complex number

Marco Atzeri marco_atzeri@yahoo.it
Wed Apr 1 14:48:00 GMT 2009


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.

I found that newlib have the function cabs (complex absolute)
but in cygwin the prototypes is

    extern double cabs();

so just a placeholder but not a useful function.
There is any reason why cygwin is missing functional
C99 complex functions ?

For what I can see mingw has not such limitation

in /usr/include/mingw/complex.h
double __MINGW_ATTRIB_CONST cabs (double _Complex);



Thanks
Marco








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