成员函数、友元函数++前缀后缀

#include<iostream> 
using namespace std;  

class over
{
	int i1 , i2 ,i3;

public:
	void init(int I1=0 , int I2 =0, int I3=0);
	void print();

public:
	over operator ++();//前缀
	over operator++(int);//后缀

	friend over operator--(over &);//友元前缀
	friend over operator--(over & , int );//友元后缀
};

void over::init(int I1 , int I2, int I3)
{
	i1 = I1 ;
	i2 = I2 ;
	i3 = I3 ;
}

void over::print()
{
	cout<<"i1 = "<<i1<<" , i2 ="<<i2<<" , i3 ="<<i3<<endl;
}
over over::operator++()//成员函数-前缀
{
	++i1 ;
	++i2 ;
	++i3 ;
	return *this ;
}
over over::operator++(int )//成员函数-后缀
{
	i1++;
	i2++;
	i3++;
	return *this ;
}
over operator--(over & op)//友元 前缀
{
	--op.i1 ;
	--op.i2 ;
	--op.i3 ;
	return op ;
}
over operator--(over & op , int )//友元后缀
{
	op.i1-- ;
	op.i2-- ;
	op.i3-- ;
	return op ;
}
int main()
{   
	 over  ob1 , ob2 , ob3 , ob4 ;
	 ob1.init();
	 ob2.init(7,7,7);
	 ob3.init(11,11,11);
	 ob4.init(13,13,13);

	 ++ob1 ;//隐式调用over operator++()
	 ob2++;//隐式调用over operator++(int)
	 --ob3;//隐式调用over operator--(over&)
	 ob4--;//隐式调用over operator--(over& ,int)

	 ob1.print();
	 ob2.print();
	 ob3.print();
	 ob4.print();
	  
	 cout<<"-------------------------"<<endl;

	 ob1.operator++();//显示调用,++ob1
	 ob2.operator++(0);//显示调用ob2++;
	 operator--(ob3);//显示调用--ob3;
	 operator--(ob4,0);//显示调用ob4--;

	 ob1.print();
	 ob2.print();
	 ob3.print();
	 ob4.print();

	getchar();
	return 0 ; 
}