# Problem 1

Write a function `last` that returns the last element of a list. An empty list doesn't have a last element, therefore `last` must return a Maybe.

## Example

Cut and paste the following code into the online compiler http://elm-lang.org/try. Insert your implementation of `last` and test.

``````import Html exposing (text)
import Maybe

last : List a -> Maybe a
last xs =
Nothing

main =
case last [ 1, 2, 3, 4 ] of
Just a ->
text (toString a)

Nothing ->
text "No element found"
``````

Result:

``````4
``````

## Unit Test

Let's create a more complete test, checking `last` against an empty list and lists of different types. We will use `assertEqual` which takes a tuple, where the first element will hold a test condition and the second holds the expected result. This will allow us to test multiple conditions concisely.

Cut and paste the following code into the online compiler http://elm-lang.org/try. Insert your implementation of `last` and test.

``````import Html
import List
import Maybe

last : List a -> Maybe a
last xs =
Nothing

main : Html.Html a
main =
Html.text
<| case test of
0 ->

1 ->

x ->
"Your implementation failed " ++ (toString x) ++ " tests."

test : Int
test =
List.length
<| List.filter ((==) False)
[ last (1..4) == Just 4
, last [ 1 ] == Just 1
, last [] == Nothing
, last [ 'a', 'b', 'c' ] == Just 'c'
]

(..) : Int -> Int -> List Int
(..) start end =
List.range start end
``````

## Hints

Here are 2 hints to solve the problem:

1. Use recursion.
2. How can you leverage a List's `head` function to solve this problem?

## Solutions

After you've solved the problem, check out these solutions.