| /* s_tanhl.c -- long double version of s_tanh.c. |
| * Conversion to long double by Ulrich Drepper, |
| * Cygnus Support, drepper@cygnus.com. |
| */ |
| |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| #if defined(LIBM_SCCS) && !defined(lint) |
| static char rcsid[] = "$NetBSD: $"; |
| #endif |
| |
| /* tanhl(x) |
| * Return the Hyperbolic Tangent of x |
| * |
| * Method : |
| * x -x |
| * e - e |
| * 0. tanhl(x) is defined to be ----------- |
| * x -x |
| * e + e |
| * 1. reduce x to non-negative by tanhl(-x) = -tanhl(x). |
| * 2. 0 <= x <= 2**-55 : tanhl(x) := x*(one+x) |
| * -t |
| * 2**-55 < x <= 1 : tanhl(x) := -----; t = expm1l(-2x) |
| * t + 2 |
| * 2 |
| * 1 <= x <= 23.0 : tanhl(x) := 1- ----- ; t=expm1l(2x) |
| * t + 2 |
| * 23.0 < x <= INF : tanhl(x) := 1. |
| * |
| * Special cases: |
| * tanhl(NaN) is NaN; |
| * only tanhl(0)=0 is exact for finite argument. |
| */ |
| |
| #include "math.h" |
| #include "math_private.h" |
| |
| #ifdef __STDC__ |
| static const long double one=1.0, two=2.0, tiny = 1.0e-4900L; |
| #else |
| static long double one=1.0, two=2.0, tiny = 1.0e-4900L; |
| #endif |
| |
| #ifdef __STDC__ |
| long double __tanhl(long double x) |
| #else |
| long double __tanhl(x) |
| long double x; |
| #endif |
| { |
| long double t,z; |
| int32_t se; |
| u_int32_t j0,j1,ix; |
| |
| /* High word of |x|. */ |
| GET_LDOUBLE_WORDS(se,j0,j1,x); |
| ix = se&0x7fff; |
| |
| /* x is INF or NaN */ |
| if(ix==0x7fff) { |
| /* for NaN it's not important which branch: tanhl(NaN) = NaN */ |
| if (se&0x8000) return one/x-one; /* tanhl(-inf)= -1; */ |
| else return one/x+one; /* tanhl(+inf)=+1 */ |
| } |
| |
| /* |x| < 23 */ |
| if (ix < 0x4003 || (ix == 0x4003 && j0 < 0xb8000000u)) {/* |x|<23 */ |
| if ((ix|j0|j1) == 0) |
| return x; /* x == +- 0 */ |
| if (ix<0x3fc8) /* |x|<2**-55 */ |
| return x*(one+tiny); /* tanh(small) = small */ |
| if (ix>=0x3fff) { /* |x|>=1 */ |
| t = __expm1l(two*fabsl(x)); |
| z = one - two/(t+two); |
| } else { |
| t = __expm1l(-two*fabsl(x)); |
| z= -t/(t+two); |
| } |
| /* |x| > 23, return +-1 */ |
| } else { |
| z = one - tiny; /* raised inexact flag */ |
| } |
| return (se&0x8000)? -z: z; |
| } |
| weak_alias (__tanhl, tanhl) |
