sysdeps/libm-ieee754/e_acoshf.c

   1 /* e_acoshf.c -- float version of e_acosh.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 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: e_acoshf.c,v 1.5 1995/05/12 04:57:20 jtc Exp $";
  18 #endif
  19
  20 #include "math.h"
  21 #include "math_private.h"
  22
  23 #ifdef __STDC__
  24 static const float
  25 #else
  26 static float
  27 #endif
  28 one     = 1.0,
  29 ln2     = 6.9314718246e-01;  /* 0x3f317218 */
  30
  31 #ifdef __STDC__
  32         float __ieee754_acoshf(float x)
  33 #else
  34         float __ieee754_acoshf(x)
  35         float x;
  36 #endif
  37 {
  38         float t;
  39         int32_t hx;
  40         GET_FLOAT_WORD(hx,x);
  41         if(hx<0x3f800000) {             /* x < 1 */
  42             return (x-x)/(x-x);
  43         } else if(hx >=0x4d800000) {    /* x > 2**28 */
  44             if(hx >=0x7f800000) {       /* x is inf of NaN */
  45                 return x+x;
  46             } else
  47                 return __ieee754_logf(x)+ln2;   /* acosh(huge)=log(2x) */
  48         } else if (hx==0x3f800000) {
  49             return 0.0;                 /* acosh(1) = 0 */
  50         } else if (hx > 0x40000000) {   /* 2**28 > x > 2 */
  51             t=x*x;
  52             return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
  53         } else {                        /* 1<x<2 */
  54             t = x-one;
  55             return __log1pf(t+__sqrtf((float)2.0*t+t*t));
  56         }
  57 }