#include <stdio.h>

#include <math.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_fft_complex.h>

#define REAL(z,i) ((z)[2*(i)])

#define IMAG(z,i) ((z)[2*(i)+1])

int

main (void)

{

  int i; double data[2*128];

  for (i = 0; i < 128; i++)

    {

       REAL(data,i) = 0.0; IMAG(data,i) = 0.0;

    }

  REAL(data,0) = 1.0;

  for (i = 1; i <= 10; i++)

    {

       REAL(data,i) = REAL(data,128-i) = 1.0;

    }

  for (i = 0; i < 128; i++)

    {

      printf ("%d %e %e\n", i, 

              REAL(data,i), IMAG(data,i));

    }

  printf ("\n\n");

  gsl_fft_complex_radix2_forward (data, 1, 128);

  for (i = 0; i < 128; i++)

    {

      printf ("%d %e %e\n", i, 

              REAL(data,i)/sqrt(128), 

              IMAG(data,i)/sqrt(128));

    }

  return 0;

}