| |
| /* |
| * 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. |
| */ |
| |
| /* asinh(x) |
| * Method : |
| * Based on |
| * asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ] |
| * we have |
| * asinh(x) := x if 1+x*x=1, |
| * := sign(x)*(log(x)+ln2)) for large |x|, else |
| * := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else |
| * := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2))) |
| */ |
| |
| #include "fdlibm.h" |
| |
| #ifdef __STDC__ |
| static const double |
| #else |
| static double |
| #endif |
| one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */ |
| ln2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */ |
| huge= 1.00000000000000000000e+300; |
| |
| #ifdef __STDC__ |
| double asinh(double x) |
| #else |
| double asinh(x) |
| double x; |
| #endif |
| { |
| double t,w; |
| int hx,ix; |
| hx = __HI(x); |
| ix = hx&0x7fffffff; |
| if(ix>=0x7ff00000) return x+x; /* x is inf or NaN */ |
| if(ix< 0x3e300000) { /* |x|<2**-28 */ |
| if(huge+x>one) return x; /* return x inexact except 0 */ |
| } |
| if(ix>0x41b00000) { /* |x| > 2**28 */ |
| w = __ieee754_log(fabs(x))+ln2; |
| } else if (ix>0x40000000) { /* 2**28 > |x| > 2.0 */ |
| t = fabs(x); |
| w = __ieee754_log(2.0*t+one/(sqrt(x*x+one)+t)); |
| } else { /* 2.0 > |x| > 2**-28 */ |
| t = x*x; |
| w =log1p(fabs(x)+t/(one+sqrt(one+t))); |
| } |
| if(hx>0) return w; else return -w; |
| } |
