Haskell Higher Order Functions

• filter (function) list

            ghci> filter (>6) [1,2,3,4,5,6,7,8,9]      
            [7,8,9]
            

• map (function) list

            ghci> map (+2) [1,2,3,4,5,6,7,8,9]
            [3,4,5,6,7,8,9,10.11]
            

• foldl/foldr (function) start_value list

            ghci> foldl (-) 100 [3,4,5] -- fold from the left
            88  -- is ((100 - 3) - 4) - 5
            ghc > foldr (-) 100 [3,4,5] -- fold from the right         
            -96 -- is 3 - (4 - (5 - 100))