xref: /minix3/lib/libm/src/e_acoshf.c (revision 2fe8fb192fe7e8720e3e7a77f928da545e872a6a)
1*2fe8fb19SBen Gras /* e_acoshf.c -- float version of e_acosh.c.
2*2fe8fb19SBen Gras  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*2fe8fb19SBen Gras  */
4*2fe8fb19SBen Gras 
5*2fe8fb19SBen Gras /*
6*2fe8fb19SBen Gras  * ====================================================
7*2fe8fb19SBen Gras  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*2fe8fb19SBen Gras  *
9*2fe8fb19SBen Gras  * Developed at SunPro, a Sun Microsystems, Inc. business.
10*2fe8fb19SBen Gras  * Permission to use, copy, modify, and distribute this
11*2fe8fb19SBen Gras  * software is freely granted, provided that this notice
12*2fe8fb19SBen Gras  * is preserved.
13*2fe8fb19SBen Gras  * ====================================================
14*2fe8fb19SBen Gras  */
15*2fe8fb19SBen Gras 
16*2fe8fb19SBen Gras #include <sys/cdefs.h>
17*2fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
18*2fe8fb19SBen Gras __RCSID("$NetBSD: e_acoshf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $");
19*2fe8fb19SBen Gras #endif
20*2fe8fb19SBen Gras 
21*2fe8fb19SBen Gras #include "math.h"
22*2fe8fb19SBen Gras #include "math_private.h"
23*2fe8fb19SBen Gras 
24*2fe8fb19SBen Gras static const float
25*2fe8fb19SBen Gras one	= 1.0,
26*2fe8fb19SBen Gras ln2	= 6.9314718246e-01;  /* 0x3f317218 */
27*2fe8fb19SBen Gras 
28*2fe8fb19SBen Gras float
__ieee754_acoshf(float x)29*2fe8fb19SBen Gras __ieee754_acoshf(float x)
30*2fe8fb19SBen Gras {
31*2fe8fb19SBen Gras 	float t;
32*2fe8fb19SBen Gras 	int32_t hx;
33*2fe8fb19SBen Gras 	GET_FLOAT_WORD(hx,x);
34*2fe8fb19SBen Gras 	if(hx<0x3f800000) {		/* x < 1 */
35*2fe8fb19SBen Gras 	    return (x-x)/(x-x);
36*2fe8fb19SBen Gras 	} else if(hx >=0x4d800000) {	/* x > 2**28 */
37*2fe8fb19SBen Gras 	    if(hx >=0x7f800000) {	/* x is inf of NaN */
38*2fe8fb19SBen Gras 	        return x+x;
39*2fe8fb19SBen Gras 	    } else
40*2fe8fb19SBen Gras 		return __ieee754_logf(x)+ln2;	/* acosh(huge)=log(2x) */
41*2fe8fb19SBen Gras 	} else if (hx==0x3f800000) {
42*2fe8fb19SBen Gras 	    return 0.0;			/* acosh(1) = 0 */
43*2fe8fb19SBen Gras 	} else if (hx > 0x40000000) {	/* 2**28 > x > 2 */
44*2fe8fb19SBen Gras 	    t=x*x;
45*2fe8fb19SBen Gras 	    return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
46*2fe8fb19SBen Gras 	} else {			/* 1<x<2 */
47*2fe8fb19SBen Gras 	    t = x-one;
48*2fe8fb19SBen Gras 	    return log1pf(t+sqrtf((float)2.0*t+t*t));
49*2fe8fb19SBen Gras 	}
50*2fe8fb19SBen Gras }
51