On Mon, 5 Jan 2009, Luke Palmer wrote:
Oh bother! My new year's resolution: think before I speak.
While I do think this is the right answer, it is not the right answer in the
status quo. This is
because ErrorT e m is only a monad when e is an Error, which Either (and most
types) are not. It
will be the right answer when fail is factored out of Monad into MonadFail
(which will happen
someday hopefully), because then the typechecker will verify that the above
composition cannot
fail.
But now I can't think of a good answer. Darn.
In the explicit-exception package I omit 'fail' and allow an exception
type without constraints._______________________________________________
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