## C++, other, easter.cpp

``````/*
* @file
* @brief Determines the [Date of
* Easter](https://en.wikipedia.org/wiki/Date_of_Easter) after 1582
*
* @details
* The date of Easter is determined in each year through a calculation known as
* "computus." Easter is celebrated on the first Sunday after the Paschal full
* moon, which is the first full moon on or after 21 March. Determining this
* date in advance requires a correlation between the lunar months and the solar
* year, while also accounting for the month, date, and weekday of the Julian or
* Gregorian calendar. The complexity of the algorithm arises because of the
* desire to associate the date of Easter with the date of the Jewish feast of
* Passover which, Christians believe, is when Jesus was crucified.
*
*
* @author [AlternateWalls](https://github.com/AlternateWalls)
*/

#include <cassert>   /// for assert
#include <iostream>  /// for IO operations

/*
* @brief Contains information for Easter date
*/
class EasterYearMonthDay {
public:
uint64_t year;   ///< year Easter is on
uint64_t month;  ///< month Easter is on
uint64_t day;    ///< day Easter is on

EasterYearMonthDay(uint64_t newYear, uint64_t newMonth, uint64_t newDay) {
year = newYear;  // Assigns year to class
month = newMonth;
day = newDay;
}
};

/*
* @brief Function that finds the month and day of Easter
* @params param1 An int "y" of the year you want to find Easter on after
* 1582
* @returns An instance of the easterYearMonthDay calss that contains the
* information (Ex. 420 - 4/20 or April 20th)
*/
EasterYearMonthDay findEaster(uint64_t y) {
if (y > 1582) {
uint64_t a = y % 19;   // Year's location on Metonic Calendar
uint64_t b = y / 100;  // Century index
uint64_t c = y % 100;
uint64_t d = b / 4;
uint64_t e = b % 4;  // Takes into account leap years
uint64_t f = (b + 8) / 25;
uint64_t g = (b - f + 1) / 3;
uint64_t h = (19 * a + b - d - g + 15) %
30;  // Days from Mar. 21st until the full moon
uint64_t i = c / 4;
uint64_t k = c % 4;
uint64_t r =
(32 + 2 * e + 2 * i - h - k) %
7;  // The number of days from Paschal full moon to next Sunday
uint64_t m = (a + 11 * h + 22 * r) / 451;
uint64_t n = (h + r - 7 * m + 114) / 31;  // Month of Easter
uint64_t p = (h + r - 7 * m + 114) % 31;  // p + 1 is the day of Easter

// Assign values
EasterYearMonthDay date(
y, n, p + 1);  // Assign values to new instance of class

// Return date
return date;
} else {
EasterYearMonthDay date(0, 0, 0);

// Return date
return date;
}
}

/**
* @brief Self-test implementations
* @returns void
*/
static void test() {
// 2003 | April 20th
assert(findEaster(2003).month == 4);  // Should return true
assert(findEaster(2003).day == 20);   // Should return true

// 1910 | March 27th
assert(findEaster(1910).month == 3);  // Should return true
assert(findEaster(1910).day == 27);   // Should return true

// 1877 | April 1st
assert(findEaster(1877).month != 3);  // Should return true
assert(findEaster(1877).day != 22);   // Should return true

// 1400 | Invalid date
assert(findEaster(1400).month == 0);  // Should return true
assert(findEaster(1400).day == 0);    // Should return true
}

/**
* @brief Main function
* @returns 0 on exit
*/
int main() {
test();  // run self-test implementations
return 0;
}
``````