sysdeps/ieee754/flt-32/e_acoshf.c

   1 /* e_acoshf.c -- float version of e_acosh.c.
   2  */
   3
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 #if defined(LIBM_SCCS) && !defined(lint)
  16 static char rcsid[] = "$NetBSD: e_acoshf.c,v 1.5 1995/05/12 04:57:20 jtc Exp $";
  17 #endif
  18
  19 #include <math.h>
  20 #include <math_private.h>
  21 #include <libm-alias-finite.h>
  22
  23 static const float
  24 one     = 1.0,
  25 ln2     = 6.9314718246e-01;  /* 0x3f317218 */
  26
  27 float __ieee754_acoshf(float x)
  28 {
  29         float t;
  30         int32_t hx;
  31         GET_FLOAT_WORD(hx,x);
  32         if(hx<0x3f800000) {             /* x < 1 */
  33             return (x-x)/(x-x);
  34         } else if(hx >=0x4d800000) {    /* x > 2**28 */
  35             if(hx >=0x7f800000) {       /* x is inf of NaN */
  36                 return x+x;
  37             } else
  38                 return __ieee754_logf(x)+ln2;   /* acosh(huge)=log(2x) */
  39         } else if (hx==0x3f800000) {
  40             return 0.0;                 /* acosh(1) = 0 */
  41         } else if (hx > 0x40000000) {   /* 2**28 > x > 2 */
  42             t=x*x;
  43             return __ieee754_logf((float)2.0*x-one/(x+sqrtf(t-one)));
  44         } else {                        /* 1<x<2 */
  45             t = x-one;
  46             return __log1pf(t+sqrtf((float)2.0*t+t*t));
  47         }
  48 }
  49 libm_alias_finite (__ieee754_acoshf, __acoshf)