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to Leap in the F# Track

Published at Nov 04 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.

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.

Autoformatting the code

F# source code can be formatted with the Fantomas tool.

After installing it with dotnet tool restore, run dotnet fantomas . to format code within the current 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

LeapTests.fs

// This file was auto-generated based on version 1.6.0 of the canonical data.

module LeapTests

open FsUnit.Xunit
open Xunit

open Leap

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

[<Fact(Skip = "Remove this Skip property to run this test")>]
let ``Year divisible by 2, not divisible by 4 in common year`` () =
    leapYear 1970 |> should equal false

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

[<Fact(Skip = "Remove this Skip property to run this test")>]
let ``Year divisible by 4 and 5 is still a leap year`` () =
    leapYear 1960 |> should equal true

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

[<Fact(Skip = "Remove this Skip property to run this test")>]
let ``Year divisible by 100 but not by 3 is still not a leap year`` () =
    leapYear 1900 |> should equal false

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

[<Fact(Skip = "Remove this Skip property to run this test")>]
let ``Year divisible by 400 but not by 125 is still a leap year`` () =
    leapYear 2400 |> should equal true

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

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

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