【C++编程】类与对象 -- 运算符重载：加号、左移运算符、递增运算符、函数调用运算符(仿函数) ...

• 加号 + ：Person operator+(Person p);

  #include <iostream>
  using namespace std;
  
  class Person
  {
  public:
  	Person(int a, int b): m_A(a), m_B(b)
  	{
  	}
  	int m_A;
  	int m_B;
  	Person operator+(Person p)  // 通过成员函数重载 +
  	{
  		Person temp(0, 0);
  		temp.m_A = this->m_A + p.m_A;
  		temp.m_B = this->m_B + p.m_B;
  		return temp;
  	};
  };
  
  int main()
  {
  	Person p1(10, 20);
  	Person p2(10, 20);
  	Person p3 = p1 + p2;  // p3.m_A: 20, p3.m_B: 40  
  	cout << p3.m_A << "****" << p3.m_B << endl;       
  }
  

• 左移运算符 << ：ostream & operator<<(ostream &cout, Person p);

  #include <iostream>
  using namespace std;
  
  class Person
  {
  	friend ostream &operator<<(ostream &cout, Person p); // 如果涉及 private 成员
  
  public:
  	Person(int a, int b): m_A(a), m_B(b)
  	{
  	}
  	int m_A;
  	int m_B;
  };
  
  ostream & operator<<(ostream &cout, Person p) // 无法利用成员函数实现
  {
  	cout << " m_A = " << p.m_A << " m_B = " << p.m_B << endl;
  	return cout;
  }
  
  int main()
  {
  	Person p(10, 20);
  	cout << p << endl;  //  m_A = 10 m_B = 20
  }
  

• 递增运算符 ++ ：Person & operator++(), Person operator++(int)

  #include <iostream>
  using namespace std;
  
  class Person
  {
  	friend ostream &operator<<(ostream &cout, Person p); // 如果涉及 private 成员
  
  public:
  	Person(int a, int b): m_A(a), m_B(b)
  	{
  	}
      Person & operator++()   // 前置递增，返回引用
      {
          this->m_A++;
          return *this;
      }
      Person operator++(int)  // 后置递增，返回值，参数 int 占位
      {
          Person temp = *this;
          this->m_A++;
          return temp;
      }
  
  	int m_A;
  	int m_B;
  };
  
  ostream & operator<<(ostream &cout, Person p)
  {
  	cout << " m_A = " << p.m_A << " m_B = " << p.m_B << endl;
  	return cout;
  }
  
  int main()
  {
  	Person p(10, 20);
  	cout << p << endl;   // m_A = 10 m_B = 20
  	cout << ++p << endl; // m_A = 11 m_B = 20
  	cout << p++ << endl; // m_A = 11 m_B = 20
  }
  

• 函数调用运算符(): 自选返回类型 operator()(自选形参);

  #include <iostream>
  using namespace std;
  
  class Person
  {
  	friend ostream &operator<<(ostream &cout, Person p); // 如果涉及 private 成员
  
  public:
  	Person(int a, int b): m_A(a), m_B(b)
  	{
  	}
      void operator()()   // 函数调用运算符 -> 仿函数
      {
          cout << "here" << endl;
      }
  	int m_A;
  	int m_B;
  };
  
  
  int main()
  {
  	Person p(10, 20);
  	p();  
  }
  

• 其他不赘述，仅给出 函数名称和参数返回类型
  • 赋值运算符=： Person& operator=(Person p);
  • 关系运算符==： bool operator==(Person p);

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