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

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.

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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