Modulefused-effects-1.1.2.7Haskell2010

Control.Carrier.Writer.Strict

A carrier for Writer effects. This carrier performs its append operations strictly and thus avoids the space leaks inherent in lazy writer monads. These appends are left-associative; as such, [] is a poor choice of monoid for computations that entail many calls to tell. The Seq or DList monoids may be a superior choice.

This implementation is based on a post Gabriel Gonzalez made to the Haskell mailing list: https://mail.haskell.org/pipermail/libraries/2013-March/019528.html

1 type
2 values

Packagefused-effects-1.1.2.7
Exports3
LanguageHaskell2010
LicenceBSD-3-Clause
SourceStrict.hs

Writer carrier

3 declarations

valuerunWriter :: Monoid w => WriterC w m a -> m (w, a)

Run a Writer effect with a Monoidal log, producing the final log alongside the result value.

runWriter (tell w) = pure (w, ())

runWriter (pure a) = pure (mempty, a)

valueexecWriter :: (Monoid w, Functor m) => WriterC w m a -> m w

Run a Writer effect with a Monoidal log, producing the final log and discarding the result value.

execWriter m = fmap fst (runWriter m)

newtypenewtype WriterC w (m :: Type -> Type) a

A space-efficient carrier for Writer effects, implemented atop Control.Carrier.State.Strict.

Constructors

WriterC
- runWriterC :: StateC w m a

Instances10MonadTrans, Monad, Functor, MonadFix, MonadFail, Applicative, …

MonadTrans (WriterC w)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
Monad m => Monad (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
Functor m => Functor (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
MonadFix m => MonadFix (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
MonadFail m => MonadFail (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
Monad m => Applicative (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
(Alternative m, Monad m) => Alternative (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
(Alternative m, Monad m) => MonadPlus (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
MonadIO m => MonadIO (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict
(Monoid w, Algebra sig m) => Algebra (Writer w :+: sig) (WriterC w m)Defined in fused-effects-1.1.2.7 · Control.Carrier.Writer.Strict

Writer effect

0 declarations

module Control.Effect.Writer