mainbak01_00.hs

module Mainbak01_00 where
import Stack

comb :: (Stack a -> (a, Stack a)) 
     -> (Stack a -> (a, Stack a))
     ->  Stack a -> (a, Stack a)
comb m n = \stack0 ->
           let (_, stack1) = m stack0
               (x, stack2) = n stack1
           in  (x, stack2)

main = do 
  print $ comb pop pop $ s
  print $ comb (comb pop pop) pop $ s
  print $ pop `comb` pop `comb` pop $ s