重载运算符C++的逻辑错误

Logical error with overloaded operator C++

本文关键字：错误 运算符 C++ 重载      更新时间：2023-10-16

我一直在制作一个名为Complex的类，用于存储和处理复数。我遇到了一些问题，重载的+和*函数返回了一个非常大的数字，我只能推测这与指针有关，但我对使用它们非常陌生。我在这里复制了输出：

c1: 1 - i5
c2: -4 + i3
c1 + c2: -9.25596e+061 - i9.255
c1 * c2: -9.25596e+061 - i9.255
Press any key to continue . . .

这是类架构：

// Complex.h
#include <iostream>
#include <cmath>    
using namespace std;
class Complex
{
    friend std::ostream &operator<<(std::ostream &, const Complex &);
    friend std::istream &operator>>(std::istream &, Complex &);
    friend Complex &operator+(const Complex &, const Complex &);
    friend Complex &operator+(const Complex &, const double &);
    friend Complex &operator+(const double &, const Complex &);
    friend Complex &operator*(const Complex &, const Complex &);
    friend Complex &operator*(const Complex &, const double &);
    friend Complex &operator*(const double &, const Complex &);
public:
    explicit Complex(double re=0, double im=0);
    void setReal(double re);
    void setImag(double im);
    double &getReal();
    double &getImag();
    ~Complex();
private:
    double real;
    double imag;
};

这里我有我的程序的相关部分：

// Complex.cpp
#include "Complex.h"
ostream &operator<<(ostream &output, const Complex &num)
{
    output << num.real << (num.imag >= 0 ? " + i" : " - i") << abs(num.imag);
    return output;
}
Complex &operator+(const Complex &num1, const Complex &num2)
{
    Complex sum(num1.real + num2.real, num1.imag + num2.imag); // Create new complex by summing elements
    return sum;
}
Complex &operator*(const Complex &num1, const Complex &num2)
{
    Complex prod(num1.real * num2.real - num1.imag * num2.imag, num1.real * num2.imag + num1.imag * num2.real); // Create new complex by expansion
    return prod;
}
Complex::Complex(double re, double im)
{
    real = re;
    imag = im;
}
int main() {
    Complex c1(1.0, -5.0);
    Complex c2(-4.0, 3.0);
    cout << "c1: " << c1 << endl;
    cout << "c2: " << c2 << endl;
    cout << "c1 + c2: " << c1 + c2 << endl;
    cout << "c1 * c2: " << c1 * c2 << endl;
    system("pause");
}

我很抱歉为此打扰你们。你可能知道有哪个网站能很好地解释C++的概念，比如指针、最小特权、多态性、继承等吗？

很抱歉在这里问了一些基本问题，但很难找到能清楚解释这些内容的资源。

错误的返回类型：

Complex &operator+(const Complex &num1, const Complex &num2)
^^^^^^^^^

您正在创建一个临时Complex并通过引用返回它，然后它被销毁，所以您有一个悬空引用。由于operator+正在构造一个新对象并返回它，它应该通过值来返回它。。。所以签名应该是：

Complex operator+(Complex const&, Complex const& );

问题是，大多数重载运算符都会返回对本地var的引用，当运算符函数返回时，该引用会被破坏，留下一个悬空引用。尝试更改运算符以返回Complex而不是Complex &:

Complex operator+(const Complex &num1, const Complex &num2)
{
    Complex sum(num1.real + num2.real, num1.imag + num2.imag); // Create new complex by summing elements
    return sum;
}
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