Control.Monad.Writer.Lazy

Portability	non-portable (multi-param classes, functional dependencies)
Stability	experimental
Maintainer	libraries@haskell.org

Description

Lazy writer monads.

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.

Documentation

module Control.Monad.Writer.Class

newtype Writer w a

Source

Constructors

Writer

runWriter :: (a, w)

Instances

Monoid w => MonadWriter w (Writer w)

Monoid w => Monad (Writer w)

Functor (Writer w)

Monoid w => MonadFix (Writer w)

execWriter :: Writer w a -> w

Source

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

Source

newtype WriterT w m a

Source

Constructors

WriterT

runWriterT :: m (a, w)

Instances

(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 w

Source

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

Source

module Control.Monad.Trans

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