使用类

Question

所以，我在一本书中找到了这个代码：

class complex
{ 
    public:
        float x,y;
        complex(float a, float b) // CONSTRUCTOR
        {
            x=a; y=b;
    }
    complex sum (complex z)
    {
        ***complex c;*** // i get the error here
        c.x=x+z.x;
        c.y=y+z.y;
        return c;
    }
};

这段代码可以帮助我总结2个复数，如：

int main ()
{   
    complex a(1,2),b(1,1),c; // first number in paranthesis is the real part, the 
                             // second one is the imaginary part
    c=a.sum(b) ; // c should get the value of a+b (c.x=2, c.y=3)
    return 0;
}

但每次我尝试编译它时都会收到此错误： “没有用于调用complex :: complex（）的匹配函数” 为什么？我该怎么办？

Answer 1

您定义了自己的构造函数，因此默认构造函数定义为complex() = delete;。您需要自己的构造函数或强制创建默认构造函数

class complex
{
public:
    float x = 0;
    float y = 0;

    complex() = default; // Compiler will generate the default constructor
    complex(float a, float b): x(a), y(b) {}

    complex sum (complex z)
    {
        complex c;
        c.x=x+z.x;
        c.y=y+z.y;
        return c;
    }
};

我会创建非成员sum

，而不是创建operator+成员函数

// No need to make it friend because you declared x and y as public
complex operator+(complex const& a, complex const& b) {
    return complex(a.x + b.x, a.y + b.y);
}

并像这样使用

complex a(3, 4), b(5, 6);
complex c = a + b;