On 26 December 2010 19:00, michael rice <[email protected]> wrote: > > I lifted the code below from here: > > http://en.wikibooks.org/wiki/Haskell/Monad_transformers > > Since the wiki page doesn't say what needs to be imported, I'm guessing. > > Not sure what is happening. Maybe someone can tell me.
> instance Monad m => MonadPlus (MaybeT m) where > mzero = MaybeT $ return Nothing > mplus x y = MaybeT $ do maybe_value <- runMaybeT x > case maybe_value of > Nothing -> runMaybeT y > Just value -> runMaybeT x > I haven't run the code but the definition of mplus here looks cyclic. _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
