Problem casting STL complex<double> to fftw_complex

Asked 2010-11-18T11:48:31.790

The FFTW manual says that its fftw_complex type is bit compatible to std::complex<double> class in STL. But that doesn't work for me:

#include <complex>
#include <fftw3.h>
int main()
{
   std::complex<double> x(1,0);
   fftw_complex fx;
   fx = reinterpret_cast<fftw_complex>(x);
}

This gives me an error:

error: invalid cast from type ‘std::complex<double>’ to type ‘double [2]’

What am I doing wrong?

c++ fftw complex-numbers reinterpret-cast

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1 Answer

reinterpret_cast only works for pointers and references. So you'd have to do this:

#include <complex>
#include <fftw3.h>
int main()
{
   std::complex<double> x(1,0);
   fftw_complex fx(*reinterpret_cast<fftw_complex*>(&x));
}

This assumes that fftw_complex has a copy constructor. To avoid problems with strict aliasing, Goz's solution should be preferred.

answered 2010-11-18T11:51:55.943