Copyright	(C) 2008-2014 Edward Kmett
License	BSD-style (see the file LICENSE)
Maintainer	Edward Kmett <ekmett@gmail.com>
Stability	experimental
Portability	non-portable (fundeps, MPTCs)
Safe Haskell	Safe
Language	Haskell2010

Control.Comonad.Env

Contents

Description

The Env comonad (aka the Coreader, Environment, or Product comonad)

A co-Kleisli arrow in the Env comonad is isomorphic to a Kleisli arrow in the reader monad.

(a -> e -> m) ~ (a, e) -> m ~ Env e a -> m

Synopsis

ComonadEnv class

class Comonad w => ComonadEnv e w | w -> e where

Methods

ask :: w a -> e

Instances

ComonadEnv e w => ComonadEnv e (IdentityT w)
ComonadEnv e (Arg e)
ComonadEnv e ((,) e)
(ComonadEnv e w, Monoid m) => ComonadEnv e (TracedT m w)
ComonadEnv e w => ComonadEnv e (StoreT t w)
Comonad w => ComonadEnv e (EnvT e w)

asks :: ComonadEnv e w => (e -> e') -> w a -> e'

local :: (e -> e') -> EnvT e w a -> EnvT e' w a

Modifies the environment using the specified function.

The Env comonad

env :: e -> a -> Env e a

Create an Env using an environment and a value

runEnv :: Env e a -> (e, a)

data EnvT e w a

Constructors

EnvT e (w a)

Instances

Comonad w => ComonadEnv e (EnvT e w)
ComonadStore s w => ComonadStore s (EnvT e w)
ComonadTraced m w => ComonadTraced m (EnvT e w)
ComonadTrans (EnvT e)
ComonadHoist (EnvT e)
Functor w => Functor (EnvT e w)
Foldable w => Foldable (EnvT e w)
Traversable w => Traversable (EnvT e w)
(Semigroup e, ComonadApply w) => ComonadApply (EnvT e w)
Comonad w => Comonad (EnvT e w)
(Data e, Typeable (* -> *) w, Data (w a), Data a) => Data (EnvT e w a)

runEnvT :: EnvT e w a -> (e, w a)