eff | Eff monad for cats - https | Functional Programming library

data Console a
  = PutStrLn String a
  | GetLine (String -> a)
  deriving (Functor)

type ConsoleM = Free Console

runConsole :: Console (IO a) -> IO a
runConsole cmd =
  case cmd of
    (PutStrLn s next) -> do
      putStrLn s
      next
    (GetLine nextF) -> do
      s <- getLine
      nextF s

runConsoleM :: ConsoleM a -> IO a
runConsoleM = iterM runConsole

consolePutStrLn :: String -> ConsoleM ()
consolePutStrLn str = liftF $ PutStrLn str ()
consoleGetLine :: ConsoleM String
consoleGetLine = liftF $ GetLine id


data File a
  = ReadFile FilePath (String -> a)
  | WriteFile FilePath String a
  deriving (Functor)

type FileM = Free File

runFile :: File (MaybeT IO a) -> MaybeT IO a
runFile cmd = case cmd of
  ReadFile path next -> do
    fileData <- safeReadFile path
    next fileData
  WriteFile path fileData next -> do
    safeWriteFile path fileData
    next

runFileM :: FileM a -> MaybeT IO a
runFileM = iterM runFile

rightToMaybe :: Either a b -> Maybe b
rightToMaybe = either (const Nothing) Just

safeReadFile :: FilePath -> MaybeT IO String
safeReadFile path =
  MaybeT $ rightToMaybe <$> (try $ readFile path :: IO (Either IOException String))

safeWriteFile :: FilePath -> String -> MaybeT IO ()
safeWriteFile path fileData =
  MaybeT $ rightToMaybe <$> (try $ writeFile path fileData :: IO (Either IOException ()))

fileReadFile :: FilePath -> FileM String
fileReadFile path = liftF $ ReadFile path id
fileWriteFile :: FilePath -> String -> FileM ()
fileWriteFile path fileData = liftF $ WriteFile path fileData ()


data Program a = File (File a) | Console (Console a)
  deriving (Functor)
type ProgramM = Free Program

runProgram :: Program (MaybeT IO a) -> MaybeT IO a
runProgram cmd = case cmd of
  File cmd' ->
    runFile cmd'
  Console cmd' ->
    -- ????

runProgramM :: ProgramM a -> MaybeT IO a
runProgramM = iterM runProgram

    var br = document.createElement("br");
    function productCheck() {

        var form = document.createElement("form");

        var price = document.createElement("input");
        price.setAttribute("type", "number");
        price.setAttribute("id", "number1");
        price.setAttribute("placeholder", "Product Price");
        price.onchange = handleChange;

        var qty = document.createElement("input");
        qty.setAttribute("type", "number");
        qty.setAttribute("id", "number2");
        qty.setAttribute("placeholder", "quantity");
        qty.onchange = handleChange;

        var discount = document.createElement("input");
        discount.setAttribute("type", "number");
        discount.setAttribute("id", "number3");
        discount.setAttribute("placeholder", "discount");
        discount.onchange = handleChange;

        var div = document.createElement("div");
        div.setAttribute("id", "total");
        form.appendChild(br.cloneNode());
        div.onchange = handleChange;

        form.appendChild(price);
        // Inserting a line break
        form.appendChild(br.cloneNode());
        ...

        form.appendChild(qty);
        ...

        form.appendChild(discount);
        ...

        form.appendChild(div);
       ...

        document.getElementsByTagName("body")[0]
            .appendChild(form);
    }

    function handleChange() {
        var p = document.getElementById("number1").value;
        var q = document.getElementById("number2").value;
        var d = document.getElementById("number3").value;

        var total = parseFloat(p) * parseInt(q);
        var discount_applied = parseFloat(total * d / 100);
        var eff_price = parseFloat(total) - parseFloat(discount_applied);

        if (!isNaN(eff_price))
            return " ";

        if (p > 0 && q > 0){
            var eff = document.querySelector("#total");
            eff.innerHTML = eff_price.toFixed(2);
       }
    }