-- Hoogle documentation, generated by Haddock -- See Hoogle, http://www.haskell.org/hoogle/ -- | Concrete functor and monad transformers -- -- A portable library of functor and monad transformers, inspired by the -- paper -- -- -- -- This package contains: -- -- -- -- The package can be used on its own in portable Haskell code, in which -- case operations need to be manually lifted through transformer stacks -- (see Control.Monad.Trans.Class for some examples). -- Alternatively, it can be used with the non-portable monad classes in -- the mtl or monads-tf packages, which automatically -- lift operations introduced by monad transformers through other -- transformers. @package transformers @version 0.5.6.2 -- | Making functors with an Applicative instance that performs -- actions in the reverse order. module Control.Applicative.Backwards -- | The same functor, but with an Applicative instance that -- performs actions in the reverse order. newtype Backwards f a Backwards :: f a -> Backwards f a [forwards] :: Backwards f a -> f a instance Data.Functor.Classes.Eq1 f => Data.Functor.Classes.Eq1 (Control.Applicative.Backwards.Backwards f) instance Data.Functor.Classes.Ord1 f => Data.Functor.Classes.Ord1 (Control.Applicative.Backwards.Backwards f) instance Data.Functor.Classes.Read1 f => Data.Functor.Classes.Read1 (Control.Applicative.Backwards.Backwards f) instance Data.Functor.Classes.Show1 f => Data.Functor.Classes.Show1 (Control.Applicative.Backwards.Backwards f) instance (Data.Functor.Classes.Eq1 f, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Applicative.Backwards.Backwards f a) instance (Data.Functor.Classes.Ord1 f, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Applicative.Backwards.Backwards f a) instance (Data.Functor.Classes.Read1 f, GHC.Read.Read a) => GHC.Read.Read (Control.Applicative.Backwards.Backwards f a) instance (Data.Functor.Classes.Show1 f, GHC.Show.Show a) => GHC.Show.Show (Control.Applicative.Backwards.Backwards f a) instance GHC.Base.Functor f => GHC.Base.Functor (Control.Applicative.Backwards.Backwards f) instance GHC.Base.Applicative f => GHC.Base.Applicative (Control.Applicative.Backwards.Backwards f) instance GHC.Base.Alternative f => GHC.Base.Alternative (Control.Applicative.Backwards.Backwards f) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Applicative.Backwards.Backwards f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Applicative.Backwards.Backwards f) instance Data.Functor.Contravariant.Contravariant f => Data.Functor.Contravariant.Contravariant (Control.Applicative.Backwards.Backwards f) -- | Signatures for monad operations that require specialized lifting. Each -- signature has a uniformity property that the lifting should satisfy. module Control.Monad.Signatures -- | Signature of the callCC operation, introduced in -- Control.Monad.Trans.Cont. Any lifting function -- liftCallCC should satisfy -- -- type CallCC m a b = ((a -> m b) -> m a) -> m a -- | Signature of the catchE operation, introduced in -- Control.Monad.Trans.Except. Any lifting function -- liftCatch should satisfy -- -- type Catch e m a = m a -> (e -> m a) -> m a -- | Signature of the listen operation, introduced in -- Control.Monad.Trans.Writer. Any lifting function -- liftListen should satisfy -- -- type Listen w m a = m a -> m (a, w) -- | Signature of the pass operation, introduced in -- Control.Monad.Trans.Writer. Any lifting function -- liftPass should satisfy -- -- type Pass w m a = m (a, w -> w) -> m a -- | The class of monad transformers. -- -- A monad transformer makes a new monad out of an existing monad, such -- that computations of the old monad may be embedded in the new one. To -- construct a monad with a desired set of features, one typically starts -- with a base monad, such as Identity, [] or IO, -- and applies a sequence of monad transformers. module Control.Monad.Trans.Class -- | The class of monad transformers. Instances should satisfy the -- following laws, which state that lift is a monad -- transformation: -- -- class MonadTrans t -- | Lift a computation from the argument monad to the constructed monad. lift :: (MonadTrans t, Monad m) => m a -> t m a -- | Continuation monads. -- -- Delimited continuation operators are taken from Kenichi Asai and Oleg -- Kiselyov's tutorial at CW 2011, "Introduction to programming with -- shift and reset" -- (http://okmij.org/ftp/continuations/#tutorial). module Control.Monad.Trans.Cont -- | Continuation monad. Cont r a is a CPS ("continuation-passing -- style") computation that produces an intermediate result of type -- a within a CPS computation whose final result type is -- r. -- -- The return function simply creates a continuation which -- passes the value on. -- -- The >>= operator adds the bound function into the -- continuation chain. type Cont r = ContT r Identity -- | Construct a continuation-passing computation from a function. (The -- inverse of runCont) cont :: ((a -> r) -> r) -> Cont r a -- | The result of running a CPS computation with a given final -- continuation. (The inverse of cont) runCont :: Cont r a -> (a -> r) -> r -- | The result of running a CPS computation with the identity as the final -- continuation. -- -- evalCont :: Cont r r -> r -- | Apply a function to transform the result of a continuation-passing -- computation. -- -- mapCont :: (r -> r) -> Cont r a -> Cont r a -- | Apply a function to transform the continuation passed to a CPS -- computation. -- -- withCont :: ((b -> r) -> a -> r) -> Cont r a -> Cont r b -- | reset m delimits the continuation of any shift -- inside m. -- -- reset :: Cont r r -> Cont r' r -- | shift f captures the continuation up to the nearest -- enclosing reset and passes it to f: -- -- shift :: ((a -> r) -> Cont r r) -> Cont r a -- | The continuation monad transformer. Can be used to add continuation -- handling to any type constructor: the Monad instance and most -- of the operations do not require m to be a monad. -- -- ContT is not a functor on the category of monads, and many -- operations cannot be lifted through it. newtype ContT r m a ContT :: ((a -> m r) -> m r) -> ContT r m a [runContT] :: ContT r m a -> (a -> m r) -> m r -- | The result of running a CPS computation with return as the -- final continuation. -- -- evalContT :: Monad m => ContT r m r -> m r -- | Apply a function to transform the result of a continuation-passing -- computation. This has a more restricted type than the map -- operations for other monad transformers, because ContT does not -- define a functor in the category of monads. -- -- mapContT :: (m r -> m r) -> ContT r m a -> ContT r m a -- | Apply a function to transform the continuation passed to a CPS -- computation. -- -- withContT :: ((b -> m r) -> a -> m r) -> ContT r m a -> ContT r m b -- | callCC (call-with-current-continuation) calls its argument -- function, passing it the current continuation. It provides an escape -- continuation mechanism for use with continuation monads. Escape -- continuations one allow to abort the current computation and return a -- value immediately. They achieve a similar effect to throwE and -- catchE within an ExceptT monad. The advantage of this -- function over calling return is that it makes the continuation -- explicit, allowing more flexibility and better control. -- -- The standard idiom used with callCC is to provide a -- lambda-expression to name the continuation. Then calling the named -- continuation anywhere within its scope will escape from the -- computation, even if it is many layers deep within nested -- computations. callCC :: ((a -> ContT r m b) -> ContT r m a) -> ContT r m a -- | resetT m delimits the continuation of any -- shiftT inside m. -- -- resetT :: Monad m => ContT r m r -> ContT r' m r -- | shiftT f captures the continuation up to the nearest -- enclosing resetT and passes it to f: -- -- shiftT :: Monad m => ((a -> m r) -> ContT r m r) -> ContT r m a -- | liftLocal ask local yields a local function -- for ContT r m. liftLocal :: Monad m => m r' -> ((r' -> r') -> m r -> m r) -> (r' -> r') -> ContT r m a -> ContT r m a instance forall k (r :: k) (m :: k -> *). GHC.Base.Functor (Control.Monad.Trans.Cont.ContT r m) instance forall k (r :: k) (m :: k -> *). GHC.Base.Applicative (Control.Monad.Trans.Cont.ContT r m) instance forall k (r :: k) (m :: k -> *). GHC.Base.Monad (Control.Monad.Trans.Cont.ContT r m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Cont.ContT r m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Cont.ContT r) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Cont.ContT r m) -- | This monad transformer adds the ability to fail or throw exceptions to -- a monad. -- -- A sequence of actions succeeds, producing a value, only if all the -- actions in the sequence are successful. If one fails with an error, -- the rest of the sequence is skipped and the composite action fails -- with that error. -- -- If the value of the error is not required, the variant in -- Control.Monad.Trans.Maybe may be used instead. -- -- Note: This module will be removed in a future release. Instead, -- use Control.Monad.Trans.Except, which does not restrict the -- exception type, and also includes a base exception monad. -- | Deprecated: Use Control.Monad.Trans.Except instead module Control.Monad.Trans.Error -- | An exception to be thrown. -- -- Minimal complete definition: noMsg or strMsg. class Error a -- | Creates an exception without a message. The default implementation is -- strMsg "". noMsg :: Error a => a -- | Creates an exception with a message. The default implementation of -- strMsg s is noMsg. strMsg :: Error a => String -> a -- | Workaround so that we can have a Haskell 98 instance Error -- String. class ErrorList a listMsg :: ErrorList a => String -> [a] -- | The error monad transformer. It can be used to add error handling to -- other monads. -- -- The ErrorT Monad structure is parameterized over two things: -- -- -- -- The return function yields a successful computation, while -- >>= sequences two subcomputations, failing on the first -- error. newtype ErrorT e m a ErrorT :: m (Either e a) -> ErrorT e m a [runErrorT] :: ErrorT e m a -> m (Either e a) -- | Map the unwrapped computation using the given function. -- -- mapErrorT :: (m (Either e a) -> n (Either e' b)) -> ErrorT e m a -> ErrorT e' n b -- | Signal an error value e. -- -- throwError :: Monad m => e -> ErrorT e m a -- | Handle an error. -- -- catchError :: Monad m => ErrorT e m a -> (e -> ErrorT e m a) -> ErrorT e m a -- | Lift a callCC operation to the new monad. liftCallCC :: CallCC m (Either e a) (Either e b) -> CallCC (ErrorT e m) a b -- | Lift a listen operation to the new monad. liftListen :: Monad m => Listen w m (Either e a) -> Listen w (ErrorT e m) a -- | Lift