1 
2 /* @(#)w_acos.c 5.1 93/09/24 */
3 /*
4  * ====================================================
5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6  *
7  * Developed at SunPro, a Sun Microsystems, Inc. business.
8  * Permission to use, copy, modify, and distribute this
9  * software is freely granted, provided that this notice
10  * is preserved.
11  * ====================================================
12  */
13 
14 /*
15 FUNCTION
16         <<acos>>, <<acosf>>---arc cosine
17 
18 INDEX
19 	acos
20 INDEX
21 	acosf
22 
23 ANSI_SYNOPSIS
24         #include <math.h>
25         double acos(double <[x]>);
26         float acosf(float <[x]>);
27 
28 TRAD_SYNOPSIS
29         #include <math.h>
30         double acos(<[x]>)
31         double <[x]>;
32 
33         float acosf(<[x]>)
34         float <[x]>;
35 
36 
37 
38 DESCRIPTION
39 
40 	<<acos>> computes the inverse cosine (arc cosine) of the input value.
41 	Arguments to <<acos>> must be in the range @minus{}1 to 1.
42 
43 	<<acosf>> is identical to <<acos>>, except that it performs
44 	its calculations on <<floats>>.
45 
46 RETURNS
47 	@ifnottex
48 	<<acos>> and <<acosf>> return values in radians, in the range of 0 to pi.
49 	@end ifnottex
50 	@tex
51 	<<acos>> and <<acosf>> return values in radians, in the range of <<0>> to $\pi$.
52 	@end tex
53 
54 	If <[x]> is not between @minus{}1 and 1, the returned value is NaN
55 	(not a number) the global variable <<errno>> is set to <<EDOM>>, and a
56 	<<DOMAIN error>> message is sent as standard error output.
57 
58 	You can modify error handling for these functions using <<matherr>>.
59 
60 
61 QUICKREF
62  ansi svid posix rentrant
63  acos	 y,y,y,m
64  acosf   n,n,n,m
65 
66 MATHREF
67  acos, [-1,1], acos(arg),,,
68  acos, NAN,    arg,DOMAIN,EDOM
69 
70 MATHREF
71  acosf, [-1,1], acosf(arg),,,
72  acosf, NAN,    argf,DOMAIN,EDOM
73 
74 */
75 
76 /*
77  * wrap_acos(x)
78  */
79 
80 #include "fdlibm.h"
81 #include <errno.h>
82 
83 #ifndef _DOUBLE_IS_32BITS
84 
85 #ifdef __STDC__
acos(double x)86 	double acos(double x)		/* wrapper acos */
87 #else
88 	double acos(x)			/* wrapper acos */
89 	double x;
90 #endif
91 {
92 #ifdef _IEEE_LIBM
93 	return __ieee754_acos(x);
94 #else
95 	double z;
96        	struct exception exc;
97        	z = __ieee754_acos(x);
98 	if(_LIB_VERSION == _IEEE_ || isnan(x)) return z;
99 	if(fabs(x)>1.0) {
100 	    /* acos(|x|>1) */
101 	    exc.type = DOMAIN;
102 	    exc.name = "acos";
103 	    exc.err = 0;
104 	    exc.arg1 = exc.arg2 = x;
105 	    exc.retval = nan("");
106 	    if (_LIB_VERSION == _POSIX_)
107 	       errno = EDOM;
108 	    else if (!matherr(&exc)) {
109 	       errno = EDOM;
110             }
111             if (exc.err != 0)
112 	       errno = exc.err;
113 	    return exc.retval;
114 	} else
115 	    return z;
116 #endif
117 }
118 
119 #endif /* defined(_DOUBLE_IS_32BITS) */
120