# billwanjohi's solution

## to Leap in the F# Track

Published at Dec 14 2018 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

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.

## Notes

The DateTime class in F# provides a built-in IsLeapYear method which you should pretend doesn't exist for the purposes of implementing this exercise.

## Running the tests

To run the tests, run the command `dotnet test` from within the exercise directory.

## Further information

For more detailed information about the F# track, including how to get help if you're having trouble, please visit the exercism.io F# language page.

## 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.

### LeapTest.fs

``````// This file was auto-generated based on version 1.4.0 of the canonical data.

module LeapTest

open FsUnit.Xunit
open Xunit

open Leap

[<Fact>]
let ``Year not divisible by 4: common year`` () =
leapYear 2015 |> should equal false

[<Fact(Skip = "Remove to run test")>]
let ``Year divisible by 4, not divisible by 100: leap year`` () =
leapYear 1996 |> should equal true

[<Fact(Skip = "Remove to run test")>]
let ``Year divisible by 100, not divisible by 400: common year`` () =
leapYear 2100 |> should equal false

[<Fact(Skip = "Remove to run test")>]
let ``Year divisible by 400: leap year`` () =
leapYear 2000 |> should equal true

[<Fact(Skip = "Remove to run test")>]
let ``Year divisible by 200, not divisible by 400: common year`` () =
leapYear 1800 |> should equal false``````
``````ï»¿module Leap

let leapYear (year: int): bool =
year % 4 = 0 && (year % 100 <> 0 || year % 400 = 0)``````