/* dht/gsl_dht.h

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman

 * 

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 3 of the License, or (at

 * your option) any later version.

 * 

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * General Public License for more details.

 * 

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

/* Author:  G. Jungman

 */

#ifndef __GSL_DHT_H__

#define __GSL_DHT_H__

#undef __BEGIN_DECLS

#undef __END_DECLS

#ifdef __cplusplus

# define __BEGIN_DECLS extern "C" {

# define __END_DECLS }

#else

# define __BEGIN_DECLS /* empty */

# define __END_DECLS /* empty */

#endif

__BEGIN_DECLS

struct gsl_dht_struct {

  size_t    size;  /* size of the sample arrays to be transformed    */

  double    nu;    /* Bessel function order                          */

  double    xmax;  /* the upper limit to the x-sampling domain       */

  double    kmax;  /* the upper limit to the k-sampling domain       */

  double *  j;     /* array of computed J_nu zeros, j_{nu,s} = j[s]  */

  double *  Jjj;   /* transform numerator, J_nu(j_i j_m / j_N)       */

  double *  J2;    /* transform denominator, J_{nu+1}^2(j_m)         */

};

typedef struct gsl_dht_struct gsl_dht;

/* Create a new transform object for a given size

 * sampling array on the domain [0, xmax].

 */

gsl_dht * gsl_dht_alloc(size_t size);

gsl_dht * gsl_dht_new(size_t size, double nu, double xmax);

/* Recalculate a transform object for given values of nu, xmax.

 * You cannot change the size of the object since the internal

 * allocation is reused.

 */

int gsl_dht_init(gsl_dht * t, double nu, double xmax);

/* The n'th computed x sample point for a given transform.

 * 0 <= n <= size-1

 */

double gsl_dht_x_sample(const gsl_dht * t, int n);

/* The n'th computed k sample point for a given transform.

 * 0 <= n <= size-1

 */

double gsl_dht_k_sample(const gsl_dht * t, int n);

/* Free a transform object.

 */

void gsl_dht_free(gsl_dht * t);

/* Perform a transform on a sampled array.

 * f_in[0] ... f_in[size-1] and similarly for f_out[]

 */

int gsl_dht_apply(const gsl_dht * t, double * f_in, double * f_out);

__END_DECLS

#endif /* __GSL_DHT_H__ */