Well, I guess you could try something like:
{-# LANGUAGE GADTs #-}
import Control.Exception (bracketOnError) import Control.Monad ((>=>))
-- from package 'operational' import Control.Monad.Operational
data BracketedOperation a where Bracketed :: IO a -> (a -> IO b) -> BracketedOperation a
type BracketedProgram a = ProgramT BracketedOperation IO a
interpret :: BracketedProgram a -> IO a interpret = viewT >=> eval where eval :: ProgramViewT BracketedOperation IO a -> IO a eval (Return a) = return a eval (Bracketed acquire release :>>= is) = bracketOnError acquire release $ interpret . is
Now you could have: ] attachN :: Nerve n -> BracketedProgram (LiveNeuron n) ] attachN n = singleton (Bracketed (attach n) dettach) And your code would become: ] neurons <- interpret $ do ] attachN nerve1 ] attachN nerve2 ] attachN nerve3 Note that I haven't tested this code, but it compiles :). Cheers! -- Felipe.