a pass operation to the new monad. liftPass :: Monad m => Pass w m (Either e a) -> Pass w (ErrorT e m) a instance (GHC.Classes.Eq e, Data.Functor.Classes.Eq1 m) => Data.Functor.Classes.Eq1 (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Classes.Ord e, Data.Functor.Classes.Ord1 m) => Data.Functor.Classes.Ord1 (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Read.Read e, Data.Functor.Classes.Read1 m) => Data.Functor.Classes.Read1 (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Show.Show e, Data.Functor.Classes.Show1 m) => Data.Functor.Classes.Show1 (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Classes.Eq e, Data.Functor.Classes.Eq1 m, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Monad.Trans.Error.ErrorT e m a) instance (GHC.Classes.Ord e, Data.Functor.Classes.Ord1 m, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Monad.Trans.Error.ErrorT e m a) instance (GHC.Read.Read e, Data.Functor.Classes.Read1 m, GHC.Read.Read a) => GHC.Read.Read (Control.Monad.Trans.Error.ErrorT e m a) instance (GHC.Show.Show e, Data.Functor.Classes.Show1 m, GHC.Show.Show a) => GHC.Show.Show (Control.Monad.Trans.Error.ErrorT e m a) instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Error.ErrorT e m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Monad.Trans.Error.ErrorT e f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Monad.Trans.Error.ErrorT e f) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Base.Functor m, GHC.Base.Monad m, Control.Monad.Trans.Error.Error e) => GHC.Base.Alternative (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Base.Monad m, Control.Monad.Trans.Error.Error e) => GHC.Base.Monad (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Base.Monad m, Control.Monad.Trans.Error.Error e) => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Error.ErrorT e m) instance (GHC.Base.Monad m, Control.Monad.Trans.Error.Error e) => GHC.Base.MonadPlus (Control.Monad.Trans.Error.ErrorT e m) instance (Control.Monad.Fix.MonadFix m, Control.Monad.Trans.Error.Error e) => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Error.ErrorT e m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Error.ErrorT e) instance (Control.Monad.Trans.Error.Error e, Control.Monad.IO.Class.MonadIO m) => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Error.ErrorT e m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.Error.ErrorT e m) instance Control.Monad.Trans.Error.ErrorList a => Control.Monad.Trans.Error.Error [a] instance Control.Monad.Trans.Error.ErrorList GHC.Types.Char instance Control.Monad.Trans.Error.Error e => GHC.Base.Alternative (Data.Either.Either e) instance Control.Monad.Trans.Error.Error e => GHC.Base.MonadPlus (Data.Either.Either e) instance Control.Monad.Trans.Error.Error GHC.IO.Exception.IOException -- | This monad transformer extends a monad with the ability to throw -- exceptions. -- -- A sequence of actions terminates normally, producing a value, only if -- none of the actions in the sequence throws an exception. If one throws -- an exception, the rest of the sequence is skipped and the composite -- action exits with that exception. -- -- If the value of the exception is not required, the variant in -- Control.Monad.Trans.Maybe may be used instead. module Control.Monad.Trans.Except -- | The parameterizable exception monad. -- -- Computations are either exceptions or normal values. -- -- The return function returns a normal value, while -- >>= exits on the first exception. For a variant that -- continues after an error and collects all the errors, see -- Errors. type Except e = ExceptT e Identity -- | Constructor for computations in the exception monad. (The inverse of -- runExcept). except :: Monad m => Either e a -> ExceptT e m a -- | Extractor for computations in the exception monad. (The inverse of -- except). runExcept :: Except e a -> Either e a -- | Map the unwrapped computation using the given function. -- -- mapExcept :: (Either e a -> Either e' b) -> Except e a -> Except e' b -- | Transform any exceptions thrown by the computation using the given -- function (a specialization of withExceptT). withExcept :: (e -> e') -> Except e a -> Except e' a -- | A monad transformer that adds exceptions to other monads. -- -- ExceptT constructs a monad parameterized over two things: -- -- -- -- The return function yields a computation that produces the -- given value, while >>= sequences two subcomputations, -- exiting on the first exception. newtype ExceptT e m a ExceptT :: m (Either e a) -> ExceptT e m a -- | The inverse of ExceptT. runExceptT :: ExceptT e m a -> m (Either e a) -- | Map the unwrapped computation using the given function. -- -- mapExceptT :: (m (Either e a) -> n (Either e' b)) -> ExceptT e m a -> ExceptT e' n b -- | Transform any exceptions thrown by the computation using the given -- function. withExceptT :: Functor m => (e -> e') -> ExceptT e m a -> ExceptT e' m a -- | Signal an exception value e. -- -- throwE :: Monad m => e -> ExceptT e m a -- | Handle an exception. -- -- catchE :: Monad m => ExceptT e m a -> (e -> ExceptT e' m a) -> ExceptT e' m a -- | Lift a callCC operation to the new monad. liftCallCC :: CallCC m (Either e a) (Either e b) -> CallCC (ExceptT e m) a b -- | Lift a listen operation to the new monad. liftListen :: Monad m => Listen w m (Either e a) -> Listen w (ExceptT e m) a -- | Lift a pass operation to the new monad. liftPass :: Monad m => Pass w m (Either e a) -> Pass w (ExceptT e m) a instance (GHC.Classes.Eq e, Data.Functor.Classes.Eq1 m) => Data.Functor.Classes.Eq1 (Control.Monad.Trans.Except.ExceptT e m) instance (GHC.Classes.Ord e, Data.Functor.Classes.Ord1 m) => Data.Functor.Classes.Ord1 (Control.Monad.Trans.Except.ExceptT e m) instance (GHC.Read.Read e, Data.Functor.Classes.Read1 m) => Data.Functor.Classes.Read1 (Control.Monad.Trans.Except.ExceptT e m) instance (GHC.Show.Show e, Data.Functor.Classes.Show1 m) => Data.Functor.Classes.Show1 (Control.Monad.Trans.Except.ExceptT e m) instance (GHC.Classes.Eq e, Data.Functor.Classes.Eq1 m, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Monad.Trans.Except.ExceptT e m a) instance (GHC.Classes.Ord e, Data.Functor.Classes.Ord1 m, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Monad.Trans.Except.ExceptT e m a) instance (GHC.Read.Read e, Data.Functor.Classes.Read1 m, GHC.Read.Read a) => GHC.Read.Read (Control.Monad.Trans.Except.ExceptT e m a) instance (GHC.Show.Show e, Data.Functor.Classes.Show1 m, GHC.Show.Show a) => GHC.Show.Show (Control.Monad.Trans.Except.ExceptT e m a) instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Except.ExceptT e m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Monad.Trans.Except.ExceptT e f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Monad.Trans.Except.ExceptT e f) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.Except.ExceptT e m) instance (GHC.Base.Functor m, GHC.Base.Monad m, GHC.Base.Monoid e) => GHC.Base.Alternative (Control.Monad.Trans.Except.ExceptT e m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.Except.ExceptT e m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Except.ExceptT e m) instance (GHC.Base.Monad m, GHC.Base.Monoid e) => GHC.Base.MonadPlus (Control.Monad.Trans.Except.ExceptT e m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Except.ExceptT e m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Except.ExceptT e) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Except.ExceptT e m) instance Control.Monad.Zip.MonadZip m => Control.Monad.Zip.MonadZip (Control.Monad.Trans.Except.ExceptT e m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.Except.ExceptT e m) -- | The identity monad transformer. -- -- This is useful for functions parameterized by a monad transformer. module Control.Monad.Trans.Identity -- | The trivial monad transformer, which maps a monad to an equivalent -- monad. newtype IdentityT f a IdentityT :: f a -> IdentityT f a [runIdentityT] :: IdentityT f a -> f a -- | Lift a unary operation to the new monad. mapIdentityT :: (m a -> n b) -> IdentityT m a -> IdentityT n b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m a -> Catch e (IdentityT m) a -- | Lift a callCC operation to the new monad. liftCallCC :: CallCC m a b -> CallCC (IdentityT m) a b instance Data.Functor.Classes.Eq1 f => Data.Functor.Classes.Eq1 (Control.Monad.Trans.Identity.IdentityT f) instance Data.Functor.Classes.Ord1 f => Data.Functor.Classes.Ord1 (Control.Monad.Trans.Identity.IdentityT f) instance Data.Functor.Classes.Read1 f => Data.Functor.Classes.Read1 (Control.Monad.Trans.Identity.IdentityT f) instance Data.Functor.Classes.Show1 f => Data.Functor.Classes.Show1 (Control.Monad.Trans.Identity.IdentityT f) instance (Data.Functor.Classes.Eq1 f, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Monad.Trans.Identity.IdentityT f a) instance (Data.Functor.Classes.Ord1 f, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Monad.Trans.Identity.IdentityT f a) instance (Data.Functor.Classes.Read1 f, GHC.Read.Read a) => GHC.Read.Read (Control.Monad.Trans.Identity.IdentityT f a) instance (Data.Functor.Classes.Show1 f, GHC.Show.Show a) => GHC.Show.Show (Control.Monad.Trans.Identity.IdentityT f a) instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Identity.IdentityT m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Monad.Trans.Identity.IdentityT f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Monad.Trans.Identity.IdentityT f) instance GHC.Base.Applicative m => GHC.Base.Applicative (Control.Monad.Trans.Identity.IdentityT m) instance GHC.Base.Alternative m => GHC.Base.Alternative (Control.Monad.Trans.Identity.IdentityT m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.Identity.IdentityT m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Identity.IdentityT m) instance GHC.Base.MonadPlus m => GHC.Base.MonadPlus (Control.Monad.Trans.Identity.IdentityT m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Identity.IdentityT m) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Identity.IdentityT m) instance Control.Monad.Zip.MonadZip m => Control.Monad.Zip.MonadZip (Control.Monad.Trans.Identity.IdentityT m) instance Control.Monad.Trans.Class.MonadTrans Control.Monad.Trans.Identity.IdentityT instance Data.Functor.Contravariant.Contravariant f => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.Identity.IdentityT f) -- | The ListT monad transformer, adding backtracking to a given monad, -- which must be commutative. -- | Deprecated: This transformer is invalid on most monads module Control.Monad.Trans.List -- | Parameterizable list monad, with an inner monad. -- -- Note: this does not yield a monad unless the argument monad is -- commutative. newtype ListT m a ListT :: m [a] -> ListT m a [runListT] :: ListT m a -> m [a] -- | Map between