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Question about inheritance

raynierl (16)
I need class "Vector4D" to initialize all the variables,I have to create a default and a generic constructor in Vector4D to initialize all variables in all three classes regardless of the constructor call. Where am i going wrong.(The Comments are failed attempts)
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  #include<iostream>
using namespace std;
class Vector2D
{
	protected:
	int x,y;
	public:
		Vector2D() {x=y=0;}
	//	Vector2D(int x1, int y1){x = x1; y = y1;}
	
};
class Vector3D
{
	protected:
		int z;
	public:
		Vecotr3D() {z=0;}
	//	Vector3D(int z1) {z = z1;}
	
};
class Vector4D: public Vector2D, public Vector3D
{
	protected:
		int t;
	public:
		Vector3D v3;
		Vector2D v2;
		Vector4D(){t=0;}
		Vector4D(int,int,int,int);
};
Vector4D::Vector4D(int a,int b, int c, int d)
{
//	Vector3D::Vector3D() ;
//	Vector2D::Vector2D();
//	x=a;
//	y=b;
//	z=c;

v2.x = a;
v2.y = b;
v3.z = c;
t=d;

	cout << x  << endl<<y <<endl << z  << endl<< t;
}
int main ()
{
	Vector4D x,y(1,2,3,20);
	x;
	y;
	return 0;
}
keskiverto (10402)
Look up "member initializer list". Plenty of goog links.

Also http://www.informit.com/articles/article.aspx?p=1852519


The logic of your design is ... odd.

The Vector2D does make sense; it holds two values.

The Vector3D ... is one integer?

The Vector4D:
* is-a Vector2D
* is-a Vector3D
* has-a Vector2D object
* has-a Vector3D object
* has-a integer object

... sums up to 7 integers?
raynierl (16)
The reason the design is odd is due to my failed attempts,and just moving things around to see what works and what doesn't.
I can get it to work, but apparently that is not the way my professor wants it.
My real question is how do I intialize the variables from Vector2D and Vector3D from Vector4D
without initializing them directly in Vector4D such as:
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class Vector2D
{
	protected:
	int x,y;
	public:
		Vector2D() {x=y=0;}
	
};
class Vector3D
{
	protected:
		int z;
	public:
		Vecotr3D() {z=0;}
	
};
class Vector4D: public Vector2D, public Vector3D
{
	protected:
		int t;
	public:
		
		Vector4D(){t=0;}
		Vector4D(int,int,int,int);
};
Vector4D::Vector4D(int a,int b, int c, int d)
{

	x=a;
	y=b;
	z=c;
	t=d;

	cout << x  << endl<<y <<endl << z  << endl<< t;
}

This is how I had it originally which is incorrect.
AbstractionAnon (6954)
First off, I would say you inheritance is wrong.
Vector3D should inherit Vector2D.
Vector4D should inherit only from Vector3D.

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class Vector2D
{   int x,y;
public:
	Vector2D () : x(0), y(0)
	{}
	Vector2D (int _x, int _y) : x(_x), y(_y)   //  2 arg constuctor
	{}
};

class Vector3D : public Vector2D
{   int z;
public:
	Vector3D() : z(0)   //  Invokes Vector2D's default constructor
	{}
	Vector3D(int x,int y,int _z) : Vector2D(x,y), z(_z)  //  3 arg constructor
	{}
};

class Vector4D: public Vector3D
{   int t;
public:
	Vector4D() : t(0)       //  Invokes Vector3D's default constructor
	{}
	Vector4D(int x,int y,int z,int _t) : Vector3D(x,y,z), t(_t)  // 4 arg constructor
	{}
};

raynierl (16)
@AbstractionAnon follow up question.
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public:
	Vector2D () : x(0), y(0) // <----------------
	{}
	Vector2D (int _x, int _y) : x(_x), y(_y)   //  2 arg constuctor
	{}
};

Why do you initialize this way? Was it part of my issue?
AbstractionAnon (6954)
It's called initializer list member initialization. It's generally preferred over the following form which does the same thing:
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	Vector2D () 
	{ x=0; y=0; }
	Vector2D (int _x, int _y) //  2 arg constuctor
	{ x=_x; y=_y; }


raynierl (16)
Thank you very much for your help.
JosephDaniels1982 (2)
You saved my life. I had the same problem for school project!
navdeepk (4)
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