IO.Base

Documentation

module Control.Monad.Base

module Control.Monad.Trans.Control

data IO a :: * -> *

A value of type IO a is a computation which, when performed, does some I/O before returning a value of type a.

There is really only one way to "perform" an I/O action: bind it to Main.main in your program. When your program is run, the I/O will be performed. It isn't possible to perform I/O from an arbitrary function, unless that function is itself in the IO monad and called at some point, directly or indirectly, from Main.main.

IO is a monad, so IO actions can be combined using either the do-notation or the >> and >>= operations from the Monad class.

Instances

Monad IO

Since: 2.1

Methods

(>>=) :: IO a -> (a -> IO b) -> IO b

(>>) :: IO a -> IO b -> IO b

return :: a -> IO a

fail :: String -> IO a

Functor IO

Since: 2.1

Methods

fmap :: (a -> b) -> IO a -> IO b

(<$) :: a -> IO b -> IO a

MonadFix IO

Since: 2.1

Methods

mfix :: (a -> IO a) -> IO a

MonadFail IO

Since: 4.9.0.0

Methods

fail :: String -> IO a

Applicative IO

Since: 2.1

Methods

pure :: a -> IO a

(<*>) :: IO (a -> b) -> IO a -> IO b

liftA2 :: (a -> b -> c) -> IO a -> IO b -> IO c

(*>) :: IO a -> IO b -> IO b

(<*) :: IO a -> IO b -> IO a

Alternative IO

Since: 4.9.0.0

Methods

empty :: IO a

(<|>) :: IO a -> IO a -> IO a

some :: IO a -> IO [a]

many :: IO a -> IO [a]

MonadPlus IO

Since: 4.9.0.0

Methods

mzero :: IO a

mplus :: IO a -> IO a -> IO a

MonadIO IO

Since: 4.9.0.0

Methods

liftIO :: IO a -> IO a

MonadThrow IO

Methods

throwM :: Exception e => e -> IO a

MonadCatch IO

Methods

catch :: Exception e => IO a -> (e -> IO a) -> IO a

MonadMask IO

Methods

mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b

uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b

PrimMonad IO

Associated Types

type PrimState (IO :: * -> *) :: *

Methods

primitive :: (State# (PrimState IO) -> (#TupleRep [RuntimeRep], LiftedRep, State# (PrimState IO), a#)) -> IO a

PrimBase IO

Methods

internal :: IO a -> State# (PrimState IO) -> (#TupleRep [RuntimeRep], LiftedRep, State# (PrimState IO), a#)

Quasi IO

Methods

qNewName :: String -> IO Name

qReport :: Bool -> String -> IO ()

qRecover :: IO a -> IO a -> IO a

qLookupName :: Bool -> String -> IO (Maybe Name)

qReify :: Name -> IO Info

qReifyFixity :: Name -> IO (Maybe Fixity)

qReifyInstances :: Name -> [Type] -> IO [Dec]

qReifyRoles :: Name -> IO [Role]

qReifyAnnotations :: Data a => AnnLookup -> IO [a]

qReifyModule :: Module -> IO ModuleInfo

qReifyConStrictness :: Name -> IO [DecidedStrictness]

qLocation :: IO Loc

qRunIO :: IO a -> IO a

qAddDependentFile :: FilePath -> IO ()

qAddTopDecls :: [Dec] -> IO ()

qAddForeignFile :: ForeignSrcLang -> String -> IO ()

qAddModFinalizer :: Q () -> IO ()

qGetQ :: Typeable * a => IO (Maybe a)

qPutQ :: Typeable * a => a -> IO ()

qIsExtEnabled :: Extension -> IO Bool

qExtsEnabled :: IO [Extension]

MonadBaseControl IO IO

Associated Types

type StM (IO :: * -> *) a :: *

Methods

liftBaseWith :: (RunInBase IO IO -> IO a) -> IO a

restoreM :: StM IO a -> IO a

MonadBase IO IO

Methods

liftBase :: IO α -> IO α

Semigroup a => Semigroup (IO a)

Since: 4.10.0.0

Methods

(<>) :: IO a -> IO a -> IO a

sconcat :: NonEmpty (IO a) -> IO a

stimes :: Integral b => b -> IO a -> IO a

Monoid a => Monoid (IO a)

Since: 4.9.0.0

Methods

mempty :: IO a

mappend :: IO a -> IO a -> IO a

mconcat :: [IO a] -> IO a

type PrimState IO

type PrimState IO = RealWorld

type StM IO a

type StM IO a = a