e_acoshf.c revision 97407 
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#ifndef lint
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/e_acoshf.c 97407 2002-05-28 17:03:12Z alfred $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23static const float
24one	= 1.0,
25ln2	= 6.9314718246e-01;  /* 0x3f317218 */
26
27float
28__ieee754_acoshf(float x)
29{
30	float t;
31	int32_t hx;
32	GET_FLOAT_WORD(hx,x);
33	if(hx<0x3f800000) {		/* x < 1 */
34	    return (x-x)/(x-x);
35	} else if(hx >=0x4d800000) {	/* x > 2**28 */
36	    if(hx >=0x7f800000) {	/* x is inf of NaN */
37	        return x+x;
38	    } else
39		return __ieee754_logf(x)+ln2;	/* acosh(huge)=log(2x) */
40	} else if (hx==0x3f800000) {
41	    return 0.0;			/* acosh(1) = 0 */
42	} else if (hx > 0x40000000) {	/* 2**28 > x > 2 */
43	    t=x*x;
44	    return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
45	} else {			/* 1<x<2 */
46	    t = x-one;
47	    return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t));
48	}
49}
50