text: typedef struct config {
  	double nu;
  	double c_window_width;
  	int derivative;
  	long N_pad;
  } config;
  
  void cfftlog(double *x, double *fx, long N, config *config, double ell, double *y, double *Fy);
  
  void cfftlog_ells(double *x, double *fx, long N, config *config, double* ell, long Nell, double **y, double **Fy);
  
  void cfftlog_ells_increment(double *x, double *fx, long N, config *config, double* ell, long Nell, double **y, double **Fy);