fibs - Haskell

fibs.hs

fib_slow :: Int -> Int
fib_slow 0 = 1
fib_slow 1 = 1
fib_slow n = fib_slow (n - 2) + fib_slow (n - 1)

fibs_slow :: Int -> [Int]
fibs_slow len = take len $ map fib_slow [0..]

fib :: Int -> Int
fib 0 = 1
fib 1 = 1
fib n = fib' n 1 1

fib' :: Int -> Int -> Int -> Int
fib' 1 _ acc = acc
fib' n x succ = fib' (n-1) succ (x + succ)

-- this causes overflow
fibs :: Int -> [Int]
fibs len = take len $ map fib [0..]

-- this causes overflow
fibs_idx :: Int -> Int
fibs_idx idx = map fib [0..] !! idx