1 #include "FEATURE/uwin" 2 3 #if !_UWIN || _lib_acosh 4 5 void _STUB_acosh(){} 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[] = "@(#)acosh.c 8.1 (Berkeley) 6/4/93"; 40 #endif /* not lint */ 41 42 /* ACOSH(X) 43 * RETURN THE INVERSE HYPERBOLIC COSINE OF X 44 * DOUBLE PRECISION (VAX D FORMAT 56 BITS, IEEE DOUBLE 53 BITS) 45 * CODED IN C BY K.C. NG, 2/16/85; 46 * REVISED BY K.C. NG on 3/6/85, 3/24/85, 4/16/85, 8/17/85. 47 * 48 * Required system supported functions : 49 * sqrt(x) 50 * 51 * Required kernel function: 52 * log1p(x) ...return log(1+x) 53 * 54 * Method : 55 * Based on 56 * acosh(x) = log [ x + sqrt(x*x-1) ] 57 * we have 58 * acosh(x) := log1p(x)+ln2, if (x > 1.0E20); else 59 * acosh(x) := log1p( sqrt(x-1) * (sqrt(x-1) + sqrt(x+1)) ) . 60 * These formulae avoid the over/underflow complication. 61 * 62 * Special cases: 63 * acosh(x) is NaN with signal if x<1. 64 * acosh(NaN) is NaN without signal. 65 * 66 * Accuracy: 67 * acosh(x) returns the exact inverse hyperbolic cosine of x nearly 68 * rounded. In a test run with 512,000 random arguments on a VAX, the 69 * maximum observed error was 3.30 ulps (units of the last place) at 70 * x=1.0070493753568216 . 71 * 72 * Constants: 73 * The hexadecimal values are the intended ones for the following constants. 74 * The decimal values may be used, provided that the compiler will convert 75 * from decimal to binary accurately enough to produce the hexadecimal values 76 * shown. 77 */ 78 79 #include "mathimpl.h" 80 81 vc(ln2hi, 6.9314718055829871446E-1 ,7217,4031,0000,f7d0, 0, .B17217F7D00000) 82 vc(ln2lo, 1.6465949582897081279E-12 ,bcd5,2ce7,d9cc,e4f1, -39, .E7BCD5E4F1D9CC) 83 84 ic(ln2hi, 6.9314718036912381649E-1, -1, 1.62E42FEE00000) 85 ic(ln2lo, 1.9082149292705877000E-10,-33, 1.A39EF35793C76) 86 87 #ifdef vccast 88 #define ln2hi vccast(ln2hi) 89 #define ln2lo vccast(ln2lo) 90 #endif 91 92 extern double acosh(x) 93 double x; 94 { 95 double t,big=1.E20; /* big+1==big */ 96 97 #if !defined(vax)&&!defined(tahoe) 98 if(x!=x) return(x); /* x is NaN */ 99 #endif /* !defined(vax)&&!defined(tahoe) */ 100 101 /* return log1p(x) + log(2) if x is large */ 102 if(x>big) {t=log1p(x)+ln2lo; return(t+ln2hi);} 103 104 t=sqrt(x-1.0); 105 return(log1p(t*(t+sqrt(x+1.0)))); 106 } 107 108 #endif 109