Category : Files from Magazines
Archive   : CUJ9302.ZIP
Filename : 1102124B

// date.cpp: Implement the Date class

#include "date.h"

inline int isleap(int y)
{return y%4 == 0 && y%100 != 0 || y%400 == 0;}

static int Dtab[2][13] =
{
{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
};

Date * Date::interval(const Date& d2)
{
static Date result;
int months, days, years, prev_month;

// Compute the interval - assume d1 precedes d2
years = d2.year - year;
months = d2.month - month;
days = d2.day - day;

// Do obvious corrections (days before months!)
//
// This is a loop in case the previous month is
// February, and days < -28.
prev_month = d2.month - 1;
while (days < 0)
{
// Borrow from the previous month
if (prev_month == 0)
prev_month = 12;
--months;
days += Dtab[isleap(d2.year)][prev_month--];
}

if (months < 0)
{
// Borrow from the previous year
--years;
months += 12;
}

/* Prepare output */
result.month = months;
result.day = days;
result.year = years;
return &result;
}