Movatterモバイル変換

{-# LANGUAGE NoImplicitPrelude #-}{-# OPTIONS_HADDOCK not-home #-}-- | Maybe typemoduleGHC.Maybe(Maybe(..))whereimportGHC.Integer()-- See Note [Depend on GHC.Integer] in GHC.BaseimportGHC.Classesdefault()--------------------------------------------------------------------------------- Maybe type--------------------------------------------------------------------------------- | 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 'Prelude.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 'Data.Either.Either' type.--dataMaybea=Nothing|Justaderiving(Eq-- ^ @since 2.01,Ord-- ^ @since 2.01)