[Haskell-cafe] converting IOException to Either in ErrorT
dave at zednenem.com
Mon May 4 01:05:56 EDT 2009
On Sun, May 3, 2009 at 6:36 PM, <brian at lorf.org> wrote:
> I wrote this to make it a little nicer to catch IO exceptions and
> convert them to ErrorT failure:
> :: (Error ce) =>
> IO a
> -> (String -> ce)
> -> ErrorT ce IO a
> onExceptionThrowError a ce =
> liftIO (try a) >>=
> (\(e :: IOException) -> throwError (ce (show e)))
> So now I can do, e.g.,
> writeFile fp s `onExceptionThrowError` SpecificErrorConstructor ...
> It works, but seems bad. Please let me know if you see ways to improve
> it. Thanks.
What about this?
liftCatch :: (IOException -> e) -> IO a -> ErrorT e IO a
liftCatch f m = ErrorT $ liftM (either (Left . f) Right) (try m)
Dave Menendez <dave at zednenem.com>
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