ListT computations. -- -- mapListT :: (m [a] -> n [b]) -> ListT m a -> ListT n b -- | Lift a callCC operation to the new monad. liftCallCC :: CallCC m [a] [b] -> CallCC (ListT m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m [a] -> Catch e (ListT m) a instance Data.Functor.Classes.Eq1 m => Data.Functor.Classes.Eq1 (Control.Monad.Trans.List.ListT m) instance Data.Functor.Classes.Ord1 m => Data.Functor.Classes.Ord1 (Control.Monad.Trans.List.ListT m) instance Data.Functor.Classes.Read1 m => Data.Functor.Classes.Read1 (Control.Monad.Trans.List.ListT m) instance Data.Functor.Classes.Show1 m => Data.Functor.Classes.Show1 (Control.Monad.Trans.List.ListT m) instance (Data.Functor.Classes.Eq1 m, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Monad.Trans.List.ListT m a) instance (Data.Functor.Classes.Ord1 m, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Monad.Trans.List.ListT m a) instance (Data.Functor.Classes.Read1 m, GHC.Read.Read a) => GHC.Read.Read (Control.Monad.Trans.List.ListT m a) instance (Data.Functor.Classes.Show1 m, GHC.Show.Show a) => GHC.Show.Show (Control.Monad.Trans.List.ListT m a) instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.List.ListT m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Monad.Trans.List.ListT f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Monad.Trans.List.ListT f) instance GHC.Base.Applicative m => GHC.Base.Applicative (Control.Monad.Trans.List.ListT m) instance GHC.Base.Applicative m => GHC.Base.Alternative (Control.Monad.Trans.List.ListT m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.List.ListT m) instance GHC.Base.Monad m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.List.ListT m) instance GHC.Base.Monad m => GHC.Base.MonadPlus (Control.Monad.Trans.List.ListT m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.List.ListT m) instance Control.Monad.Trans.Class.MonadTrans Control.Monad.Trans.List.ListT instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.List.ListT m) instance Control.Monad.Zip.MonadZip m => Control.Monad.Zip.MonadZip (Control.Monad.Trans.List.ListT m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.List.ListT m) -- | The MaybeT monad transformer extends a monad with the ability -- to exit the computation without returning a value. -- -- A sequence of actions produces a value only if all the actions in the -- sequence do. If one exits, the rest of the sequence is skipped and the -- composite action exits. -- -- For a variant allowing a range of exception values, see -- Control.Monad.Trans.Except. module Control.Monad.Trans.Maybe -- | The parameterizable maybe monad, obtained by composing an arbitrary -- monad with the Maybe monad. -- -- Computations are actions that may produce a value or exit. -- -- The return function yields a computation that produces that -- value, while >>= sequences two subcomputations, exiting -- if either computation does. newtype MaybeT m a MaybeT :: m (Maybe a) -> MaybeT m a [runMaybeT] :: MaybeT m a -> m (Maybe a) -- | Transform the computation inside a MaybeT. -- -- mapMaybeT :: (m (Maybe a) -> n (Maybe b)) -> MaybeT m a -> MaybeT n b -- | Convert a MaybeT computation to ExceptT, with a default -- exception value. maybeToExceptT :: Functor m => e -> MaybeT m a -> ExceptT e m a -- | Convert a ExceptT computation to MaybeT, discarding the -- value of any exception. exceptToMaybeT :: Functor m => ExceptT e m a -> MaybeT m a -- | Lift a callCC operation to the new monad. liftCallCC :: CallCC m (Maybe a) (Maybe b) -> CallCC (MaybeT m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (Maybe a) -> Catch e (MaybeT m) a -- | Lift a listen operation to the new monad. liftListen :: Monad m => Listen w m (Maybe a) -> Listen w (MaybeT m) a -- | Lift a pass operation to the new monad. liftPass :: Monad m => Pass w m (Maybe a) -> Pass w (MaybeT m) a instance Data.Functor.Classes.Eq1 m => Data.Functor.Classes.Eq1 (Control.Monad.Trans.Maybe.MaybeT m) instance Data.Functor.Classes.Ord1 m => Data.Functor.Classes.Ord1 (Control.Monad.Trans.Maybe.MaybeT m) instance Data.Functor.Classes.Read1 m => Data.Functor.Classes.Read1 (Control.Monad.Trans.Maybe.MaybeT m) instance Data.Functor.Classes.Show1 m => Data.Functor.Classes.Show1 (Control.Monad.Trans.Maybe.MaybeT m) instance (Data.Functor.Classes.Eq1 m, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Monad.Trans.Maybe.MaybeT m a) instance (Data.Functor.Classes.Ord1 m, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Monad.Trans.Maybe.MaybeT m a) instance (Data.Functor.Classes.Read1 m, GHC.Read.Read a) => GHC.Read.Read (Control.Monad.Trans.Maybe.MaybeT m a) instance (Data.Functor.Classes.Show1 m, GHC.Show.Show a) => GHC.Show.Show (Control.Monad.Trans.Maybe.MaybeT m a) instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Maybe.MaybeT m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Monad.Trans.Maybe.MaybeT f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Monad.Trans.Maybe.MaybeT f) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.Maybe.MaybeT m) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Alternative (Control.Monad.Trans.Maybe.MaybeT m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.Maybe.MaybeT m) instance GHC.Base.Monad m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Maybe.MaybeT m) instance GHC.Base.Monad m => GHC.Base.MonadPlus (Control.Monad.Trans.Maybe.MaybeT m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Maybe.MaybeT m) instance Control.Monad.Trans.Class.MonadTrans Control.Monad.Trans.Maybe.MaybeT instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Maybe.MaybeT m) instance Control.Monad.Zip.MonadZip m => Control.Monad.Zip.MonadZip (Control.Monad.Trans.Maybe.MaybeT m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.Maybe.MaybeT m) -- | A monad transformer that combines ReaderT, WriterT -- and StateT. This version uses continuation-passing-style for -- the writer part to achieve constant space usage. For a lazy version -- with the same interface, see Control.Monad.Trans.RWS.Lazy. module Control.Monad.Trans.RWS.CPS -- | A monad containing an environment of type r, output of type -- w and an updatable state of type s. type RWS r w s = RWST r w s Identity -- | Construct an RWS computation from a function. (The inverse of -- runRWS.) rws :: Monoid w => (r -> s -> (a, s, w)) -> RWS r w s a -- | Unwrap an RWS computation as a function. (The inverse of rws.) runRWS :: Monoid w => RWS r w s a -> r -> s -> (a, s, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final value and output, discarding the final state. evalRWS :: Monoid w => RWS r w s a -> r -> s -> (a, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final state and output, discarding the final value. execRWS :: Monoid w => RWS r w s a -> r -> s -> (s, w) -- | Map the return value, final state and output of a computation using -- the given function. -- -- mapRWS :: (Monoid w, Monoid w') => ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b -- | withRWS f m executes action m with an initial -- environment and state modified by applying f. -- -- withRWS :: (r' -> s -> (r, s)) -> RWS r w s a -> RWS r' w s a -- | A monad transformer adding reading an environment of type r, -- collecting an output of type w and updating a state of type -- s to an inner monad m. data RWST r w s m a -- | Construct an RWST computation from a function. (The inverse of -- runRWST.) rwsT :: (Functor m, Monoid w) => (r -> s -> m (a, s, w)) -> RWST r w s m a -- | Unwrap an RWST computation as a function. (The inverse of -- rwsT.) runRWST :: Monoid w => RWST r w s m a -> r -> s -> m (a, s, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final value and output, discarding the final state. evalRWST :: (Monad m, Monoid w) => RWST r w s m a -> r -> s -> m (a, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final state and output, discarding the final value. execRWST :: (Monad m, Monoid w) => RWST r w s m a -> r -> s -> m (s, w) -- | Map the inner computation using the given function. -- -- mapRWST :: (Monad n, Monoid w, Monoid w') => (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b -- | withRWST f m executes action m with an -- initial environment and state modified by applying f. -- -- withRWST :: (r' -> s -> (r, s)) -> RWST r w s m a -> RWST r' w s m a -- | Constructor for computations in the reader monad (equivalent to -- asks). reader :: Monad m => (r -> a) -> RWST r w s m a -- | Fetch the value of the environment. ask :: Monad m => RWST r w s m r -- | Execute a computation in a modified environment -- -- local :: (r -> r) -> RWST r w s m a -> RWST r w s m a -- | Retrieve a function of the current environment. -- -- asks :: Monad m => (r -> a) -> RWST r w s m a -- | Construct a writer computation from a (result, output) pair. writer :: (Monoid w, Monad m) => (a, w) -> RWST r w s m a -- | tell w is an action that produces the output -- w. tell :: (Monoid w, Monad m) => w -> RWST r w s m () -- | listen m is an action that executes the action -- m and adds its output to the value of the computation. -- -- listen :: (Monoid w, Monad m) => RWST r w s m a -> RWST r w s m (a, w) -- | listens f m is an action that executes the action -- m and adds the result of applying f to the output to -- the value of the computation. -- -- listens :: (Monoid w, Monad m) => (w -> b) -> RWST r w s m a -> RWST r w s m (a, b) -- | pass m is an action that executes the action -- m, which returns a value and a function, and returns the -- value, applying the function to the output. -- -- pass :: (Monoid w, Monoid w', Monad m) => RWST r w s m (a, w -> w') -> RWST r w' s m a -- | censor f m is an action that executes the action -- m and applies the function f to its output, leaving -- the return value unchanged. -- -- censor :: (Monoid w, Monad m) => (w -> w) -> RWST r w s m a -> RWST r w s m a -- | Construct a state monad computation from a state transformer function. state :: Monad m => (s -> (a, s)) -> RWST r w s m a -- | Fetch the current value of the state within the monad. get :: Monad m => RWST r w s m s -- | put s sets the state within the monad to s. put :: Monad m => s -> RWST r w s m () -- | modify f is an action that updates the state to the -- result of applying f to the current state. -- -- modify :: Monad m => (s -> s) -> RWST r w s m () -- | Get a specific component of the state, using a projection function -- supplied. -- -- gets :: Monad m => (s -> a) -> RWST r w s m a -- | Uniform lifting of a callCC operation to the new monad. This -- version rolls back to the original state on entering the continuation. liftCallCC :: CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b -- | In-situ lifting of a callCC operation to the new monad. This -- version uses the current state on entering the