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Postings from August 2010
On Mon, 2 Aug 2010, Bo Lindbergh wrote:
> Nicholas Clark wrote:
> > What I can't work out is whether there is any shortcut way in ANSI C to find
> > out whether a value is -0, distinct from 0, short of *printf().
>
> As long as the compiler is sufficiently C99-like:
>
> fpclassify(value)==FP_ZERO && signbit(value)
Yes, both copysign() and signbit() are widely available. The challenge
arises in that perl tries to rely only on C89-like behavior, since not all
compilers support the C99 standard. To help provide appropriate warnings
to developers who use gcc, we often add -ansi to gcc's flags, which
effectively hides things like signbit().
In ANSI C, if signbit() isn't available, the only other thing I can think
of doing is to assume IEEE-754 and explicitly check the correct bit some
way or another.
--
Andrew Dougherty doughera@lafayette.edu
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