Derived classes, please help

[Mikey_S]

How come the following code

#include <iostream>
using namespace std;

class A {
	int Num;
	char Word[12];

public:
	A(int num, char* word) : Num(num) {
		strncpy(Word, word, 12);
		cout << "Building A!\n";
	}
	void Print()
	{
		cout << "Num = " << Num << " Word = " << Word << endl;
	}

};

class B: private A {
	float fNum;

public:
	B(int num, char* word, float f) : A(num, word), fNum(f) {
		cout << "Building B! \n";
	}

	void Print() {
		cout << "I'm B!\n";
		cout << "fNum = " << fNum << endl;
		A::Print();
	}
};

class C: public B {
	A myA;

public:
	C(int num, char* word) : B(num, word, 5.3), myA(num, word) {
		cout << "Building C!\n";
	}

	void Print() {
		cout << "I'm C!\n"; myA.Print(); B::Print();
	}
};

void main() {
	C FunAndAmusement(3, "Seven");
	FunAndAmusement.Print();
}

Gives me the following error:

Error	2	error C2247: 'A' not accessible because 'B' uses 'private' to inherit from 'A'

It is true that B uses private to inherit from A, but how does this have to do with the fact that i'm using an A data member inside C and using C's constructor init line to initialize it's A datamember?

EDIT: Is this because B inherits private from A and that includes A's constructor as well, and that's why C cannot use A's constructor since it doesnt have access to it? if so, is there a way to override it and use A as it's datamember? like putting A's constructor in the "protected" or "public" section in class C?
Thanks.

[laserlight]

Okay, I am a little stumped by this, but on a hunch I decided to qualify A as being in the global namespace, and the error was fixed, but I am afraid that I cannot really explain why (nor can I explain my intuition).

class C: public B {
	::A myA;

public:
	C(int num, char* word) : B(num, word, 5.3), myA(num, word) {
		cout << "Building C!\n";
	}

	void Print() {
		cout << "I'm C!\n"; myA.Print(); B::Print();
	}
};

If I should take a stab at it, my guess would be that the use of the unqualified A in C refers to the A indirect base class sub-object.

[Mikey_S]

I was thinking about this to.
If that's the case, how come I cannot fix this by stating A::A inside the "protected" or "public" fields of the B class? that way I can use A's constructor using C because now I'll have access to it ... what do you think?

[Cactus_Hugger]

First: int main().

Second:
Wow, interesting problem. After a bit of Googling, this article seems to have some info that might be related. Your code will compile if you change:

A myA;

to:

::A myA;

Edit: Wow, posts while I was exploring... :P

[Mikey_S]

Thanks alot, that does solve the problem... but how come this issue cannot be solved with "public"ing A::A inside class B (after inheriting "private") anyone has a clue?

[laserlight]

but how come this issue cannot be solved with "public"ing A::A inside class B (after inheriting "private")

What do you mean by that?

[CornedBee]

Thanks alot, that does solve the problem... but how come this issue cannot be solved with "public"ing A::A inside class B (after inheriting "private") anyone has a clue?

Because the problem is not the constructor, it's the class. The class A contains its own name for lookup unqualified lookup. However, qualified lookup of the form A::A cannot find it; it always names the constructor. Thus, you cannot make A::A public in B.

The unqualified lookup for A in C first searches the bases and finds the A in A, but that is private. So it fails.