On Apr 3, 2008, at 6:03 , Jinwoo Lee wrote:
Recently I wrote a code that uses readline library (System.Console.Readline). I had to maintain a state (file path) and do IO throughout the code, so I decided to use StateT monad.
The problem was that in order to retrieve the current state (file path) inside the handler that had been registered by using bindKey function of readline, I had to resort back to using IORef rather than using the state stored in the StateT monad. It's because the handler for bindKey should have the type of Int -> Char -> IO Int.
You can hide the IORef inside the StateT... but this is one of several cases where I *really* wish the callbacks were MonadIO a => ... -> a t. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH