当我输入一个非整数值时，我的二次方程代码终止，我怎样才能让它正确循环？

Question

所以我试图让我的二次方程求解代码循环，除非输入“0”作为二次系数中的任何 1。它可以正常工作，直到输入一个非整数值，程序终止。我希望代码吐出一条消息，提示用户输入一个数值，然后继续正常循环。

#include <iostream>

#include <cmath>

using namespace std;

int main() {
for ( ; ; ){
float a, b, c, D, x1, x2, real, im;
cout << "Please enter the Quadratic Coefficients" << endl;
cin >> a >> b >> c;
if (cin.fail()){
    cout << "Error, please enter numerical values!" << endl;
    cin >> a >> b >> c;
}
if ((a == 0) || (b == 0) || (c == 0)){
    break;
}
D = b*b - 4*a*c;
if (D < 0) {
    real = -b/(2*a); 
    im = sqrt(-D)/(2*a);
    cout << "Roots are Complex" << endl;
    cout << "x1 = " << real << "+" << im << "i" << endl;
    cout << "x2 = " << real << "-" << im << "i" << endl;

      }
else if (D == 0) {
x1 = (-b + sqrt(D)) / (2*a);
cout << "Real and Repeated Roots" << endl;      
cout << "x1 = " << x1 << endl;
   }
 else if (D > 0) 
{   
  x1 = (-b + sqrt(D)) / (2*a);

  x2 = (-b - sqrt(D)) / (2*a);

cout << "Real and Distinct Roots" << endl;
cout << "x1 = " << x1 << endl;
cout << "x2 = " << x2 << endl;
} } 

  return 0; 
    }

Answer 1

This solution here should help。

cin.fail() 将输入流设置为失败状态，您需要手动重置它才能让它做任何进一步的工作。当你再次调用 cin 时，它会注意到它的失败状态并继续，否则。

cin >> a >> b >> c;
if (cin.fail()){
  cin.clear(); //removes error flags
  cin.ignore(); //ignores last input
  cout << "Error, please enter numerical values!" << endl;
  cin >> a >> b >> c;
}

当我输入一个非整数值时，我的二次方程代码终止，我怎样才能让它正确循环？

My Quadratic equation code terminates when I enter a non integer value, how can I get it to loop properly?

c++

math

loops

quadratic