From Scala to Haskell

Create a non-empty Option

Scala

val a: Option[Int] = Some(5)

Haskell

a :: Maybe Int
a = Just 5

Create an empty Option

Scala

val a: Option[Int] = None

Haskell

a :: Maybe Int
a = Nothing

Fold over an Option

Scala

Some(5).fold(0)(x => x * x)

Haskell

maybe 0 (\x -> x * x) (Just 5)

Map over an Option

Scala

Some(5).map(x => x * x)

Haskell

(\x -> x * x) <$> (Just 5)

<$> is not Maybe-specific: <$> is an infix operator for fmap. fmap is defined in terms of Functor and Maybe has an instance of Functor