text: #include "FEATURE/uwin"
  
  #if !_UWIN
  
  void _STUB_exp(){}
  
  #else
  
  /*
   * Copyright (c) 1985, 1993
   *	The Regents of the University of California.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   */
  
  #ifndef lint
  static char sccsid[] = "@(#)exp.c	8.1 (Berkeley) 6/4/93";
  #endif /* not lint */
  
  /* EXP(X)
   * RETURN THE EXPONENTIAL OF X
   * DOUBLE PRECISION (IEEE 53 bits, VAX D FORMAT 56 BITS)
   * CODED IN C BY K.C. NG, 1/19/85; 
   * REVISED BY K.C. NG on 2/6/85, 2/15/85, 3/7/85, 3/24/85, 4/16/85, 6/14/86.
   *
   * Required system supported functions:
   *	scalb(x,n)	
   *	copysign(x,y)	
   *	finite(x)
   *
   * Method:
   *	1. Argument Reduction: given the input x, find r and integer k such 
   *	   that
   *	                   x = k*ln2 + r,  |r| <= 0.5*ln2 .  
   *	   r will be represented as r := z+c for better accuracy.
   *
   *	2. Compute exp(r) by 
   *
   *		exp(r) = 1 + r + r*R1/(2-R1),
   *	   where
   *		R1 = x - x^2*(p1+x^2*(p2+x^2*(p3+x^2*(p4+p5*x^2)))).
   *
   *	3. exp(x) = 2^k * exp(r) .
   *
   * Special cases:
   *	exp(INF) is INF, exp(NaN) is NaN;
   *	exp(-INF)=  0;
   *	for finite argument, only exp(0)=1 is exact.
   *
   * Accuracy:
   *	exp(x) returns the exponential of x nearly rounded. In a test run
   *	with 1,156,000 random arguments on a VAX, the maximum observed
   *	error was 0.869 ulps (units in the last place).
   *
   * Constants:
   * The hexadecimal values are the intended ones for the following constants.
   * The decimal values may be used, provided that the compiler will convert
   * from decimal to binary accurately enough to produce the hexadecimal values
   * shown.
   */
  
  #include "mathimpl.h"
  
  vc(ln2hi,  6.9314718055829871446E-1  ,7217,4031,0000,f7d0,   0, .B17217F7D00000)
  vc(ln2lo,  1.6465949582897081279E-12 ,bcd5,2ce7,d9cc,e4f1, -39, .E7BCD5E4F1D9CC)
  vc(lnhuge, 9.4961163736712506989E1   ,ec1d,43bd,9010,a73e,   7, .BDEC1DA73E9010)
  vc(lntiny,-9.5654310917272452386E1   ,4f01,c3bf,33af,d72e,   7,-.BF4F01D72E33AF)
  vc(invln2, 1.4426950408889634148E0   ,aa3b,40b8,17f1,295c,   1, .B8AA3B295C17F1)
  vc(p1,     1.6666666666666602251E-1  ,aaaa,3f2a,a9f1,aaaa,  -2, .AAAAAAAAAAA9F1)
  vc(p2,    -2.7777777777015591216E-3  ,0b60,bc36,ec94,b5f5,  -8,-.B60B60B5F5EC94)
  vc(p3,     6.6137563214379341918E-5  ,b355,398a,f15f,792e, -13, .8AB355792EF15F)
  vc(p4,    -1.6533902205465250480E-6  ,ea0e,b6dd,5f84,2e93, -19,-.DDEA0E2E935F84)
  vc(p5,     4.1381367970572387085E-8  ,bb4b,3431,2683,95f5, -24, .B1BB4B95F52683)
  
