/* specfunc/elementary.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 2 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., 675 Mass Ave, Cambridge, MA 02139, USA. *//* Author:  G. Jungman */#include <config.h>#include <gsl/gsl_math.h>#include <gsl/gsl_errno.h>#include <gsl/gsl_sf_elementary.h>#include "error.h"#include "check.h"intgsl_sf_multiply_e(const double x, const double y, gsl_sf_result * result){  const double ax = fabs(x);  const double ay = fabs(y);  if(x == 0.0 || y == 0.0) {    /* It is necessary to eliminate this immediately.     */    result->val = 0.0;    result->err = 0.0;    return GSL_SUCCESS;  }  else if((ax <= 1.0 && ay >= 1.0) || (ay <= 1.0 && ax >= 1.0)) {    /* Straddling 1.0 is always safe.     */    result->val = x*y;    result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val);    return GSL_SUCCESS;  }  else {    const double f = 1.0 - 2.0 * GSL_DBL_EPSILON;    const double min = GSL_MIN_DBL(fabs(x), fabs(y));    const double max = GSL_MAX_DBL(fabs(x), fabs(y));    if(max < 0.9 * GSL_SQRT_DBL_MAX || min < (f * DBL_MAX)/max) {      result->val = GSL_COERCE_DBL(x*y);      result->err = 2.0 * GSL_DBL_EPSILON * fabs(result->val);      CHECK_UNDERFLOW(result);      return GSL_SUCCESS;    }    else {      OVERFLOW_ERROR(result);    }  }}intgsl_sf_multiply_err_e(const double x, const double dx,                         const double y, const double dy,                         gsl_sf_result * result){  int status = gsl_sf_multiply_e(x, y, result);  result->err += fabs(dx*y) + fabs(dy*x);  return status;}/*-*-*-*-*-*-*-*-*-* Functions w/ Natural Prototypes *-*-*-*-*-*-*-*-*-*-*/#include "eval.h"double gsl_sf_multiply(const double x, const double y){  EVAL_RESULT(gsl_sf_multiply_e(x, y, &result));}