On 11/22/07, apfelmus <[EMAIL PROTECTED]> wrote:
>
> A context passing implementation (yielding the ContT monad transformer)
> will remedy this.
Wait, are you saying that if you apply ContT to any monad that has the "left
recursion on >>= takes quadratic time" problem, and represent all primitive
operations via lift (never using >>= within "lift"), that you will get a new
monad that doesn't have that problem?
If so, that's pretty cool.
To be clear, by ContT I mean this monad:
newtype ContT m a = ContT { runContT :: forall b. (a -> m b) -> m b }
instance Monad m => Monad (ContT m) where
return x = ContT $ \c -> c x
m >>= f = ContT $ \c -> runContT m $ \a -> runContT (f a) c
fail = lift . fail
instance MonadTrans ContT where
lift m = ContT $ \c -> m >>= c
evalContT :: Monad m => ContT m a -> m a
evalContT m = runContT m return
-- ryan
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