pipes-2.4.0: Compositional pipelines

Safe HaskellSafe-Inferred

Control.Proxy.Trans.Maybe

Contents

Description

This module provides the proxy transformer equivalent of MaybeT.

Synopsis

MaybeP

newtype MaybeP p a' a b' b m r Source

The Maybe proxy transformer

Constructors

MaybeP 

Fields

runMaybeP :: p a' a b' b m (Maybe r)
 

Instances

ProxyTrans MaybeP 
Channel p => Channel (MaybeP p) 
MonadTrans (p a' a b' b) => MonadTrans (MaybeP p a' a b' b) 
MFunctor (p a' a b' b) => MFunctor (MaybeP p a' a b' b) 
Monad (p a' a b' b m) => Monad (MaybeP p a' a b' b m) 
Monad (p a' a b' b m) => Functor (MaybeP p a' a b' b m) 
(Monad (MaybeP p a' a b' b m), Monad (p a' a b' b m)) => MonadPlus (MaybeP p a' a b' b m) 
(Functor (MaybeP p a' a b' b m), Monad (p a' a b' b m)) => Applicative (MaybeP p a' a b' b m) 
(Applicative (MaybeP p a' a b' b m), Monad (p a' a b' b m)) => Alternative (MaybeP p a' a b' b m) 
(Monad (MaybeP p a' a b' b m), MonadIO (p a' a b' b m)) => MonadIO (MaybeP p a' a b' b m) 

runMaybeK :: (q -> MaybeP p a' a b' b m r) -> q -> p a' a b' b m (Maybe r)Source

Run a MaybeP 'K'leisli arrow, returning the result or Nothing

Maybe operations

nothing :: Monad (p a' a b' b m) => MaybeP p a' a b' b m rSource

A synonym for mzero

just :: Monad (p a' a b' b m) => r -> MaybeP p a' a b' b m rSource

A synonym for return