diff options
Diffstat (limited to 'sysdeps/libm-ieee754/s_tanhl.c')
| -rw-r--r-- | sysdeps/libm-ieee754/s_tanhl.c | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/sysdeps/libm-ieee754/s_tanhl.c b/sysdeps/libm-ieee754/s_tanhl.c new file mode 100644 index 0000000000..984f67108b --- /dev/null +++ b/sysdeps/libm-ieee754/s_tanhl.c @@ -0,0 +1,91 @@ +/* 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-16380L; +#else +static long double one=1.0, two=2.0, tiny = 1.0e-16380L; +#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,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) { + if (se>=0x7fff) return one/x+one; /* tanhl(+-inf)=+-1 */ + else return one/x-one; /* tanhl(NaN) = NaN */ + } + + /* |x| < 23 */ + if (ix < 0x4003 || (ix == 0x4003 && j0 < 0xb8000000)) { /* |x|<23 */ + if (ix<0x3fc8) /* |x|<2**-55 */ + return x*(one+x); /* 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>0x7fff)? z: -z; +} +weak_alias (__tanhl, tanhl) |