Control.Eff.Operational

Operational Monad (https://wiki.haskell.org/Operational) implemented with extensible effects.

Documentation

data Program instr v where

Lift values to an effect. You can think this is a generalization of Lift.

Constructors

Singleton :: instr a -> Program instr a

Instances

Handle (Program f) r a (Intrprtr f r' -> Eff r' a)

Given a continuation and a program, interpret it Usually, we have r ~ [Program f : r']

Defined in Control.Eff.Operational

Methods

handle :: (Eff r a -> Intrprtr f r' -> Eff r' a) -> Arrs r v a -> Program f v -> Intrprtr f r' -> Eff r' a

handle_relay :: (r ~ (Program f ': r'0), Relay (Intrprtr f r' -> Eff r' a) r'0) => (a -> Intrprtr f r' -> Eff r' a) -> (Eff r a -> Intrprtr f r' -> Eff r' a) -> Eff r a -> Intrprtr f r' -> Eff r' a

respond_relay :: (a -> Intrprtr f r' -> Eff r' a) -> (Eff r a -> Intrprtr f r' -> Eff r' a) -> Eff r a -> Intrprtr f r' -> Eff r' a

withOperational :: a -> Intrprtr f r -> Eff r a

Embed a pure value

newtype Intrprtr f r

General form of an interpreter

Constructors

Intrprtr

Fields

• runIntrprtr :: forall x. f x -> Eff r x

Instances

Handle (Program f) r a (Intrprtr f r' -> Eff r' a)

Given a continuation and a program, interpret it Usually, we have r ~ [Program f : r']

Defined in Control.Eff.Operational

Methods

handle :: (Eff r a -> Intrprtr f r' -> Eff r' a) -> Arrs r v a -> Program f v -> Intrprtr f r' -> Eff r' a

handle_relay :: (r ~ (Program f ': r'0), Relay (Intrprtr f r' -> Eff r' a) r'0) => (a -> Intrprtr f r' -> Eff r' a) -> (Eff r a -> Intrprtr f r' -> Eff r' a) -> Eff r a -> Intrprtr f r' -> Eff r' a

respond_relay :: (a -> Intrprtr f r' -> Eff r' a) -> (Eff r a -> Intrprtr f r' -> Eff r' a) -> Eff r a -> Intrprtr f r' -> Eff r' a

singleton :: Member (Program instr) r => instr a -> Eff r a

Lift a value to a monad.

runProgram :: forall f r a. (forall x. f x -> Eff r x) -> Eff (Program f ': r) a -> Eff r a

Convert values using given interpreter to effects.

Usage

See Control.Eff.Operational.Example for an example of defining data using GADTs and implementing interpreters from the data to effects.

To use the interpreter, see below or consult the tests.

main :: IO ()
main = do
    let comp = runProgram adventPure prog
    putStrLn . fst . run . runMonoidWriter $ evalState comp ["foo","bar"]
    runLift $ runProgram adventIO prog