| Safe Haskell | Safe | 
|---|
Maybe
Documentation
listToMaybe :: [a] -> Maybe aSource
The listToMaybe function returns Nothing on an empty list
 or Just aa is the first element of the list.
maybeToList :: Maybe a -> [a]Source
The maybeToList function returns an empty list when given
 Nothing or a singleton list when not given Nothing.
The Maybe type encapsulates an optional value.  A value of type
 Maybe aa (represented as Just aNothing).  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.