1 /* e_coshf.c -- float version of e_cosh.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 "math.h"
17 #include "math_private.h"
18 
19 static const volatile float huge = 1.0e30;
20 static const float one = 1.0, half=0.5;
21 
22 float
23 coshf(float x)
24 {
25 	float t,w;
26 	int32_t ix;
27 
28 	GET_FLOAT_WORD(ix,x);
29 	ix &= 0x7fffffff;
30 
31     /* x is INF or NaN */
32 	if(ix>=0x7f800000) return x*x;
33 
34     /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
35 	if(ix<0x3eb17218) {
36 	    t = expm1f(fabsf(x));
37 	    w = one+t;
38 	    if (ix<0x24000000) return w;	/* cosh(tiny) = 1 */
39 	    return one+(t*t)/(w+w);
40 	}
41 
42     /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
43 	if (ix < 0x41b00000) {
44 		t = expf(fabsf(x));
45 		return half*t+half/t;
46 	}
47 
48     /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
49 	if (ix < 0x42b17180)  return half*expf(fabsf(x));
50 
51     /* |x| in [log(maxdouble), overflowthresold] */
52 	if (ix<=0x42b2d4fc) {
53 	    w = expf(half*fabsf(x));
54 	    t = half*w;
55 	    return t*w;
56 	}
57 
58     /* |x| > overflowthresold, cosh(x) overflow */
59 	return huge*huge;
60 }
61