c++ - C++程序中的浮点异常

Question

#include <iostream>
#include <string>

using namespace std;
int main()
{
int num1, num2; // numerator                                                                                                                       
int den1, den2; // denominator                                                                                                                     

cin >> num1 >> den1 >> num2 >> den2;
if (den1<=0 || den2<=0)
cout << "problem could not be solved because denominator is zero and division by zero is        not defined" << endl;
else
if ((num1/den1)+(num2/den2))
cout << num1 << "/" << den1 << " + " << num2 << "/" << den2 << " = " << ((num1*den2)+  (den1*num2)) << "/" << (den1*den2) << endl;
else
  if ((num1/den1)-(num2/den2))
    cout << num1 << "/" << den1 << " - " << num2 << "/" << den2 << " = " <<    ((num1*den2)-(den1*num2)) << "/ " << (den1*den2) << endl;
else
  if ((num1/den1)*(num2/den2))
      cout << num1 << "/" << den1 << " * " << num2 << "/" << den2 << " = " <<     (num1*num2) << "/ " << (den1*den2) << endl;
    else
      if ((num1/den1)/(num2/den2) && num2 != 0)
        cout << num1 << "/" << den1 << " * " << num2 << "/" << den2 << " = " << (num1*den2) << "/ " << (den1*num2) << endl;
      else
        if ((num1/den1)/(num2/den2) && num2==0)
          cout << num1 << "/" << den1 << " * " << num2 << "/" << den2 << " could not be   solved because division by zero is not defined" << endl;\

 return 0;
 }

嘿伙计们，当我运行这个程序时，我总是遇到 float 异常。我真的无法弄清楚问题是什么。非常感谢您的帮助。

Answer 1

问题出在这几行:

  if ((num1/den1)/(num2/den2) && num2 != 0)
    cout << num1 << "/" << den1 << " * " << num2 << "/" << den2 << " = " << (num1*den2) << "/ " << (den1*num2) << endl;
  else
    if ((num1/den1)/(num2/den2) && num2==0)
      cout << num1 << "/" << den1 << " * " << num2 << "/" << den2 << " could not be   solved because division by zero is not defined" << endl;\

&& 的参数是从左到右处理的。因此，如果 num2 为 0，您将在测试 num2 != 0 之前尝试进行除法；所以你需要先进行零测试。您还需要测试 num2/den2 是否为零，而不仅仅是 num2，因为即使 num2 不是，除法也可能向下舍入为零零。

  if (num2/den2 != 0 && (num1/den1)/(num2/den2))
    cout << num1 << "/" << den1 << " * " << num2 << "/" << den2 << " = " << (num1*den2) << "/ " << (den1*num2) << endl;
  else
    cout << num1 << "/" << den1 << " * " << num2 << "/" << den2 << " could not be   solved because division by zero is not defined" << endl;