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 #ifndef lint 17 static char rcsid[] = "$FreeBSD$"; 18 #endif 19 20 #include "math.h" 21 #include "math_private.h" 22 23 static const float one=1.0, two=2.0, tiny = 1.0e-30; 24 25 float 26 tanhf(float x) 27 { 28 float t,z; 29 int32_t jx,ix; 30 31 GET_FLOAT_WORD(jx,x); 32 ix = jx&0x7fffffff; 33 34 /* x is INF or NaN */ 35 if(ix>=0x7f800000) { 36 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ 37 else return one/x-one; /* tanh(NaN) = NaN */ 38 } 39 40 /* |x| < 22 */ 41 if (ix < 0x41b00000) { /* |x|<22 */ 42 if (ix<0x24000000) /* |x|<2**-55 */ 43 return x*(one+x); /* tanh(small) = small */ 44 if (ix>=0x3f800000) { /* |x|>=1 */ 45 t = expm1f(two*fabsf(x)); 46 z = one - two/(t+two); 47 } else { 48 t = expm1f(-two*fabsf(x)); 49 z= -t/(t+two); 50 } 51 /* |x| > 22, return +-1 */ 52 } else { 53 z = one - tiny; /* raised inexact flag */ 54 } 55 return (jx>=0)? z: -z; 56 } 57