1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 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 } 74