Re: /tset/ANSI.os/maths/pow/T.pow 4

[George Kraft IV <gk4@austin.ibm.com>]

Dave Prosser wrote:
> 
> Matt Wilson wrote:
> > From lsb-distribution-test-1.1.3-1
> >
> > ************************************************************************
> > /tset/ANSI.os/maths/pow/T.pow 4 Warning
> >
> >         Test Information:
> > pow(0.0, -1.0) gave
> > RETURN VALUES: expected: -inf, observed: inf
> >     Bit Representation: expected value: \000\000\000\000\000\000\360\377
> >     Bit Representation: observed value: \000\000\000\000\000\000\360\177
> >
> > ************************************************************************
> >
> > Isn't pow(0.0, -1.0) undefined?  From the looks of C99, pow(long
> > double x, long double y) may cause a domain error if x is zero and y
> > is less than or equal to zero.
> 
> For IEEE F.P. systems, C99 says (F.9.4.4):
> 
>   pow(+-0, y) returns +-infinity and raises the "divide-by-zero"
>   floating point exception for y an odd integer < 0.

And the SUSv2 that the LSB refers to also says there are mutiple answers:

http://www.opengroup.org/onlinepubs/007908799/xsh/pow.html

> 
> So the problem with the test is that it expects the wrong sign
> for the infinity returned given the information in your message.
> 
> --
> Dave Prosser   dfp@caldera.com   (908)790-2358   Caldera, Murray Hill, NJ
> 
> --
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-- 
George Kraft IV
gk4@austin.ibm.com