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
19static const float one = 1.0, half=0.5, huge = 1.0e30;
20
21float
22coshf(float x)
23{
24	float t,w;
25	int32_t ix;
26
27	GET_FLOAT_WORD(ix,x);
28	ix &= 0x7fffffff;
29
30    /* x is INF or NaN */
31	if(ix>=0x7f800000) return x*x;
32
33    /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
34	if(ix<0x3eb17218) {
35	    t = expm1f(fabsf(x));
36	    w = one+t;
37	    if (ix<0x39800000) return one;	/* cosh(tiny) = 1 */
38	    return one+(t*t)/(w+w);
39	}
40
41    /* |x| in [0.5*ln2,9], return (exp(|x|)+1/exp(|x|))/2; */
42	if (ix < 0x41100000) {
43		t = expf(fabsf(x));
44		return half*t+half/t;
45	}
46
47    /* |x| in [9, log(maxfloat)] return half*exp(|x|) */
48	if (ix < 0x42b17217)  return half*expf(fabsf(x));
49
50    /* |x| in [log(maxfloat), overflowthresold] */
51	if (ix<=0x42b2d4fc)
52	    return __ldexp_expf(fabsf(x), -1);
53
54    /* |x| > overflowthresold, cosh(x) overflow */
55	return huge*huge;
56}
57