c++学校oj题目分析

代码：

#define  _CRT_SECURE_NO_WARNINGS
#include 
#include 
#include 
using namespace std;

class Complex
{
public:
	double r; // real
	double i; // image
public:
	Complex() :r(0), i(0) {}
	Complex(double a, double b) :r(a), i(b) {}
	void Show() const
	{
		cout << "(" << noshowpos << r << showpos << i << noshowpos << "i)" << endl;
	}

	Complex(Complex& d1)
	{
		r = d1.r * 2;
		i = d1.i * 2;
	}

	Complex operator=(const Complex& d1)
	{
		r = 3 * d1.r;
		i = 3 * d1.i;
		return *this;
	}
};

int main()
{
	double a, b;
	cin >> a >> b;

	Complex c1(a, b);
	Complex c3 = c1;
	Complex c4, c5;
	c5 = c4 = c1;
	const Complex& c6 = c4 = c1;

 	c1.Show();
	c3.Show();
	c4.Show();
	c5.Show();
	c6.Show();

	return 0;
}

1、为什么赋值运算符重载必须加const，否则编译器报错

因为c1赋值的c4的时候会创建一份临时变量，而c5则被这个临时变量赋值，因为是个临时变量，所以是const的，如果赋值运算符参数不加const，则const传给非const参数，权限扩大，就会发生报错