Re: [Haskell-cafe] Using the ContT monads for early exits of IO ?

On Thu, Jun 10, 2010 at 8:45 PM, Derek Elkins wrote:

Or... one could just use the exceptions that are already built into the IO monad...

It feels to me like this discussion has a lot of speculation in it. I would like to see concrete examples of the code and the suggested improvements.

2010/6/10 Yitzchak Gale :

...

Lennart Augustsson wrote:

...

I would not use the continuation monad just for early exit. Sounds like the error monad to me.

I.e., the Either/ErrorT monad. But the mtl/transformers packages have an orphan instance for Either that requires the exit type to be an instance of the Error class. If that doesn't work in your case, use the Exit monad:

http://www.haskell.org/haskellwiki/New_monads/MonadExit

Or use the Maybe monad written additively, i.e. mplus in place of >> (more or less).

Regards, Yitz _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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