Data.Strict.Maybe

Strict Maybe.

Same as the standard Haskell Maybe, but Just _|_ = _|_

Note that strict Maybe is not a monad since return _|_ >>= f = _|_ which is not necessarily the same as f _|_.

Documentation

data Maybe a

The type of strict optional values.

Constructors

Nothing

Just !a

Instances

Functor Maybe

Eq a => Eq (Maybe a)

Ord a => Ord (Maybe a)

Read a => Read (Maybe a)

Show a => Show (Maybe a)

isJust :: Maybe a -> Bool

Yields True iff the argument is of the form Just _.

isNothing :: Maybe a -> Bool

Yields True iff the argument is Nothing.

fromJust :: Maybe a -> a

Extracts the element out of a Just and throws an error if the argument is Nothing.

fromMaybe :: a -> Maybe a -> a

Given a default value and a Maybe, yield the default value if the Maybe argument is Nothing and extract the value out of the Just otherwise.

maybe :: b -> (a -> b) -> Maybe a -> b

Given a default value, a function and a Maybe value, yields the default value if the Maybe value is Nothing and applies the function to the value stored in the Just otherwise.