Haskell - What is Control.Applicative.Alternative good for?

Question

I was looking at the Applicative class within Haskell libraries and stumbled across Alternative.

What is this class good for? A google sear

Answer 1

It's commonly used with parser combinators. For example, if space is a parser combinator that matches a single whitespace character, many space would be one that would match consecutive whitespace.

I can agree that it's slightly out of place in Control.Applicative, though.

Answer 2

Sometimes the <|> operator is quite useful:

foldl1 (<|>) [Nothing, Just 5, Just 3]
-- Just 5