On Tue, 27 Jan 2009, Nicholas Clark wrote:
> On Tue, Jan 27, 2009 at 10:24:46AM -0800, parti...@cvs.perl.org wrote:
>
> > + else if (thefloat != thefloat) {
>
> The above is the valid test for a NaN.
>
> Note, Intel chose that the default optimiser setting on their compiler should
> be buggy. (Advice from Klortho #11912). The perl 5 Linux hints file suggests
> that one needs to add -we147 to enable correct floating point behaviour.
>
> The best test that I'm aware of for "is it NaN or Inf?" is val != val * 0;
> Then, NaN is val != val, +Inf is val > 0, -Inf is val < 0;
Well, if they are available, isnan() and isinf() are probably worth
trying. You can piggy back on perl 5's $Config{d_isnan} and
$Config{d_isinf}. To distinguish +NaN from -NaN, I suspect you might also
want to use signbit() (which, alas, perl 5 doesn't probe for).
Some of these functions might only be available under certain compiler
options or with certain extra libraries, depending on how a particular
system attempts to adhere to different standards, but it's probably worth
trying them.
--
Andy Dougherty dough...@lafayette.edu
