monadology-0.1: src/Control/Monad/Ology/Specific/ResultT.hs

module Control.Monad.Ology.Specific.ResultT where

import Control.Monad.Ology.Data.Exn
import Control.Monad.Ology.General
import Control.Monad.Ology.Specific.ComposeInner
import Control.Monad.Ology.Specific.Result
import Import

type ResultT e = ComposeInner (Result e)

runResultT :: forall m e a. ResultT e m a -> m (Result e a)
runResultT = unComposeInner

-- | Throw the parameterised exception type.
throwR ::
       forall m e a. Monad m
    => e
    -> ResultT e m a
throwR e = liftInner $ throwExc e

-- | Catch the parameterised exception type.
catchR ::
       forall m e e' a. Monad m
    => ResultT e m a
    -> (e -> ResultT e' m a)
    -> ResultT e' m a
catchR (MkComposeInner rma) handler =
    MkComposeInner $ do
        rea <- rma
        case rea of
            SuccessResult a -> return $ SuccessResult a
            FailureResult e -> unComposeInner $ handler e

resultExn ::
       forall m e. Monad m
    => Exn (ResultT e m) e
resultExn = MkExn throwR catchR