Control.Monad.Sharing.Classes

Documentation

class Sharing m where

Interface of monads that support explicit sharing.

Methods

share :: Trans m a a => m a -> m (m a)

Yields an action that returns the same results as the given | action but whose effects are only executed once. Especially, | when the resulting action is duplicated it returns the same | result at every occurrence.

Instances

Monad m => Sharing (Lazy m)

We provide instances of the Trans class for some predefined | Haskell types. For flat types the function trans just returns | its argument which has no arguments to which the given function | could be applied.

class Trans m a b where

Interface to transform nested monadic data types. The provided | function trans is supposed to map the given function on every | monadic argument. The result of trans may be of the same type | as the argument but can also be of a different type, e.g. to | convert a value with nested monadic arguments to a corresponding | value without.

Methods

trans :: (forall c d. Trans m c d => m c -> m (m d)) -> a -> m b

Instances

Monad m => Trans m Double Double

Monad m => Trans m Float Float

Monad m => Trans m Char Char

Monad m => Trans m Int Int

Monad m => Trans m Bool Bool

(Monad m, Trans m a a) => Trans m [m a] [a]

An instance for lists with monadic elements that lifts all | monadic effects to the top level and yields a list with | non-monadic elements.

(Monad m, Trans m a a) => Trans m [m a] [m a]

An instance for lists with monadic elements.

Monad m => Trans m [Double] [Double]

Monad m => Trans m [Float] [Float]

Monad m => Trans m [Char] [Char]

Monad m => Trans m [Int] [Int]

Monad m => Trans m [Bool] [Bool]

(Monad m, Trans m a b) => Trans m [a] (List m b)

This instance enables the function Control.Monad.Sharing.eval | to transform ordinary Haskell lists into nested monadic lists.

(Monad m, Trans m a b) => Trans m (List m a) [b]

This instance enables the function Control.Monad.Sharing.eval | to transform nested monadic lists into ordinary Haskell lists.

(Monad m, Trans m a b) => Trans m (List m a) (List m b)

This instance allows to use nested monadic lists as argument to | the Control.Monad.Sharing.share combinator.

eval :: (Monad m, Trans m a b) => a -> m b

Lifts all monadic effects in nested monadic values to the top | level. If m is a monad for non-determinism and the argument a | data structure with nested non-determinism then the result | corresponds to the normal form of the argument.