[Haskell-beginners] New style exceptions...

10 Aug 2011

      Hi there,
Exception handling in RWH is called old-style and deprecated. I didn't
find a tutorial telling how to do the new style.

Here I created two examples both dealing with an exception when
creating a directory.

I would like to know if the way I did is ok or not.
Improvements resp. corrections are most welcome

First way:

<--------------snip------------------------------------>
{-# LANGUAGE ScopedTypeVariables #-}
module Main where

import System.Exit
import System.Directory
import Control.Exception

import Prelude hiding ( catch, readFile )

main :: IO ()
main = do 
  handle (\(e :: SomeException) -> print $ show e) $ do
    createDirectoryIfMissing True "/tmr/a/b/c/d"
    _ <- exitWith $ ExitFailure 1
    return ()
  print "Directory created successfully"
<--------------snap------------------------------------>

Second way:

<--------------snip------------------------------------>
module Main where

import System.Exit
import System.Directory
import Control.Exception

import Prelude hiding ( catch, readFile )

main :: IO ()
main = do 
  catch (createDirectoryIfMissing True "/tmr/a/b/c/d") exhandler
  print "Directory created successfully"
  where
    exhandler :: SomeException -> IO ()
    exhandler e = do print e
                     _ <- exitWith $ ExitFailure 1
                     return ()
<--------------snap------------------------------------>

-- 
Tnanks, 
Manfred

[Haskell-beginners] New style exceptions...

Manfred Lotz