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;
}