#include<iostream> using namespace std; class Complex { double real,imag; public: Complex(double r=0,double i=0):real(r),imag(i) {} //只是让代码看起来简短而已 double get_real() {return real;} double get_imag() {return imag;} void print_complex() {cout<<real<<"+"<<"j"<<imag<<endl;} Complex operator + (double a); Complex operator + (Complex x); friend ostream &operator << (ostream &out,Complex &A ); } ostream &operator << (ostream &out,Complex &A ) { out<<A.real<<"+"<<A.imag<<"j"; return out; } Complex Complex:: operator + (double a) { Complex m; m.real=real+a;//实数 m.imag=imag; return m; } Complex Complex::operator +(Complex x)//加不加都可以，引用调用 { Complex t; t.imag=imag+x.imag; t.real=real+x.real; return t; } int main() { Complex c1(1,2),c2(4,5),c3; c1=c1+4.2; //重载 复数类+整型 cout<<c1<<endl; cout<<c2<<endl; c3=c1+c2; //重载 复述类+复数类 cout<<c3<<endl; return 0; } 哪里有问题以及怎么解决

这段代码中有两个问题：

1. 在重载<<运算符时，应该将Complex对象作为常量引用传递，即：

friend ostream &operator << (ostream &out, const Complex &A );

2. 在Complex类的构造函数中，应该使用成员初始化列表来初始化real和imag成员变量，即：

Complex(double r=0, double i=0): real(r), imag(i) {}

修改后的代码如下：

#include<iostream> 
using namespace std; 

class Complex {      
    double real, imag; 
public:     
    Complex(double r=0, double i=0): real(r), imag(i) {}     
    double get_real() {return real;}     
    double get_imag() {return imag;}     
    void print_complex() {cout<<real<<"+"<<"j"<<imag<<endl;}     
    Complex operator + (double a);     
    Complex operator + (Complex x);  
    friend ostream &operator << (ostream &out, const Complex &A ); 
};  

ostream &operator << (ostream &out, const Complex &A ) {     
    out<<A.real<<"+"<<A.imag<<"j";     
    return out; 
}   

Complex Complex:: operator + (double a) {             
    Complex m;             
    m.real=real+a; //实数             
    m.imag=imag;             
    return m;         
} 

Complex Complex::operator +(Complex x) {             
    Complex t;             
    t.imag=imag+x.imag;             
    t.real=real+x.real;             
    return t;         
} 

int main() {     
    Complex c1(1,2),c2(4,5),c3;     
    c1=c1+4.2; //重载 复数类+整型     
    cout<<c1<<endl;     
    cout<<c2<<endl;     
    c3=c1+c2; //重载 复数类+复数类     
    cout<<c3<<endl;   
    return 0; 
}