| The Maybe type, and associated operations.
|data Maybe a|
The Maybe type encapsulates an optional value. A value of type
Maybe a either contains a value of type a (represented as Just a),
or it is empty (represented as Nothing). Using Maybe is a good way to
deal with errors or exceptional cases without resorting to drastic
measures such as error.
The Maybe type is also a monad. It is a simple kind of error
monad, where all errors are represented by Nothing. A richer
error monad can be built using the Either type.
|maybe :: b -> (a -> b) -> Maybe a -> b|
|isJust :: Maybe a -> Bool|
|isNothing :: Maybe a -> Bool|
|fromJust :: Maybe a -> a|
|fromMaybe :: a -> Maybe a -> a|
|listToMaybe :: [a] -> Maybe a|
|maybeToList :: Maybe a -> [a]|
|catMaybes :: [Maybe a] -> [a]|
|mapMaybe :: (a -> Maybe b) -> [a] -> [b]|
|Produced by Haddock version 0.4|