On Apr 1 16:58, Marco Atzeri wrote:
> --- Mer 1/4/09, Corinna Vinschen ha scritto:
> > > I was trying to understand why this code
> > >
> > > #include <iostream>
> > > #include <complex>
> > >
> > > int main()
> > > {
> > > double a = 0;
> > > double b = 1. / a;
> > > a += 1;
> > > std::cout << std::abs
> > (std::complex<double> (b, a)) << '\n';
> > > }
> > >
> > > produce Inf on most platform and NaN on cygwin.
> >
> > That's the result of the newlib function which is defined
> > as
> >
> > double
> > cabs(z)
> > struct complex z;
> > {
> > return hypot(z.x, z.y);
> > }
> >
>
> Hi Corinna,
> that is not correct as hypot( 0, Inf)
> return Inf and not NaN.
>
> There is a cabs backup implementation in libgcc that is probably
> the one used when system cabs is not available.
But cabs *is* exported by Cygwin and the function is the newlib
function. I can't tell you why you see what you see. I'm not
on good terms with this complex math thingy. That's why I think
you should really discuss this on the newlib list :}
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
Red Hat
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