On Apr 1 14:48, Marco Atzeri wrote:
>
> Dear All,
> 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);
}
> I found that newlib have the function cabs (complex absolute)
> but in cygwin the prototypes is
>
> extern double cabs();
The math.h header is from newlib as well. I don't know why the
math.h header is missing a normal prototype. I *assume* that nobody
ever made the effort to convert these old functions (cabs is from 1994)
to the ANSI C style. You should ask this question on the newlib list.
> so just a placeholder but not a useful function.
> There is any reason why cygwin is missing functional
> C99 complex functions ?
Sorry, it's all about newlib.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
Red Hat
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