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/*
** DAYNUM.C - Functions to return statistics about a given date.
**
** public domain by Bob Stout - uses Ray Gardner's SCALDATE.C
*/
#include "scaldate.h"
static long jan1date;
/*
** Determine if a given date is valid
*/
int valiDate(unsigned yr, unsigned mo, unsigned day)
{
unsigned int days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
if (1 > mo || 12 < mo)
return 0;
if (1 > day || day > (days[mo - 1] + (2 == mo && isleap(yr))))
return 0;
else return 1;
}
/*
** Return the day of the week
*/
int dow(unsigned yr, unsigned mo, unsigned day)
{
#if (!ISO) /* Sunday(0) -> Saturday(6) (i.e. U.S.) calendars */
return (ymd_to_scalar(yr, mo, day) % 7L);
#else /* International Monday(0) -> Sunday(6) calendars */
return ((ymd_to_scalar(yr, mo, day) - 1L) % 7L);
#endif
}
/*
** Return the day of the year (1 - 365/6)
*/
int daynum(int year, int month, int day)
{
jan1date = ymd_to_scalar(year, 1, 1);
return (int)(ymd_to_scalar(year, month, day) - jan1date + 1L);
}
/*
** Return the week of the year (1 - 52, 0 - 52 if ISO)
*/
int weeknum(int year, int month, int day)
{
int wn, j1n, dn = daynum(year, month, day);
dn += (j1n = (int)((jan1date - (long)ISO) % 7L)) - 1;
wn = dn / 7;
if (ISO)
wn += (j1n < 4);
else ++wn;
return wn;
}
#ifdef TEST
#include <stdio.h>
#include <stdlib.h>
void do_err(void);
void main(int argc, char *argv[])
{
int day, month, year;
char *days[] =
#if (!ISO)
{"Sunday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Saturday"};
#else
{"Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Saturday", "Sunday"};
#endif
if (4 > argc)
{
puts("Usage: DAYNUM month day year");
return;
}
month = atoi(argv[1]);
day = atoi(argv[2]);
year = atoi(argv[3]);
if (100 > year)
year += 1900;
if (!valiDate(year, month, day))
printf("%d/%d/%d is invalid!\n", month, day, year);
else printf("%d/%d/%d is a %s, day #%d in week %d\n", month, day, year,
days[dow(year, month, day)], daynum(year, month, day),
weeknum(year, month, day));
}
#endif /* TEST */
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