Re: [Haskell-cafe] Custom monad using ST

On Wed, 9 Mar 2011, Yves Parès wrote:

Hello,

I am trying to make a monad that uses ST internally. But even when reducing this to the simplest case I'm still cramped by the 's' phantom type :

{-# LANGUAGE Rank2Types #-}

newtype MyST a = MyST (forall s. ST s a) -- ^ I cannot use " deriving (Monad) " through GeneralizedNewtypeDeriving

Would it make sense to make the 's' type explicit? newtype MyST s a = MyST (ST s a)