Question

即使我一直输入数字，我的代码也不会输出多行。为什么我的while循环会这样做，我该如何解决？

当我输入r 12.3 45.6然后输入p 12.3 45.6时，它仅输出第一个输入。
如果我输入了R r P p以外的任何内容，则应该输出Format error并继续执行循环，除非用户输入q才能停止循环。

#include <iostream>
using namespace std;
#include <cmath>
#include <iomanip>

int main() {
    float x;
    float y;
    float M;
    float th;
    char input;

    cin >> input; 

    while ((input != 'q') && (input != 'Q')) {// starts while loop wile not inputting eirther q or Q
        if ((input == 'r') || (input == 'R')) {

           cin >> x >> y; //user inputs x and y
         M = sqrt(pow(x, 2) + pow(y, 2)); // M 
         th =  atan2(y,x) * (180 / M_PI);// theta in degrees

            cout << "POL -> REC: REC: X = " << fixed << setprecision(2)  << x << " Y = " << y << " POL: M = " << M << " A = " << th<< endl;
        }

        if((input == 'p') || (input == 'P')) { //If user inputs p or P excute rest of code below

         cin >> M;//user enters M
         cin >> th;// User enters theta
         
         x = (M * cos(M_PI / 180 * th)); // X into degrees
         y = M * sin(th * M_PI/180);// y into degrees

            cout << "REC -> POL: REC: X = " << fixed << setprecision(2)  << x << " Y = " << y << " POL: M = " << M << " A = " << th << endl;

        }

        if ((input != 'r') && (input != 'R') && (input != 'p') && (input != 'P')) {//if user enters anything besides p P q Q then output format error
            cout << "Format Error!" << endl;

        }
               break; //stops loop
    }
    return 0;
}

Answer 1

您需要移动

cin >> input;

进入while循环和break语句仅应在输入q或Q的情况下执行。另外，您还需要在下一个循环之前将输入重置为某些内容。在下面的示例中，我将其空白。

#include <iostream>
using namespace std;
#include <cmath>
#include <iomanip>

int main() {
   float x;
   float y;
   float M;
   float th;
   char input;

   while (true) 
   {
      cin >> input;

      if ((input == 'r') || (input == 'R')) {

         cin >> x >> y; //user inputs x and y
         M = sqrt(pow(x, 2) + pow(y, 2)); // M 
         th = atan2(y, x) * (180 / M_PI);// theta in degrees

         cout << "POL -> REC: REC: X = " << fixed << setprecision(2) << x << " Y = " << y << " POL: M = " << M << " A = " << th << endl;


      }

      if ((input == 'p') || (input == 'P')) { //If user inputs p or P excute rest of code below


         cin >> M;//user enters M
         cin >> th;// User enters theta

         x = (M * cos(M_PI / 180 * th)); // X into degrees
         y = M * sin(th * M_PI / 180);// y into degrees

         cout << "REC -> POL: REC: X = " << fixed << setprecision(2) << x << " Y = " << y << " POL: M = " << M << " A = " << th << endl;


      }

      if ((input != 'r') && (input != 'R') && (input != 'p') && (input != 'P')) {//if user enters anything besides p P q Q then output format error
         cout << "Format Error!" << endl;
         break;
      }

      if (input == 'q' || input == 'Q')
       break; //stops loop

      input = ' ';
   }

   return 0;
}

循环帮助While循环无法正常工作

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