continuation. liftCallCC' :: CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, s, w) -> Catch e (RWST r w s m) a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.RWS.CPS.RWST r w s m) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.RWS.CPS.RWST r w s m) instance (GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.RWS.CPS.RWST r w s m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.RWS.CPS.RWST r w s m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.RWS.CPS.RWST r w s m) instance (GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.MonadPlus (Control.Monad.Trans.RWS.CPS.RWST r w s m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.RWS.CPS.RWST r w s m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.RWS.CPS.RWST r w s) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.RWS.CPS.RWST r w s m) -- | A monad transformer that combines ReaderT, WriterT -- and StateT. This version is lazy; for a constant-space -- version with almost the same interface, see -- Control.Monad.Trans.RWS.CPS. module Control.Monad.Trans.RWS.Lazy -- | A monad containing an environment of type r, output of type -- w and an updatable state of type s. type RWS r w s = RWST r w s Identity -- | Construct an RWS computation from a function. (The inverse of -- runRWS.) rws :: (r -> s -> (a, s, w)) -> RWS r w s a -- | Unwrap an RWS computation as a function. (The inverse of rws.) runRWS :: RWS r w s a -> r -> s -> (a, s, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final value and output, discarding the final state. evalRWS :: RWS r w s a -> r -> s -> (a, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final state and output, discarding the final value. execRWS :: RWS r w s a -> r -> s -> (s, w) -- | Map the return value, final state and output of a computation using -- the given function. -- -- mapRWS :: ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b -- | withRWS f m executes action m with an initial -- environment and state modified by applying f. -- -- withRWS :: (r' -> s -> (r, s)) -> RWS r w s a -> RWS r' w s a -- | A monad transformer adding reading an environment of type r, -- collecting an output of type w and updating a state of type -- s to an inner monad m. newtype RWST r w s m a RWST :: (r -> s -> m (a, s, w)) -> RWST r w s m a [runRWST] :: RWST r w s m a -> r -> s -> m (a, s, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final value and output, discarding the final state. evalRWST :: Monad m => RWST r w s m a -> r -> s -> m (a, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final state and output, discarding the final value. execRWST :: Monad m => RWST r w s m a -> r -> s -> m (s, w) -- | Map the inner computation using the given function. -- -- mapRWST :: (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b -- | withRWST f m executes action m with an -- initial environment and state modified by applying f. -- -- withRWST :: (r' -> s -> (r, s)) -> RWST r w s m a -> RWST r' w s m a -- | Constructor for computations in the reader monad (equivalent to -- asks). reader :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a -- | Fetch the value of the environment. ask :: (Monoid w, Monad m) => RWST r w s m r -- | Execute a computation in a modified environment -- -- local :: (r -> r) -> RWST r w s m a -> RWST r w s m a -- | Retrieve a function of the current environment. -- -- asks :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a -- | Construct a writer computation from a (result, output) pair. writer :: Monad m => (a, w) -> RWST r w s m a -- | tell w is an action that produces the output -- w. tell :: Monad m => w -> RWST r w s m () -- | listen m is an action that executes the action -- m and adds its output to the value of the computation. -- -- listen :: Monad m => RWST r w s m a -> RWST r w s m (a, w) -- | listens f m is an action that executes the action -- m and adds the result of applying f to the output to -- the value of the computation. -- -- listens :: Monad m => (w -> b) -> RWST r w s m a -> RWST r w s m (a, b) -- | pass m is an action that executes the action -- m, which returns a value and a function, and returns the -- value, applying the function to the output. -- -- pass :: Monad m => RWST r w s m (a, w -> w) -> RWST r w s m a -- | censor f m is an action that executes the action -- m and applies the function f to its output, leaving -- the return value unchanged. -- -- censor :: Monad m => (w -> w) -> RWST r w s m a -> RWST r w s m a -- | Construct a state monad computation from a state transformer function. state :: (Monoid w, Monad m) => (s -> (a, s)) -> RWST r w s m a -- | Fetch the current value of the state within the monad. get :: (Monoid w, Monad m) => RWST r w s m s -- | put s sets the state within the monad to s. put :: (Monoid w, Monad m) => s -> RWST r w s m () -- | modify f is an action that updates the state to the -- result of applying f to the current state. -- -- modify :: (Monoid w, Monad m) => (s -> s) -> RWST r w s m () -- | Get a specific component of the state, using a projection function -- supplied. -- -- gets :: (Monoid w, Monad m) => (s -> a) -> RWST r w s m a -- | Uniform lifting of a callCC operation to the new monad. This -- version rolls back to the original state on entering the continuation. liftCallCC :: Monoid w => CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b -- | In-situ lifting of a callCC operation to the new monad. This -- version uses the current state on entering the continuation. liftCallCC' :: Monoid w => CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, s, w) -> Catch e (RWST r w s m) a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.Monad m) => GHC.Base.Monad (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance (GHC.Base.Monoid w, Control.Monad.Fail.MonadFail m) => Control.Monad.Fail.MonadFail (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.MonadPlus m) => GHC.Base.MonadPlus (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance (GHC.Base.Monoid w, Control.Monad.Fix.MonadFix m) => Control.Monad.Fix.MonadFix (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance GHC.Base.Monoid w => Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.RWS.Lazy.RWST r w s) instance (GHC.Base.Monoid w, Control.Monad.IO.Class.MonadIO m) => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.RWS.Lazy.RWST r w s m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.RWS.Lazy.RWST r w s m) -- | A monad transformer that combines ReaderT, WriterT -- and StateT. This version is lazy; for a constant-space -- version with almost the same interface, see -- Control.Monad.Trans.RWS.CPS. module Control.Monad.Trans.RWS -- | A monad transformer that combines ReaderT, WriterT -- and StateT. This version is strict; for a lazy version with -- the same interface, see Control.Monad.Trans.RWS.Lazy. Although -- the output is built strictly, it is not possible to achieve constant -- space behaviour with this transformer: for that, use -- Control.Monad.Trans.RWS.CPS instead. module Control.Monad.Trans.RWS.Strict -- | A monad containing an environment of type r, output of type -- w and an updatable state of type s. type RWS r w s = RWST r w s Identity -- | Construct an RWS computation from a function. (The inverse of -- runRWS.) rws :: (r -> s -> (a, s, w)) -> RWS r w s a -- | Unwrap an RWS computation as a function. (The inverse of rws.) runRWS :: RWS r w s a -> r -> s -> (a, s, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final value and output, discarding the final state. evalRWS :: RWS r w s a -> r -> s -> (a, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final state and output, discarding the final value. execRWS :: RWS r w s a -> r -> s -> (s, w) -- | Map the return value, final state and output of a computation using -- the given function. -- -- mapRWS :: ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b -- | withRWS f m executes action m with an initial -- environment and state modified by applying f. -- -- withRWS :: (r' -> s -> (r, s)) -> RWS r w s a -> RWS r' w s a -- | A monad transformer adding reading an environment of type r, -- collecting an output of type w and updating a state of type -- s to an inner monad m. newtype RWST r w s m a RWST :: (r -> s -> m (a, s, w)) -> RWST r w s m a [runRWST] :: RWST r w s m a -> r -> s -> m (a, s, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final value and output, discarding the final state. evalRWST :: Monad m => RWST r w s m a -> r -> s -> m (a, w) -- | Evaluate a computation with the given initial state and environment, -- returning the final state and output, discarding the final value. execRWST :: Monad m => RWST r w s m a -> r -> s -> m (s, w) -- | Map the inner computation using the given function. -- -- mapRWST :: (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b -- | withRWST f m executes action m with an -- initial environment and state modified by applying f. -- -- withRWST :: (r' -> s -> (r, s)) -> RWST r w s m a -> RWST r' w s m a -- | Constructor for computations in the reader monad (equivalent to -- asks). reader :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a -- | Fetch the value of the environment. ask :: (Monoid w, Monad m) => RWST r w s m r -- | Execute a computation in a modified environment -- -- local :: (r -> r) -> RWST r w s m a -> RWST r w s m a -- | Retrieve a function of the current environment. -- -- asks :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a -- | Construct a writer computation from a (result, output) pair. writer :: Monad m => (a, w) -> RWST r w s m a -- | tell w is an action that produces the output -- w. tell :: Monad m => w -> RWST r w s m () -- | listen m is an action that executes the action -- m and adds its output to the value of the computation. -- -- listen :: Monad m => RWST r w s m a -> RWST r w s m (a, w) -- | listens f m is an action that executes the action -- m and adds the result of applying f to the output to -- the value of the computation. -- -- listens :: Monad m => (w -> b) -> RWST r w s m a -> RWST r w s m (a, b) -- | pass m is an action that executes the action -- m, which returns a value and a function, and returns the -- value, applying the function to the output. -- -- pass :: Monad m => RWST r w s m (a, w -> w) -> RWST r w s m a -- | censor f m is an action that executes the action -- m and applies the function f to its output, leaving -- the return value unchanged. -- -- censor :: Monad m => (w -> w) -> RWST r w s m a -> RWST r w s m a -- | Construct a state monad computation from a state transformer function. state :: (Monoid w, Monad m) => (s -> (a, s)) -> RWST r w s m a -- | Fetch the current value of the state within the monad. get :: (Monoid w, Monad m) => RWST r w s m s -- | put