Nick Coghlan wrote:
> Tim Peters wrote:
>> OTOH, in the long discussion about PEP 357, I'm not sure anyone except
>> Travis was clear on whether nb_index was meant to apply only to
>> sequence /slicing/ or was meant to apply "everywhere an object gets
>> used in an index-like context". Clipping makes sense only for the
>> former, but it looks like the implementation treats it more like the
>> latter. This was probably exacerbated by:
>>
>> http://mail.python.org/pipermail/python-dev/2006-February/060663.html
>>
>> [Travis]
>> There are other places in Python that check specifically for int objects
>> and long integer objects and fail with anything else. Perhaps all of
>> these should aslo call the __index__ slot.
>>
>> [Guido]
>> Right, absolutely.
>>
>> This is a mess :-)
>
> I've been trawling through the code a bit, and I don't think it's as bad as
> all that.
Damn, it really is a mess. . . nb_index returns the Pyssize_t directly, and a
whole heap of the code expects errors to be signalled via returning -1 before
checking PyErr_Occurred().
To get it to work without clipping everywhere, wrap_lenfunc (typeobject.c),
_PyEval_SliceIndex (ceval.c), PyNumber_Index (abstract.c) and sequence_repeat
(abstract.c) all had to be modified to recognize PY_SSIZE_T_MIN and
PY_SSIZE_T_MAX as potential error flags (in order to clear the overflow error
for _PyEval_SliceIndex, and in order to propagate the exception for the other
three).
And using this approach still means that (2**100).__index__() raises an
OverflowError.
It would probably be cleaner to change the signature of nb_index to return a
PyObject *, and let the code that uses it worry about how (or even whether!)
to convert PyLong results to a Py_ssize_t.
Cheers,
Nick.
--
Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
---------------------------------------------------------------
http://www.boredomandlaziness.org
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