Safe Haskell	Safe-Inferred
Language	Haskell2010

Control.Monad.Trans.Has.Accum

Synopsis

type HasAccum w m = Has (AccumT w) m
add :: HasAccum w m => w -> m ()
newtype AccumT w (m :: Type -> Type) a = AccumT (w -> m (a, w))

Documentation

type HasAccum w m = Has (AccumT w) m Source #

add :: HasAccum w m => w -> m () Source #

newtype AccumT w (m :: Type -> Type) a #

An accumulation monad parameterized by:

w - the output to accumulate.
m - The inner monad.

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

a restricted append-only version of a state monad transformer or
a writer monad transformer with the extra ability to read all previous output.

Constructors

AccumT (w -> m (a, w))

Instances

Instances details

Monoid w => MonadTrans (AccumT w)
Instance details Defined in Control.Monad.Trans.Accum Methods lift :: Monad m => m a -> AccumT w m a #
(Monoid w, Functor m, Monad m) => Monad (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods (>>=) :: AccumT w m a -> (a -> AccumT w m b) -> AccumT w m b # (>>) :: AccumT w m a -> AccumT w m b -> AccumT w m b # return :: a -> AccumT w m a #
Functor m => Functor (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods fmap :: (a -> b) -> AccumT w m a -> AccumT w m b # (<$) :: a -> AccumT w m b -> AccumT w m a #
(Monoid w, Functor m, MonadFix m) => MonadFix (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods mfix :: (a -> AccumT w m a) -> AccumT w m a #
(Monoid w, MonadFail m) => MonadFail (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods fail :: String -> AccumT w m a #
(Monoid w, Functor m, Monad m) => Applicative (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods pure :: a -> AccumT w m a # (<>) :: AccumT w m (a -> b) -> AccumT w m a -> AccumT w m b # liftA2 :: (a -> b -> c) -> AccumT w m a -> AccumT w m b -> AccumT w m c # (>) :: AccumT w m a -> AccumT w m b -> AccumT w m b # (<*) :: AccumT w m a -> AccumT w m b -> AccumT w m a #
(Monoid w, Functor m, MonadIO m) => MonadIO (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods liftIO :: IO a -> AccumT w m a #
(Monoid w, Functor m, MonadPlus m) => Alternative (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods empty :: AccumT w m a # (<\|>) :: AccumT w m a -> AccumT w m a -> AccumT w m a # some :: AccumT w m a -> AccumT w m [a] # many :: AccumT w m a -> AccumT w m [a] #
(Monoid w, Functor m, MonadPlus m) => MonadPlus (AccumT w m)
Instance details Defined in Control.Monad.Trans.Accum Methods mzero :: AccumT w m a # mplus :: AccumT w m a -> AccumT w m a -> AccumT w m a #