[Haskell-cafe] How to catch all exceptions that could be caught?

[Gregory Crosswhite]

On 01/12/12 17:23, Gregory Crosswhite wrote:
> Indeed, and in fact this situation is a very natural occurrence whenever
> you are writing code that takes an arbitrary IO action, executes it, and
> then returns either the result or the exception that it threw. The code
> that I last used for this took advantage of catchJust and looked roughly
> like the following:
>
> execute :: IO a → IO (Either SomeException a)
> execute action =
> catchJust
> (\e → case fromException e of {Just (_ :: AsyncException) → Nothing; _ →
> Just e})
> (Right <$> action)
> (return . Left)
>
> Cheers,
> Greg

Ugh, I have no idea why the spacing got eaten;  it was meant to look like:

execute :: IO a -> IO (Either SomeException a)
execute action =
    catchJust
        (\e -> case fromException e of
            Just (_ :: AsyncException) -> Nothing;
            _ -> Just e
        )
        (Right <$> action)
        (return . Left)

Cheers,
Greg