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 1.5 1997/10/09 11:33:43 lukem Exp $"); 19 #endif 20 21 #include "math.h" 22 #include "math_private.h" 23 24 #ifdef __STDC__ 25 static const float one=1.0, two=2.0, tiny = 1.0e-30; 26 #else 27 static float one=1.0, two=2.0, tiny = 1.0e-30; 28 #endif 29 30 #ifdef __STDC__ 31 float tanhf(float x) 32 #else 33 float tanhf(x) 34 float x; 35 #endif 36 { 37 float t,z; 38 int32_t jx,ix; 39 40 GET_FLOAT_WORD(jx,x); 41 ix = jx&0x7fffffff; 42 43 /* x is INF or NaN */ 44 if(ix>=0x7f800000) { 45 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ 46 else return one/x-one; /* tanh(NaN) = NaN */ 47 } 48 49 /* |x| < 22 */ 50 if (ix < 0x41b00000) { /* |x|<22 */ 51 if (ix<0x24000000) /* |x|<2**-55 */ 52 return x*(one+x); /* tanh(small) = small */ 53 if (ix>=0x3f800000) { /* |x|>=1 */ 54 t = expm1f(two*fabsf(x)); 55 z = one - two/(t+two); 56 } else { 57 t = expm1f(-two*fabsf(x)); 58 z= -t/(t+two); 59 } 60 /* |x| > 22, return +-1 */ 61 } else { 62 z = one - tiny; /* raised inexact flag */ 63 } 64 return (jx>=0)? z: -z; 65 } 66