Subversion Repositories Kolibri OS

Rev

Go to most recent revision | Blame | Last modification | View Log | Download | RSS feed

  1. /* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */
  2. /* @(#)s_asinh.c 5.1 93/09/24 */
  3. /*
  4.  * ====================================================
  5.  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
  6.  *
  7.  * Developed at SunPro, a Sun Microsystems, Inc. business.
  8.  * Permission to use, copy, modify, and distribute this
  9.  * software is freely granted, provided that this notice
  10.  * is preserved.
  11.  * ====================================================
  12.  */
  13.  
  14. #if defined(LIBM_SCCS) && !defined(lint)
  15. static char rcsid[] = "$Id: s_asinh.c,v 1.6 1994/08/18 23:06:20 jtc Exp $";
  16. #endif
  17.  
  18. /* asinh(x)
  19.  * Method :
  20.  *      Based on
  21.  *              asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
  22.  *      we have
  23.  *      asinh(x) := x  if  1+x*x=1,
  24.  *               := sign(x)*(log(x)+ln2)) for large |x|, else
  25.  *               := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
  26.  *               := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))  
  27.  */
  28.  
  29. #include "math.h"
  30. #include "math_private.h"
  31.  
  32. #ifdef __STDC__
  33. static const double
  34. #else
  35. static double
  36. #endif
  37. one =  1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
  38. ln2 =  6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
  39. huge=  1.00000000000000000000e+300;
  40.  
  41. #ifdef __STDC__
  42.         double asinh(double x)
  43. #else
  44.         double asinh(x)
  45.         double x;
  46. #endif
  47. {      
  48.         double t,w;
  49.         int32_t hx,ix;
  50.         GET_HIGH_WORD(hx,x);
  51.         ix = hx&0x7fffffff;
  52.         if(ix>=0x7ff00000) return x+x;  /* x is inf or NaN */
  53.         if(ix< 0x3e300000) {    /* |x|<2**-28 */
  54.             if(huge+x>one) return x;    /* return x inexact except 0 */
  55.         }
  56.         if(ix>0x41b00000) {     /* |x| > 2**28 */
  57.             w = __ieee754_log(fabs(x))+ln2;
  58.         } else if (ix>0x40000000) {     /* 2**28 > |x| > 2.0 */
  59.             t = fabs(x);
  60.             w = __ieee754_log(2.0*t+one/(sqrt(x*x+one)+t));
  61.         } else {                /* 2.0 > |x| > 2**-28 */
  62.             t = x*x;
  63.             w =log1p(fabs(x)+t/(one+sqrt(one+t)));
  64.         }
  65.         if(hx>0) return w; else return -w;
  66. }
  67.