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Skip Montanaro's patch, SF 559833, exposing xrange type in builtins.

Browse source 
Also, added more regression tests to cover the new type and test its
conformity with range().
This commit is contained in:
Raymond Hettinger 2002-06-05 23:12:45 +00:00
parent f97b2d7dad
commit c4c453f5ae
4 changed files with 91 additions and 46 deletions
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86
Objects/rangeobject.c
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@ -47,6 +47,76 @@ PyRange_New(long start, long len, long step, int reps)
return (PyObject *) obj;
}
/* Return number of items in range/xrange (lo, hi, step). step > 0
* required. Return a value < 0 if & only if the true value is too
* large to fit in a signed long.
*/
static long
get_len_of_range(long lo, long hi, long step)
{
/* -------------------------------------------------------------
If lo >= hi, the range is empty.
Else if n values are in the range, the last one is
lo + (n-1)*step, which must be <= hi-1. Rearranging,
n <= (hi - lo - 1)/step + 1, so taking the floor of the RHS gives
the proper value. Since lo < hi in this case, hi-lo-1 >= 0, so
the RHS is non-negative and so truncation is the same as the
floor. Letting M be the largest positive long, the worst case
for the RHS numerator is hi=M, lo=-M-1, and then
hi-lo-1 = M-(-M-1)-1 = 2*M. Therefore unsigned long has enough
precision to compute the RHS exactly.
---------------------------------------------------------------*/
long n = 0;
if (lo < hi) {
unsigned long uhi = (unsigned long)hi;
unsigned long ulo = (unsigned long)lo;
unsigned long diff = uhi - ulo - 1;
n = (long)(diff / (unsigned long)step + 1);
}
return n;
}
static PyObject *
range_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
long ilow = 0, ihigh = 0, istep = 1;
long n;
if (PyTuple_Size(args) <= 1) {
if (!PyArg_ParseTuple(args,
"l;xrange() requires 1-3 int arguments",
&ihigh))
return NULL;
}
else {
if (!PyArg_ParseTuple(args,
"ll|l;xrange() requires 1-3 int arguments",
&ilow, &ihigh, &istep))
return NULL;
}
if (istep == 0) {
PyErr_SetString(PyExc_ValueError, "xrange() arg 3 must not be zero");
return NULL;
}
if (istep > 0)
n = get_len_of_range(ilow, ihigh, istep);
else
n = get_len_of_range(ihigh, ilow, -istep);
if (n < 0) {
PyErr_SetString(PyExc_OverflowError,
"xrange() result has too many items");
return NULL;
}
return PyRange_New(ilow, n, istep, 1);
}
static char range_doc[] =
"xrange([start,] stop[, step]) -> xrange object\n\
\n\
Like range(), but instead of returning a list, returns an object that\n\
generates the numbers in the range on demand. This is slightly slower\n\
than range() but more memory efficient.";
static PyObject *
range_item(rangeobject *r, int i)
{
@ -118,12 +188,24 @@ PyTypeObject PyRange_Type = {
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT, /* tp_flags */
0, /* tp_doc */
range_doc, /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
(getiterfunc)range_iter, /* tp_iter */
(getiterfunc)range_iter, /* tp_iter */
0, /* 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 */
0, /* tp_alloc */
range_new, /* tp_new */
};
/*********************** Xrange Iterator **************************/