Merlijn van Deen <[email protected]> added the comment:
Although there is one use case which I now realise due to your post: easier
1-on-1 implementation of existing algorithms.
Another possible reason to implement it is that it's not that hard to implement
the sign() function wrongly, if it also has to work with nans. This
implementation:
def signum(x):
return (x > 0) - (x < 0)
returns 0 for nan, which is wrong (it should return nan). Another naive
implementation
def signum(x):
return math.copysign(1, x)
also fails for nan, and gives a result for +/- 0 that could be right or wrong,
depending on context.
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Python tracker <[email protected]>
<http://bugs.python.org/issue829370>
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