#ifndef GSL_FFT_HPP
#define  GSL_FFT_HPP
// Use data: either std::vector or std::valarray or armadillo vector 
#include <gsl/gsl_errno.h>
#include <gsl/gsl_fft_complex.h>

template <class T>
int fft(T& data, int direction){
  int status;
  const size_t stride=1;
  size_t n;
#ifdef ARMA
  n=data.n_elem; // Armadillo data has no member size, use nelem 
#else
  n = data.size();
#endif
  double* pdata = reinterpret_cast<double*> (&data[0]);
  if(direction>0){    
    status = gsl_fft_complex_radix2_forward(pdata, stride, n);
  } 
  else {
    status = gsl_fft_complex_radix2_backward(pdata, stride, n);
  }      
  if(status!=GSL_SUCCESS) return 1;
  return 0;
}
#endif