usr/src/lib/libast/common/uwin/acosh.c

   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 static char sccsid[] = "@(#)acosh.c     8.1 (Berkeley) 6/4/93";
  39
  40 /* ACOSH(X)
  41  * RETURN THE INVERSE HYPERBOLIC COSINE OF X
  42  * DOUBLE PRECISION (VAX D FORMAT 56 BITS, IEEE DOUBLE 53 BITS)
  43  * CODED IN C BY K.C. NG, 2/16/85;
  44  * REVISED BY K.C. NG on 3/6/85, 3/24/85, 4/16/85, 8/17/85.
  45  *
  46  * Required system supported functions :
  47  *      sqrt(x)
  48  *
  49  * Required kernel function:
  50  *      log1p(x)                ...return log(1+x)
  51  *
  52  * Method :
  53  *      Based on
  54  *              acosh(x) = log [ x + sqrt(x*x-1) ]
  55  *      we have
  56  *              acosh(x) := log1p(x)+ln2,       if (x > 1.0E20); else
  57  *              acosh(x) := log1p( sqrt(x-1) * (sqrt(x-1) + sqrt(x+1)) ) .
  58  *      These formulae avoid the over/underflow complication.
  59  *
  60  * Special cases:
  61  *      acosh(x) is NaN with signal if x<1.
  62  *      acosh(NaN) is NaN without signal.
  63  *
  64  * Accuracy:
  65  *      acosh(x) returns the exact inverse hyperbolic cosine of x nearly
  66  *      rounded. In a test run with 512,000 random arguments on a VAX, the
  67  *      maximum observed error was 3.30 ulps (units of the last place) at
  68  *      x=1.0070493753568216 .
  69  *
  70  * Constants:
  71  * The hexadecimal values are the intended ones for the following constants.
  72  * The decimal values may be used, provided that the compiler will convert
  73  * from decimal to binary accurately enough to produce the hexadecimal values
  74  * shown.
  75  */
  76
  77 #include "mathimpl.h"
  78
  79 vc(ln2hi, 6.9314718055829871446E-1  ,7217,4031,0000,f7d0,   0, .B17217F7D00000)
  80 vc(ln2lo, 1.6465949582897081279E-12 ,bcd5,2ce7,d9cc,e4f1, -39, .E7BCD5E4F1D9CC)
  81
  82 ic(ln2hi, 6.9314718036912381649E-1,  -1, 1.62E42FEE00000)
  83 ic(ln2lo, 1.9082149292705877000E-10,-33, 1.A39EF35793C76)
  84
  85 #ifdef vccast
  86 #define    ln2hi    vccast(ln2hi)
  87 #define    ln2lo    vccast(ln2lo)
  88 #endif
  89
  90 extern double acosh(x)
  91 double x;
  92 {
  93         double t,big=1.E20; /* big+1==big */
  94
  95 #if !defined(vax)&&!defined(tahoe)
  96         if(x!=x) return(x);     /* x is NaN */
  97 #endif  /* !defined(vax)&&!defined(tahoe) */
  98
  99     /* return log1p(x) + log(2) if x is large */
 100         if(x>big) {t=log1p(x)+ln2lo; return(t+ln2hi);}
 101
 102         t=sqrt(x-1.0);
 103         return(log1p(t*(t+sqrt(x+1.0))));
 104 }
 105
 106 #endif