s sets the state within the monad to s. put :: (Monoid w, Monad m) => s -> RWST r w s m () -- | modify f is an action that updates the state to the -- result of applying f to the current state. -- -- modify :: (Monoid w, Monad m) => (s -> s) -> RWST r w s m () -- | Get a specific component of the state, using a projection function -- supplied. -- -- gets :: (Monoid w, Monad m) => (s -> a) -> RWST r w s m a -- | Uniform lifting of a callCC operation to the new monad. This -- version rolls back to the original state on entering the continuation. liftCallCC :: Monoid w => CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b -- | In-situ lifting of a callCC operation to the new monad. This -- version uses the current state on entering the continuation. liftCallCC' :: Monoid w => CallCC m (a, s, w) (b, s, w) -> CallCC (RWST r w s m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, s, w) -> Catch e (RWST r w s m) a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.Monad m) => GHC.Base.Monad (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance (GHC.Base.Monoid w, Control.Monad.Fail.MonadFail m) => Control.Monad.Fail.MonadFail (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance (GHC.Base.Monoid w, GHC.Base.MonadPlus m) => GHC.Base.MonadPlus (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance (GHC.Base.Monoid w, Control.Monad.Fix.MonadFix m) => Control.Monad.Fix.MonadFix (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance GHC.Base.Monoid w => Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.RWS.Strict.RWST r w s) instance (GHC.Base.Monoid w, Control.Monad.IO.Class.MonadIO m) => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.RWS.Strict.RWST r w s m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.RWS.Strict.RWST r w s m) -- | Declaration of the ReaderT monad transformer, which adds a -- static environment to a given monad. -- -- If the computation is to modify the stored information, use -- Control.Monad.Trans.State instead. module Control.Monad.Trans.Reader -- | The parameterizable reader monad. -- -- Computations are functions of a shared environment. -- -- The return function ignores the environment, while -- >>= passes the inherited environment to both -- subcomputations. type Reader r = ReaderT r Identity -- | Constructor for computations in the reader monad (equivalent to -- asks). reader :: Monad m => (r -> a) -> ReaderT r m a -- | Runs a Reader and extracts the final value from it. (The -- inverse of reader.) runReader :: Reader r a -> r -> a -- | Transform the value returned by a Reader. -- -- mapReader :: (a -> b) -> Reader r a -> Reader r b -- | Execute a computation in a modified environment (a specialization of -- withReaderT). -- -- withReader :: (r' -> r) -> Reader r a -> Reader r' a -- | The reader monad transformer, which adds a read-only environment to -- the given monad. -- -- The return function ignores the environment, while -- >>= passes the inherited environment to both -- subcomputations. newtype ReaderT r m a ReaderT :: (r -> m a) -> ReaderT r m a [runReaderT] :: ReaderT r m a -> r -> m a -- | Transform the computation inside a ReaderT. -- -- mapReaderT :: (m a -> n b) -> ReaderT r m a -> ReaderT r n b -- | Execute a computation in a modified environment (a more general -- version of local). -- -- withReaderT :: (r' -> r) -> ReaderT r m a -> ReaderT r' m a -- | Fetch the value of the environment. ask :: Monad m => ReaderT r m r -- | Execute a computation in a modified environment (a specialization of -- withReaderT). -- -- local :: (r -> r) -> ReaderT r m a -> ReaderT r m a -- | Retrieve a function of the current environment. -- -- asks :: Monad m => (r -> a) -> ReaderT r m a -- | Lift a callCC operation to the new monad. liftCallCC :: CallCC m a b -> CallCC (ReaderT r m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m a -> Catch e (ReaderT r m) a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Reader.ReaderT r m) instance GHC.Base.Applicative m => GHC.Base.Applicative (Control.Monad.Trans.Reader.ReaderT r m) instance GHC.Base.Alternative m => GHC.Base.Alternative (Control.Monad.Trans.Reader.ReaderT r m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.Reader.ReaderT r m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Reader.ReaderT r m) instance GHC.Base.MonadPlus m => GHC.Base.MonadPlus (Control.Monad.Trans.Reader.ReaderT r m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Reader.ReaderT r m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Reader.ReaderT r) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Reader.ReaderT r m) instance Control.Monad.Zip.MonadZip m => Control.Monad.Zip.MonadZip (Control.Monad.Trans.Reader.ReaderT r m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.Reader.ReaderT r m) -- | Selection monad transformer, modelling search algorithms. -- -- module Control.Monad.Trans.Select -- | Selection monad. type Select r = SelectT r Identity -- | Constructor for computations in the selection monad. select :: ((a -> r) -> a) -> Select r a -- | Runs a Select computation with a function for evaluating -- answers to select a particular answer. (The inverse of select.) runSelect :: Select r a -> (a -> r) -> a -- | Apply a function to transform the result of a selection computation. -- -- mapSelect :: (a -> a) -> Select r a -> Select r a -- | Selection monad transformer. -- -- SelectT is not a functor on the category of monads, and many -- operations cannot be lifted through it. newtype SelectT r m a SelectT :: ((a -> m r) -> m a) -> SelectT r m a -- | Runs a SelectT computation with a function for evaluating -- answers to select a particular answer. (The inverse of select.) runSelectT :: SelectT r m a -> (a -> m r) -> m a -- | Apply a function to transform the result of a selection computation. -- This has a more restricted type than the map operations for -- other monad transformers, because SelectT does not define a -- functor in the category of monads. -- -- mapSelectT :: (m a -> m a) -> SelectT r m a -> SelectT r m a -- | Convert a selection computation to a continuation-passing computation. selectToContT :: Monad m => SelectT r m a -> ContT r m a -- | Deprecated name for selectToContT. -- | Deprecated: Use selectToContT instead selectToCont :: Monad m => SelectT r m a -> ContT r m a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Select.SelectT r m) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.Select.SelectT r m) instance (GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.Select.SelectT r m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.Select.SelectT r m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Select.SelectT r m) instance GHC.Base.MonadPlus m => GHC.Base.MonadPlus (Control.Monad.Trans.Select.SelectT r m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Select.SelectT r) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Select.SelectT r m) -- | Lazy state monads, passing an updatable state through a computation. -- See below for examples. -- -- Some computations may not require the full power of state -- transformers: -- -- -- -- In this version, sequencing of computations is lazy, so that for -- example the following produces a usable result: -- -- 
--   evalState (sequence $ repeat $ do { n <- get; put (n*2); return n }) 1
--
-- -- For a strict version with the same interface, see -- Control.Monad.Trans.State.Strict. module Control.Monad.Trans.State.Lazy -- | A state monad parameterized by the type s of the state to -- carry. -- -- The return function leaves the state unchanged, while -- >>= uses the final state of the first computation as -- the initial state of the second. type State s = StateT s Identity -- | Construct a state monad computation from a function. (The inverse of -- runState.) state :: Monad m => (s -> (a, s)) -> StateT s m a -- | Unwrap a state monad computation as a function. (The inverse of -- state.) runState :: State s a -> s -> (a, s) -- | Evaluate a state computation with the given initial state and return -- the final value, discarding the final state. -- -- evalState :: State s a -> s -> a -- | Evaluate a state computation with the given initial state and return -- the final state, discarding the final value. -- -- execState :: State s a -> s -> s -- | Map both the return value and final state of a computation using the -- given function. -- -- mapState :: ((a, s) -> (b, s)) -> State s a -> State s b -- | withState f m executes action m on a state -- modified by applying f. -- -- withState :: (s -> s) -> State s a -> State s a -- | A state transformer monad parameterized by: -- -- -- -- The return function leaves the state unchanged, while -- >>= uses the final state of the first computation as -- the initial state of the second. newtype StateT s m a StateT :: (s -> m (a, s)) -> StateT s m a [runStateT] :: StateT s m a -> s -> m (a, s) -- | Evaluate a state computation with the given initial state and return -- the final value, discarding the final state. -- -- evalStateT :: Monad m => StateT s m a -> s -> m a -- | Evaluate a state computation with the given initial state and return -- the final state, discarding the final value. -- -- execStateT :: Monad m => StateT s m a -> s -> m s -- | Map both the return value and final state of a computation using the -- given function. -- -- mapStateT :: (m (a, s) -> n (b, s)) -> StateT s m a -> StateT s n b -- | withStateT f m executes action m on a state -- modified by applying f. -- -- withStateT :: (s -> s) -> StateT s m a -> StateT s m a -- | Fetch the current value of the state within the monad. get :: Monad m => StateT s m s -- | put s sets the state within the monad to s. put :: Monad m => s -> StateT s m () -- | modify f is an action that updates the state to the -- result of applying f to the current state. -- -- modify :: Monad m => (s -> s) -> StateT s m () -- | A variant of modify in which the computation is strict in the -- new state. -- -- modify' :: Monad m => (s -> s) -> StateT s m () -- | Get a specific component of the state, using a projection function -- supplied. -- -- gets :: Monad m => (s -> a) -> StateT s m a -- | Uniform lifting of a callCC operation to the new monad. This -- version rolls back to the original state on entering the continuation. liftCallCC :: CallCC m (a, s) (b, s) -> CallCC (StateT s m) a b -- | In-situ lifting of a callCC operation to the new monad. This -- version uses the current state on entering the continuation. It does -- not satisfy the uniformity property (see -- Control.Monad.Signatures). liftCallCC' :: CallCC m (a, s) (b, s) -> CallCC (StateT s m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, s) -> Catch e (StateT s m) a -- | Lift a listen operation to the new monad. liftListen :: Monad m => Listen w m (a, s) -> Listen w (StateT s m) a -- | Lift a pass operation to the new monad. liftPass :: Monad m => Pass w m (a, s) -> Pass w (StateT s m) a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.State.Lazy.StateT s m) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.State.Lazy.StateT s m) instance (GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.State.Lazy.StateT s m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.State.Lazy.StateT s m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.State.Lazy.StateT s m) instance GHC.Base.MonadPlus m => GHC.Base.MonadPlus (Control.Monad.Trans.State.Lazy.StateT s m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.State.Lazy.StateT s m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.State.Lazy.StateT s) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.State.Lazy.StateT s m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.State.Lazy.StateT s m) -- | State monads, passing an updatable state through a computation. -- -- Some computations may not require the full power of state -- transformers: -- -- -- -- This version is lazy; for a strict version, see -- Control.Monad.Trans.State.Strict, which has the same interface. module Control.Monad.Trans.State -- | Strict state monads, passing an updatable state through a computation. -- See below for examples. -- -- Some computations may not require the full power of state -- transformers: -- -- -- -- In this version, sequencing of computations is strict (but -- computations are not strict in the state unless you force it with -- seq or the like). For a lazy version with the same interface, -- see Control.Monad.Trans.State.Lazy. module Control.Monad.Trans.State.Strict -- | A state monad parameterized by the type s of the state to -- carry. -- -- The return function leaves the state unchanged, while -- >>= uses the final state of the first computation as -- the initial state of the second. type State s = StateT s Identity -- | Construct a state monad computation from a function. (The inverse of -- runState.) state :: Monad m => (s -> (a, s)) -> StateT s m a -- | Unwrap a state monad computation as a function. (The inverse of -- state.) runState :: State s a -> s -> (a, s) -- | Evaluate a state computation with the given initial state and return -- the final value, discarding the final state. -- -- evalState :: State s a -> s -> a -- | Evaluate a state computation with the given initial state and return -- the final state, discarding the final value. -- -- execState :: State s a -> s -> s -- | Map both the return value and final state of a computation using the -- given function. -- -- mapState :: ((a, s) -> (b, s)) -> State s a -> State s b -- | withState f m executes action m on a state -- modified by applying f. -- -- withState :: (s -> s) -> State s a -> State s a -- | A state transformer monad parameterized by: -- -- -- -- The return function leaves the state unchanged, while -- >>= uses the final state of the first computation as -- the initial state of the second. newtype StateT s m a StateT :: (s -> m (a, s)) -> StateT s m a [runStateT] :: StateT s m a -> s -> m (a, s) -- | Evaluate a state computation with the given initial state and return -- the final value, discarding the final state. -- -- evalStateT :: Monad m => StateT s m a -> s -> m a -- | Evaluate a state computation with the given initial state and return -- the final state, discarding the final value. -- -- execStateT :: Monad m => StateT s m a -> s -> m s -- | Map both the return value and final state of a computation using the -- given function. -- -- mapStateT :: (m (a, s) -> n (b, s)) -> StateT s m a -> StateT s n b -- | withStateT f m executes action m on a state -- modified by applying f. -- -- withStateT :: (s -> s) -> StateT s m a -> StateT s m a -- | Fetch the current value of the state within the monad. get :: Monad m => StateT s m s -- | put s sets the state within the monad to s. put :: Monad m => s -> StateT s m () -- | modify f is an action that updates the state to the -- result of applying f to the current state. -- -- modify :: Monad m => (s -> s) -> StateT s m () -- | A variant of modify in which the computation is strict in the -- new state. -- -- modify' :: Monad m => (s -> s) -> StateT s m () -- | Get a specific component of the state, using a projection function -- supplied. -- -- gets :: Monad m => (s -> a) -> StateT s m a -- | Uniform lifting of a callCC operation to the new monad. This -- version rolls back to the original state on entering the continuation. liftCallCC :: CallCC m (a, s) (b, s) -> CallCC (StateT s m) a b -- | In-situ lifting of a callCC operation to the new monad. This -- version uses the current state on entering the continuation. It does -- not satisfy the uniformity property (see -- Control.Monad.Signatures). liftCallCC' :: CallCC m (a, s) (b, s) -> CallCC (StateT s m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, s) -> Catch e (StateT s m) a -- | Lift a listen operation to the new monad. liftListen :: Monad m => Listen w m (a, s) -> Listen w (StateT s m) a -- | Lift a pass operation to the new monad. liftPass :: Monad m => Pass w m (a, s) -> Pass w (StateT s m) a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.State.Strict.StateT s m) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.State.Strict.StateT s m) instance (GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.State.Strict.StateT s m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.State.Strict.StateT s m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.State.Strict.StateT s m) instance GHC.Base.MonadPlus m => GHC.Base.MonadPlus (Control.Monad.Trans.State.Strict.StateT s m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.State.Strict.StateT s m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.State.Strict.StateT s) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.State.Strict.StateT s m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.State.Strict.StateT s m) -- | The strict WriterT monad transformer, which adds collection of -- outputs (such as a count or string output) to a given monad. -- -- This monad transformer provides only limited access to the output -- during the computation. For more general access, use -- Control.Monad.Trans.State instead. -- -- This version builds its output strictly and uses -- continuation-passing-style to achieve constant space usage. This -- transformer can be used as a drop-in replacement for -- Control.Monad.Trans.Writer.Strict. module Control.Monad.Trans.Writer.CPS -- | A writer monad parameterized by the type w of output to -- accumulate. -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. type Writer w = WriterT w Identity -- | Construct a writer computation from a (result, output) pair. (The -- inverse of runWriter.) writer :: (Monoid w, Monad m) => (a, w) -> WriterT w m a -- | Unwrap a writer computation as a (result, output) pair. (The inverse -- of writer.) runWriter :: Monoid w => Writer w a -> (a, w) -- | Extract the output from a writer computation. -- -- execWriter :: Monoid w => Writer w a -> w -- | Map both the return value and output of a computation using the given -- function. -- -- mapWriter :: (Monoid w, Monoid w') => ((a, w) -> (b, w')) -> Writer w a -> Writer w' b -- | A writer monad parameterized by: -- -- -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. data WriterT w m a -- | Construct a writer computation from a (result, output) computation. -- (The inverse of runWriterT.) writerT :: (Functor m, Monoid w) => m (a, w) -> WriterT w m a -- | Unwrap a writer computation. (The inverse of writerT.) runWriterT :: Monoid w => WriterT w m a -> m (a, w) -- | Extract the output from a writer computation. -- -- execWriterT :: (Monad m, Monoid w) => WriterT w m a -> m w -- | Map both the return value and output of a computation using the given -- function. -- -- mapWriterT :: (Monad n, Monoid w, Monoid w') => (m (a, w) -> n (b, w')) -> WriterT w m a -> WriterT w' n b -- | tell w is an action that produces the output -- w. tell :: (Monoid w, Monad m) => w -> WriterT w m () -- | listen m is an action that executes the action -- m and adds its output to the value of the computation. -- -- listen :: (Monoid w, Monad m) => WriterT w m a -> WriterT w m (a, w) -- | listens f m is an action that executes the action -- m and adds the result of applying f to the output to -- the value of the computation. -- -- listens :: (Monoid w, Monad m) => (w -> b) -> WriterT w m a -> WriterT w m (a, b) -- | pass m is an action that executes the action -- m, which returns a value and a function, and returns the -- value, applying the function to the output. -- -- pass :: (Monoid w, Monoid w', Monad m) => WriterT w m (a, w -> w') -> WriterT w' m a -- | censor f m is an action that executes the action -- m and applies the function f to its output, leaving -- the return value unchanged. -- -- censor :: (Monoid w, Monad m) => (w -> w) -> WriterT w m a -> WriterT w m a -- | Uniform lifting of a callCC operation to the new monad. This -- version rolls back to the original state on entering the continuation. liftCallCC :: CallCC m (a, w) (b, w) -> CallCC (WriterT w m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, w) -> Catch e (WriterT w m) a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Writer.CPS.WriterT w m) instance (GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.Writer.CPS.WriterT w m) instance (GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.Writer.CPS.WriterT w m) instance GHC.Base.Monad m => GHC.Base.Monad (Control.Monad.Trans.Writer.CPS.WriterT w m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Writer.CPS.WriterT w m) instance (GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.MonadPlus (Control.Monad.Trans.Writer.CPS.WriterT w m) instance Control.Monad.Fix.MonadFix m => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Writer.CPS.WriterT w m) instance Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Writer.CPS.WriterT w) instance Control.Monad.IO.Class.MonadIO m => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Writer.CPS.WriterT w m) -- | The lazy WriterT monad transformer, which adds collection of -- outputs (such as a count or string output) to a given monad. -- -- This monad transformer provides only limited access to the output -- during the computation. For more general access, use -- Control.Monad.Trans.State instead. -- -- This version builds its output lazily; for a constant-space version -- with almost the same interface, see -- Control.Monad.Trans.Writer.CPS. module Control.Monad.Trans.Writer.Lazy -- | A writer monad parameterized by the type w of output to -- accumulate. -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. type