c++ - 我无法让循​​环工作，当我按下按钮退出我的开关时它不起作用

Question

现在我可以使用 while 循环，但现在它正在循环第一个操作的答案，而不是要求输入另一个数字以进行更多操作，并且当我按 x 退出时它不会退出。我只是想知道将要求输入另一组数字的代码行放在哪里。然后输入 Y 或 X yes 继续，x 退出我可以放置代码行的地方。我只需要知道这些都在哪里，谢谢 :)

#include <iostream>
using namespace std;
char op, x, y;





double scanNumber() {
    double d;

    cin >> d;

    return d;
}

bool readOperator(string s, char &operation) {
    char c;
    cout << "\nEnter Operator: ";
    cin >> c;
    if (s.find(c) != -1) {
        operation = c;
        return true;
    }
    return false;
}

double add(double d1, double d2) {
    return d1 + d2;
}

double sub(double d1, double d2) {
    return d1 - d2;
}

double mul(double d1, double d2) {
    return d1*d2;
}


double division(double d1, double d2) {
    return d1 / d2;
}
int main()

{

    double d1, d2;


    cout << "Enter 1st Number: ";
    d1 = scanNumber();

    cout << "Enter 2nd Number: ";
    d2 = scanNumber();

    char operation;
    while (!readOperator("+-*/", operation)) {
        cout << "Invalid Operator Please Pick Another One" << endl;


    }

    bool valid;
    double result;



    do{
        switch (operation)
        {

        case '+':
            result = add(d1, d2);
            break;
        case '-':
            result = sub(d1, d2);
            break;
        case '*':
            result = mul(d1, d2);
            break;
        case '/':
            if (d2 == 0) {
                cout << "For division, 2nd operator can't be 0." << endl;

            }
            else {
                result = division(d1, d2);
            }
            break;
        case 'c':
            cout << "Clearing the Calculator " << endl;
            valid = false;
            break;
        case 'x':
            exit(0);
        default:
            cout << "invalid input";

        }

    cout << "\nResult: " << result << endl;
    cout << "\nDo another?(Enter 'y'for yes or 'x' to exit )  ";

    cin >> y, x;
}while (op != 'x');

return 0;
}

Answer 1

您没有逻辑可以在计算后再次重复循环。因此，您需要一个 do 来与最后留下的单独 while (op != 'x'); 配对。

你可以这样做:

int main() {

    double d1, d2;

    do {  //main loop now starts here
        cout << "Enter 1st Number: ";
        d1 = scanNumber();
        cout << "Enter 2nd Number: ";
        d2 = scanNumber();

        char operation;

        //since you have a switch on the c and x operator they need to be taken into 
        //consideration in this while loop
        while (!readOperator("+-*/cCxX", operation)) {
            cout << "Invalid Operator Please Pick Another One" << endl;
        }

        bool valid;
        double result;

        switch (operation) {
        case '+': result = add(d1, d2); break;
        case '-': result = sub(d1, d2); break;
        case '*': result = mul(d1, d2); break;
        case '/':
            if (d2 == 0) {
                cout << "For division, 2nd operator can't be 0." << endl;
            }
            else {
                result = division(d1, d2);
            }
            break;
        case 'c':
        case 'C':
            cout << "Clearing the Calculator " << endl;
            valid = false;
            break;
        case 'x':
        case 'X': return 0;
        default: cout << "invalid input";
        }

        //You need to use the valid as well to know if you show the result
        if (valid) cout << "\nResult: " << result << endl;
        cout << "\nDo another(Enter 'y'for yes or 'x' to exit ) ? ";
        cin >> ch;

    } while (ch != 'x'); //now the } ends here and the condition uses ch

    return 0; //return is now after the while
}

使用建议的输入运行示例: