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 1.7 1999/07/02 15:37:38 simonb Exp $");
19#endif
20
21#include "math.h"
22#include "math_private.h"
23
24static const float
25one	= 1.0,
26ln2	= 6.9314718246e-01;  /* 0x3f317218 */
27
28float
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