Writer w = WriterT w Identity -- | Construct a writer computation from a (result, output) pair. (The -- inverse of runWriter.) writer :: Monad m => (a, w) -> WriterT w m a -- | Unwrap a writer computation as a (result, output) pair. (The inverse -- of writer.) runWriter :: Writer w a -> (a, w) -- | Extract the output from a writer computation. -- -- execWriter :: Writer w a -> w -- | Map both the return value and output of a computation using the given -- function. -- -- mapWriter :: ((a, w) -> (b, w')) -> Writer w a -> Writer w' b -- | A writer monad parameterized by: -- -- -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. newtype WriterT w m a WriterT :: m (a, w) -> WriterT w m a [runWriterT] :: WriterT w m a -> m (a, w) -- | Extract the output from a writer computation. -- -- execWriterT :: Monad m => WriterT w m a -> m w -- | Map both the return value and output of a computation using the given -- function. -- -- mapWriterT :: (m (a, w) -> n (b, w')) -> WriterT w m a -> WriterT w' n b -- | tell w is an action that produces the output -- w. tell :: Monad m => w -> WriterT w m () -- | listen m is an action that executes the action -- m and adds its output to the value of the computation. -- -- listen :: Monad m => WriterT w m a -> WriterT w m (a, w) -- | listens f m is an action that executes the action -- m and adds the result of applying f to the output to -- the value of the computation. -- -- listens :: Monad m => (w -> b) -> WriterT w m a -> WriterT w m (a, b) -- | pass m is an action that executes the action -- m, which returns a value and a function, and returns the -- value, applying the function to the output. -- -- pass :: Monad m => WriterT w m (a, w -> w) -> WriterT w m a -- | censor f m is an action that executes the action -- m and applies the function f to its output, leaving -- the return value unchanged. -- -- censor :: Monad m => (w -> w) -> WriterT w m a -> WriterT w m a -- | Lift a callCC operation to the new monad. liftCallCC :: Monoid w => CallCC m (a, w) (b, w) -> CallCC (WriterT w m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, w) -> Catch e (WriterT w m) a instance (GHC.Classes.Eq w, Data.Functor.Classes.Eq1 m) => Data.Functor.Classes.Eq1 (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Classes.Ord w, Data.Functor.Classes.Ord1 m) => Data.Functor.Classes.Ord1 (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Read.Read w, Data.Functor.Classes.Read1 m) => Data.Functor.Classes.Read1 (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Show.Show w, Data.Functor.Classes.Show1 m) => Data.Functor.Classes.Show1 (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Classes.Eq w, Data.Functor.Classes.Eq1 m, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Monad.Trans.Writer.Lazy.WriterT w m a) instance (GHC.Classes.Ord w, Data.Functor.Classes.Ord1 m, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Monad.Trans.Writer.Lazy.WriterT w m a) instance (GHC.Read.Read w, Data.Functor.Classes.Read1 m, GHC.Read.Read a) => GHC.Read.Read (Control.Monad.Trans.Writer.Lazy.WriterT w m a) instance (GHC.Show.Show w, Data.Functor.Classes.Show1 m, GHC.Show.Show a) => GHC.Show.Show (Control.Monad.Trans.Writer.Lazy.WriterT w m a) instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Monad.Trans.Writer.Lazy.WriterT w f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Monad.Trans.Writer.Lazy.WriterT w f) instance (GHC.Base.Monoid w, GHC.Base.Applicative m) => GHC.Base.Applicative (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Base.Monoid w, GHC.Base.Alternative m) => GHC.Base.Alternative (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Base.Monoid w, GHC.Base.Monad m) => GHC.Base.Monad (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Base.Monoid w, Control.Monad.Fail.MonadFail m) => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Base.Monoid w, GHC.Base.MonadPlus m) => GHC.Base.MonadPlus (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Base.Monoid w, Control.Monad.Fix.MonadFix m) => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance GHC.Base.Monoid w => Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Writer.Lazy.WriterT w) instance (GHC.Base.Monoid w, Control.Monad.IO.Class.MonadIO m) => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance (GHC.Base.Monoid w, Control.Monad.Zip.MonadZip m) => Control.Monad.Zip.MonadZip (Control.Monad.Trans.Writer.Lazy.WriterT w m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.Writer.Lazy.WriterT w m) -- | The WriterT monad transformer. This version builds its output lazily; -- for a constant-space version with almost the same interface, see -- Control.Monad.Trans.Writer.CPS. module Control.Monad.Trans.Writer -- | The lazy AccumT monad transformer, which adds accumulation -- capabilities (such as declarations or document patches) to a given -- monad. -- -- This monad transformer provides append-only accumulation during the -- computation. For more general access, use -- Control.Monad.Trans.State instead. module Control.Monad.Trans.Accum -- | An accumulation monad parameterized by the type w of output -- to accumulate. -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. type Accum w = AccumT w Identity -- | Construct an accumulation computation from a (result, output) pair. -- (The inverse of runAccum.) accum :: Monad m => (w -> (a, w)) -> AccumT w m a -- | Unwrap an accumulation computation as a (result, output) pair. (The -- inverse of accum.) runAccum :: Accum w a -> w -> (a, w) -- | Extract the output from an accumulation computation. -- -- execAccum :: Accum w a -> w -> w -- | Evaluate an accumulation computation with the given initial output -- history and return the final value, discarding the final output. -- -- evalAccum :: Monoid w => Accum w a -> w -> a -- | Map both the return value and output of a computation using the given -- function. -- -- mapAccum :: ((a, w) -> (b, w)) -> Accum w a -> Accum w b -- | An accumulation monad parameterized by: -- -- -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. -- -- This monad transformer is similar to both state and writer monad -- transformers. Thus it can be seen as -- -- newtype AccumT w m a AccumT :: (w -> m (a, w)) -> AccumT w m a -- | Unwrap an accumulation computation. runAccumT :: AccumT w m a -> w -> m (a, w) -- | Extract the output from an accumulation computation. -- -- execAccumT :: Monad m => AccumT w m a -> w -> m w -- | Evaluate an accumulation computation with the given initial output -- history and return the final value, discarding the final output. -- -- evalAccumT :: (Monad m, Monoid w) => AccumT w m a -> w -> m a -- | Map both the return value and output of a computation using the given -- function. -- -- mapAccumT :: (m (a, w) -> n (b, w)) -> AccumT w m a -> AccumT w n b -- | look is an action that fetches all the previously -- accumulated output. look :: (Monoid w, Monad m) => AccumT w m w -- | look is an action that retrieves a function of the -- previously accumulated output. looks :: (Monoid w, Monad m) => (w -> a) -> AccumT w m a -- | add w is an action that produces the output -- w. add :: Monad m => w -> AccumT w m () -- | Uniform lifting of a callCC operation to the new monad. This -- version rolls back to the original output history on entering the -- continuation. liftCallCC :: CallCC m (a, w) (b, w) -> CallCC (AccumT w m) a b -- | In-situ lifting of a callCC operation to the new monad. This -- version uses the current output history on entering the continuation. -- It does not satisfy the uniformity property (see -- Control.Monad.Signatures). liftCallCC' :: CallCC m (a, w) (b, w) -> CallCC (AccumT w m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, w) -> Catch e (AccumT w m) a -- | Lift a listen operation to the new monad. liftListen :: Monad m => Listen w m (a, s) -> Listen w (AccumT s m) a -- | Lift a pass operation to the new monad. liftPass :: Monad m => Pass w m (a, s) -> Pass w (AccumT s m) a -- | Convert a read-only computation into an accumulation computation. readerToAccumT :: (Functor m, Monoid w) => ReaderT w m a -> AccumT w m a -- | Convert a writer computation into an accumulation computation. writerToAccumT :: WriterT w m a -> AccumT w m a -- | Convert an accumulation (append-only) computation into a fully -- stateful computation. accumToStateT :: (Functor m, Monoid s) => AccumT s m a -> StateT s m a instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Accum.AccumT w m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Applicative (Control.Monad.Trans.Accum.AccumT w m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.Alternative (Control.Monad.Trans.Accum.AccumT w m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.Monad m) => GHC.Base.Monad (Control.Monad.Trans.Accum.AccumT w m) instance (GHC.Base.Monoid w, Control.Monad.Fail.MonadFail m) => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Accum.AccumT w m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, GHC.Base.MonadPlus m) => GHC.Base.MonadPlus (Control.Monad.Trans.Accum.AccumT w m) instance (GHC.Base.Monoid w, GHC.Base.Functor m, Control.Monad.Fix.MonadFix m) => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Accum.AccumT w m) instance GHC.Base.Monoid w => Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Accum.AccumT w) instance (GHC.Base.Monoid w, GHC.Base.Functor m, Control.Monad.IO.Class.MonadIO m) => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Accum.AccumT w m) -- | The strict WriterT monad transformer, which adds collection of -- outputs (such as a count or string output) to a given monad. -- -- This monad transformer provides only limited access to the output -- during the computation. For more general access, use -- Control.Monad.Trans.State instead. -- -- This version builds its output strictly; for a lazy version with the -- same interface, see Control.Monad.Trans.Writer.Lazy. Although -- the output is built strictly, it is not possible to achieve constant -- space behaviour with this transformer: for that, use -- Control.Monad.Trans.Writer.CPS instead. module Control.Monad.Trans.Writer.Strict -- | A writer monad parameterized by the type w of output to -- accumulate. -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. type Writer w = WriterT w Identity -- | Construct a writer computation from a (result, output) pair. (The -- inverse of runWriter.) writer :: Monad m => (a, w) -> WriterT w m a -- | Unwrap a writer computation as a (result, output) pair. (The inverse -- of writer.) runWriter :: Writer w a -> (a, w) -- | Extract the output from a writer computation. -- -- execWriter :: Writer w a -> w -- | Map both the return value and output of a computation using the given -- function. -- -- mapWriter :: ((a, w) -> (b, w')) -> Writer w a -> Writer w' b -- | A writer monad parameterized by: -- -- -- -- The return function produces the output mempty, while -- >>= combines the outputs of the subcomputations using -- mappend. newtype WriterT w m a WriterT :: m (a, w) -> WriterT w m a [runWriterT] :: WriterT w m a -> m (a, w) -- | Extract the output from a writer computation. -- -- execWriterT :: Monad m => WriterT w m a -> m w -- | Map both the return value and output of a computation using the given -- function. -- -- mapWriterT :: (m (a, w) -> n (b, w')) -> WriterT w m a -> WriterT w' n b -- | tell w is an action that produces the output -- w. tell :: Monad m => w -> WriterT w m () -- | listen m is an action that executes the action -- m and adds its output to the value of the computation. -- -- listen :: Monad m => WriterT w m a -> WriterT w m (a, w) -- | listens f m is an action that executes the action -- m and adds the result of applying f to the output to -- the value of the computation. -- -- listens :: Monad m => (w -> b) -> WriterT w m a -> WriterT w m (a, b) -- | pass m is an action that executes the action -- m, which returns a value and a function, and returns the -- value, applying the function to the output. -- -- pass :: Monad m => WriterT w m (a, w -> w) -> WriterT w m a -- | censor f m is an action that executes the action -- m and applies the function f to its output, leaving -- the return value unchanged. -- -- censor :: Monad m => (w -> w) -> WriterT w m a -> WriterT w m a -- | Lift a callCC operation to the new monad. liftCallCC :: Monoid w => CallCC m (a, w) (b, w) -> CallCC (WriterT w m) a b -- | Lift a catchE operation to the new monad. liftCatch :: Catch e m (a, w) -> Catch e (WriterT w m) a instance (GHC.Classes.Eq w, Data.Functor.Classes.Eq1 m) => Data.Functor.Classes.Eq1 (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Classes.Ord w, Data.Functor.Classes.Ord1 m) => Data.Functor.Classes.Ord1 (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Read.Read w, Data.Functor.Classes.Read1 m) => Data.Functor.Classes.Read1 (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Show.Show w, Data.Functor.Classes.Show1 m) => Data.Functor.Classes.Show1 (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Classes.Eq w, Data.Functor.Classes.Eq1 m, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Monad.Trans.Writer.Strict.WriterT w m a) instance (GHC.Classes.Ord w, Data.Functor.Classes.Ord1 m, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Monad.Trans.Writer.Strict.WriterT w m a) instance (GHC.Read.Read w, Data.Functor.Classes.Read1 m, GHC.Read.Read a) => GHC.Read.Read (Control.Monad.Trans.Writer.Strict.WriterT w m a) instance (GHC.Show.Show w, Data.Functor.Classes.Show1 m, GHC.Show.Show a) => GHC.Show.Show (Control.Monad.Trans.Writer.Strict.WriterT w m a) instance GHC.Base.Functor m => GHC.Base.Functor (Control.Monad.Trans.Writer.Strict.WriterT w m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Monad.Trans.Writer.Strict.WriterT w f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Monad.Trans.Writer.Strict.WriterT w f) instance (GHC.Base.Monoid w, GHC.Base.Applicative m) => GHC.Base.Applicative (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Base.Monoid w, GHC.Base.Alternative m) => GHC.Base.Alternative (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Base.Monoid w, GHC.Base.Monad m) => GHC.Base.Monad (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Base.Monoid w, Control.Monad.Fail.MonadFail m) => Control.Monad.Fail.MonadFail (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Base.Monoid w, GHC.Base.MonadPlus m) => GHC.Base.MonadPlus (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Base.Monoid w, Control.Monad.Fix.MonadFix m) => Control.Monad.Fix.MonadFix (Control.Monad.Trans.Writer.Strict.WriterT w m) instance GHC.Base.Monoid w => Control.Monad.Trans.Class.MonadTrans (Control.Monad.Trans.Writer.Strict.WriterT w) instance (GHC.Base.Monoid w, Control.Monad.IO.Class.MonadIO m) => Control.Monad.IO.Class.MonadIO (Control.Monad.Trans.Writer.Strict.WriterT w m) instance (GHC.Base.Monoid w, Control.Monad.Zip.MonadZip m) => Control.Monad.Zip.MonadZip (Control.Monad.Trans.Writer.Strict.WriterT w m) instance Data.Functor.Contravariant.Contravariant m => Data.Functor.Contravariant.Contravariant (Control.Monad.Trans.Writer.Strict.WriterT w m) -- | The constant functor. module Data.Functor.Constant -- | Constant functor. newtype Constant a b Constant :: a -> Constant a b [getConstant] :: Constant a b -> a instance forall a k (b :: k). GHC.Classes.Ord a => GHC.Classes.Ord (Data.Functor.Constant.Constant a b) instance forall a k (b :: k). GHC.Classes.Eq a => GHC.Classes.Eq (Data.Functor.Constant.Constant a b) instance forall k a (b :: k). GHC.Read.Read a => GHC.Read.Read (Data.Functor.Constant.Constant a b) instance forall k a (b :: k). GHC.Show.Show a => GHC.Show.Show (Data.Functor.Constant.Constant a b) instance Data.Functor.Classes.Eq2 Data.Functor.Constant.Constant instance Data.Functor.Classes.Ord2 Data.Functor.Constant.Constant instance Data.Functor.Classes.Read2 Data.Functor.Constant.Constant instance Data.Functor.Classes.Show2 Data.Functor.Constant.Constant instance GHC.Classes.Eq a => Data.Functor.Classes.Eq1 (Data.Functor.Constant.Constant a) instance GHC.Classes.Ord a => Data.Functor.Classes.Ord1 (Data.Functor.Constant.Constant a) instance GHC.Read.Read a => Data.Functor.Classes.Read1 (Data.Functor.Constant.Constant a) instance GHC.Show.Show a => Data.Functor.Classes.Show1 (Data.Functor.Constant.Constant a) instance GHC.Base.Functor (Data.Functor.Constant.Constant a) instance Data.Foldable.Foldable (Data.Functor.Constant.Constant a) instance Data.Traversable.Traversable (Data.Functor.Constant.Constant a) instance forall k a (b :: k). GHC.Base.Semigroup a => GHC.Base.Semigroup (Data.Functor.Constant.Constant a b) instance GHC.Base.Monoid a => GHC.Base.Applicative (Data.Functor.Constant.Constant a) instance forall k a (b :: k). GHC.Base.Monoid a => GHC.Base.Monoid (Data.Functor.Constant.Constant a b) instance Data.Bifunctor.Bifunctor Data.Functor.Constant.Constant instance Data.Bifoldable.Bifoldable Data.Functor.Constant.Constant instance Data.Bitraversable.Bitraversable Data.Functor.Constant.Constant instance Data.Functor.Contravariant.Contravariant (Data.Functor.Constant.Constant a) -- | Adding a new kind of pure computation to an applicative functor. module Control.Applicative.Lift -- | Applicative functor formed by adding pure computations to a given -- applicative functor. data Lift f a Pure :: a -> Lift f a Other :: f a -> Lift f a -- | Projection to the other functor. unLift :: Applicative f => Lift f a -> f a -- | Apply a transformation to the other computation. mapLift :: (f a -> g a) -> Lift f a -> Lift g a -- | Eliminator for Lift. -- -- elimLift :: (a -> r) -> (f a -> r) -> Lift f a -> r -- | An applicative functor that collects a monoid (e.g. lists) of errors. -- A sequence of computations fails if any of its components do, but -- unlike monads made with ExceptT from -- Control.Monad.Trans.Except, these computations continue after -- an error, collecting all the errors. -- -- type Errors e = Lift (Constant e) -- | Extractor for computations with accumulating errors. -- -- runErrors :: Errors e a -> Either e a -- | Report an error. failure :: e -> Errors e a -- | Convert from Either to Errors (inverse of -- runErrors). eitherToErrors :: Either e a -> Errors e a instance Data.Functor.Classes.Eq1 f => Data.Functor.Classes.Eq1 (Control.Applicative.Lift.Lift f) instance Data.Functor.Classes.Ord1 f => Data.Functor.Classes.Ord1 (Control.Applicative.Lift.Lift f) instance Data.Functor.Classes.Read1 f => Data.Functor.Classes.Read1 (Control.Applicative.Lift.Lift f) instance Data.Functor.Classes.Show1 f => Data.Functor.Classes.Show1 (Control.Applicative.Lift.Lift f) instance (Data.Functor.Classes.Eq1 f, GHC.Classes.Eq a) => GHC.Classes.Eq (Control.Applicative.Lift.Lift f a) instance (Data.Functor.Classes.Ord1 f, GHC.Classes.Ord a) => GHC.Classes.Ord (Control.Applicative.Lift.Lift f a) instance (Data.Functor.Classes.Read1 f, GHC.Read.Read a) => GHC.Read.Read (Control.Applicative.Lift.Lift f a) instance (Data.Functor.Classes.Show1 f, GHC.Show.Show a) => GHC.Show.Show (Control.Applicative.Lift.Lift f a) instance GHC.Base.Functor f => GHC.Base.Functor (Control.Applicative.Lift.Lift f) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Control.Applicative.Lift.Lift f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Control.Applicative.Lift.Lift f) instance GHC.Base.Applicative f => GHC.Base.Applicative (Control.Applicative.Lift.Lift f) instance GHC.Base.Alternative f => GHC.Base.Alternative (Control.Applicative.Lift.Lift f) -- | Making functors whose elements are notionally in the reverse order -- from the original functor. module Data.Functor.Reverse -- | The same functor, but with Foldable and Traversable -- instances that process the elements in the reverse order. newtype Reverse f a Reverse :: f a -> Reverse f a [getReverse] :: Reverse f a -> f a instance Data.Functor.Classes.Eq1 f => Data.Functor.Classes.Eq1 (Data.Functor.Reverse.Reverse f) instance Data.Functor.Classes.Ord1 f => Data.Functor.Classes.Ord1 (Data.Functor.Reverse.Reverse f) instance Data.Functor.Classes.Read1 f => Data.Functor.Classes.Read1 (Data.Functor.Reverse.Reverse f) instance Data.Functor.Classes.Show1 f => Data.Functor.Classes.Show1 (Data.Functor.Reverse.Reverse f) instance (Data.Functor.Classes.Eq1 f, GHC.Classes.Eq a) => GHC.Classes.Eq (Data.Functor.Reverse.Reverse f a) instance (Data.Functor.Classes.Ord1 f, GHC.Classes.Ord a) => GHC.Classes.Ord (Data.Functor.Reverse.Reverse f a) instance (Data.Functor.Classes.Read1 f, GHC.Read.Read a) => GHC.Read.Read (Data.Functor.Reverse.Reverse f a) instance (Data.Functor.Classes.Show1 f, GHC.Show.Show a) => GHC.Show.Show (Data.Functor.Reverse.Reverse f a) instance GHC.Base.Functor f => GHC.Base.Functor (Data.Functor.Reverse.Reverse f) instance GHC.Base.Applicative f => GHC.Base.Applicative (Data.Functor.Reverse.Reverse f) instance GHC.Base.Alternative f => GHC.Base.Alternative (Data.Functor.Reverse.Reverse f) instance GHC.Base.Monad m => GHC.Base.Monad (Data.Functor.Reverse.Reverse m) instance Control.Monad.Fail.MonadFail m => Control.Monad.Fail.MonadFail (Data.Functor.Reverse.Reverse m) instance GHC.Base.MonadPlus m => GHC.Base.MonadPlus (Data.Functor.Reverse.Reverse m) instance Data.Foldable.Foldable f => Data.Foldable.Foldable (Data.Functor.Reverse.Reverse f) instance Data.Traversable.Traversable f => Data.Traversable.Traversable (Data.Functor.Reverse.Reverse f) instance Data.Functor.Contravariant.Contravariant f => Data.Functor.Contravariant.Contravariant (Data.Functor.Reverse.Reverse f)