-- The decimal number, 585 = 1001001001_2 (binary), is palindromic in both bases.
--
-- Find the sum of all numbers, less than one million, which are palindromic in base 10 and base 2.
--
-- (Please note that the palindromic number, in either base, may not include leading zeros.)

toBinary :: Int -> [Int]
toBinary 0 = []
toBinary 1 = [1]
toBinary n = toBinary (n `div` 2) ++ [n `mod` 2]

doublePalindrome :: Int -> Bool
doublePalindrome n = show n == reverse (show n) && toBinary n == reverse (toBinary n)

main = do
    let result = sum $ filter doublePalindrome [1..999999]
    putStrLn $ "Project Euler, Problem 36\n"
        ++ "Answer: " ++ show result