Re: [Haskell-cafe] Re: Doing without IORef

Thanks Bryan, To summarize, embed IORef inside ReaderT and use that IORef to read/change the file path info, both in IO monad and MyState monad. Is this right? Thank you all! jinwoo On Sat, Apr 5, 2008 at 1:56 AM, Bryan O'Sullivan wrote:

Jinwoo Lee wrote:

...

I haven't used ReaderT. What are the advantages when using ReaderT instead of StateT in this case?

A StateT lets you replace one IORef with another, since it gives you mutable state. A ReaderT gives you *immutable* state, so the type system guarantees that you'll always be using the same IORef.

-- Jinwoo Lee Always remember that you are unique. Just like everyone else.