Control.Proxy.Trans

You can define your own proxy extensions by writing your own "proxy transformers". Proxy transformers are monad transformers that also correctly lift all proxy operations from the base proxy type to the extended proxy type. Stack multiple proxy transformers to chain features together.

Proxy Transformers

class ProxyTrans t where

Uniform interface to lifting proxies

Minimal complete definition

liftP

Methods

liftP :: (Monad m, Proxy p) => p a' a b' b m r -> t p a' a b' b m r

Instances

ProxyTrans IdentityP

Methods

liftP :: (Monad m, Proxy p) => p a' a b' b m r -> IdentityP p a' a b' b m r

ProxyTrans MaybeP

Methods

liftP :: (Monad m, Proxy p) => p a' a b' b m r -> MaybeP p a' a b' b m r

ProxyTrans (EitherP e)

Methods

liftP :: (Monad m, Proxy p) => p a' a b' b m r -> EitherP e p a' a b' b m r

ProxyTrans (ReaderP i)

Methods

liftP :: (Monad m, Proxy p) => p a' a b' b m r -> ReaderP i p a' a b' b m r

ProxyTrans (StateP s)

Methods

liftP :: (Monad m, Proxy p) => p a' a b' b m r -> StateP s p a' a b' b m r

ProxyTrans (WriterP w)

Methods

liftP :: (Monad m, Proxy p) => p a' a b' b m r -> WriterP w p a' a b' b m r

mapP :: (Monad m, Proxy p, ProxyTrans t) => (q -> p a' a b' b m r) -> q -> t p a' a b' b m r

Lift a Proxy Kleisli arrow

mapP = (lift .)

Laws

mapP defines a functor that preserves five categories:

• Kleisli category
• The two Proxy categories
• "request" category
• "respond" category

Laws:

• Functor between Proxy categories

mapP (f >-> g) = mapP f >-> mapP g

mapP idT = idT

mapP (f >~> g) = mapP f >~> mapP g

mapP idPush = idPush

• Functor between Kleisli categories

mapP (f <=< g) = mapP f <=< mapP g

mapP return = return

• Functor between "request" categories

mapP (f /</ g) = mapP f /</ mapP g -- when /</ is defined

mapP request = request

• Functor between "respond" categories

mapP (f \<\ g) = mapP f \<\ mapP g -- when \<\ is defined

mapP respond = respond