#include <stdio.h>

#include <math.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_fft_real.h>

#include <gsl/gsl_fft_halfcomplex.h>

int

main (void)

{

  int i, n = 100;

  double data[n];

  gsl_fft_real_wavetable * real;

  gsl_fft_halfcomplex_wavetable * hc;

  gsl_fft_real_workspace * work;

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

    {

      data[i] = 0.0;

    }

  for (i = n / 3; i < 2 * n / 3; i++)

    {

      data[i] = 1.0;

    }

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

    {

      printf ("%d: %e\n", i, data[i]);

    }

  printf ("\n");

  work = gsl_fft_real_workspace_alloc (n);

  real = gsl_fft_real_wavetable_alloc (n);

  gsl_fft_real_transform (data, 1, n, 

                          real, work);

  gsl_fft_real_wavetable_free (real);

  for (i = 11; i < n; i++)

    {

      data[i] = 0;

    }

  hc = gsl_fft_halfcomplex_wavetable_alloc (n);

  gsl_fft_halfcomplex_inverse (data, 1, n, 

                               hc, work);

  gsl_fft_halfcomplex_wavetable_free (hc);

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

    {

      printf ("%d: %e\n", i, data[i]);

    }

  gsl_fft_real_workspace_free (work);

  return 0;

}