Project Euler - Problem 4

gistfile1.hs

import System.IO

main = do
    putStrLn $ biggest "0" [ show (a*b) | a <- [100..999], b <- [100..999], isPalindromicNum (show (a*b))]

isPalindromicNum []     = True
isPalindromicNum (_:[]) = True
isPalindromicNum (x:xs) | x == last xs  = isPalindromicNum (init xs)
                        | otherwise = False

biggest m []    = m
biggest m (x:xs)    | x' > m' = biggest x xs
                    | otherwise = biggest m xs
                        where   x'  = (read x)::Integer
                                m'  = (read m)::Integer