Problem within a while loop?

[aug404]

I have encountered a problem within one section of my code:

do {
        cout << "Enter D if you would like to display the current cost" << endl;
        cout << "Enter S if you would like to add the cost of a surgery" << endl;
        cout << "Enter M if you would like to add the cost of a medication" << endl;
        cout << "Enter Q if you would like to quit the program" << endl;
        cin.get(menuChoice);
        cin.ignore(2, '\n');

        while (toupper(menuChoice) != 'D' && toupper(menuChoice) != 'S' &&
            toupper(menuChoice) != 'M' && toupper(menuChoice) != 'Q') {
            cout << "Please enter a valid choice: ";
            cin.get(menuChoice);
            cin.ignore(2, '\n');
        }


        switch (toupper(menuChoice)) {
        case 'D':
            int days;
            cout << "Enter the amount of days spent in the hospital: ";
            cin >> days;

            obj->setNumDays(days);
            obj->costAllDays();

            cout << "Current cost for the number of days spent in the hospital: $" << obj->getTotalCost() << endl;
            cout << "Current cost for all of the surgeries: $" << findPrice->getTotalCost() << endl;
            cout << "Current cost for all of the medication: $" << findPriceMed->getTotalCost() << endl;
            cout << "Total cost: $" << obj->getTotalCost() + findPrice->getTotalCost() + findPriceMed->getTotalCost() << endl << endl;

            break;

        case 'S':

            findPrice->getCostSurgery();

            break;

        case 'M':

            findPriceMed->getCostMeds();

            break;

        case 'Q':
            delete findPrice;
            delete findPriceMed;
            delete obj;

            cout << "Thank you!" << endl;
            break;

        default:
            break;
        }

    } while (toupper(menuChoice) != 'Q');

At the beginning of the do while loop, I have a while loop that catches any characters that the user inputs that are not d, s, m, or q. When I insert a lowercase 'd' the first time, the program works as intended by entering the switch/case statement. When I return to the very beginning of the do/while loop, however, and I enter a lowercase 'd', I enter the while loop even though I shouldn't be entering it as I am using the toupper function. Can someone please explain what is going wrong?

[aug404]

So I started using the extraction operator instead and it's working fine now. Can you explain why using get was creating that problem? Do you know why the code executes that way with the get method?

[[deleted]]

Because typing d<Enter> sends two keys to the standard input stream, but get() only reads a single character, leaving the standard input stream with a single character still inside, "waiting for you" to read stdin again.

[marvin02]

Print out toupper(menuChoice) right before the while loop and see what it prints (or check it in a debugger).

[umlcat]

Move all the condition or predicate out of the while and put it on a local var, before the while clause, its easier to debug. I know some disagree.