source: buchla-68k/orig/DATE/POM.C@ f7c91fc

/* pom.c -- The phase of the moon, for your safety and convenience.
**
**  Stolen from ArchMach & converted from PL/I by Brian Hess.
**  Extensively cleaned up by Rich Salz.
**
**  Minor bug fixes by D.N. Lynx Crowe  1985-06-05
**
**  If you can figure out how this program works, then YOU deserve
**  to be working on it, sucker!  Here's a hint:  The epoch is 13:23,
**  10/1/78.
*/

#ifdef  UNIX
#include <math.h>
#include <sys/types.h>
#include <time.h>
#else
#include "math.h"
#include "types.h"
#include "time.h"
#endif

/* Globals. */

long             Day;
long             Hour;
long             Minute;
double           Fraction;

char            *Moon[] = {

    "new",
    "first quarter of the",
    "full",
    "last quarter of the"
};


/* Linked in later. */

time_t           time();
struct tm       *localtime();


#define LINES           24
#define WIDTH           80
#define CENTER          ((WIDTH - 2 * LINES) / 2)
#define BRIGHT          '@'
#define LEDGE           '('
#define REDGE           ')'
#define FULL            0.5
#define TwoPi           (2 * 3.1415927)
#define ZERO            0.03

#define Plural(X)       if (X != 1) printf("s");


/*
   -----------------------------------------------------------------------
        Calculate() -- calculate the phase of the moon
   -----------------------------------------------------------------------
*/

long
Calculate()
{
    register struct tm  *tm;
    register long        Length;
    register long        Phase;
    register long        DeltaH;
    register long        Delta;
    register long        offset;
    time_t               tick;
    long                 julian;
    long                 year;
    long                 hour;
    long                 minute;

    tick        = time((time_t *)0);
    tm          = localtime(&tick);
    julian      = tm->tm_yday + 1;
    year        = tm->tm_year - 78;
    hour        = tm->tm_hour;
    minute      = tm->tm_min;

    Length      = (double)2551 / 60 * 1000 + (double)443 / 60;
    offset      = ((year * 365L + julian) * 24L + hour) * 60L + minute;
    Delta       = offset - (273L * 24L + 13L) * 60L + 23L;
    Phase       = Delta - (Delta / Length) * Length;

    Fraction    = (double)Phase / (double)Length;

    Length      = Length / 4;
    Phase       = Phase / Length;
    Delta       = Delta - (Delta / Length) * Length;
    DeltaH      = Delta / 60;
    Minute      = Delta - DeltaH * 60;
    Day         = DeltaH / 24;
    Hour        = DeltaH - Day * 24;
    return(Phase);
}


/*
   -----------------------------------------------------------------------
        CharPos(x) -- calculate character position for Draw
   -----------------------------------------------------------------------
*/

int
CharPos(x)
    double              x;
{
    register int        i;

    i = x * LINES + 0.5;
    if ((i += LINES + CENTER) < 1)
        i = 1;
    return(i);
}


/*
   -----------------------------------------------------------------------
        Draw() -- draw the moon
   -----------------------------------------------------------------------
*/

void
Draw()
{
    register char       *p;
    register int         i;
    register int         end;
    register double      y;
    register double      cht;
    register double      squisher;
    register double      horizon;
    register double      terminator;
    char                 Buffer[256];

    /* Clear screen? */

    if (Fraction < FULL)
        squisher = cos(TwoPi * Fraction);
    else
        squisher = cos(TwoPi * (Fraction - FULL));

    cht = (double)2.0 / (LINES - 6.0);
    for (y = 0.93; y > -1.0; y -= cht)
    {
        for (i = sizeof Buffer, p = Buffer; --i >= 0; )
            *p++ = ' ';
        horizon = sqrt(1.0 - y * y);
        Buffer[    CharPos(-horizon)]   = LEDGE;
        Buffer[i = CharPos( horizon)]   = REDGE;
        Buffer[++i]                     = '\0';
        terminator = horizon * squisher;
        if (Fraction > ZERO && Fraction < (1.0 - ZERO))
        {
            if (Fraction < FULL)
            {
                i   = CharPos( terminator);
                end = CharPos( horizon);
            }
            else
            {
                i   = CharPos(-horizon);
                end = CharPos( terminator);
            }
            while (i <= end)
                Buffer[i++] = BRIGHT;
        }
        printf(" %s\n", Buffer);
    }
}


/*
   -----------------------------------------------------------------------
        main(ac) -- calculate the phase of the moon and optionally draw it
   -----------------------------------------------------------------------
*/

main(ac)
    int                  ac;
{
    register long        Phase;

    Phase = Calculate();

    if (ac != 1)
        Draw();

    printf("\nIt is ");

    if (Day == 0 && Hour == 0 && Minute == 0)
        printf("exactly");
    else {

        if (Day) {

            printf("%ld day", Day);
            Plural(Day);

            if (Hour | Day)
                printf(", ");
        }

        if (Hour) {

            printf("%ld hour", Hour);
            Plural(Hour);

            if (Minute)
                printf(", ");
        }

        if (Minute) {

            printf("%ld minute", Minute);
            Plural(Minute);
        }

        printf(" since");
    }

    printf(" the %s moon.\n", Moon[Phase]);

    exit(0);
}