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 #include <sys/cdefs.h>
17 #if defined(LIBM_SCCS) && !defined(lint)
18 __RCSID("$NetBSD: e_acoshf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $");
19 #endif
20
21 #include "math.h"
22 #include "math_private.h"
23
24 static const float
25 one = 1.0,
26 ln2 = 6.9314718246e-01; /* 0x3f317218 */
27
28 float
__ieee754_acoshf(float x)29 __ieee754_acoshf(float x)
30 {
31 float t;
32 int32_t hx;
33 GET_FLOAT_WORD(hx,x);
34 if(hx<0x3f800000) { /* x < 1 */
35 return (x-x)/(x-x);
36 } else if(hx >=0x4d800000) { /* x > 2**28 */
37 if(hx >=0x7f800000) { /* x is inf of NaN */
38 return x+x;
39 } else
40 return __ieee754_logf(x)+ln2; /* acosh(huge)=log(2x) */
41 } else if (hx==0x3f800000) {
42 return 0.0; /* acosh(1) = 0 */
43 } else if (hx > 0x40000000) { /* 2**28 > x > 2 */
44 t=x*x;
45 return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
46 } else { /* 1<x<2 */
47 t = x-one;
48 return log1pf(t+sqrtf((float)2.0*t+t*t));
49 }
50 }
51