5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 */
25 /*
26 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
27 * Use is subject to license terms.
28 */
29
30 #pragma weak __atanhl = atanhl
31
32 #include "libm.h"
33
34 #define GENERIC long double
35 #define ATANH atanhl
36
37 /* ATANH(x)
38 * 1 2x x
39 * ATANH(x) = --- * LOG(1 + -------) = 0.5 * LOG1P(2 * --------)
40 * 2 1 - x 1 - x
41 * Note: to guarantee ATANH(-x) = -ATANH(x), we use
42 * sign(x) |x|
43 * ATANH(x) = ------- * LOG1P(2*-------).
44 * 2 1 - |x|
45 *
46 * Special cases:
47 * ATANH(x) is NaN if |x| > 1 with signal;
48 * ATANH(NaN) is that NaN with no signal;
49 * ATANH(+-1) is +-INF with signal.
50 *
51 */
52
53 #define FABS fabsl
54 #define LOG1P log1pl
55 #define COPYSIGN copysignl
56
57
58 extern GENERIC FABS(),LOG1P(),COPYSIGN();
59
60 static GENERIC
61 zero = (GENERIC) 0.0,
62 half = (GENERIC) 0.5,
63 one = (GENERIC) 1.0;
64
65 GENERIC ATANH(x)
66 GENERIC x;
67 {
68 GENERIC t;
69 t = FABS(x);
70 if (t == one) return x/zero;
71 t = t/(one-t);
72 return COPYSIGN(half,x)*LOG1P(t+t);
73 }
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5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 */
25
26 /*
27 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
28 * Use is subject to license terms.
29 */
30
31 #pragma weak __atanhl = atanhl
32
33 #include "libm.h"
34
35 #define GENERIC long double
36 #define ATANH atanhl
37
38 /* BEGIN CSTYLED */
39 /*
40 * ATANH(x)
41 * 1 2x x
42 * ATANH(x) = --- * LOG(1 + -------) = 0.5 * LOG1P(2 * --------)
43 * 2 1 - x 1 - x
44 * Note: to guarantee ATANH(-x) = -ATANH(x), we use
45 * sign(x) |x|
46 * ATANH(x) = ------- * LOG1P(2*-------).
47 * 2 1 - |x|
48 *
49 * Special cases:
50 * ATANH(x) is NaN if |x| > 1 with signal;
51 * ATANH(NaN) is that NaN with no signal;
52 * ATANH(+-1) is +-INF with signal.
53 *
54 */
55 /* END CSTYLED */
56
57 #define FABS fabsl
58 #define LOG1P log1pl
59 #define COPYSIGN copysignl
60
61 extern GENERIC FABS(), LOG1P(), COPYSIGN();
62
63 static GENERIC zero = (GENERIC)0.0, half = (GENERIC)0.5, one = (GENERIC)1.0;
64
65 GENERIC
66 ATANH(GENERIC x)
67 {
68 GENERIC t;
69
70 t = FABS(x);
71
72 if (t == one)
73 return (x / zero);
74
75 t = t / (one - t);
76 return (COPYSIGN(half, x) * LOG1P(t + t));
77 }
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