运算符重载

+ -运算符重载

#include<iostream>
using namespace std;
/*常函数可以访问非const数据成员，非const成员函数可以读取常数据成员，
常成员函数不可以调用非const成员函数*/
class A {
private:
	int x;
	int y;
public:
	A(int x1 = 0, int y1 = 0) :x(x1), y(y1) {}
	void show() const;
	A operator+(const A &a) const;
	friend A operator-(const A &a1, const A &a2);
};
void A::show() const
{
	cout << x << ' ' << y << endl;
}
A A::operator+(const A &a) const
{
	return A(x + a.x, y + a.y);
}
A operator-(const A &a1, const A & a2)
{
	return A(a1.x - a2.x, a1.y - a2.y);
}
int main()
{
	A a1(1, 3);
	A a2(4, 5);
	A a;
	a1.show();
	a2.show();
	a = a1 + a2;
	a.show();
	a = a1 - a2;
	a.show();
	system("pause");
	return 0;
}

前置++ ++（int）重载

```
#include<iostream>
using namespace std;
class A {
private:
	int x;
	int y;
public:
	A(int x1 = 0, int y1 = 0) :x(x1), y(y1) {}
	void show() const;
	A operator++();
	A operator++(int);//后置
};
void A::show() const
{
	cout << x << ' ' << y << endl;
}
A A::operator++()
{
	++x;
	++y;
	return *this;
}
A A::operator++(int)
{
	A a = *this;
	++(*this);
	return a;
}
int main()
{
	A a1(1, 2);
	A a2(3, 4);
	(a1++).show();
	(++a2).show();
	system("pause");
	return 0;
}

//    输入输出重载
#include<iostream>
using namespace std;
class A {
private:
	int x;
	int y;
public:
	A(int x1 = 0, int y1 = 0) :x(x1), y(y1) {}
	friend ostream& operator<<(ostream &os, const A &a);
	friend istream& operator >> (istream &is, A &a);
};
ostream& operator<<(ostream &os, const A &a)
{
	os << a.x << ' ' << a.y << endl;
	return os;
}
istream& operator >> (istream &is, A &a)
{
	is >> a.x >> a.y;
	return is;
}
int main()
{
	A a1(1, 2);
	A a2(3, 4);
	cout << a1;
	cout << a2;
	cin >> a2;
	cout << a2;
	system("pause"); 
	return 0;
}

#include<iostream>
using namespace std;
class Student {
private:
	int id;
	double score;
public:
	friend bool operator==(const Student &st1, const Student &st2);
	friend ostream& operator<<(ostream &os, const Student &st)
	{
		os << st.id << ' ' << st.score << endl;
		return os;
	}
	friend istream& operator >> (istream &is, Student &st)
	{
		is >> st.id >> st.score;
		return is;
	}
};
bool operator==(const Student &st1, const Student &st2)
{
	return (st1.score == st2.score);
}
int main()
{
	Student st1, st2;
	cin >> st1 >> st2;
	if (st1 == st2)
		cout << st1;
	system("pause"); 
	return 0;
}

赋值运算符重载

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstring>
using namespace std;
class Internet {
public:
	char *name;
	char *url;
public:
	Internet(char *name, char *url);
	Internet(Internet &temp);
	~Internet()
	{
		delete[] name;
		delete[] url;
	}
	Internet& operator=(Internet &temp);
};
Internet::Internet(char *name, char *url)
{
	this->name = new char[strlen(name) + 1];
	this->url = new char[strlen(url) + 1];
	if (name)
		strcpy(this->name, name);
	if (url)
		strcpy(this->url, url);
}
Internet::Internet(Internet &temp)
{
	this->name = new char[strlen(temp.name) + 1];
	this->url = new char[strlen(temp.url) + 1];
	if (name)
		strcpy(this->name, temp.name);
	if (url)
		strcpy(this->url,temp.url);
}
Internet& Internet::operator=(Internet &temp)
{
	delete[] name;
	delete[] url;
	this->name = new char[strlen(temp.name) + 1];
	this->url = new char[strlen(temp.url) + 1];
	if (name)
		strcpy(this->name, temp.name);
	if (url)
		strcpy(this->url, temp.url);
	return *this;
}
int main()
{
	Internet a("lixain", "hahah");
	cout << a.name << ' ' << a.url << endl;
	Internet b(a);
	cout << b.name << ' ' << b.url << endl;
	Internet c("uigj", "ouihknp");
	cout << c.name << ' ' << c.url << endl;
	b = c;
	cout << b.name << ' ' << b.url << endl;
	system("pause"); 
	return 0;
}

下标运算符重载

//可以像普通数组一样哈
#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
using namespace std;
class Array {
private:
	int size;
	char *buf;
public:
	Array(int n);
	Array(char *src);
	Array()
	{
		delete[] buf;
	}
	char& operator[](int n);
	void show()
	{
		for (int i = 0; i < size; i++)
		{
			cout << buf[i];
		}
		cout << endl;
	}
};
Array::Array(int n)
{
	size = n;
	buf = new char[n + 1];
	*(buf + size) = '\0';
}
Array::Array(char *src)
{
	buf = new char[strlen(src) + 1];
	strcpy(buf, src);
	size = strlen(buf);
}
char& Array::operator[](int n)
{
	static char ch = 0;//
	if (n > size || n < 0)
	{
		cout << "yuejie" << endl;
		return ch;
	}
	else
		return *(buf + n);
}
int main()
{
	/*在构造arr1对象时，指定了数组的大小，然后通过【】运算符来给数组赋值*/
	Array arr1(20);
	for (int i = 0; i < 20; i++)
	{
		arr1[i] = 65 + i;
	}
	arr1.show();
	/*由一个字符串直接创建一个数组，然后调用【】运算符读取某一个字符元素，也可以进行修改*/
	Array arr2("hahahahah");
	cout << arr2[6] << endl;
	arr2[6] = 'l';
	arr2.show();
	system("pause"); 
	return 0;
}
``

//类型转换函数
#include<iostream>
using namespace std;
class Swap {
	private:
		int a, b;
public:
	Swap(int m, int n) :a(m), b(n) {}
	operator char()
	{
		return static_cast<char>(a);
	}
	void show()
	{
		cout << a << ' ' << b << endl;;
	}
};
int main()
{
	Swap s1(65, 2);
	s1.show();
	char ch = s1;
	cout << ch;
	system("pause"); 
	return 0;
}