Control.Monad.Trans.Has.Accum

Documentation

type HasAccum w m = Has (AccumT w) m

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

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

Monoid w => MonadTrans (AccumT w)

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)

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)

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)

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)

Defined in Control.Monad.Trans.Accum

Methods

fail :: String -> AccumT w m a

(Monoid w, Functor m, Monad m) => Applicative (AccumT w m)

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)

Defined in Control.Monad.Trans.Accum

Methods

liftIO :: IO a -> AccumT w m a

(Monoid w, Functor m, MonadPlus m) => Alternative (AccumT w m)

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)

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