#ifndef __COMPLEX__
#define __COMPLEX__

#include <iostream> //实际上include不一定要写在前面，只要在函数外面就行
using std::ostream;

class complex
{
public:
    complex (double r = 0, double i = 0) : re(r), im(i){}

    complex& operator += (const complex&);

    double real() const {return re;}

    double imag() const {return im;}

private:
    double re, im;

    friend complex& __doapl(complex*, const complex);
};

#endif


//do assignment-plus,函数中想直接取得re和im，所以声明成友元函数
complex& __doapl(complex* ths, const complex r){
    ths->re += r.re;
    ths->im += r.im;
    return *ths;
}

inline complex& complex::operator += (const complex& r){
    return __doapl(this, r);
}


//非成员函数
//把+不设计为成员函数是因为不只是复数加复数，还可以是实数加复数
inline complex operator + (const complex& x, const complex& y){
    return complex(x.real() + y.real(), x.imag() + y.imag());
}

inline complex operator + (const complex& x, double y){
    return complex(x.real() + y, x.imag());
}

//操作符重载只能用在左边的变量上
inline complex operator + (double x, const complex& y){
    return complex(x + y.real(), y.imag());
}

//由于希望能够连用，如cout << c1 << endl; 所以有返回值
ostream& operator << (ostream& os, const complex& x){
    return os << '(' << x.real() << x.imag() << ')';
}