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## to Leap in the PureScript Track

Published at May 11 2020 · 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.

## 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.

### Main.purs

``````module Test.Main where

import Prelude

import Effect (Effect)
import Test.Unit (TestSuite, suite, test)
import Test.Unit.Main (runTest)
import Test.Unit.Assert as Assert
import Leap as Leap

main :: Effect Unit
main = runTest suites

suites :: TestSuite
suites = do
suite "Leap.isLeapYear" do
test "leap year" do
Assert.equal true \$ Leap.isLeapYear 1996
test "non-leap year" do
Assert.equal false \$ Leap.isLeapYear 1997
test "non-leap even year" do
Assert.equal false \$ Leap.isLeapYear 1998
test "century" do
Assert.equal false \$ Leap.isLeapYear 1900
test "second century" do
Assert.equal false \$ Leap.isLeapYear 1800
test "fourth century" do
Assert.equal true \$ Leap.isLeapYear 2400
test "y2k" do
Assert.equal true \$ Leap.isLeapYear 2000``````
``````module Leap where

import Prelude

isLeapYear :: Int -> Boolean
isLeapYear year = div4 && (not div100 || div400)
where
divisible y x = (y `mod` x) == 0

div4 = divisible year 4

div100 = divisible year 100

div400 = divisible year 400``````