{-# LANGUAGE LambdaCase #-}
module Main where

import Control.Monad
import System.IO

{-@ data NumberType = Normal (i :: {v:Int | v mod 3 /= 0 && v mod 5 /= 0})
                    | Fizz
                    | Buzz
                    | FizzBuzz @-}

data NumberType = Normal Int
                | Fizz
                | Buzz
                | FizzBuzz

{-@ fizz :: {v:Int | v mod 3 == 0 && v mod 5 /= 0} -> NumberType @-}
fizz :: Int -> NumberType
fizz _ = Fizz

{-@ buzz :: {v:Int | v mod 3 /= 0 && v mod 5 == 0} -> NumberType @-}
buzz :: Int -> NumberType
buzz _ = Buzz

{-@ fizzbuzz :: {v:Int | v mod 3 == 0 && v mod 5 == 0} -> NumberType @-}
fizzbuzz :: Int -> NumberType
fizzbuzz _ = FizzBuzz

numberType :: Int -> NumberType
numberType i = case (i `mod` 3 == 0, i `mod` 5 == 0) of
  (True, False) -> fizz i
  (False, True) -> buzz i
  (True, True) -> fizzbuzz i
  _ -> Normal i

main :: IO ()
main = do
  putStrLn "FizzBuzz v. 1.0.0"
  putStr "From: "
  hFlush stdout
  from <- getLine
  putStr "To: "
  hFlush stdout
  to <- getLine
  forM_ (map numberType [read from .. read to]) $ \case
    Normal i -> putStrLn $ show i
    Fizz -> putStrLn "Fizz"
    Buzz -> putStrLn "Buzz"
    FizzBuzz -> putStrLn "FizzBuzz"