Published at Jul 13 2018
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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.

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.

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

Julia 1.0 and 0.7 are the only supported Julia versions on Exercism.
For the most part, the test suites and solutions should be compatible to 0.6, but you will have to change `using Test`

back to `using Base.Test`

in the `runtests.jl`

file.
Note that 0.7 and 1.0 are almost identical, except for deprecation warnings, which have all been removed in 1.0.

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

```
using Test
include("leap.jl")
@testset "Year not divisible by 4: common year" begin
@test !is_leap_year(2015)
end
@testset "Year divisible by 4, not divisible by 100: leap year" begin
@test is_leap_year(2016)
end
@testset "Year divisible by 100, not divisible by 400: common year" begin
@test !is_leap_year(2100)
end
@testset "Year divisible by 400: leap year" begin
@test is_leap_year(2000)
end
```

```
function is_leap_year(year::Int)
divisible(x) = year % x == 0
divisible(4) && (!divisible(100) || divisible(400))
end
```

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

- What compromises have been made?
- Are there new concepts here that you could read more about to improve your understanding?

## Community comments