Operators +, - overloading

A variable operation:
a ++: to find a value of a variable store, performs a = a + 1; return to the previous calculation value
++ a: performing a = a + 1; returns a value
a-: find a variable storage value a, performs a = a-1; the value before the operation returns
-a: performing a = a-1; a return value of

#include <iostream>//++，--的重载
using namespace std;

//返回参数需要做左值时返回引用
class Test{
	int m_a;
public:
	Test(int a = 0) :
		m_a(a)
	{

	}

	Test operator ++(){//++不传引用，前置++
		m_a++;
		return *this;
	}
	Test operator ++(int){
		Test tmp = *this;
		m_a++;
		return tmp;
	}

	Test operator --(){//--不传引用，前置--
		m_a--;
		return *this;
	}
	Test operator --(int){
		Test tmp = *this;
		m_a--;
		return tmp;
	}
	friend ostream & operator << (ostream & os, Test &t);
};

ostream & operator << (ostream & os, Test &t){
	cout << t.m_a;
	return os;
}

int main(){
	Test t(7);
	cout << t++ << endl;//隐式调用
	cout << t.operator--() << endl;//显示调用
	cout << t << endl;

	Test t1(3);
	cout << t1-- << endl;
	cout << t1 << endl;

	system("pause");
	return 0;
}