On Mon, Mar 15, 2010 at 9:59 PM, Anders Kaseorg
On Mon, 15 Mar 2010, Bas van Dijk wrote:
What about deprecating all the cgi exception handling functions: throwCGI, catchCGI and tryCGI in favor of the CatchIO ones?
Yeah, that’s basically the direction I want to go in. This patch makes the new CatchIO functions work by adding a MonadCatchIO interface, without breaking the old ones (though the old ones get a little bit of generalization for free).
Yes we should do that. But in addition we can advice the users of catchCGI to actually use the CatchIO.catch instead by adding a deprecated pragma like: {-# DEPRECATED catchCGI "Use Control.Monad.CatchIO.catch instead." #-} Or is this to rude? Something else: which MonadCatchIO package are you proposing to use: MonadCatchIO-mtl or MonadCatchIO-transformers? I guess the former because cgi depends on mtl. In that case we should contact the maintainer of MonadCatchIO-mtl and ask if he can add the following functions: bracket_, bracketOnError and finally (types and definitions below). Then the API is equivalent to Control.Exception. (I CCed this message to the maintainer) (I wrote a patch a while ago that added these to MonadCatchIO-transformers because I needed them in my regions package. But they are not present in MonadCatchIO-mtl) regards, Bas -- | A variant of 'bracket' where the return value from the first computation -- is not required. bracket_ :: MonadCatchIO m => m a -- ^ computation to run first (\"acquire resource\") -> m b -- ^ computation to run last (\"release resource\") -> m c -- ^ computation to run in-between -> m c -- returns the value from the in-between computation bracket_ before after thing = block $ do before r <- unblock thing `onException` after after return r -- | A specialised variant of 'bracket' with just a computation to run -- afterward. finally :: MonadCatchIO m => m a -- ^ computation to run first -> m b -- ^ computation to run afterward (even if an exception was -- raised) -> m a -- returns the value from the first computation thing `finally` after = block $ do r <- unblock thing `onException` after after return r -- | Like 'bracket', but only performs the final action if there was an -- exception raised by the in-between computation. bracketOnError :: MonadCatchIO m => m a -- ^ computation to run first (\"acquire resource\") -> (a -> m b) -- ^ computation to run last (\"release resource\") -> (a -> m c) -- ^ computation to run in-between -> m c -- returns the value from the in-between computation bracketOnError before after thing = block $ do a <- before unblock (thing a) `onException` after a