t2ex/bsd_source/lib/libc/src_bsd/math/s_tanhf.c | bare source | permlink (0.02 seconds) |
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 "math.h" 17: #include "math_private.h" 18: 19: static const float one=1.0, two=2.0, tiny = 1.0e-30; 20: 21: float 22: tanhf(float x) 23: { 24: float t,z; 25: int32_t jx,ix; 26: 27: GET_FLOAT_WORD(jx,x); 28: ix = jx&0x7fffffff; 29: 30: /* x is INF or NaN */ 31: if(ix>=0x7f800000) { 32: if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ 33: else return one/x-one; /* tanh(NaN) = NaN */ 34: } 35: 36: /* |x| < 22 */ 37: if (ix < 0x41b00000) { /* |x|<22 */ 38: if (ix == 0) 39: return x; /* x == +-0 */ 40: if (ix<0x24000000) /* |x|<2**-55 */ 41: return x*(one+x); /* tanh(small) = small */ 42: if (ix>=0x3f800000) { /* |x|>=1 */ 43: t = expm1f(two*fabsf(x)); 44: z = one - two/(t+two); 45: } else { 46: t = expm1f(-two*fabsf(x)); 47: z= -t/(t+two); 48: } 49: /* |x| > 22, return +-1 */ 50: } else { 51: z = one - tiny; /* raised inexact flag */ 52: } 53: return (jx>=0)? z: -z; 54: }