Here is a generalized version, using type classes and some extensions. Tiago, in order to compile this you'll have to use: -fglasgow-exts -fallow-undecidable-instances -fallow-overlapping-instances Cheers, Jorge. ------------- module Main where class Pipeline t1 t2 t3 | t1 t2 -> t3 where pipeline::t1 -> t2 -> t3 instance Pipeline t1 t2 t3 => Pipeline (a -> t1) t2 (a -> t3) where pipeline f g a = pipeline (f a) g -- same as: pipeline f g = \a -> pipeline (f a) g instance Pipeline (a -> b) (b -> c) (a -> c) where pipeline = flip (.) f a b c = even (a+b+c) h = pipeline f not main = do putStrLn . show $ h 1 2 3 ----------------

On 10/4/07, Dominic Steinitz wrote:

Look at the type of (.).(.).(.)

Indeed, this generalizes to functions of any arity on the "RHS": Prelude> :t (.) (.) :: (b -> c) -> (a -> b) -> a -> c Prelude> :t (.).(.) (.).(.) :: (b -> c) -> (a -> a1 -> b) -> a -> a1 -> c Prelude> :t (.).(.).(.) (.).(.).(.) :: (b -> c) -> (a -> a1 -> a2 -> b) -> a -> a1 -> a2 -> c Prelude> :t (.).(.).(.).(.) (.).(.).(.).(.) :: (b -> c) -> (a -> a1 -> a2 -> a3 -> b) -> a -> a1 -> a2 -> a3 -> c Of course, if you want higher-arity functions anywhere *other* than the head of your composition chain, you'll have to resort to tupling and uncurrying. Stuart