1/* s_tanhf.c -- float version of s_tanh.c. 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5/* 6 * ==================================================== 7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 8 * 9 * Developed at SunPro, a Sun Microsystems, Inc. business. 10 * Permission to use, copy, modify, and distribute this 11 * software is freely granted, provided that this notice 12 * is preserved. 13 * ==================================================== 14 */ 15 16#include <sys/cdefs.h> 17#if defined(LIBM_SCCS) && !defined(lint) 18__RCSID("$NetBSD: s_tanhf.c,v 1.6 1999/07/02 15:37:43 simonb Exp $"); 19#endif 20 21#include "math.h" 22#include "math_private.h" 23 24static const float one=1.0, two=2.0, tiny = 1.0e-30; 25 26float 27tanhf(float x) 28{ 29 float t,z; 30 int32_t jx,ix; 31 32 GET_FLOAT_WORD(jx,x); 33 ix = jx&0x7fffffff; 34 35 /* x is INF or NaN */ 36 if(ix>=0x7f800000) { 37 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ 38 else return one/x-one; /* tanh(NaN) = NaN */ 39 } 40 41 /* |x| < 22 */ 42 if (ix < 0x41b00000) { /* |x|<22 */ 43 if (ix<0x24000000) /* |x|<2**-55 */ 44 return x*(one+x); /* tanh(small) = small */ 45 if (ix>=0x3f800000) { /* |x|>=1 */ 46 t = expm1f(two*fabsf(x)); 47 z = one - two/(t+two); 48 } else { 49 t = expm1f(-two*fabsf(x)); 50 z= -t/(t+two); 51 } 52 /* |x| > 22, return +-1 */ 53 } else { 54 z = one - tiny; /* raised inexact flag */ 55 } 56 return (jx>=0)? z: -z; 57} 58