[Haskell-cafe] Haskell stacktrace

[Donn Cave]

> This :
> Prelude> let f = (\x -> return "something went wrong")  ::   IOError -> IO String
> Prelude> let t = return $ show $ "too short list" !! 100 :: IO String
> Prelude> catch t f
> "*** Exception: Prelude.(!!): index too large
>
> doesn't work.

You might be interested in the difference between Prelude.catch and
Control.Exception.catch

Though in an example like that, you'll need to force evaluation to
actually catch the exception.

  f _ = return "something went wrong"
  t = return $! show $ "too short list" !! 100
  ... Control.Exception.catch t f

(note $! instead of $ in "t".)

	Donn Cave, donn at avvanta.com