e_coshf.c revision 50476 
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#ifndef lint
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/e_coshf.c 50476 1999-08-28 00:22:10Z peter $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23#ifdef __STDC__
24static const float one = 1.0, half=0.5, huge = 1.0e30;
25#else
26static float one = 1.0, half=0.5, huge = 1.0e30;
27#endif
28
29#ifdef __STDC__
30	float __ieee754_coshf(float x)
31#else
32	float __ieee754_coshf(x)
33	float x;
34#endif
35{
36	float t,w;
37	int32_t ix;
38
39	GET_FLOAT_WORD(ix,x);
40	ix &= 0x7fffffff;
41
42    /* x is INF or NaN */
43	if(ix>=0x7f800000) return x*x;
44
45    /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
46	if(ix<0x3eb17218) {
47	    t = expm1f(fabsf(x));
48	    w = one+t;
49	    if (ix<0x24000000) return w;	/* cosh(tiny) = 1 */
50	    return one+(t*t)/(w+w);
51	}
52
53    /* |x| in [0.5*ln2,22], return (exp(|x|)+1/exp(|x|)/2; */
54	if (ix < 0x41b00000) {
55		t = __ieee754_expf(fabsf(x));
56		return half*t+half/t;
57	}
58
59    /* |x| in [22, log(maxdouble)] return half*exp(|x|) */
60	if (ix < 0x42b17180)  return half*__ieee754_expf(fabsf(x));
61
62    /* |x| in [log(maxdouble), overflowthresold] */
63	if (ix<=0x42b2d4fc) {
64	    w = __ieee754_expf(half*fabsf(x));
65	    t = half*w;
66	    return t*w;
67	}
68
69    /* |x| > overflowthresold, cosh(x) overflow */
70	return huge*huge;
71}
72