diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/s_tanhl.c')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/s_tanhl.c | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/s_tanhl.c b/sysdeps/ieee754/ldbl-128ibm/s_tanhl.c new file mode 100644 index 0000000000..851ca125f6 --- /dev/null +++ b/sysdeps/ieee754/ldbl-128ibm/s_tanhl.c @@ -0,0 +1,90 @@ +/* @(#)s_tanh.c 5.1 93/09/24 */ +/* + * ==================================================== + * 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: s_tanh.c,v 1.7 1995/05/10 20:48:22 jtc Exp $"; +#endif + +/* Tanh(x) + * Return the Hyperbolic Tangent of x + * + * Method : + * x -x + * e - e + * 0. tanh(x) is defined to be ----------- + * x -x + * e + e + * 1. reduce x to non-negative by tanh(-x) = -tanh(x). + * 2. 0 <= x <= 2**-57 : tanh(x) := x*(one+x) + * -t + * 2**-57 < x <= 1 : tanh(x) := -----; t = expm1(-2x) + * t + 2 + * 2 + * 1 <= x <= 22.0 : tanh(x) := 1- ----- ; t=expm1(2x) + * t + 2 + * 22.0 < x <= INF : tanh(x) := 1. + * + * Special cases: + * tanh(NaN) is NaN; + * only tanh(0)=0 is exact for finite argument. + */ + +#include "math.h" +#include "math_private.h" +#include <math_ldbl_opt.h> + +#ifdef __STDC__ +static const long double one=1.0L, two=2.0L, tiny = 1.0e-300L; +#else +static long double one=1.0L, two=2.0L, tiny = 1.0e-300L; +#endif + +#ifdef __STDC__ + long double __tanhl(long double x) +#else + long double __tanhl(x) + long double x; +#endif +{ + long double t,z; + int64_t jx,ix,lx; + + /* High word of |x|. */ + GET_LDOUBLE_WORDS64(jx,lx,x); + ix = jx&0x7fffffffffffffffLL; + + /* x is INF or NaN */ + if(ix>=0x7ff0000000000000LL) { + if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ + else return one/x-one; /* tanh(NaN) = NaN */ + } + + /* |x| < 22 */ + if (ix < 0x4036000000000000LL) { /* |x|<22 */ + if ((ix | (lx&0x7fffffffffffffffLL)) == 0) + return x; /* x == +-0 */ + if (ix<0x3c60000000000000LL) /* |x|<2**-57 */ + return x*(one+x); /* tanh(small) = small */ + if (ix>=0x3ff0000000000000LL) { /* |x|>=1 */ + t = __expm1l(two*fabsl(x)); + z = one - two/(t+two); + } else { + t = __expm1l(-two*fabsl(x)); + z= -t/(t+two); + } + /* |x| > 22, return +-1 */ + } else { + z = one - tiny; /* raised inexact flag */ + } + return (jx>=0)? z: -z; +} +long_double_symbol (libm, __tanhl, tanhl); |