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SF patch #408326 by Robin Thomas: slice objects comparable, not

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hashable

This patch changes the behavior of slice objects in the following
manner:

- Slice objects are now comparable with other slice objects as though
they were logically tuples of (start,stop,step). The tuple is not
created in the comparison function, but the comparison behavior is
logically equivalent.

- Slice objects are not hashable. With the above change to being
comparable, slice objects now cannot be used as keys in dictionaries.

[I've edited the patch for style.  Note that this fixes the problem
that dict[i:j] seemed to work but was meaningless.  --GvR]
This commit is contained in:
Guido van Rossum 2001-03-20 12:41:34 +00:00
parent 26ae7cd75a
commit a1351fbd88
1 changed files with 23 additions and 3 deletions
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26
Objects/sliceobject.c
View file

@ -155,6 +155,26 @@ static PyObject *slice_getattr(PySliceObject *self, char *name)
return ret;
}
static int
slice_compare(PySliceObject *v, PySliceObject *w)
{
int result = 0;
if (v == w)
return 0;
if (PyObject_Cmp(v->start, w->start, &result) < 0)
return -2;
if (result != 0)
return result;
if (PyObject_Cmp(v->stop, w->stop, &result) < 0)
return -2;
if (result != 0)
return result;
if (PyObject_Cmp(v->step, w->step, &result) < 0)
return -2;
return result;
}
PyTypeObject PySlice_Type = {
PyObject_HEAD_INIT(&PyType_Type)
@ -166,9 +186,9 @@ PyTypeObject PySlice_Type = {
0, /*tp_print*/
(getattrfunc)slice_getattr, /*tp_getattr*/
0, /*tp_setattr*/
0, /*tp_compare*/
(reprfunc)slice_repr, /*tp_repr*/
(cmpfunc)slice_compare, /*tp_compare*/
(reprfunc)slice_repr, /*tp_repr*/
0, /*tp_as_number*/
0, /*tp_as_sequence*/
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
};