  #ifdef vccast
  #define    ln2hi    vccast(ln2hi)
  #define    ln2lo    vccast(ln2lo)
  #define   lnhuge    vccast(lnhuge)
  #define   lntiny    vccast(lntiny)
  #define   invln2    vccast(invln2)
  #define       p1    vccast(p1)
  #define       p2    vccast(p2)
  #define       p3    vccast(p3)
  #define       p4    vccast(p4)
  #define       p5    vccast(p5)
  #endif
  
  ic(p1,     1.6666666666666601904E-1,  -3,  1.555555555553E)
  ic(p2,    -2.7777777777015593384E-3,  -9, -1.6C16C16BEBD93)
  ic(p3,     6.6137563214379343612E-5, -14,  1.1566AAF25DE2C)
  ic(p4,    -1.6533902205465251539E-6, -20, -1.BBD41C5D26BF1)
  ic(p5,     4.1381367970572384604E-8, -25,  1.6376972BEA4D0)
  ic(ln2hi,  6.9314718036912381649E-1,  -1,  1.62E42FEE00000)
  ic(ln2lo,  1.9082149292705877000E-10,-33,  1.A39EF35793C76)
  ic(lnhuge, 7.1602103751842355450E2,    9,  1.6602B15B7ECF2)
  ic(lntiny,-7.5137154372698068983E2,    9, -1.77AF8EBEAE354)
  ic(invln2, 1.4426950408889633870E0,    0,  1.71547652B82FE)
  
  #if !_lib_exp
  
  extern double exp(x)
  double x;
  {
  	double  z,hi,lo,c;
  	int k;
  
  #if !defined(vax)&&!defined(tahoe)
  	if(x!=x) return(x);	/* x is NaN */
  #endif	/* !defined(vax)&&!defined(tahoe) */
  	if( x <= lnhuge ) {
  		if( x >= lntiny ) {
  
  		    /* argument reduction : x --> x - k*ln2 */
  
  			k=invln2*x+copysign(0.5,x);	/* k=NINT(x/ln2) */
  
  		    /* express x-k*ln2 as hi-lo and let x=hi-lo rounded */
  
  			hi=x-k*ln2hi;
  			x=hi-(lo=k*ln2lo);
  
  		    /* return 2^k*[1+x+x*c/(2+c)]  */
  			z=x*x;
  			c= x - z*(p1+z*(p2+z*(p3+z*(p4+z*p5))));
  			return  scalb(1.0+(hi-(lo-(x*c)/(2.0-c))),k);
  
  		}
  		/* end of x > lntiny */
  
  		else 
  		     /* exp(-big#) underflows to zero */
  		     if(finite(x))  return(scalb(1.0,-5000));
  
  		     /* exp(-INF) is zero */
  		     else return(0.0);
  	}
  	/* end of x < lnhuge */
  
  	else 
  	/* exp(INF) is INF, exp(+big#) overflows to INF */
  	    return( finite(x) ?  scalb(1.0,5000)  : x);
  }
  
  #endif
  
  /* returns exp(r = x + c) for |c| < |x| with no overlap.  */
  
  double __exp__D(x, c)
  double x, c;
  {
  	double  z,hi,lo;
  	int k;
  
  #if !defined(vax)&&!defined(tahoe)
  	if (x!=x) return(x);	/* x is NaN */
  #endif	/* !defined(vax)&&!defined(tahoe) */
  	if ( x <= lnhuge ) {
  		if ( x >= lntiny ) {
  
  		    /* argument reduction : x --> x - k*ln2 */
  			z = invln2*x;
  			k = (int)z + copysign(.5, x);
  
  		    /* express (x+c)-k*ln2 as hi-lo and let x=hi-lo rounded */
  
  			hi=(x-k*ln2hi);			/* Exact. */
  			x= hi - (lo = k*ln2lo-c);
  		    /* return 2^k*[1+x+x*c/(2+c)]  */
  			z=x*x;
  			c= x - z*(p1+z*(p2+z*(p3+z*(p4+z*p5))));
  			c = (x*c)/(2.0-c);
  
  			return  scalb(1.+(hi-(lo - c)), k);
  		}
  		/* end of x > lntiny */
  
  		else 
  		     /* exp(-big#) underflows to zero */
  		     if(finite(x))  return(scalb(1.0,-5000));
  
  		     /* exp(-INF) is zero */
  		     else return(0.0);
  	}
  	/* end of x < lnhuge */
  
  	else 
  	/* exp(INF) is INF, exp(+big#) overflows to INF */
  	    return( finite(x) ?  scalb(1.0,5000)  : x);
  }
  
  #endif
  