On Sat, Jul 28, 2012 at 8:00 AM, Thiago Negri <evoh...@gmail.com> wrote:
> I'm solving this exercise: > > http://www.haskell.org/haskellwiki/All_About_Monads#Exercise_4:_Using_the_Monad_class_constraint > > I'm missing a function to transform a Maybe a into a MonadPlus m => m a. > I did search on Hoogle with no luck. > > There is no standard definition for the "g" function I'm defining? g :: (MonadPlus m) => Maybe a -> m a > g Nothing = mzero > g (Just a) = return a > I doubt there is a "standard" named function for this, since conversions between monads are typically not "unique" and there are lots and lots of pairs of monads you can convert between. You can define g in terms of Data.Maybe.maybe as: g = maybe mzero return
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