I've got this fizzbuzz project I am using for a blog series, among other things. In this version, the fizzbuzz function is fed from a Fibonacci generator. I'm particularly concerned with the efficiency of the Fibonacci generator, but all scrutiny is welcomed.I'll included a link to the entire project, but below are the parts I think would be sufficient to spot trouble with how I am generating Fibonacci numbers.-- Driver function performs following-- (1) checks that input is proper-- (2) creates integer list for fibonacci generator-- (3) calculates first x in fibonnaci sequence-- (4) generates fizzbuzz output using (3)fizzBuzzFib :: [Text] -> Either FizzError [Text]fizzBuzzFib str =mapM fizzbuzz          =<<mapM fibb              =<< -- Possible problem here(\x -> Right [1 .. x]) =<<convertToPInt          =<<mustHaveOne strfibb :: Integer -> Either FizzError Integerfibb n = Right $ snd . foldl' fib' (1, 0) . map (toEnum . fromIntegral) $ unfoldl divs n  where    unfoldl f x =      case f x of        Nothing     -> []        Just (u, v) -> unfoldl f v ++ [u]    divs 0 = Nothing    divs k = Just (uncurry (flip (,)) (k `divMod` 2))    fib' (f, g) p      | p = (f*(f+c*g), f^c + g^c)      | otherwise = (f^c+g^c, g*(c*f-g))      where        c :: Integer -- See codebase for reasons        c = 2
Over-engineered fizzbuzz
haskell;fizzbuzz;fibonacci sequence