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Re: complex number
- From: Marco Atzeri <marco_atzeri at yahoo dot it>
- To: cygwin at cygwin dot com, Greg Chicares <gchicares at sbcglobal dot net>
- Date: Wed, 1 Apr 2009 17:04:42 +0000 (GMT)
- Subject: Re: complex number
--- Mer 1/4/09, Greg Chicares ha scritto:
> Da: Greg Chicares
> Oggetto: Re: complex number
> A: cygwin@cygwin.com
> Data: Mercoledì 1 Aprile 2009, 17:32
> On 2009-04-01 14:48Z, Marco Atzeri
> wrote:
> >
> > 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.
>
> As I read C++2003 26.2/3, this use of std::abs has
> undefined
> behavior, so NaN would be conforming even though Inf would
> be less surprising.
>
>
you could be right but, I expect that gcc-4.3.2 work
in similar way in linux and cygwin, so a call to cabs.
In newlib cabs is wrapper for hypot and
hypot (0, Inf) gives Inf
Regards
Marco
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