foldleach and comb

comb.hs

module Main where

-- fold an operation down a list of lists
foldleach :: (a -> b -> a) -> a -> [[b]] -> [a]
foldleach f b xs = map (foldl f b) xs

foldl1each :: (a -> a -> a) -> [[a]] -> [a]
foldl1each f xs = map (foldl1 f) xs

-- find combinations from list
comb :: Int -> [a] -> [[a]]
comb n [] = []              
comb 1 xs = map (:[]) xs      
comb n (x:xs) = aa ++ bb where
    aa = map (x:) $ comb (n-1) xs
    bb = comb n xs
                
-- usage: 
-- foldl1each (*) (comb 2 [1,2,3])