Polysemy.Internal.Writer

Documentation

data Writer o m a where

An effect capable of emitting and intercepting messages.

Constructors

Tell :: o -> Writer o m ()

Listen :: forall o m a. m a -> Writer o m (o, a)

Pass :: m (o -> o, a) -> Writer o m a

Instances

type DefiningModule Writer

Defined in Polysemy.Internal.Writer

type DefiningModule Writer = "Polysemy.Internal.Writer"

pass :: forall o r a. MemberWithError (Writer o) r => Sem r (o -> o, a) -> Sem r a

listen :: forall o r a. MemberWithError (Writer o) r => Sem r a -> Sem r (o, a)

tell :: forall o r. MemberWithError (Writer o) r => o -> Sem r ()

writerToEndoWriter :: (Monoid o, Member (Writer (Endo o)) r) => Sem (Writer o ': r) a -> Sem r a

Transform a Writer o effect into a Writer (Endo o) effect, right-associating all uses of <> for o.

This can be used together with raiseUnder in order to create -AssocR variants out of regular Writer interpreters.

Since: 1.2.0.0

runWriterSTMAction :: forall o r a. (Member (Final IO) r, Monoid o) => (o -> STM ()) -> Sem (Writer o ': r) a -> Sem r a

A variant of runWriterTVar where an STM action is used instead of a TVar to commit tells.