Question

我在尝试编译以下代码时遇到错误。我是初学者。请帮我搞清楚。我试图重载运算符_，+，/，*。它在编译时显示错误。我应该使用＆＃34;朋友＆＃34;解决这个问题？

#include<stdio.h>

class complex{
private:
    double real; //real part of complex
    double imag; // imaginary part of complex
public:
    complex(double r=0., double i=0.):real(r),imag(i)
    {
    } // constructor with initialization
    complex(const complex&c):real(c.real),imag(c.imag)
    {
    } // copy constructor with initialization
    ~complex()
    {
    } // destructor
    double re() const
    {
        return real;
    } // read real part
    double im() const
    {
        return imag;
    } // read imaginary part
    const complex& operator=(const complex&c)
    {
        real=c.real;
        imag=c.imag;
        return *this;
    } //assignment operator
    const complex& operator+=(const complex&c)
    {
        real += c.real;
        imag += c.imag;
        return *this;
    } // addition of current complex
    const complex& operator-=(const complex&c)
    {
        real -= c.real;
        imag -= c.imag;
        return *this;
    } // subtract from current complex
    const complex& operator*=(const complex&c)
    {
        double keepreal = real;
        real = real*c.real-imag*c.imag;
        imag = keepreal*c.imag+imag*c.real;
        return *this;
    } // multiply current complex with a complex
    const complex& operator/=(double d)
    {
        real /= d;
        imag /= d;
        return *this;
    } // divide current complex with real
    void print(const complex&c)
    {
        printf("(%f,%f)\n",c.re(),c.im() );
    } // printing complex number
    friend complex operator !(const complex& c)
    {
        return complex(c.re(),-c.im());
    }
    friend double abs2(const complex& c)
    {
        return c.re()*c.re()+c.im()*c.im();
    } // absolute value of complex
    const complex& operator/=(const complex&c)
    {
        return *this *= (!c)/=abs2(c);
    } // divide the current complex by a complex
    const complex operator-(const complex& c)
    {
        return complex(-c.re(),-c.im());
    } // negative of complex number
    const complex operator-(const complex& c,const complex& d)
    {
        return complex(c.re()-d.re(),c.im()-d.im());
    } // difference between complex numbers
    const complex operator+(const complex& c,const complex& d)
    {
        return complex(c.re()+d.re(),c.im()+d.im());
    } // addition of complex numbers
    const complex operator*(const complex& c,const complex& d)
    {
        return complex(c)*=d;
    } // multiplication of complex numbers
    const complex operator/(const complex& c,const complex& d)
    {
        return complex(c)/=d;
    } // division of complex numbers
};

int main(){
    complex c(1.,0.),d(3.,4.);
    print(c-d);
    print(c/d);
    return 0;
}

我得到的输出是：

complex_nums.cpp:76:59: error: ‘const complex complex::operator-(const complex&, const complex&)’ must take either zero or one argument
  const complex operator-(const complex& c,const complex& d)
                                                           ^
complex_nums.cpp:80:59: error: ‘const complex complex::operator+(const complex&, const complex&)’ must take either zero or one argument
  const complex operator+(const complex& c,const complex& d)
                                                           ^
complex_nums.cpp:84:59: error: ‘const complex complex::operator*(const complex&, const complex&)’ must take either zero or one argument
  const complex operator*(const complex& c,const complex& d)
                                                           ^
complex_nums.cpp:88:59: error: ‘const complex complex::operator/(const complex&, const complex&)’ must take exactly one argument
  const complex operator/(const complex& c,const complex& d)
                                                           ^
complex_nums.cpp: In function ‘int main()’:
complex_nums.cpp:96:11: error: ‘print’ was not declared in this scope
  print(c-d);
           ^
complex_nums.cpp:97:9: error: no match for ‘operator/’ (operand types are ‘complex’ and ‘complex’)
  print(c/d);

Answer 1

所有运算符（AppTheme）只需要一个或不需要参数，除非它们是友元函数。将所有<item name="android:fastScrollTextColor">@color/apptheme_color</item> //this is used for the color of the Alphabetical Fast scrollView <item name="android:fastScrollPreviewBackgroundRight">@drawable/bg_default_focused_holo_light</item> //this is the image or and drawable file you want to set on Alphabetical Fast scrollView函数标记为+,-,*,/，代码应该有效。否则，从每个运算符中消除1个参数，而不是使用当前实例（operator）。已删除参数的friend运算符示例：

this

+算术运算符的引用：

下一个错误

你在使用const complex operator+(const complex& c) { return complex(c.re()+re(),c.im()+im()); }功能做什么？它应该在全局范围内，因为它需要friend作为参数。将print()移出全局范围，就像这样。如果您仍想为对象本身保留complex，请执行此操作，但您的课程应如下所示：

print()

Answer 2

二元运算符是带有2个参数的自由函数（首选）或带有一个参数的成员函数（不太好）。

您已使用2个参数定义了成员函数。

通过添加friend将其转换为免费功能是一种方式。

另一种方法是让它们成为自由函数，在类之外定义，但是按成员函数编写（正如你所做的那样）：

struct complex
{
 /* ... */ 
};
// class definition ends

//free function
inline complex operator/(const complex& c,const complex& d)
{
    return complex(c)/=d;
} // division of complex numbers

注意，这个功能可以改进：

inline complex operator/(complex c,const complex& d)
{
    c /= d;
    return c;
}

此外，一元运算符应返回complex&，而不是const complex&。你返回的东西是可变的，因为你只是改变了它。

Answer 3

对于运算符must take either zero or one argument的错误，这是因为您将非成员函数实现为成员函数。这些应该是自由函数才能正常工作，或者只应该使用一个参数并使用this作为另一个参数。

请参阅此问题以澄清：

Operator overloading : member function vs. non-member function?

对于打印错误，我猜您正在尝试调用打印成员函数。要做到这一点，你需要做，例如以下内容：

complex(c-d).print();

在c ++中重载operator +， - ，*，/时出错

3 个答案:

下一个错误