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 /* 35 * 1 2x x 36 * atanhl(x) = --- * LOG(1 + -------) = 0.5 * log1pl(2 * --------) 37 * 2 1 - x 1 - x 38 * Note: to guarantee atanhl(-x) = -atanhl(x), we use 39 * sign(x) |x| 40 * atanhl(x) = ------- * log1pl(2*-------). 41 * 2 1 - |x| 42 * 43 * Special cases: 44 * atanhl(x) is NaN if |x| > 1 with signal; 45 * atanhl(NaN) is that NaN with no signal; 46 * atanhl(+-1) is +-INF with signal. 47 * 48 */ 49 50 static const long double zero = 0.0L, half = 0.5L, one = 1.0L; 51 52 long double 53 atanhl(long double x) { 54 long double t; 55 56 t = fabsl(x); 57 if (t == one) 58 return (x / zero); 59 t = t / (one - t); 60 return (copysignl(half, x) * log1pl(t + t)); 61 } 62