Add the DragonFly cvs id and perform general cleanups on cvs/rcs/sccs ids. Most
[dragonfly.git] / games / pom / pom.c
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1/*
2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * This code is derived from software posted to USENET.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. All advertising materials mentioning features or use of this software
16 * must display the following acknowledgement:
17 * This product includes software developed by the University of
18 * California, Berkeley and its contributors.
19 * 4. Neither the name of the University nor the names of its contributors
20 * may be used to endorse or promote products derived from this software
21 * without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
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34 *
35 * @(#) Copyright (c) 1989, 1993 The Regents of the University of California. All rights reserved.
36 * @(#)pom.c 8.1 (Berkeley) 5/31/93
37 * $FreeBSD: src/games/pom/pom.c,v 1.9 1999/11/30 03:49:09 billf Exp $
38 * $DragonFly: src/games/pom/pom.c,v 1.2 2003/06/17 04:25:24 dillon Exp $
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39 */
40
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41/*
42 * Phase of the Moon. Calculates the current phase of the moon.
43 * Based on routines from `Practical Astronomy with Your Calculator',
44 * by Duffett-Smith. Comments give the section from the book that
45 * particular piece of code was adapted from.
46 *
47 * -- Keith E. Brandt VIII 1984
48 *
49 */
50
51#include <time.h>
52#include <stdio.h>
53#include <math.h>
54
55#ifndef PI
56#define PI 3.14159265358979323846
57#endif
58#define EPOCH 85
59#define EPSILONg 279.611371 /* solar ecliptic long at EPOCH */
60#define RHOg 282.680403 /* solar ecliptic long of perigee at EPOCH */
61#define ECCEN 0.01671542 /* solar orbit eccentricity */
62#define lzero 18.251907 /* lunar mean long at EPOCH */
63#define Pzero 192.917585 /* lunar mean long of perigee at EPOCH */
64#define Nzero 55.204723 /* lunar mean long of node at EPOCH */
65#define isleap(y) ((((y) % 4) == 0 && ((y) % 100) != 0) || ((y) % 400) == 0)
66
67static void adj360 __P((double *));
68static double dtor __P((double));
69static double potm __P((double));
70
71int
72main()
73{
74 time_t tt;
75 struct tm *GMT;
76 double days, today, tomorrow;
77 int cnt;
78
79 (void) time(&tt);
80 GMT = gmtime(&tt);
81 days = (GMT->tm_yday + 1) + ((GMT->tm_hour +
82 (GMT->tm_min / 60.0) + (GMT->tm_sec / 3600.0)) / 24.0);
83 for (cnt = EPOCH; cnt < GMT->tm_year; ++cnt)
84 days += isleap(1900 + cnt) ? 366 : 365;
85 today = potm(days) + .5;
86 (void)printf("The Moon is ");
87 if ((int)today == 100)
88 (void)printf("Full\n");
89 else if (!(int)today)
90 (void)printf("New\n");
91 else {
92 tomorrow = potm(days + 1);
93 if ((int)today == 50)
94 (void)printf("%s\n", tomorrow > today ?
95 "at the First Quarter" : "at the Last Quarter");
96 else {
97 (void)printf("%s ", tomorrow > today ?
98 "Waxing" : "Waning");
99 if (today > 50)
100 (void)printf("Gibbous (%1.0f%% of Full)\n",
101 today);
102 else if (today < 50)
103 (void)printf("Crescent (%1.0f%% of Full)\n",
104 today);
105 }
106 }
107
108 return 0;
109}
110
111/*
112 * potm --
113 * return phase of the moon
114 */
115static double
116potm(days)
117 double days;
118{
119 double N, Msol, Ec, LambdaSol, l, Mm, Ev, Ac, A3, Mmprime;
120 double A4, lprime, V, ldprime, D, Nm;
121
122 N = 360 * days / 365.2422; /* sec 42 #3 */
123 adj360(&N);
124 Msol = N + EPSILONg - RHOg; /* sec 42 #4 */
125 adj360(&Msol);
126 Ec = 360 / PI * ECCEN * sin(dtor(Msol)); /* sec 42 #5 */
127 LambdaSol = N + Ec + EPSILONg; /* sec 42 #6 */
128 adj360(&LambdaSol);
129 l = 13.1763966 * days + lzero; /* sec 61 #4 */
130 adj360(&l);
131 Mm = l - (0.1114041 * days) - Pzero; /* sec 61 #5 */
132 adj360(&Mm);
133 Nm = Nzero - (0.0529539 * days); /* sec 61 #6 */
134 adj360(&Nm);
135 Ev = 1.2739 * sin(dtor(2*(l - LambdaSol) - Mm)); /* sec 61 #7 */
136 Ac = 0.1858 * sin(dtor(Msol)); /* sec 61 #8 */
137 A3 = 0.37 * sin(dtor(Msol));
138 Mmprime = Mm + Ev - Ac - A3; /* sec 61 #9 */
139 Ec = 6.2886 * sin(dtor(Mmprime)); /* sec 61 #10 */
140 A4 = 0.214 * sin(dtor(2 * Mmprime)); /* sec 61 #11 */
141 lprime = l + Ev + Ec - Ac + A4; /* sec 61 #12 */
142 V = 0.6583 * sin(dtor(2 * (lprime - LambdaSol))); /* sec 61 #13 */
143 ldprime = lprime + V; /* sec 61 #14 */
144 D = ldprime - LambdaSol; /* sec 63 #2 */
145 return(50 * (1 - cos(dtor(D)))); /* sec 63 #3 */
146}
147
148/*
149 * dtor --
150 * convert degrees to radians
151 */
152static double
153dtor(deg)
154 double deg;
155{
156 return(deg * PI / 180);
157}
158
159/*
160 * adj360 --
161 * adjust value so 0 <= deg <= 360
162 */
163static void
164adj360(deg)
165 double *deg;
166{
167 for (;;)
168 if (*deg < 0)
169 *deg += 360;
170 else if (*deg > 360)
171 *deg -= 360;
172 else
173 break;
174}