On Fri, 14 May 2010, Derek Elkins wrote:
You did it wrong. All you did was Church encode the Either type. Your bind is still doing a case-analysis. All you have to do is use ContT r (Either e). The bind implementation for ContT is completely independent of the underlying monad. It doesn't even require the m in ContT r m to be a functor, let alone a monad. Therefore the ContT bind doesn't do any case-analysis because it doesn't know anything about the underlying monad. One way to look at what is happening is to compare it to Andrzej Filiniski's work in "Representing Monads" and "Representing Layered Monads".
What I don't get is that the bind operation for ContT and ErrCPS look so similar to me ContT (stripping off the newtype constructor/destructors): m >>= k = \c -> m (\a -> k a c) ErrCPS (stripping off the newtype constructor/destructors): m >>= f = \err good -> m err (\x -> f x err good) I don't get why one is slow but not the other? -- Russell O'Connor http://r6.ca/ ``All talk about `theft,''' the general counsel of the American Graphophone Company wrote, ``is the merest claptrap, for there exists no property in ideas musical, literary or artistic, except as defined by statute.''