"Fredrik Lundh" <effbot@telia.com> writes:
> greg wrote:
>
> > I think there are some big conceptual problems with allowing
> > negative steps in a slice.
>
> wasn't "slices" supposed to work the same way as "ranges"?
The problem is that for slices (& indexes in general) that negative
indices have a special interpretation:
range(10,-1,-1)
range(10)[:-1]
Personally I don't think it's that bad (you just have to remember to
write :: instead of :-1: when you want to step all the way back to the
beginning). More serious is what you do with out of range indices -
and NumPy is a bit odd with this one, it seems:
>>> l = Numeric.arrayrange(10)
>>> l[30::-2]
array([0, 8, 6, 4, 2, 0])
What's that initial "0" doing there? Can someone who actually
understands NumPy explain this?
Cheers,
M.
(PS: PySlice_GetIndices is in practice a bit useless because when it
fails it offers no explanation of why! Does any one use this
function, or should I submit a patch to make it a bit more helpful (&
support longs)?)
--
-Dr. Olin Shivers,
Ph.D., Cranberry-Melon School of Cucumber Science
-- seen in comp.lang.scheme
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