++) {
			it = PyTuple_GET_ITEM(lz->ittuple, i);
			assert(PyIter_Check(it));
			item = (*it->ob_type->tp_iternext)(it);
			if (item == NULL) {
				Py_DECREF(result);
				return NULL;
			}
			PyTuple_SET_ITEM(result, i, item);
		}
	}
	return result;
}

static PyObject *
izip_getiter(PyObject *lz)
{
	Py_INCREF(lz);
	return lz;
}

PyDoc_STRVAR(izip_doc,
"izip(iter1 [,iter2 [...]]) --> izip object\n\
\n\
Return a izip object whose .next() method returns a tuple where\n\
the i-th element comes from the i-th iterable argument.  The .next()\n\
method continues until the shortest iterable in the argument sequence\n\
is exhausted and then it raises StopIteration.  Works like the zip()\n\
function but consumes less memory by returning an iterator instead of\n\
a list.");

PyTypeObject izip_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.izip",		/* tp_name */
	sizeof(izipobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)izip_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 */
	izip_doc,			/* tp_doc */
	(traverseproc)izip_traverse,    /* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)izip_getiter,	/* tp_iter */
	(iternextfunc)izip_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 */
	izip_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* repeat object ************************************************************/

typedef struct {
	PyObject_HEAD
	PyObject *element;
	long cnt;
} repeatobject;

PyTypeObject repeat_type;

static PyObject *
repeat_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
	repeatobject *ro;
	PyObject *element;
	long cnt = -1;

	if (!PyArg_ParseTuple(args, "O|l:repeat", &element, &cnt))
		return NULL;

	ro = (repeatobject *)type->tp_alloc(type, 0);
	if (ro == NULL)
		return NULL;
	Py_INCREF(element);
	ro->element = element;
	ro->cnt = cnt;
	return (PyObject *)ro;
}

static void
repeat_dealloc(repeatobject *ro)
{
	PyObject_GC_UnTrack(ro);
	Py_XDECREF(ro->element);
	ro->ob_type->tp_free(ro);
}

static int
repeat_traverse(repeatobject *ro, visitproc visit, void *arg)
{
	if (ro->element)
		return visit(ro->element, arg);
	return 0;
}

static PyObject *
repeat_next(repeatobject *ro)
{
	if (ro->cnt == 0)
		return NULL;
	if (ro->cnt > 0)
		ro->cnt--;
	Py_INCREF(ro->element);
	return ro->element;
}

static PyObject *
repeat_getiter(PyObject *ro)
{
	Py_INCREF(ro);
	return ro;
}

PyDoc_STRVAR(repeat_doc,
"repeat(element [,times]) -> create an iterator which returns the element\n\
for the specified number of times.  If not specified, returns the element\n\
endlessly.");

PyTypeObject repeat_type = {
	PyObject_HEAD_INIT(NULL)
	0,				/* ob_size */
	"itertools.repeat",		/* tp_name */
	sizeof(repeatobject),		/* tp_basicsize */
	0,				/* tp_itemsize */
	/* methods */
	(destructor)repeat_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 */
	repeat_doc,			/* tp_doc */
	(traverseproc)repeat_traverse,	/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	(getiterfunc)repeat_getiter,	/* tp_iter */
	(iternextfunc)repeat_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 */
	repeat_new,			/* tp_new */
	PyObject_GC_Del,		/* tp_free */
};


/* module level code ********************************************************/

PyDoc_STRVAR(module_doc,
"Functional tools for creating and using iterators.\n\
\n\
Infinite iterators:\n\
count([n]) --> n, n+1, n+2, ...\n\
cycle(p) --> p0, p1, ... plast, p0, p1, ...\n\
repeat(elem [,n]) --> elem, elem, elem, ... endlessly or upto n times\n\
\n\
Iterators terminating on the shortest input sequence:\n\
izip(p, q, ...) --> (p[0], q[0]), (p[1], q[1]), ... \n\
ifilter(pred, seq) --> elements of seq where pred(elem) is True\n\
ifilterfalse(pred, seq) --> elements of seq where pred(elem) is False\n\
islice(seq, [start,] stop [, step]) --> elements from\n\
       seq[start:stop:step]\n\
imap(fun, p, q, ...) --> fun(p0, q0), fun(p1, q1), ...\n\
starmap(fun, seq) --> fun(*seq[0]), fun(*seq[1]), ...\n\
chain(p, q, ...) --> p0, p1, ... plast, q0, q1, ... \n\
takewhile(pred, seq) --> seq[0], seq[1], until pred fails\n\
dropwhile(pred, seq) --> seq[n], seq[n+1], starting when pred fails\n\
");


PyMODINIT_FUNC
inititertools(void)
{
	int i;
	PyObject *m;
	char *name;
	PyTypeObject *typelist[] = {
		&cycle_type,
		&dropwhile_type,
		&takewhile_type,
		&islice_type,
		&starmap_type,
		&imap_type,
		&chain_type,
		&ifilter_type,
		&ifilterfalse_type,
		&count_type,
		&izip_type,
		&repeat_type,
		NULL
	};

	m = Py_InitModule3("itertools", NULL, module_doc);

	for (i=0 ; typelist[i] != NULL ; i++) {
		if (PyType_Ready(typelist[i]) < 0)
			return;
		name = strchr(typelist[i]->tp_name, '.') + 1;
		assert (name != NULL);
		Py_INCREF(typelist[i]);
		PyModule_AddObject(m, name, (PyObject *)typelist[i]);
	}
}