[Haskell-cafe] Using the ContT monads for early exits of IO ?
dagit at codersbase.com
Fri Jun 11 00:10:40 EDT 2010
On Thu, Jun 10, 2010 at 8:45 PM, Derek Elkins <derek.a.elkins at gmail.com>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 <gale at sefer.org>:
> > 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
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