{-# OPTIONS -fglasgow-exts #-}
    
    class BuildList a r  | r-> a where
      build' :: [a] -> a -> r
    
    instance BuildList a [a] where
      build' l x = reverse$ x:l
    
    instance BuildList a r => BuildList a (a->r) where
      build' l x y = build'(x:l) y
    
    varargs x = build' [] x
    
    main = print $ ( sum $ varargs 1 2 3 4 5 6 100)


    $ ./Test
    121