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This is my nearly two year old patch

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[ 400998 ] experimental support for extended slicing on lists

somewhat spruced up and better tested than it was when I wrote it.

Includes docs & tests.  The whatsnew section needs expanding, and arrays
should support extended slices -- later.
This commit is contained in:
Michael W. Hudson 2002-06-11 10:55:12 +00:00
parent f90ae20354
commit 5efaf7eac8
13 changed files with 570 additions and 22 deletions
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53
Objects/sliceobject.c
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@ -109,6 +109,59 @@ PySlice_GetIndices(PySliceObject *r, int length,
return 0;
}
int
PySlice_GetIndicesEx(PySliceObject *r, int length,
int *start, int *stop, int *step, int *slicelength)
{
/* this is harder to get right than you might think */
int defstart, defstop;
if (r->step == Py_None) {
*step = 1;
} else {
*step = PyInt_AsLong(r->step);
if (*step == -1 && PyErr_Occurred()) {
return -1;
}
else if (*step == 0) {
PyErr_SetString(PyExc_ValueError,
"slice step cannot be zero");
return -1;
}
}
defstart = *step < 0 ? length-1 : 0;
defstop = *step < 0 ? -1 : length;
if (r->start == Py_None) {
*start = defstart;
} else {
if (!_PyEval_SliceIndex(r->start, start)) return -1;
if (*start < 0) *start += length;
if (*start < 0) *start = (*step < 0) ? -1 : 0;
if (*start >= length)
*start = (*step < 0) ? length - 1 : length;
}
if (r->stop == Py_None) {
*stop = defstop;
} else {
if (!_PyEval_SliceIndex(r->stop, stop)) return -1;
if (*stop < 0) *stop += length;
if (*stop < 0) *stop = -1;
if (*stop > length) *stop = length;
}
if (*step < 0) {
*slicelength = (*stop-*start+1)/(*step)+1;
} else {
*slicelength = (*stop-*start-1)/(*step)+1;
}
if (*slicelength < 0) *slicelength = 0;
return 0;
}
static void
slice_dealloc(PySliceObject *r)
{