mtl- Monad transformer librarySource codeContentsIndex
Portabilitynon-portable (multi-param classes, functional dependencies)

Lazy writer monads.

Inspired by the paper /Functional Programming with Overloading and Higher-Order Polymorphism/, Mark P Jones ( Advanced School of Functional Programming, 1995.

module Control.Monad.Writer.Class
newtype Writer w a Source
runWriter :: (a, w)
show/hide Instances
execWriter :: Writer w a -> wSource
mapWriter :: ((a, w) -> (b, w')) -> Writer w a -> Writer w' bSource
newtype WriterT w m a Source
runWriterT :: m (a, w)
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(Monoid w, Monad m) => MonadWriter w (WriterT w m)
(Monoid w, MonadState s m) => MonadState s (WriterT w m)
(Monoid w, MonadReader r m) => MonadReader r (WriterT w m)
(Monoid w, MonadError e m) => MonadError e (WriterT w m)
Monoid w => MonadTrans (WriterT w)
(Monoid w, Monad m) => Monad (WriterT w m)
Monad m => Functor (WriterT w m)
(Monoid w, MonadFix m) => MonadFix (WriterT w m)
(Monoid w, MonadPlus m) => MonadPlus (WriterT w m)
(Monoid w, MonadIO m) => MonadIO (WriterT w m)
(Monoid w, MonadCont m) => MonadCont (WriterT w m)
execWriterT :: Monad m => WriterT w m a -> m wSource
mapWriterT :: (m (a, w) -> n (b, w')) -> WriterT w m a -> WriterT w' n bSource
module Control.Monad
module Control.Monad.Fix
module Control.Monad.Trans
module Data.Monoid
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