/* cosh.c - hyperbolic routines *//* Copyright 1992-1993 Wind River Systems, Inc. *//*modification history--------------------01e,05feb93,jdi  doc changes based on kdl review.01d,02dec92,jdi  doc tweaks.01c,28oct92,jdi  documentation cleanup.01b,20sep92,smb  documentation additions01a,08jul92,smb  documentation*//*DESCRIPTION* Copyright (c) 1985 Regents of the University of California.* All rights reserved.** Redistribution and use in source and binary forms are permitted* provided that the above copyright notice and this paragraph are* duplicated in all such forms and that any documentation,* advertising materials, and other materials related to such* distribution and use acknowledge that the software was developed* by the University of California, Berkeley.  The name of the* University may not be used to endorse or promote products derived* from this software without specific prior written permission.* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.** All recipients should regard themselves as participants in an ongoing* research project and hence should feel obligated to report their* experiences (good or bad) with these elementary function codes, using* the sendbug(8) program, to the authors.*SEE ALSO: American National Standard X3.159-1989NOMANUAL*/#include "vxWorks.h"#include "math.h"#if defined(vax)||defined(tahoe)#ifdef vax#define _0x(A,B)	0x/**/A/**/B#else	/* vax */#define _0x(A,B)	0x/**/B/**/A#endif	/* vax *//* static double  *//* mln2hi =  8.8029691931113054792E1     , Hex  2^  7   *  .B00F33C7E22BDB *//* mln2lo = -4.9650192275318476525E-16   , Hex  2^-50   * -.8F1B60279E582A *//* lnovfl =  8.8029691931113053016E1     ; Hex  2^  7   *  .B00F33C7E22BDA */static long    mln2hix[] = { _0x(0f33,43b0), _0x(2bdb,c7e2)};static long    mln2lox[] = { _0x(1b60,a70f), _0x(582a,279e)};static long    lnovflx[] = { _0x(0f33,43b0), _0x(2bda,c7e2)};#define   mln2hi    (*(double*)mln2hix)#define   mln2lo    (*(double*)mln2lox)#define   lnovfl    (*(double*)lnovflx)#else	/* defined(vax)||defined(tahoe) */static doublemln2hi =  7.0978271289338397310E2     , /*Hex  2^ 10   *  1.62E42FEFA39EF */mln2lo =  2.3747039373786107478E-14   , /*Hex  2^-45   *  1.ABC9E3B39803F */lnovfl =  7.0978271289338397310E2     ; /*Hex  2^  9   *  1.62E42FEFA39EF */#endif	/* defined(vax)||defined(tahoe) */#if defined(vax)||defined(tahoe)static max = 126                      ;#else	/* defined(vax)||defined(tahoe) */static max = 1023                     ;#endif	/* defined(vax)||defined(tahoe) *//********************************************************************************* cosh - compute a hyperbolic cosine (ANSI)** This routine returns the hyperbolic cosine of <x> in* double precision (IEEE double, 53 bits).** A range error occurs if <x> is too large.** INTERNAL:* Method:* (1) Replace <x> by |x|.* (2)*                                                 [ exp(x) - 1 ]^2*     0        <= x <= 0.3465  :  cosh(x) := 1 + -------------------*                                                    2*exp(x)**                                            exp(x) +  1/exp(x)*     0.3465   <= x <= 22      :  cosh(x) := -------------------*                                                    2*     22       <= x <= lnovfl  :  cosh(x) := exp(x)/2*     lnovfl   <= x <= lnovfl+log(2)*                              :  cosh(x) := exp(x)/2 (avoid overflow)*     log(2)+lnovfl <  x <  INF:  overflow to INF**         Note: .3465 is a number near one half of ln2.** INCLUDE FILES: math.h** RETURNS:* The double-precision hyperbolic cosine of <x>.** Special cases:*     If <x> is +INF, -INF, or NaN, cosh() returns <x>.** SEE ALSO: mathALib** INTERNAL:* Coded in C by K.C. Ng, 1/8/85;* Revised by K.C. Ng on 2/8/85, 2/23/85, 3/7/85, 3/29/85, 4/16/85.*/double cosh    (    double x	/* value to compute the hyperbolic cosine of */    )    {	static double half=1.0/2.0,one=1.0, small=1.0E-18; /* fl(1+small)==1 */	double scalb(),copysign(),exp(),exp__E(),t;#if !defined(vax)&&!defined(tahoe)	if(x!=x) return(x);	/* x is NaN */#endif	/* !defined(vax)&&!defined(tahoe) */	if((x=copysign(x,one)) <= 22)	    if(x<0.3465)		if(x<small) return(one+x);		else {t=x+exp__E(x,0.0);x=t+t; return(one+t*t/(2.0+x)); }	    else /* for x lies in [0.3465,22] */	        { t=exp(x); return((t+one/t)*half); }	if( lnovfl <= x && x <= (lnovfl+0.7))        /* for x lies in [lnovfl, lnovfl+ln2], decrease x by ln(2^(max+1))         * and return 2^max*exp(x) to avoid unnecessary overflow         */	    return(scalb(exp((x-mln2hi)-mln2lo), max));	else	    return(exp(x)*half);	/* for large x,  cosh(x)=exp(x)/2 */    }