40 lines
1 KiB
Haskell
40 lines
1 KiB
Haskell
|
{- Simple IO exception handling
|
||
|
|
-
|
||
|
|
- Copyright 2011-2012 Joey Hess <joey@kitenet.net>
|
||
|
|
-
|
||
|
|
- Licensed under the GNU GPL version 3 or higher.
|
||
|
|
-}
|
||
|
|
|
||
|
|
module Utility.Exception where
|
||
|
|
|
||
|
|
import Prelude hiding (catch)
|
||
|
|
import Control.Exception
|
||
|
|
import Control.Applicative
|
||
|
|
|
||
|
|
{- Catches IO errors and returns a Bool -}
|
||
|
|
catchBoolIO :: IO Bool -> IO Bool
|
||
|
|
catchBoolIO a = catchDefaultIO a False
|
||
|
|
|
||
|
|
{- Catches IO errors and returns a Maybe -}
|
||
|
|
catchMaybeIO :: IO a -> IO (Maybe a)
|
||
|
|
catchMaybeIO a = catchDefaultIO (Just <$> a) Nothing
|
||
|
|
|
||
|
|
{- Catches IO errors and returns a default value. -}
|
||
|
|
catchDefaultIO :: IO a -> a -> IO a
|
||
|
|
catchDefaultIO a def = catchIO a (const $ return def)
|
||
|
|
|
||
|
|
{- Catches IO errors and returns the error message. -}
|
||
|
|
catchMsgIO :: IO a -> IO (Either String a)
|
||
|
|
catchMsgIO a = dispatch <$> tryIO a
|
||
|
|
where
|
||
|
|
dispatch (Left e) = Left $ show e
|
||
|
|
dispatch (Right v) = Right v
|
||
|
|
|
||
|
|
{- catch specialized for IO errors only -}
|
||
|
|
catchIO :: IO a -> (IOException -> IO a) -> IO a
|
||
|
|
catchIO = catch
|
||
|
|
|
||
|
|
{- try specialized for IO errors only -}
|
||
|
|
tryIO :: IO a -> IO (Either IOException a)
|
||
|
|
tryIO = try
|