Control.Comonad.Env.Class

class ComonadAsk :: Type -> (Type -> Type) -> Constraintclass (Comonad w) <= ComonadAsk e w | w -> e where

The ComonadEnv type class represents those comonads which support a global environment that can be provided via the ask function.

An implementation is provided for EnvT.

Members

• ask :: forall a. w a -> e

Instances

• ComonadAsk e (Tuple e)
• (Comonad w) => ComonadAsk e (EnvT e w)

asks :: forall e1 e2 w a. ComonadAsk e1 w => (e1 -> e2) -> w a -> e2

Get a value which depends on the environment.

class ComonadEnv :: Type -> (Type -> Type) -> Constraintclass (ComonadAsk e w) <= ComonadEnv e w | w -> e where

The ComonadEnv type class extends ComonadAsk with a function local f x that allows the value of the local context to be modified for the duration of the execution of action x.

An implementation is provided for EnvT.

Laws:

• ask (local f x) = f (ask x)
• extract (local _ x) = extract a
• extend g (local f x) = extend (g <<< local f) x

Members

• local :: forall a. (e -> e) -> w a -> w a

Instances

• ComonadEnv e (Tuple e)
• (Comonad w) => ComonadEnv e (EnvT e w)