Control.Monad.Writer.CPS

Stricter writer monad using continuation-passing-style for the writer output.

Inspired by the paper Functional Programming with Overloading and Higher-Order Polymorphism, Mark P Jones (http://web.cecs.pdx.edu/~mpj/pubs/springschool.html) Advanced School of Functional Programming, 1995.

The Writer monad

type Writer w = WriterT w Identity

runWriter :: Monoid w => Writer w a -> (a, w)

execWriter :: Monoid w => Writer w a -> w

mapWriter :: (Monoid w, Monoid w') => ((a, w) -> (b, w')) -> Writer w a -> Writer w' b

The WriterT monad transformer

data WriterT w m a :: * -> (* -> *) -> * -> *

Instances

MonadTrans (WriterT w)

Methods

lift :: Monad m => m a -> WriterT w m a

Monad m => Monad (WriterT w m)

Methods

(>>=) :: WriterT w m a -> (a -> WriterT w m b) -> WriterT w m b

(>>) :: WriterT w m a -> WriterT w m b -> WriterT w m b

return :: a -> WriterT w m a

fail :: String -> WriterT w m a

Functor m => Functor (WriterT w m)

Methods

fmap :: (a -> b) -> WriterT w m a -> WriterT w m b

(<$) :: a -> WriterT w m b -> WriterT w m a

MonadFix m => MonadFix (WriterT w m)

Methods

mfix :: (a -> WriterT w m a) -> WriterT w m a

MonadFail m => MonadFail (WriterT w m)

Methods

fail :: String -> WriterT w m a

(Functor m, Monad m) => Applicative (WriterT w m)

Methods

pure :: a -> WriterT w m a

(<*>) :: WriterT w m (a -> b) -> WriterT w m a -> WriterT w m b

(*>) :: WriterT w m a -> WriterT w m b -> WriterT w m b

(<*) :: WriterT w m a -> WriterT w m b -> WriterT w m a

MonadIO m => MonadIO (WriterT w m)

Methods

liftIO :: IO a -> WriterT w m a

(Functor m, MonadPlus m) => Alternative (WriterT w m)

Methods

empty :: WriterT w m a

(<|>) :: WriterT w m a -> WriterT w m a -> WriterT w m a

some :: WriterT w m a -> WriterT w m [a]

many :: WriterT w m a -> WriterT w m [a]

(Functor m, MonadPlus m) => MonadPlus (WriterT w m)

Methods

mzero :: WriterT w m a

mplus :: WriterT w m a -> WriterT w m a -> WriterT w m a

runWriterT :: Monoid w => WriterT w m a -> m (a, w)

execWriterT :: (Monad m, Monoid w) => WriterT w m a -> m w

mapWriterT :: (Monad n, Monoid w, Monoid w') => (m (a, w) -> n (b, w')) -> WriterT w m a -> WriterT w' n b

Orphan instances

(Monoid w, Monad m) => MonadWriter w (WriterT w m)

Methods

writer :: (a, w) -> WriterT w m a

tell :: w -> WriterT w m ()

listen :: WriterT w m a -> WriterT w m (a, w)

pass :: WriterT w m (a, w -> w) -> WriterT w m a