C++重载输出运算符出错（输出复数的四则运算）

Question

问题遇到的现象

想要直接输出复数的四则运算，直接输出复数没有问题。

问题相关代码

1.重载输出函数

ostream &operator<<(ostream &out, Plural &p)
{
    out<<"{"<<p.real;
    if(p.image>0)
    out<<"+"; 
    out<<p.image<<"i"<<"}";
    return out;
}

2.重载加法运算

Plural operator+(Plural a,Plural b)
{
    Plural c;
    c.real=a.real+b.real;
    c.image=a.image+b.image;
    return c;
}

3.主函数

int main()
{
    Plural a,b;
    cin>>a;
    cin>>b;
 cout<<a<<endl;
 cout<<b<<endl;

cout<<(a+b)<<endl;
//    cout<<a-b<<endl;
//    cout<<a*b<<endl;
//    cout<<a/b<<endl;
    return 0;
}

总的代码

#include<iostream>
using namespace std;
class Plural{

    public:
            int real,image;
        Plural(int a1,int b1)
        {
            a1=real;
            b1=image;
        }
        Plural()
        {
            
        }
        friend ostream &operator<<(ostream &out,Plural &p);
        friend istream &operator>>(istream &in,Plural &p);
        friend Plural operator-(Plural a,Plural b);
        friend Plural operator+(Plural a,Plural b);
        friend Plural operator*(Plural a,Plural b);
        friend Plural operator/(Plural a,Plural b);
};
ostream &operator<<(ostream &out, Plural &p)
{
    out<<"{"<<p.real;
    if(p.image>0)
    out<<"+"; 
    out<<p.image<<"i"<<"}";
    return out;
}
istream &operator>>(istream &in,Plural &p)
{
    in>>p.real;
    in>>p.image;
    return in;
}
Plural operator-(Plural a,Plural b)
{
    Plural c;
    c.real=a.real-b.real;
    c.image=a.image-b.image;
    return c;
}
Plural operator+(Plural a,Plural b)
{
    Plural c;
    c.real=a.real+b.real;
    c.image=a.image+b.image;
    return c;
}
Plural operator*(Plural a,Plural b)
{
    Plural c;
    c.real=a.real*b.real-a.image*b.image;
    c.image=a.real*b.image+a.image*b.real;
    return c;
}
Plural operator/(Plural a,Plural b)
{
    int d;
    d=b.real*b.real-b.image*b.image;
    Plural c;
    c.real= (a.real*b.real-a.image*b.image)/d;
    c.image=(a.real*b.image+a.image*b.real)/d;
}
int main()
{
    Plural a,b;
    cin>>a;
    cin>>b;
    cout<<a<<endl;
    cout<<b<<endl;
//    cout<<(a+b)<<endl;
//    cout<<a-b<<endl;
//    cout<<a*b<<endl;
//    cout<<a/b<<endl;
    return 0;
}

运行结果及报错内容

• 输出单个复数（正常）

• 输出复数的加（报错）

我想要达到的结果

怎么样通过重载运算符来输出两个复数的和，不能添加第三个变量。

Answer 1

因为你在友元函数内试图返回函数内创建的临时变量
c在函数返回后就会被销毁,你返回到外部的值没有意义
改为动态新建并返回即可
此外你似乎没有考虑到除法会出现分数,如果用int去作为复数的成员,在计算除法时可能出错.
我只简单修改了加法和减法的部分,剩余两种运算同理
示例代码如下
有帮助望采纳~

#include <iostream>
using namespace std;
class Plural
{

public:
    int real, image;
    Plural(int a1, int b1)
    {
        a1 = real;
        b1 = image;
    }
    Plural()
    {
    }
    friend ostream &operator<<(ostream &out, Plural &p);
    friend istream &operator>>(istream &in, Plural &p);
    friend Plural &operator-(Plural a, Plural b);
    friend Plural &operator+(Plural a, Plural b);
};
ostream &operator<<(ostream &out, Plural &p)
{
    out << "{" << p.real;
    if (p.image > 0)
        out << "+";
    out << p.image << "i"
        << "}";
    return out;
}
istream &operator>>(istream &in, Plural &p)
{
    in >> p.real;
    in >> p.image;
    return in;
}
Plural &operator-(Plural a, Plural b)
{
    Plural *c = new Plural;
    c->real = a.real - b.real;
    c->image = a.image - b.image;
    return *c;
}
Plural &operator+(Plural a, Plural b)
{
    Plural *c = new Plural;
    c->real = a.real + b.real;
    c->image = a.image + b.image;
    return *c;
}

int main()
{
    Plural a, b;
    cin >> a;
    cin >> b;
    cout << a << endl;
    cout << b << endl;
    cout << (a + b) << endl;
    cout << a - b << endl;

    return 0;
}