I think that MonadZero m => ... is better than just Maybe. If you can have more general solution for free, why fight it? On 23 May 2008, at 14:55, Jules Bean wrote:
Krasimir Angelov wrote:
The monads design is used in Data.Map i.e. lookup :: (Monad m, Ord k) => k -> Map k a -> m a
which is widely considered a poor design decision and a wart on Data.Map.
:-)
Seriously, if you don't return a useful error message, then Maybe is as good as it gets, why not use it?
(And there really is only one kind of error possible here, in each case)
'fail' only adds information in the case it has a useful error message (in which case I'd encourage MonadError m =>)
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