X-Recipient:	archive-cygwin AT delorie DOT com
X-Spam-Check-By:	sourceware.org
Date:	Wed, 1 Apr 2009 19:30:54 +0200
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: complex number
Message-ID:	<20090401173054.GA10205@calimero.vinschen.de>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
References:	<8704 DOT 38224 DOT qm AT web25004 DOT mail DOT ukl DOT yahoo DOT com>
MIME-Version:	1.0
In-Reply-To:	<8704.38224.qm@web25004.mail.ukl.yahoo.com>
User-Agent:	Mutt/1.5.19 (2009-02-20)
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Unsubscribe:	<mailto:cygwin-unsubscribe-archive-cygwin=delorie DOT com AT cygwin DOT com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com

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

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/

- Raw text -