
Data.Maybe  Portability  portable  Stability  experimental  Maintainer  libraries@haskell.org 





Description 
The Maybe type, and associated operations.


Synopsis 



Documentation 

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.  Constructors   Instances  


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] 

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