Re: [Haskell-cafe] Error handling package

On Wed, Oct 21, 2009 at 12:02 AM, Michael Snoyman wrote:

On Tue, Oct 20, 2009 at 5:17 PM, Nicolas Pouillard wrote:

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On Tue, Oct 20, 2009 at 3:12 PM, Michael Snoyman wrote:

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On Tue, Oct 20, 2009 at 11:04 AM, Nicolas Pouillard wrote:

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On Sun, Oct 18, 2009 at 9:45 PM, Michael Snoyman wrote:

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While working on the next release of data-object, I wanted to represent

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About the name Attempt, I think that 'Outcome' would be a better name.

The problem with a name like "Outcome" is that it doesn't really imply the possibility of failure, simply that we are wrapping of the result for some reason.

I don't see why, the outcome of an action could be either a success or a failure. Even if the only *desired* outcome is success.

I think I'm going to stick with Attempt. The only other point that came to me is it's nicer to have a function called "attempt" than "outcome" IMO.

OK [...]

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fromAttempt :: (forall e. Exception e -> a) -> Attempt a -> a fromAttempt f a = attempt f id a

And of course I now realize this name will conflict with the FromAttempt typeclass ;). I think we'll be safe leaving this function out, considering how trivial it is to implement in terms of attempt.

:) BTW, fromAttempt instance can be nicely expressed using the 'attempt' function.

Also, I've added a monad transformer to the github repo. I've tried it out in some local code I have, and it *really* cleans up the error handling.

Having the monad transformer too is great. The only minor disadvantage is to make a choice between mtl and transformers. But transformers is slowly replacing mtl so no big deal. -- Nicolas Pouillard http://nicolaspouillard.fr