/************************************************
* leap year -- a program that calculates	*
*	whether or not a given year is a leap	*
*	year					*
*						*
* Author:  Dan Emmons				*
*						*
* Purpose:  This was written in order to	*
*	complete Exercise 6-4 in the book	*
*	"Practical C++ Programming" by Steve	*
*	Oualline				*
************************************************/

#include <iostream>
#include <assert.h>

int year;				// the year provided by the user
float year_divided4;			// the year divided by 4
float year_divided100;			// the year divided by 100
float year_divided400;			// the year divided by 400
int int_divided4;			// year_divided4 converted to an integer
int int_divided100;			// year_divided100 converted to an integer
int int_divided400;			// year_divided400 converted to an integer
float check4;				// check for divisibility by 4
float check100;				// check for divisibility by 100
float check400;				// check for divisibility by 400


int main()
{
	std::cout << "Enter a year to see if it is a leap year or enter 0 (zero) to exit: ";
	std::cin >> year;

	if(year <= 0){
		std::cout << "You must enter a positive number: ";
		std::cin >> year;
	}

	if(year > 30000){
		std::cout << "The year is too far into the future.\n";
		std::cout << "Please enter another year: ";
		std::cin >> year;
	}

	while(year != 0){

		year_divided4 = year / 4.00;
		year_divided100 = year / 100.00;
		year_divided400 = year / 400.00;

		int_divided4 = (year / 4);
		int_divided100 = (year / 100);
		int_divided400 = (year / 400);

		check4 = year_divided4 - int_divided4;
		check100 = year_divided100 - int_divided100;
		check400 = year_divided400 - int_divided400;

		assert(check4 >= 0);
		assert(check4 < 1);
		assert(check100 >= 0);
		assert(check100 < 1);
		assert(check400 >= 0);
		assert(check400 < 1);

		if(check4 != 0)
			std::cout << '\n' << year << " is not a leap year.\n\n";
		
		if((check4 == 0) && (check100 != 0))
			std::cout << '\n' << year << " is a leap year.\n\n";

		if((check4 == 0) && (check100 == 0)){

			if(check400 == 0)
				std::cout << '\n' << year << " is a leap year.\n\n";

			if(check400 != 0)
				std::cout << '\n' << year << " is not a leap year.\n\n";
		}
		std::cout << "Enter another year or enter 0 (zero) to exit: ";
		std::cin >> year;
	}

	return (0);
}