单目运算符重载格式
++a和a++通过形参确定

data1  operator++()
{
    ++this->a;
    return *this;
}

data1  operator++(int)
{
	data1 temp=*this;
    this->a++;
    return temp;
}

举例使用单目运算符重载

#include "iostream"

using namespace std;


class data1
{
  public :
  int a;
  data1(int a):a(a)
  {

  }  

data1  operator++()
{
    ++this->a;
    return *this;
}

data1  operator++(int)
{
	data1 temp=*this;
    this->a++;
    return temp;
}

};

class data2
{
  public :
  int a;
  data2(int a):a(a)
  {

  }  
};

int main()
{
    data1 a(20);
    data1 b=a++;
    cout << b.a << endl;

}