[Numpy-discussion] Binary ufuncs: minimum
Chris.Barker
Chris.Barker@noaa....
Wed May 28 02:08:32 CDT 2008
Keith Goodman wrote:
>> Interestingly, MATLAB (v7.5.0) takes a different approach:
>> ans =
>> 127 1
>>>> -A
>> ans =
>> 127 -1
can anyone explain that? -- just curious.
Charles R Harris wrote:
> We could simply define the range of int8 as [-127,127], but that is
> somewhat problematical also.
That would be nice, but probably a pain to do and could be a serious
performance hit. And would no longer match hardware/C standards.
Charles R Harris wrote:
> I disagree. By definition, abs() >= 0 always.
and 127 + 1 = 128
This is hardware integer math. It has it's own definition, and
apparently abs(-128) = -128.
> unsigned return will cause problems is in the augmented assignments,
well, could folks end up with inadvertent upcasting in mixed operations,
also?
a = np.array(..., dtype=np.int8)
b = np.array(..., dtype=np.int8)
a = abs(a)
c = a + b # or b + a
what type is c?
by the way, are you proposing that abs() always returns a unsigned
integer type?
-Chris
--
Christopher Barker, Ph.D.
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