main = do
    putStr "Starting height (ft): "
    rawStartingHeight <- getLine
    putStr "Total air time (seconds): "
    rawAirTime <- getLine
    let startingHeight = read rawStartingHeight :: Double
        airTime = read rawAirTime :: Double
    putStrLn $ "Maximum height (ft): " ++ show (maxHeight startingHeight airTime)
    putStrLn "Another? (Y/N)"
    another <- yOrN
    if another then main else return ()

yOrN :: IO Bool
yOrN = do
    character <- getChar
    case character of
        'y' -> return True
        'Y' -> return True
        'n' -> return False
        'N' -> return False
        otherwise -> yOrN

startingVelocity :: (Fractional a) => a -> a -> a
startingVelocity startingHeight airTime = 16.087 * airTime - startingHeight / airTime

maxHeight :: (Fractional a) => a -> a -> a
maxHeight startingHeight airTime =
    let v = startingVelocity startingHeight airTime
        t = v / 32.174
    in (-16.087) * ((airTime / 2) ^ 2) + v * (airTime / 2) + startingHeight