[Haskell-cafe] Composing monads

[Brandon S. Allbery KF8NH]

On Nov 22, 2007, at 13:17 , Maurí cio wrote:

> If I have two computations a->IO b
> and b->IO c, can I join them to
> get an a->IO c computation? I imagine
> something like a liftM dot operator.

If you have GHC 6.8.1, this is the Kleisli composition operator (>=>)  
in Control.Monad.  (There is also (<=<) which corresponds to (=<<).)

     Prelude Control.Monad> :i (>=>)
     (>=>) :: (Monad m) => (a -> m b) -> (b -> m c) -> a -> m c
             -- Defined in Control.Monad
     infixr 1 >=>
     Prelude Control.Monad> :i (<=<)
     (<=<) :: (Monad m) => (b -> m c) -> (a -> m b) -> a -> m c
             -- Defined in Control.Monad
     infixr 1 <=<

-- 
brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery at kf8nh.com
system administrator [openafs,heimdal,too many hats] allbery at ece.cmu.edu
electrical and computer engineering, carnegie mellon university    KF8NH