[Haskell-cafe] What pattern is this (Something.T -> IO a) in Sound.ALSA.Sequencer

[Martin Drautzburg]

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