运算符重载之何时重载为成员函数？何时重载为友元函数？

#include “pch.h”
#include
#include
using namespace std;
class S
{ public:
S()
{
str = ‘\0’; len = 0; //调用构造函数给变量置初值
}
S(const charpstr)
{
strcpy_s(str, pstr); len = strlen(pstr); //调用构造函数给变量赋值
}
char*gets()
{
return str; //返回字符串
}
int getLen()
{
return len; //返回字符串的长度
}
s&operator+(S obj); //声明重载运算符“+”函数
private:
char str[100];
int len;
};
S& S::operator+(S obj)
{
strcat_s(str, obj.str);
len = strlen(str);
return this;
} //重载运算符“+”的实现部分
int main()
{
S obj1(“Visual”), obj2(“C++”); //声明该类的对象同时调用相应的构造函数进行赋值
obj2 =obj1 + obj2;
cout << “obj2.str=” << obj2.gets() << endl;
cout << “obj2.len=” << obj2.getLen() << endl;
}

#include “pch.h”
#include
#include
using namespace std;
class Complex
{
int real;
int image;
public:
Complex(){}
Complex(int a)
{
real = a;
image = 0;
}
Complex(int a, int b)
{
real = a;
image = b;
} //前三个均为构造函数
friend Complex operator+(Complex c1,Complex c2); //用友元函数重载“+”
void gets()
{
cout << “(” << real << “,” << image << “)” << endl; //输出结果
}
};
Complex operator+(Complex c1, Complex c2)
{
Complex c;
c.real = c1.real + c2.real;
c.image = c1.image + c2.image;
return c;
} //重载函数的定义
int main()
{
Complex c, c1(1, 2);
c = c1 + 1;
c.gets();
}