Project Euler, Problem #2, Haskell

-- Each new term in the Fibonacci sequence is generated by adding the
-- previous two terms. By starting with 1 and 2, the first 10 terms
-- will be: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ... By considering the
-- terms in the Fibonacci sequence whose values do not exceed four
-- million, find the sum of the even-valued terms.

fib :: (Ord a, Integral a) => [a] -> [a]
fib xs =
  if last xs < 4000000
    then fib (xs ++ [last xs + last (init xs)])
    else init xs

main :: IO ()
main = print $ sum $ filter even $ fib [0, 1]

-- 4613732

-- real 0m0,003s
-- user 0m0,000s
-- sys  0m0,003s