>>851
fib1 40は1秒かからなかったけど
fib2 40だと37秒かかった

fib1 = (map fib1' [0 ..] !!)
where
fib1' 0 = 0
fib1' 1 = 1
fib1' n = fib1 (n - 1) + fib1 (n - 2)

fib2 x = map fib2' [0 ..] !! x
where
fib2' 0 = 0
fib2' 1 = 1
fib2' n = fib2 (n - 1) + fib2 (n - 2)