source: buchla-68k/orig/DATE/MOON.C@ 66b48e7

Last change on this file since 66b48e7 was 3ae31e9, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Imported original source code.

  • Property mode set to 100755
File size: 1.5 KB
Line 
1/*
2 =============================================================================
3 moon.c -- calculate the phase of the moon
4 Version 3 -- 1988-12-05 -- D.N. Lynx Crowe
5
6 Modified version of the public domain code "mphase.c" from Usenet.
7 Original author unknown.
8
9 Modified to run under GEMDOS.
10 =============================================================================
11*/
12
13#define MAIN 1
14
15#include "stddefs.h"
16
17/*
18 =============================================================================
19 mphase() -- return the phase of the moon
20
21 returns 0..7 where: 0 = new, 4 = full
22 =============================================================================
23*/
24
25int
26mphase(year, diy)
27register int year, diy;
28{
29 /* moon period: 29.5306 days */
30 /* year: 365.2422 days */
31
32 register int epact, golden;
33
34 golden = (year % 19) + 1;
35
36 epact = (11 * golden + 18) % 30;
37
38 if (((epact EQ 25) AND (golden > 11)) OR (epact EQ 24))
39 epact++;
40
41 return( (((((diy + epact) * 6) + 11) % 177) / 22) & 7);
42}
43
44/*
45
46*/
47
48#if MAIN
49
50#include "stdio.h"
51
52char *mph[] = {
53
54 "new",
55 "waxing, in its first quarter",
56 "in its first quarter",
57 "waxing full",
58 "full",
59 "waning full",
60 "in its last quarter",
61 "waning, in its last quarter" };
62
63main()
64{
65 register int year; /* year */
66 register int diy; /* day in year */
67
68 if (argc NE 3) {
69
70 printf("usage: moon year day-in-year\n");
71 exit(1);
72 }
73
74 year = atoi(argv[1]);
75 diy = atoi(argv[2]);
76
77 printf("The moon is %s.\n", mph[mphase(year, diy)]);
78}
79
80#endif
81
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