/*
  Name:    ex5-9.c
  Purpose: Compares two dates: which one is earlier?
  Author:  Bill Slough

  Note:    datecmp is patterned on C's string comparison function
*/

#include <stdio.h>

int datecmp(int thisMonth, int thisDay, int thisYear,
            int thatMonth, int thatDay, int thatYear);

int main() {
    int month1, day1, year1;   /* first date */
    int month2, day2, year2;   /* second date */
    
    /* Get the first date */
    printf("Enter first date (mm/dd/yy): ");
    scanf("%d/%d/%d", &month1, &day1, &year1);

    /* Get the second date */
    printf("Enter the second date (mm/dd/yy): ");
    scanf("%d/%d/%d", &month2, &day2, &year2);

    /* Compare dates and announce the outcome */
    switch (datecmp(month1, day1, year1, month2, day2, year2)) {
    case -1:
        printf("%d/%d/%2.2d is earlier than %d/%d/%2.2d\n",
               month1, day1, year1, month2, day2, year2);
        break;
    case 0:
        printf("These are identical dates.\n");
        break;
    case +1:
        printf("%d/%d/%2.2d is earlier than %d/%d/%2.2d\n",
               month2, day2, year2, month1, day1, year1);
        break;
    }
    return 0;
}

int datecmp(int thisMonth, int thisDay, int thisYear,
            int thatMonth, int thatDay, int thatYear) {
    /* Compare two dates:

       Given:  thisMonth/thisDay/thisYear vs. thatMonth/thatDay/thatYear

       Result: -1 if this date < that date
                0 if this date = that date
               +1 if this date > that date
    */

    /* Nothing is known about the dates yet */
    if (thisYear < thatYear)
        return -1;
    else if (thisYear > thatYear)
        return +1;

    /* Dates are in the same year */
    if (thisMonth < thatMonth)
        return -1;
    else if (thisMonth > thatMonth)
        return +1;

    /* Dates are in the same year and month */
    if (thisDay < thatDay)
        return -1;
    else if (thisDay == thatDay)
        return 0;
    else
        return +1;
}