Re: [Dev-C++] C++ Question (the real one)

[Bolek V. <vr...@pa...>]

> Ioannis Vranos wrote:
> 
> Ok i was stupid for my previous question. The answer is because it was
> a friend function. Here is the real question:
> 
> #include <iostream>
> 
> class Matrix
> {
>  double m[4][4];
> 
>  public:
>  void test(Matrix s);
> };
> 
> 
> void Matrix::test(Matrix s)
> {
>  for (int i=0; i<4; i++)
>  {
>   std::cout<<std::endl;
> 
>   for(int j=0; j<4; j++)
>      std:: cout<<s.m[i][j]<<std::endl;
>  }
> }
> 
> int main()
> {
> 
>  return 0;
> }
> 
> The member function test() accesses the private data member of its
> argument directly. When is it allowed for functions to access directly
> the private members of their arguments except of those declared
> as friends?

It is allowed for friends and member functions of the same class (class
A) only - but it is allowed regeradless of whether it accesses data
members of its own instance (*this) or another instance of the class.
You can also declare a whole class B as a friend. This will cause all
member functions of class B to be friends of class A.

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