operator-运算符重载"="

//Programmer.h
#pragma once
#include <iostream>  
#include <string>
class Programmer
{
public:
	Programmer() {};
	~Programmer() {};
	void SetName(std::string &in_name) { m_name = in_name; }
	void SetLanguage(std::string &in_language) { m_language = in_language; }
	void SetLevel(int in_level) { m_level = in_level; }
	std::string GetName() { return m_name; }
	std::string GetLanguage() { return m_language; }
	int GetLevel() { return m_level; }
	Programmer& operator= (const Programmer& in_programmer)
	{
		if ( this != &in_programmer )
		{
			m_name = in_programmer.m_name;
			m_language = in_programmer.m_language;
			m_level = in_programmer.m_level;
		}
		return *this;
	}
private:
	std::string m_name;
	std::string m_language;
	int m_level;
};

#include "stdafx.h"   
#include "programmer.h"
int _tmain(int argc, _TCHAR* argv[])   
{   
	Programmer a;
	std::string name = "Kevin Chen";
	std::string language = "C++";
	int level = 1;
	a.SetName(name);
	a.SetLanguage(language);
	a.SetLevel(level);
	Programmer b = a; // copy the values from a
	std::cout<<a.GetName()<<std::endl;
	std::cout<<b.GetName()<<std::endl;
	std::cout<<a.GetLanguage()<<std::endl;
	std::cout<<b.GetLanguage()<<std::endl;
	std::cout<<a.GetLevel()<<std::endl;
	std::cout<<b.GetLevel()<<std::endl;
	
	std::string name2 = "Jack Chen";
	std::string language2 = "C++";
	int level2 = 2;
	b.SetName(name2);
	b.SetLanguage(language2);
	b.SetLevel(level2);
	std::cout<<a.GetName()<<std::endl;
	std::cout<<b.GetName()<<std::endl;
	std::cout<<a.GetLanguage()<<std::endl;
	std::cout<<b.GetLanguage()<<std::endl;
	std::cout<<a.GetLevel()<<std::endl;
	std::cout<<b.GetLevel()<<std::endl;

	return 0;   
}  

输出结果:
Kevin Chen
Kevin Chen
C++
C++
1
1
Kevin Chen
Jack Chen
C++
C++
1
2