# dennisdevelops's solution

## to Leap in the Swift Track

Published at Jun 16 2021 · 0 comments
Instructions
Test suite
Solution

Given a year, report if it is a leap year.

The tricky thing here is that a leap year in the Gregorian calendar occurs:

``````on every year that is evenly divisible by 4
except every year that is evenly divisible by 100
unless the year is also evenly divisible by 400
``````

For example, 1997 is not a leap year, but 1996 is. 1900 is not a leap year, but 2000 is.

If your language provides a method in the standard library that does this look-up, pretend it doesn't exist and implement it yourself.

## Notes

Though our exercise adopts some very simple rules, there is more to learn!

For a delightful, four minute explanation of the whole leap year phenomenon, go watch this youtube video.

## Setup

Go through the project setup instructions for Xcode using Swift:

http://exercism.io/languages/swift
http://exercism.io/languages/swift/tests

Notably from the source directory:

`swift test` runs tests
`swift package generate-xcodeproj` creates an Xcode project

## Source

JavaRanch Cattle Drive, exercise 3 http://www.javaranch.com/leap.jsp

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### LeapTests.swift

``````import XCTest
@testable import Leap

class LeapTests: XCTestCase {

func testVanillaLeapYear() {
let year = Year(calendarYear: 1996)
XCTAssertTrue(year.isLeapYear)
}

func testAnyOldYear() {
let year = Year(calendarYear: 1997)
XCTAssertFalse(year.isLeapYear)
}

func testCentury() {
let year = Year(calendarYear: 1900)
XCTAssertFalse(year.isLeapYear)
}

func testExceptionalCentury() {
let year = Year(calendarYear: 2400)
XCTAssertTrue(year.isLeapYear)
}

static var allTests: [(String, (LeapTests) -> () throws -> Void)] {
return [
("testVanillaLeapYear", testVanillaLeapYear),
("testAnyOldYear", testAnyOldYear),
("testCentury", testCentury),
("testExceptionalCentury", testExceptionalCentury),
]
}
}``````

### LinuxMain.swift

``````import XCTest
@testable import LeapTests

XCTMain([
testCase(LeapTests.allTests),
])``````
``````//Solution goes in Sources

/*
Objective: given a calendarYear, report if it is a leap calendarYear

Leap years occur:
on every calendarYear that is evenly divisible by 4
except every calendarYear that is evenly divisible by 100
unless the calendarYear is also evenly divisible by 400
*/

/*
function that doesn't satisfy test requirements
func isLeapYear(calendarYear: Int) -> Bool {
if ((calendarYear % 4 == 0) && (calendarYear % 100 != 0) || (calendarYear % 400 == 0)) {
return true
} else {
return false
}
}
*/

//struct
struct Year {
let isLeapYear: Bool

init(calendarYear: Int) {
self.isLeapYear = calendarYear.isMultiple(of: 4) && !calendarYear.isMultiple(of: 100) || calendarYear.isMultiple(of: 400)
}
}``````