reader-monad

I wrote the following code. It is working and using the Reader monad. Could you give me some hints about code style in Haskell ? Mainly, I mean monads -- I am newbie. import Control.Monad.Reader data Tree a = Node a (Tree a) (Tree a) | Empty renumberM :: Tree a -> Reader Int (Tree Int) renumberM (Node _ l r) = ask >>= (\x -> return (Node x (runReader (local (+1) (renumberM l)) x) (runReader (local (+1) (renumberM r)) x))) renumberM Empty = return Empty renumber'' :: Tree a -> Tree Int renumber'' t = runReader (renumberM t) 0 I want to show you that your idea is an instance of a more general

The reader monad is so complex and seems to be useless. In an imperative language like Java or C++, there is no equivalent concept for the reader monad, if I am not mistaken. Can you give me a simple example and clear this up a little bit? Philip JF Don't be scared! The reader monad is actually not so complicated, and has real easy-to-use utility. There are two ways of approaching a monad: we can ask What does the monad do ? What operations is it equipped with? What is it good for? How is the monad implemented? From where does it arise? From the first approach, the reader monad is some