1 #include "FEATURE/uwin"
2 
3 #if !_UWIN || _lib_acosh
4 
_STUB_acosh()5 void _STUB_acosh(){}
6 
7 #else
8 
9 /*
10  * Copyright (c) 1985, 1993
11  *	The Regents of the University of California.  All rights reserved.
12  *
13  * Redistribution and use in source and binary forms, with or without
14  * modification, are permitted provided that the following conditions
15  * are met:
16  * 1. Redistributions of source code must retain the above copyright
17  *    notice, this list of conditions and the following disclaimer.
18  * 2. Redistributions in binary form must reproduce the above copyright
19  *    notice, this list of conditions and the following disclaimer in the
20  *    documentation and/or other materials provided with the distribution.
21  * 3. Neither the name of the University nor the names of its contributors
22  *    may be used to endorse or promote products derived from this software
23  *    without specific prior written permission.
24  *
25  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35  * SUCH DAMAGE.
36  */
37 
38 #ifndef lint
39 static char sccsid[] = "@(#)acosh.c	8.1 (Berkeley) 6/4/93";
40 #endif /* not lint */
41 
42 /* ACOSH(X)
43  * RETURN THE INVERSE HYPERBOLIC COSINE OF X
44  * DOUBLE PRECISION (VAX D FORMAT 56 BITS, IEEE DOUBLE 53 BITS)
45  * CODED IN C BY K.C. NG, 2/16/85;
46  * REVISED BY K.C. NG on 3/6/85, 3/24/85, 4/16/85, 8/17/85.
47  *
48  * Required system supported functions :
49  *	sqrt(x)
50  *
51  * Required kernel function:
52  *	log1p(x) 		...return log(1+x)
53  *
54  * Method :
55  *	Based on
56  *		acosh(x) = log [ x + sqrt(x*x-1) ]
57  *	we have
58  *		acosh(x) := log1p(x)+ln2,	if (x > 1.0E20); else
59  *		acosh(x) := log1p( sqrt(x-1) * (sqrt(x-1) + sqrt(x+1)) ) .
60  *	These formulae avoid the over/underflow complication.
61  *
62  * Special cases:
63  *	acosh(x) is NaN with signal if x<1.
64  *	acosh(NaN) is NaN without signal.
65  *
66  * Accuracy:
67  *	acosh(x) returns the exact inverse hyperbolic cosine of x nearly
68  *	rounded. In a test run with 512,000 random arguments on a VAX, the
69  *	maximum observed error was 3.30 ulps (units of the last place) at
70  *	x=1.0070493753568216 .
71  *
72  * Constants:
73  * The hexadecimal values are the intended ones for the following constants.
74  * The decimal values may be used, provided that the compiler will convert
75  * from decimal to binary accurately enough to produce the hexadecimal values
76  * shown.
77  */
78 
79 #include "mathimpl.h"
80 
81 vc(ln2hi, 6.9314718055829871446E-1  ,7217,4031,0000,f7d0,   0, .B17217F7D00000)
82 vc(ln2lo, 1.6465949582897081279E-12 ,bcd5,2ce7,d9cc,e4f1, -39, .E7BCD5E4F1D9CC)
83 
84 ic(ln2hi, 6.9314718036912381649E-1,  -1, 1.62E42FEE00000)
85 ic(ln2lo, 1.9082149292705877000E-10,-33, 1.A39EF35793C76)
86 
87 #ifdef vccast
88 #define    ln2hi    vccast(ln2hi)
89 #define    ln2lo    vccast(ln2lo)
90 #endif
91 
92 extern double acosh(x)
93 double x;
94 {
95 	double t,big=1.E20; /* big+1==big */
96 
97 #if !defined(vax)&&!defined(tahoe)
98 	if(x!=x) return(x);	/* x is NaN */
99 #endif	/* !defined(vax)&&!defined(tahoe) */
100 
101     /* return log1p(x) + log(2) if x is large */
102 	if(x>big) {t=log1p(x)+ln2lo; return(t+ln2hi);}
103 
104 	t=sqrt(x-1.0);
105 	return(log1p(t*(t+sqrt(x+1.0))));
106 }
107 
108 #endif
109