ITT: Fibonacci

Viani

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597,
2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418,
317811, 514229, 832040, 1346269 u.s.w.

Imipolex G

I think I've seen this before

Bunny

fibonacci :: [Integer]

fibonacci = 0 : 1 : zipWith (+) fibonacci (tail fibonacci)

isFibonacci

isFibonacci :: Integer -> Bool

isFibonacci x = fibonacciCheck x 0

fibonacciCheck :: Integer -> Integer -> Bool

fibonacciCheck x y

| x < z = False

| x == z = True

| otherwise = fibonacciCheck x (y + 1)

where z = fibonacci !! fromIntegral y