C Shell（cpp.sh，基于浏览器的编译器）正在运行Visual Studio won'；T 所以我正在为一个学校项目做C++程序。

我使用了一组条件操作符（我喜欢速记），它在C shell上运行良好（这是链接。程序在那里工作得很好）但是它不会在VisualStudioC++中运行，我很好奇在我的代码中是否存在某种错误……/P> 我的计划是：

#include <iostream>

using namespace std;

int main()
{
cout << "Please enter an angle and I will tell you which quadrant it is in.\n\n\n";
double angle;
cin >> angle;
cout << endl;
bool first, second, third, fourth, xaxis, yaxis, nxaxis, nyaxis;


if (angle < 0 || angle > 360)
    cout << "Invalid input.";
else
{
(angle > 0 && angle < 90 ? first = true : first = false);
(first == true ? cout << "The angle you entered is in the first quadrant.\n\n" : cout << "");
(angle > 90 && angle < 180 ? second = true : second = false);
(second == true ? cout << "The angle you entered is in the second quadrant.\n\n" : cout << "");
(angle > 180 && angle < 270 ? third = true : third = false);
(third == true ? cout << "The angle you entered is in the third quadrant.\n\n" : cout << "");
(angle > 270 && angle < 360 ? fourth = true : fourth = false);
(fourth == true ? cout << "The angle you entered is in the fourth quadrant.\n\n" : cout << "");
(angle == 0 || angle == 360 ? nxaxis = true : nxaxis = false);
(angle == 180 ? xaxis = true : xaxis = false);
(nxaxis == true ? cout << "This angle lies on the negative portion of the x axis.\n\n" : "");
(xaxis == true ? cout << "This angle lies on the positive portion of the x axis.\n\n" : "");
(angle == 90 ? yaxis = true : yaxis = false);
(angle == 270 ? nyaxis = true : nyaxis = false);
(yaxis == true ? cout << "This angle lies on the positive portion of the y axis.\n\n" : "");
(nyaxis == true ? cout << "This angle lies on the negative portion of the y axis.\n\n" : "");
}
system("pause");
return 0;
}

#包括
使用名称空间std；
int main（）
{
cout>角度；
cout（360）
cout 0和角度<90？第一个=真：第一个=假）；
（first==true？cout像这样的东西怎么样：

#include <iostream>

using namespace std;

int main() {
  cout << "Please enter an angle and I will tell you which quadrant it is in.\n";
  double angle;
  cin >> angle;

  int quadrant = -1;
  if (angle >= 0 && angle < 90) {
    quadrant = 1;
    cout << "The angle you entered is in the first quadrant.\n";
  } else if (angle >= 90 && angle < 180) {
    quadrant = 2;
    cout << "The angle you entered is in the second quadrant.\n";
  } ...
  } else {
    cout << "Illegal value!\n";
    ...
  }

  cin.ignore();
  return 0;
}

xaxis = angle == 180 ? true : false;

#包括
使用名称空间std；
int main（）{
cout>角度；
整数象限=-1；
如果（角度>=0和角度<90）{
象限=1；
cout=90和角度<180）{
象限=2；
cout您正在滥用三元运算符，使用它的通常和更可读的方式如下：

#include <iostream>

using namespace std;

int main() {
  cout << "Please enter an angle and I will tell you which quadrant it is in.\n";
  double angle;
  cin >> angle;

  int quadrant = -1;
  if (angle >= 0 && angle < 90) {
    quadrant = 1;
    cout << "The angle you entered is in the first quadrant.\n";
  } else if (angle >= 90 && angle < 180) {
    quadrant = 2;
    cout << "The angle you entered is in the second quadrant.\n";
  } ...
  } else {
    cout << "Illegal value!\n";
    ...
  }

  cin.ignore();
  return 0;
}

xaxis = angle == 180 ? true : false;

您使用它就像一个完整的控制结构，而不是
if
s

现在，您得到的错误是有意义的。关于三元运算符的一条规则说，
？
后面的两个表达式必须具有相同的类型。例如，在这一行：

(nxaxis == true ? cout << "This angle lies on the negative portion of the x axis.\n\n" : "");

或者你可以这样写：

cout << (nxaxis ? "This angle ..." : "");

cout
if (nxaxis)
{
    cout << "This angle ...";
}