0,0 → 1,66 |
/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */ |
/* @(#)s_asinh.c 5.1 93/09/24 */ |
/* |
* ==================================================== |
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
* |
* Developed at SunPro, a Sun Microsystems, Inc. business. |
* Permission to use, copy, modify, and distribute this |
* software is freely granted, provided that this notice |
* is preserved. |
* ==================================================== |
*/ |
|
#if defined(LIBM_SCCS) && !defined(lint) |
static char rcsid[] = "$Id: s_asinh.c,v 1.6 1994/08/18 23:06:20 jtc Exp $"; |
#endif |
|
/* asinh(x) |
* Method : |
* Based on |
* asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ] |
* we have |
* asinh(x) := x if 1+x*x=1, |
* := sign(x)*(log(x)+ln2)) for large |x|, else |
* := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else |
* := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2))) |
*/ |
|
#include "math.h" |
#include "math_private.h" |
|
#ifdef __STDC__ |
static const double |
#else |
static double |
#endif |
one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */ |
ln2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */ |
huge= 1.00000000000000000000e+300; |
|
#ifdef __STDC__ |
double asinh(double x) |
#else |
double asinh(x) |
double x; |
#endif |
{ |
double t,w; |
int32_t hx,ix; |
GET_HIGH_WORD(hx,x); |
ix = hx&0x7fffffff; |
if(ix>=0x7ff00000) return x+x; /* x is inf or NaN */ |
if(ix< 0x3e300000) { /* |x|<2**-28 */ |
if(huge+x>one) return x; /* return x inexact except 0 */ |
} |
if(ix>0x41b00000) { /* |x| > 2**28 */ |
w = __ieee754_log(fabs(x))+ln2; |
} else if (ix>0x40000000) { /* 2**28 > |x| > 2.0 */ |
t = fabs(x); |
w = __ieee754_log(2.0*t+one/(sqrt(x*x+one)+t)); |
} else { /* 2.0 > |x| > 2**-28 */ |
t = x*x; |
w =log1p(fabs(x)+t/(one+sqrt(one+t))); |
} |
if(hx>0) return w; else return -w; |
} |
Property changes: |
Added: svn:executable |
+* |
\ No newline at end of property |