Safe Haskell	None
Language	Haskell2010

Control.Monad.HashCons

Contents

Transformer
Capability type class

Description

Provides a transformer, and a capability type class in the style of mtl, for hash consing. See the Covenant wiki for how this works.

Synopsis

data HashConsT r e (m :: Type -> Type) a
runHashConsT :: HashConsT r e m a -> m (a, Bimap r e)
hashCons :: forall r e (m :: Type -> Type). (Ord r, Ord e, Bounded r, Enum r, Monad m) => e -> HashConsT r e m r
lookupRef_ :: forall r e (m :: Type -> Type). (Monad m, Ord e, Ord r) => r -> HashConsT r e m (Maybe e)
class (Eq e, Eq r, Monad m) => MonadHashCons r e (m :: Type -> Type) | m -> e r where
- refTo :: e -> m r
- lookupRef :: r -> m (Maybe e)

Transformer

data HashConsT r e (m :: Type -> Type) a Source #

A transformer implementing hash consing capabilities, with references of type r and referents of type e. It is assumed that values of type e contain values of type r in their capacity as references, though this is not a requirement of this transformer.

Important note

This implementation is not suitable for any m that throws exceptions. This includes IO, ST and anything stacked atop them. For the reasons why, see here.

Since: 1.0.0

Instances

Instances details

(Ord r, Ord e, Bounded r, Enum r, Monad m) => MonadHashCons r e (HashConsT r e m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> HashConsT r e m r Source # lookupRef :: r -> HashConsT r e m (Maybe e) Source #
MonadTrans (HashConsT r e) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods lift :: Monad m => m a -> HashConsT r e m a #
Monad m => Applicative (HashConsT r e m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods pure :: a -> HashConsT r e m a # (<>) :: HashConsT r e m (a -> b) -> HashConsT r e m a -> HashConsT r e m b # liftA2 :: (a -> b -> c) -> HashConsT r e m a -> HashConsT r e m b -> HashConsT r e m c # (>) :: HashConsT r e m a -> HashConsT r e m b -> HashConsT r e m b # (<*) :: HashConsT r e m a -> HashConsT r e m b -> HashConsT r e m a #
Functor m => Functor (HashConsT r e m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods fmap :: (a -> b) -> HashConsT r e m a -> HashConsT r e m b # (<$) :: a -> HashConsT r e m b -> HashConsT r e m a #
Monad m => Monad (HashConsT r e m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods (>>=) :: HashConsT r e m a -> (a -> HashConsT r e m b) -> HashConsT r e m b # (>>) :: HashConsT r e m a -> HashConsT r e m b -> HashConsT r e m b # return :: a -> HashConsT r e m a #

runHashConsT :: HashConsT r e m a -> m (a, Bimap r e) Source #

Execute the computation described, returning both the result and the unique pairings of r and e produced as part of it.

Since: 1.0.0

hashCons :: forall r e (m :: Type -> Type). (Ord r, Ord e, Bounded r, Enum r, Monad m) => e -> HashConsT r e m r Source #

Given a value of type e, produce the unique value of type r acting as a reference to it. This r will be cached, ensuring any future requests for the reference for this value of type e will be the same.

Since: 1.0.0

lookupRef_ :: forall r e (m :: Type -> Type). (Monad m, Ord e, Ord r) => r -> HashConsT r e m (Maybe e) Source #

Given a value of type r, fetch the cached e value, if it exists.

Since: 1.0.0

Capability type class

class (Eq e, Eq r, Monad m) => MonadHashCons r e (m :: Type -> Type) | m -> e r where Source #

An mtl-style capability type class for hash consing capability, using references of type r and values of type e.

Laws

refTo x >> refTo x = refTo x
liftA2 (/=) (refTo x) (refTo y) = refTo x *> refTo y *> pure (x /= y)
refTo x >>= (\r -> lookupRef r >>= (\y -> pure (y, r))) = (Just x, ) <$> refTo x

Since: 1.0.0

Methods

refTo :: e -> m r Source #

Produce the unique value of type r that acts as a reference for the given value of type e.

Since: 1.0.0

lookupRef :: r -> m (Maybe e) Source #

Given a value of type r, fetch the cached value of type e.

Since: 1.0.0

Instances

Instances details

MonadHashCons Id ASGNode ASGBuilder Source #	Since: 1.0.0
Instance details Defined in Covenant.ASG Methods refTo :: ASGNode -> ASGBuilder Id Source # lookupRef :: Id -> ASGBuilder (Maybe ASGNode) Source #
(Ord r, Ord e, MonadHashCons r e m) => MonadHashCons r e (MaybeT m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> MaybeT m r Source # lookupRef :: r -> MaybeT m (Maybe e) Source #
MonadHashCons r e m => MonadHashCons r e (ExceptT e' m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> ExceptT e' m r Source # lookupRef :: r -> ExceptT e' m (Maybe e) Source #
MonadHashCons r e m => MonadHashCons r e (ReaderT r' m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> ReaderT r' m r Source # lookupRef :: r -> ReaderT r' m (Maybe e) Source #
MonadHashCons r e m => MonadHashCons r e (StateT s m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> StateT s m r Source # lookupRef :: r -> StateT s m (Maybe e) Source #
MonadHashCons r e m => MonadHashCons r e (WriterT w m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> WriterT w m r Source # lookupRef :: r -> WriterT w m (Maybe e) Source #
(Ord r, Ord e, Bounded r, Enum r, Monad m) => MonadHashCons r e (HashConsT r e m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> HashConsT r e m r Source # lookupRef :: r -> HashConsT r e m (Maybe e) Source #
MonadHashCons r e m => MonadHashCons r e (RWST r' w s m) Source #	Since: 1.0.0
Instance details Defined in Control.Monad.HashCons Methods refTo :: e -> RWST r' w s m r Source # lookupRef :: r -> RWST r' w s m (Maybe e) Source #