错误C2082的帮助:重新定义形式参数 [英] Help with error C2082: redefinition of formal parameter

问题描述

我下面的代码有错误C2082:重新定义形式参数"m":

My code below has error C2082: redefinition of formal parameter ''m'':

class A {
protected:
	float Ra;
public:
	A(float a=0);
};

A::A(float a) {
	Ra = a;
}

class B: public A {
public:
	B(float r=0);
};

B::B(float r) {
	A(r); // here, I called the constructor of base class (class A)
}

然后，我尝试向基类(类A)的构造函数添加另一个参数.在类B的构造函数中，我调用了类A的构造函数，并且它起作用了(没有错误).谁能告诉我为什么?

Then I tried to add one more argument to the constructor of base class (class A). And in the constructor of class B, I called the constructor of class A and it worked (no error). Could anyone please tell me why?

class A {
protected:
    float Ra, Rb;
public:
    A(float a=0, float b=0); // additional argument: float b
};
 
A::A(float a, float B) {
    Ra=a;
    Rb=b;
}
 
class B: public A {
public:
    B(float r=0);
};
 
B::B(float r) {
    A(r,r); // here, I called the constructor of base class (class A)
}

推荐答案

在第一种情况下，编译器假定A(r)是强制转换运算符的 functional 语法.您必须将A(r)替换为A::A(r)，如

In the first case the compiler assumes A(r) is the functional syntax of the cast operator. You have to replace A(r) with A::A(r), as in

B::B(float r)
{
  A::A(r)
}

或做我们通常做的"标准人"

or do what we, ''standard humans'', usually do

B::B(float r) : A(r) 
{
}

如果要调用基类构造函数，则应采用以下方式:

If you want to call base class constructor, you should do it this way:

B::B(float r) : A(r) {
...
}

我不确定在第一个示例中是什么导致错误，但是我可以假定编译器对待

I''m not sure what causes an error in your first example, but I can assume that compiler treats

B::B(float r) {
	A(r); 
}

作为尝试初始化类型为A的新变量r的尝试.此变量名与构造函数的参数名冲突，因此会出现参数重新定义错误(float r被重新定义为A r)

as an attempt to initialize new variable r of type A. This variable name conflicts with constructor''s argument name, and thus you get an error of parameter redefinition (float r being redefined as A r)

非常感谢您的解决方案，但我真的很想知道编译器是如何工作的！再次感谢:)

Thanks very much for your solutions but I really want to know how the compiler worked! Thanks again :)

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