1 /* sf_tanh.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 "fdlibm.h" 17 18 #ifdef __STDC__ 19 static const float one=1.0, two=2.0, tiny = 1.0e-30; 20 #else 21 static float one=1.0, two=2.0, tiny = 1.0e-30; 22 #endif 23 24 #ifdef __STDC__ tanhf(float x)25 float tanhf(float x) 26 #else 27 float tanhf(x) 28 float x; 29 #endif 30 { 31 float t,z; 32 __int32_t jx,ix; 33 34 GET_FLOAT_WORD(jx,x); 35 ix = jx&0x7fffffff; 36 37 /* x is INF or NaN */ 38 if(!FLT_UWORD_IS_FINITE(ix)) { 39 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ 40 else return one/x-one; /* tanh(NaN) = NaN */ 41 } 42 43 /* |x| < 22 */ 44 if (ix < 0x41b00000) { /* |x|<22 */ 45 if (ix<0x24000000) /* |x|<2**-55 */ 46 return x*(one+x); /* tanh(small) = small */ 47 if (ix>=0x3f800000) { /* |x|>=1 */ 48 t = expm1f(two*fabsf(x)); 49 z = one - two/(t+two); 50 } else { 51 t = expm1f(-two*fabsf(x)); 52 z= -t/(t+two); 53 } 54 /* |x| > 22, return +-1 */ 55 } else { 56 z = one - tiny; /* raised inexact flag */ 57 } 58 return (jx>=0)? z: -z; 59 } 60 61 #ifdef _DOUBLE_IS_32BITS 62 63 #ifdef __STDC__ tanh(double x)64 double tanh(double x) 65 #else 66 double tanh(x) 67 double x; 68 #endif 69 { 70 return (double) tanhf((float) x); 71 } 72 73 #endif /* defined(_DOUBLE_IS_32BITS) */ 74