On Sunday, 3. March 2013 21:11:21 Roman Cheplyaka wrote:
Admittedly, programming with callbacks is not very pleasant. So we have an excellent alternative — the continuation monad transformer!
This nested code
something1 $ \x -> do something2 $ \y -> do something3 $ \z -> do
can be equivalently rewritten as this linear code
import Control.Monad.Cont
flip runContT return $ do x <- ContT something1 y <- ContT something2 z <- ContT something3 lift $ do ...
Mind-blowing. Thanks a lot. Before I dig into the continuation monad transformer, one more question (demonstrating my ignorance): The initialization actually starts with main = (do SndSeq.withDefault SndSeq.Block $ \h -> do Client.setName (h :: SndSeq.T SndSeq.DuplexMode) "Haskell-Melody" Port.withSimple h "out" (Port.caps [Port.capRead, Port.capSubsRead, Port.capWrite]) (Port.types [Port.typeMidiGeneric, Port.typeApplication]) $ \p -> do So there are some plain actions like "Client.setName" and "Port.withSimple" before it gets to the next "do" block. How would I write this in ContT style? -- Martin