Safe Haskell	None
Language	Haskell2010
Extensions	FlexibleContexts KindSignatures RankNTypes ExplicitForAll

Control.THEff.Catch

Contents

Overview
Types and functions used in mkEff
Functions that use this effect

Synopsis

Overview

{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell #-}

import Control.THEff
import Control.THEff.Catch

mkEff "MyCatch"     ''Catch     ''Float       ''NoEff

foo:: Float -> Eff (MyCatch m String) String
foo x = do
    throwCtchIf  x (==0)
    return $ "1/" ++ show x ++ " = " ++ (show $ 1 / x)
    
hndlr :: Float -> String
hndlr x = "Error : x=" ++ show x

>>> runMyCatch hndlr $ foo 4
"1/4.0 = 0.25"

>>> runMyCatch hndlr $ foo 0
"Error : x=0.0"

Types and functions used in mkEff

data Catch' v e Source

Actually, the effect type - v - Type - the parameter of the effect. - e - mkEff generated type.

data Catch m e o v a Source

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

CatchOuter (o m e)
CatchAction (Catch' v e)
CatchResult a

type CatchArgT v r = v -> r Source

Type of fourth argument of runEffCatch and first argument of runEEEE.

type CatchResT r = r Source

Result type of runEEEE.

effCatch :: EffClass Catch' v e => Catch' 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.

runEffCatch Source

Arguments

:: forall (t :: * -> ) (u :: ( -> ) -> -> ) (m :: -> ) (m1 :: -> ) (o :: ( -> ) -> -> *). Monad m
=> (u t r -> (r -> m (CatchResT z)) -> m (CatchResT z))	The outer effect function
-> (Catch m1 e o w a -> r)	The chain of effects link wrapper.
-> (r -> Catch t r u v z)	The chain of effects link unwrapper.
-> CatchArgT v z	The argument of effect. Checking and/or correction function.
-> Eff r a
-> m (CatchResT z)

The main function of the effect implementing. This function is used in the mkEff generated runEEEE functions.

Functions that use this effect

throwCtch :: EffClass Catch' v e => v -> Eff e () Source

Throw effect specific exception.

throwCtchIf :: EffClass Catch' v e => v -> (v -> Bool) -> Eff e () Source

Throw effect specific exception if first argument is True.