CocoRoboDesktop/pdf1.js/node_modules/cephes/cephes/tanh.c

/*							tanh.c
 *
 *	Hyperbolic tangent
 *
 *
 *
 * SYNOPSIS:
 *
 * double x, y, tanh();
 *
 * y = tanh( x );
 *
 *
 *
 * DESCRIPTION:
 *
 * Returns hyperbolic tangent of argument in the range MINLOG to
 * MAXLOG.
 *
 * A rational function is used for |x| < 0.625.  The form
 * x + x**3 P(x)/Q(x) of Cody _& Waite is employed.
 * Otherwise,
 *    tanh(x) = sinh(x)/cosh(x) = 1  -  2/(exp(2x) + 1).
 *
 *
 *
 * ACCURACY:
 *
 *                      Relative error:
 * arithmetic   domain     # trials      peak         rms
 *    DEC       -2,2        50000       3.3e-17     6.4e-18
 *    IEEE      -2,2        30000       2.5e-16     5.8e-17
 *
 */

/*
Cephes Math Library Release 2.8:  June, 2000
Copyright 1984, 1995, 2000 by Stephen L. Moshier
*/

#include "mconf.h"

#ifdef UNK
static double P[] = {-9.64399179425052238628E-1, -9.92877231001918586564E1,
                     -1.61468768441708447952E3};
static double Q[] = {
    /* 1.00000000000000000000E0,*/
    1.12811678491632931402E2, 2.23548839060100448583E3,
    4.84406305325125486048E3};
#endif
#ifdef DEC
static unsigned short P[] = {0140166, 0161335, 0053753, 0075126,
                             0141706, 0111520, 0070463, 0040552,
                             0142711, 0153001, 0101300, 0025430};
static unsigned short Q[] = {
    /*0040200,0000000,0000000,0000000,*/
    0041741, 0117624, 0051300, 0156060, 0043013, 0133720,
    0071251, 0127717, 0043227, 0060201, 0021020, 0020136};
#endif

#ifdef IBMPC
static unsigned short P[] = {0x6f4b, 0xaafd, 0xdc5b, 0xbfee, 0x682d, 0x0e26,
                             0xd26a, 0xc058, 0x0563, 0x3058, 0x3ac0, 0xc099};
static unsigned short Q[] = {
    /*0x0000,0x0000,0x0000,0x3ff0,*/
    0x1b86, 0x8a58, 0x33f2, 0x405c, 0x35fa, 0x0e55,
    0x76fa, 0x40a1, 0x040c, 0x2442, 0xec10, 0x40b2};
#endif

#ifdef MIEEE
static unsigned short P[] = {0xbfee, 0xdc5b, 0xaafd, 0x6f4b, 0xc058, 0xd26a,
                             0x0e26, 0x682d, 0xc099, 0x3ac0, 0x3058, 0x0563};
static unsigned short Q[] = {0x405c, 0x33f2, 0x8a58, 0x1b86, 0x40a1, 0x76fa,
                             0x0e55, 0x35fa, 0x40b2, 0xec10, 0x2442, 0x040c};
#endif

#ifdef ANSIPROT
extern double fabs(double);
extern double exp(double);
extern double polevl(double, void *, int);
extern double p1evl(double, void *, int);
#else
double fabs(), exp(), polevl(), p1evl();
#endif
extern double MAXLOG;

double tanh(x) double x;
{
  double s, z;

#ifdef MINUSZERO
  if (x == 0.0)
    return (x);
#endif
  z = fabs(x);
  if (z > 0.5 * MAXLOG) {
    if (x > 0)
      return (1.0);
    else
      return (-1.0);
  }
  if (z >= 0.625) {
    s = exp(2.0 * z);
    z = 1.0 - 2.0 / (s + 1.0);
    if (x < 0)
      z = -z;
  } else {
    if (x == 0.0)
      return (x);
    s = x * x;
    z = polevl(s, P, 2) / p1evl(s, Q, 3);
    z = x * s * z;
    z = x + z;
  }
  return (z);
}