e_acoshf.c revision 50476 
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 50476 1999-08-28 00:22:10Z peter $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23#ifdef __STDC__
24static const float
25#else
26static float
27#endif
28one	= 1.0,
29ln2	= 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+__ieee754_sqrtf((float)2.0*t+t*t));
56	}
57}
58