Find the last digit on sequentially exponentiating a list of Integer values from left to right. E.g. [3,4,5] => (3 ^ ( 4 ^ 5 )) mod 10

Kata.hs

module Kata
(
  lastDigitOnExp
 ,lastDigitListReduce
) where
lookupTable = [    [0,0,0,0],
                   [1,1,1,1],
                   [2,4,8,6],
                   [3,9,7,1],
                   [4,6,4,6],
                   [5,5,5,5],
                   [6,6,6,6],
                   [7,9,3,1],
                   [8,4,2,6],
                   [9,1,9,1] ]

lastDigitOnExp :: Int -> Int -> Int
lastDigitOnExp base exp = lookupTable !! mod base 10 !! mod (exp-1) 4

lastDigitListReduce :: [Int] -> Int
lastDigitListReduce x = foldr1 lastDigitOnExp x