1 /* ef_acosh.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 
17 #include "fdlibm.h"
18 
19 #ifdef __STDC__
20 static const float
21 #else
22 static float
23 #endif
24 one	= 1.0,
25 ln2	= 6.9314718246e-01;  /* 0x3f317218 */
26 
27 #ifdef __STDC__
__ieee754_acoshf(float x)28 	float __ieee754_acoshf(float x)
29 #else
30 	float __ieee754_acoshf(x)
31 	float x;
32 #endif
33 {
34 	float t;
35 	__int32_t hx;
36 	GET_FLOAT_WORD(hx,x);
37 	if(hx<0x3f800000) {		/* x < 1 */
38 	    return (x-x)/(x-x);
39 	} else if(hx >=0x4d800000) {	/* x > 2**28 */
40 	    if(!FLT_UWORD_IS_FINITE(hx)) {	/* x is inf of NaN */
41 	        return x+x;
42 	    } else
43 		return __ieee754_logf(x)+ln2;	/* acosh(huge)=log(2x) */
44 	} else if (hx==0x3f800000) {
45 	    return 0.0;			/* acosh(1) = 0 */
46 	} else if (hx > 0x40000000) {	/* 2**28 > x > 2 */
47 	    t=x*x;
48 	    return __ieee754_logf((float)2.0*x-one/(x+__ieee754_sqrtf(t-one)));
49 	} else {			/* 1<x<2 */
50 	    t = x-one;
51 	    return log1pf(t+__ieee754_sqrtf((float)2.0*t+t*t));
52 	}
53 }
54