/* specfunc/hyperg_2F0.c

 * 

 * 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 */

#include <config.h>

#include <gsl/gsl_math.h>

#include <gsl/gsl_errno.h>

#include <gsl/gsl_sf_hyperg.h>

#include "error.h"

#include "hyperg.h"

int

gsl_sf_hyperg_2F0_e(const double a, const double b, const double x, gsl_sf_result * result)

{

  if(x < 0.0) {

    /* Use "definition" 2F0(a,b,x) = (-1/x)^a U(a,1+a-b,-1/x).

     */

    gsl_sf_result U;

    double pre = pow(-1.0/x, a);

    int stat_U = gsl_sf_hyperg_U_e(a, 1.0+a-b, -1.0/x, &U);

    result->val = pre * U.val;

    result->err = GSL_DBL_EPSILON * fabs(result->val) + pre * U.err;

    return stat_U;

  }

  else if(x == 0.0) {

    result->val = 1.0;

    result->err = 0.0;

    return GSL_SUCCESS;

  }

  else {

    /* Use asymptotic series. ??

     */

    /* return hyperg_2F0_series(a, b, x, -1, result, &prec); */

    DOMAIN_ERROR(result);

  }

}

/*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/

#include "eval.h"

double gsl_sf_hyperg_2F0(const double a, const double b, const double x)

{

  EVAL_RESULT(gsl_sf_hyperg_2F0_e(a, b, x, &result));

}