| |
| /* |
| * Copyright (c) 1998, 2001, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* __ieee754_atanh(x) |
| * Method : |
| * 1.Reduced x to positive by atanh(-x) = -atanh(x) |
| * 2.For x>=0.5 |
| * 1 2x x |
| * atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) |
| * 2 1 - x 1 - x |
| * |
| * For x<0.5 |
| * atanh(x) = 0.5*log1p(2x+2x*x/(1-x)) |
| * |
| * Special cases: |
| * atanh(x) is NaN if |x| > 1 with signal; |
| * atanh(NaN) is that NaN with no signal; |
| * atanh(+-1) is +-INF with signal. |
| * |
| */ |
| |
| #include "fdlibm.h" |
| |
| #ifdef __STDC__ |
| static const double one = 1.0, huge = 1e300; |
| #else |
| static double one = 1.0, huge = 1e300; |
| #endif |
| |
| static double zero = 0.0; |
| |
| #ifdef __STDC__ |
| double __ieee754_atanh(double x) |
| #else |
| double __ieee754_atanh(x) |
| double x; |
| #endif |
| { |
| double t; |
| int hx,ix; |
| unsigned lx; |
| hx = __HI(x); /* high word */ |
| lx = __LO(x); /* low word */ |
| ix = hx&0x7fffffff; |
| if ((ix|((lx|(-lx))>>31))>0x3ff00000) /* |x|>1 */ |
| return (x-x)/(x-x); |
| if(ix==0x3ff00000) |
| return x/zero; |
| if(ix<0x3e300000&&(huge+x)>zero) return x; /* x<2**-28 */ |
| __HI(x) = ix; /* x <- |x| */ |
| if(ix<0x3fe00000) { /* x < 0.5 */ |
| t = x+x; |
| t = 0.5*log1p(t+t*x/(one-x)); |
| } else |
| t = 0.5*log1p((x+x)/(one-x)); |
| if(hx>=0) return t; else return -t; |
| } |
