| 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. |
| 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 $ |
| 39 | */ |
| 40 | |
| 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 | |
| 67 | static void adj360 __P((double *)); |
| 68 | static double dtor __P((double)); |
| 69 | static double potm __P((double)); |
| 70 | |
| 71 | int |
| 72 | main() |
| 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 | */ |
| 115 | static double |
| 116 | potm(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 | */ |
| 152 | static double |
| 153 | dtor(deg) |
| 154 | double deg; |
| 155 | { |
| 156 | return(deg * PI / 180); |
| 157 | } |
| 158 | |
| 159 | /* |
| 160 | * adj360 -- |
| 161 | * adjust value so 0 <= deg <= 360 |
| 162 | */ |
| 163 | static void |
| 164 | adj360(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 | } |