From Scala to Haskell
Option
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