Pierre-Alain Dorange schrieb:
> I don't find any sign(x) function in the math library (return the sign
> of the value).
> I've read that math module is a wrapper to C math lib and that C math
> lib has not sign(), so...
Starting with Python 2.6 the math and cmath modules have a copysign
function.
> I've implement my own sign function of course (it's easy) but a standard
> one in math would be better and could be faster.
Sure? :) Are you aware that the IEEE 754 standard makes a difference
between the floats +0.0 and -0.0?
from math import atan2
def sign(x):
if x > 0 or (x == 0 and atan2(x, -1.) > 0.):
return 1
else:
return -1
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