update to current master againwip/T13904

1 files changed, 31 insertions, 0 deletions

diff --git a/libraries/base/GHC/Maybe.hs b/libraries/base/GHC/Maybe.hs
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+{-# LANGUAGE NoImplicitPrelude #-}
+
+-- | Maybe type
+module GHC.Maybe
+   ( Maybe (..)
+   )
+where
+
+import GHC.Integer () -- See Note [Depend on GHC.Integer] in GHC.Base
+import GHC.Classes
+
+default ()
+
+-------------------------------------------------------------------------------
+-- 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.
+--
+data  Maybe a  =  Nothing | Just a
+  deriving ( Eq  -- ^ @since 2.01
+           , Ord -- ^ @since 2.01
+           )