/************************************************************************
 *                                                                      *
 *                              N O T I C E                             *
 *                                                                      *
 *                      Copyright Abandoned, 1987, Fred Fish            *
 *                                                                      *
 *      This previously copyrighted work has been placed into the       *
 *      public domain by the author (Fred Fish) and may be freely used  *
 *      for any purpose, private or commercial.  I would appreciate     *
 *      it, as a courtesy, if this notice is left in all copies and     *
 *      derivative works.  Thank you, and enjoy...                      *
 *                                                                      *
 *      The author makes no warranty of any kind with respect to this   *
 *      product and explicitly disclaims any implied warranties of      *
 *      merchantability or fitness for any particular purpose.          *
 *                                                                      *
 ************************************************************************
 */

/*
 *  FUNCTION
 *
 *      tanh   double precision hyperbolic tangent
 *
 *  KEY WORDS
 *
 *      tanh
 *      machine independent routines
 *      math libraries
 *
 *  DESCRIPTION
 *
 *      Returns double precision hyperbolic tangent of double precision
 *      floating point number.
 *
 *  USAGE
 *
 *      double tanh (x)
 *      double x;
 *
 *  REFERENCES
 *
 *      Fortran IV plus user's guide, Digital Equipment Corp. pp B-5
 *
 *  RESTRICTIONS
 *
 *      For precision information refer to documentation of the
 *      floating point library routines called.
 *      
 *  PROGRAMMER
 *
 *      Fred Fish
 *
 *  INTERNALS
 *
 *      Computes hyperbolic tangent from:
 *
 *              tanh(x) = 1.0 for x > TANH_MAXARG
 *                      = -1.0 for x < -TANH_MAXARG
 *                      =  sinh(x) / cosh(x) otherwise
 *
 */

#include <stdio.h>
#include "pml.h"

static char funcname[] = "tanh";


double tanh (x)
double x;
{
    struct exception xcpt;
    int positive;
    extern double sinh ();
    extern double cosh ();

    DBUG_ENTER (funcname);
    DBUG_3 ("tanhin", "arg %le", x);
    if (x > TANH_MAXARG || x < -TANH_MAXARG) {
        if (x > 0.0) {
            positive = 1;
        } else {
            positive = 0;
        }
        xcpt.type = PLOSS;
        xcpt.name = funcname;
        xcpt.arg1 = x;
        if (!matherr (&xcpt)) {
            fprintf (stderr, "%s: PLOSS error\n", funcname);
            errno = ERANGE;
            if (positive) {
                xcpt.retval = 1.0;
            } else {
                xcpt.retval = -1.0;
            }
        }
    } else {
        xcpt.retval = sinh (x) / cosh (x);
    }
    DBUG_3 ("tanhout", "result %le", xcpt.retval);
    return (xcpt.retval);
}