//Insert under App function:

//Q1: explain what the following 3 lines do.
const [numberDisplay, setNumberDisplay] = useState("");
const [previousTotal, setPreviousTotal] = useState("");
const [currentOperation, setCurrentOperation] = useState("");

//Q2: explain what `${numberDisplay}${digit}` does.   
const updateDisplay = digit => {
    setNumberDisplay(`${numberDisplay}${digit}`);
  };

//Q3: setNumberDisplay is not defined anywhere in the App, nor is it imported. How is the function properly invoked and executed then?
const changeDisplay = action => {
    if (action === 'clear') {
      setNumberDisplay("");
      setPreviousTotal("");
      setCurrentOperation("");
    } else if (action === 'delete') {
      if (typeof numberDisplay === 'string') {
        setNumberDisplay(numberDisplay.slice(0, -1));
      }
    }
  };

  const updateCalculations = op => {
//define total, entered number, and operation

//conditional statement to determine what is the operation

//conditional statement to determine new Total


//conditional statement to set the state variables

  };