1#include "FEATURE/uwin"
2
3#if !_UWIN
4
5void _STUB_log__L(){}
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
39static char sccsid[] = "@(#)log__L.c	8.1 (Berkeley) 6/4/93";
40#endif /* not lint */
41
42/* log__L(Z)
43 *		LOG(1+X) - 2S			       X
44 * RETURN      ---------------  WHERE Z = S*S,  S = ------- , 0 <= Z <= .0294...
45 *		      S				     2 + X
46 *
47 * DOUBLE PRECISION (VAX D FORMAT 56 bits or IEEE DOUBLE 53 BITS)
48 * KERNEL FUNCTION FOR LOG; TO BE USED IN LOG1P, LOG, AND POW FUNCTIONS
49 * CODED IN C BY K.C. NG, 1/19/85;
50 * REVISED BY K.C. Ng, 2/3/85, 4/16/85.
51 *
52 * Method :
53 *	1. Polynomial approximation: let s = x/(2+x).
54 *	   Based on log(1+x) = log(1+s) - log(1-s)
55 *		 = 2s + 2/3 s**3 + 2/5 s**5 + .....,
56 *
57 *	   (log(1+x) - 2s)/s is computed by
58 *
59 *	       z*(L1 + z*(L2 + z*(... (L7 + z*L8)...)))
60 *
61 *	   where z=s*s. (See the listing below for Lk's values.) The
62 *	   coefficients are obtained by a special Remez algorithm.
63 *
64 * Accuracy:
65 *	Assuming no rounding error, the maximum magnitude of the approximation
66 *	error (absolute) is 2**(-58.49) for IEEE double, and 2**(-63.63)
67 *	for VAX D format.
68 *
69 * Constants:
70 * The hexadecimal values are the intended ones for the following constants.
71 * The decimal values may be used, provided that the compiler will convert
72 * from decimal to binary accurately enough to produce the hexadecimal values
73 * shown.
74 */
75
76#include "mathimpl.h"
77
78vc(L1, 6.6666666666666703212E-1 ,aaaa,402a,aac5,aaaa,  0, .AAAAAAAAAAAAC5)
79vc(L2, 3.9999999999970461961E-1 ,cccc,3fcc,2684,cccc, -1, .CCCCCCCCCC2684)
80vc(L3, 2.8571428579395698188E-1 ,4924,3f92,5782,92f8, -1, .92492492F85782)
81vc(L4, 2.2222221233634724402E-1 ,8e38,3f63,af2c,39b7, -2, .E38E3839B7AF2C)
82vc(L5, 1.8181879517064680057E-1 ,2eb4,3f3a,655e,cc39, -2, .BA2EB4CC39655E)
83vc(L6, 1.5382888777946145467E-1 ,8551,3f1d,781d,e8c5, -2, .9D8551E8C5781D)
84vc(L7, 1.3338356561139403517E-1 ,95b3,3f08,cd92,907f, -2, .8895B3907FCD92)
85vc(L8, 1.2500000000000000000E-1 ,0000,3f00,0000,0000, -2, .80000000000000)
86
87ic(L1, 6.6666666666667340202E-1, -1, 1.5555555555592)
88ic(L2, 3.9999999999416702146E-1, -2, 1.999999997FF24)
89ic(L3, 2.8571428742008753154E-1, -2, 1.24924941E07B4)
90ic(L4, 2.2222198607186277597E-1, -3, 1.C71C52150BEA6)
91ic(L5, 1.8183562745289935658E-1, -3, 1.74663CC94342F)
92ic(L6, 1.5314087275331442206E-1, -3, 1.39A1EC014045B)
93ic(L7, 1.4795612545334174692E-1, -3, 1.2F039F0085122)
94
95#ifdef vccast
96#define	L1	vccast(L1)
97#define	L2	vccast(L2)
98#define	L3	vccast(L3)
99#define	L4	vccast(L4)
100#define	L5	vccast(L5)
101#define	L6	vccast(L6)
102#define	L7	vccast(L7)
103#define	L8	vccast(L8)
104#endif
105
106double __log__L(z)
107double z;
108{
109#if defined(vax)||defined(tahoe)
110    return(z*(L1+z*(L2+z*(L3+z*(L4+z*(L5+z*(L6+z*(L7+z*L8))))))));
111#else	/* defined(vax)||defined(tahoe) */
112    return(z*(L1+z*(L2+z*(L3+z*(L4+z*(L5+z*(L6+z*L7)))))));
113#endif	/* defined(vax)||defined(tahoe) */
114}
115
116#endif
117