| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
| Extensions |
|
Control.THEff.State
- data State' v e
- data State m e o v a
- = StateOuter (o m e)
- | StateAction (State' v e)
- | StateResult a
- type StateArgT v = v
- type StateResT r v = (r, v)
- effState :: EffClass State' v e => State' v r -> Eff e r
- runEffState :: forall t u m z v m1 e o w a r. Monad m => (u t r -> (r -> m (StateResT z v)) -> m (StateResT z v)) -> (State m1 e o w a -> r) -> (r -> State t r u v z) -> StateArgT v -> Eff r a -> m (StateResT z v)
- get :: EffClass State' v e => Eff e v
- put :: EffClass State' v e => v -> Eff e ()
- modify :: EffClass State' v e => (v -> v) -> Eff e ()
- stateOnly :: forall v e r t. (t -> e -> (r, v)) -> t -> e -> v
- withoutState :: forall v e r t. (t -> e -> (r, v)) -> t -> e -> r
Overview
This version builds its output lazily; for a strict version with the same interface, see Control.THEff.State.Strict.
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell #-}
import Control.THEff
import Control.THEff.State
mkEff "Example1" ''State ''Int ''NoEff
mkEff "Example2" ''State ''Float ''Example1
main:: IO ()
main = print $ runExample1 123
$ runExample2 pi $ do
i <- get
modify ((1 :: Int) +)
put $ i * (2 :: Float)
return $ show i Output : (("3.1415927",6.2831855),124)
Types and functions used in mkEff
Actually, the effect type - v - Type - the parameter of the effect. - e - mkEff generated type.
Type implements link in the chain of effects.
Constructors must be named {EffectName}{Outer|WriterAction|WriterResult}
and have a specified types of fields.
- m - Or Monad (if use the Lift) or phantom type - stub (if used NoEff).
- o - Type of outer effect.
- a - The result of mkEff generated runEEEE... function.
Constructors
| StateOuter (o m e) | |
| StateAction (State' v e) | |
| StateResult a |
effState :: EffClass State' v e => State' v r -> Eff e r Source
This function is used in the mkEff generated runEEEE functions and typically
in effect action functions. Calling the effect action.
Arguments
| :: forall (t :: * -> *) (u :: (* -> *) -> * -> *) (m :: * -> *) (m1 :: * -> *) (o :: (* -> *) -> * -> *). Monad m | |
| => (u t r -> (r -> m (StateResT z v)) -> m (StateResT z v)) | The outer effect function |
| -> (State m1 e o w a -> r) | The chain of effects link wrapper. |
| -> (r -> State t r u v z) | The chain of effects link unwrapper. |
| -> StateArgT v | The initial value of argument of effect. |
| -> Eff r a | |
| -> m (StateResT z v) |
The main function of the effect implementing.
This function is used in the mkEff generated runEEEE functions.
Functions that use this effect
Helper functions
Arguments
| :: (t -> e -> (r, v)) | State effect runEEEE function |
| -> t | The initial value of argument of effect. |
| -> e | Eff (MyState m ...) ... |
| -> v |
stateOnly runExample1 123 === snd (runExample1 123)
Arguments
| :: (t -> e -> (r, v)) | State effect runEEEE function |
| -> t | The initial value of argument of effect. |
| -> e | Eff (MyState m ...) ... |
| -> r |
withoutState runExample1 123 === fst (runExample1 123)