1 #include "FEATURE/uwin" 2 3 #if !_UWIN || _lib_atanh 4 5 void _STUB_atanh(){} 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[] = "@(#)atanh.c 8.1 (Berkeley) 6/4/93"; 40 #endif /* not lint */ 41 42 /* ATANH(X) 43 * RETURN THE HYPERBOLIC ARC TANGENT OF X 44 * DOUBLE PRECISION (VAX D format 56 bits, IEEE DOUBLE 53 BITS) 45 * CODED IN C BY K.C. NG, 1/8/85; 46 * REVISED BY K.C. NG on 2/7/85, 3/7/85, 8/18/85. 47 * 48 * Required kernel function: 49 * log1p(x) ...return log(1+x) 50 * 51 * Method : 52 * Return 53 * 1 2x x 54 * atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) 55 * 2 1 - x 1 - x 56 * 57 * Special cases: 58 * atanh(x) is NaN if |x| > 1 with signal; 59 * atanh(NaN) is that NaN with no signal; 60 * atanh(+-1) is +-INF with signal. 61 * 62 * Accuracy: 63 * atanh(x) returns the exact hyperbolic arc tangent of x nearly rounded. 64 * In a test run with 512,000 random arguments on a VAX, the maximum 65 * observed error was 1.87 ulps (units in the last place) at 66 * x= -3.8962076028810414000e-03. 67 */ 68 #include "mathimpl.h" 69 70 #if defined(vax)||defined(tahoe) 71 #include <errno.h> 72 #endif /* defined(vax)||defined(tahoe) */ 73 74 extern double atanh(x) 75 double x; 76 { 77 double z; 78 z = copysign(0.5,x); 79 x = copysign(x,1.0); 80 #if defined(vax)||defined(tahoe) 81 if (x == 1.0) { 82 return(copysign(1.0,z)*infnan(ERANGE)); /* sign(x)*INF */ 83 } 84 #endif /* defined(vax)||defined(tahoe) */ 85 x = x/(1.0-x); 86 return( z*log1p(x+x) ); 87 } 88 89 #endif 90