Problem Creating an array of pointers

[myk45]

Hello everyone,
i'm having some problem with the following code:

CODE

inputSouce is an abstract class and the rest are derived from it. The definitions for these are elsewhere.
Now,

inputSource *irSources[4];
irSources[0] = new irSource();

This is giving me errors. i'm using VS2008.

error C2466: cannot allocate an array of constant size 0
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
error C2040: 'irSources' : 'int []' differs in levels of indirection from 'inputSource *[4]'
error C2440: 'initializing' : cannot convert from 'irSource *' to 'int []'

Those are the errors. Could anyone please provide some help as to where i'm going wrong?

PS:

inputSource *irOne = new irSource;

This works fine. i'm getting the problem only when i declare an array of pointers and try to allocate memory to them.

Thanks.

[gerard4143]

You can't create abstract objects, hence the term abstract. You can create a pointer to an abstract type but its must point to a derived object.

Here's a simple coded example

#include <iostream>

class expr_node//abstract
{
public:

    virtual ~expr_node() {}

    virtual std::ostream& print(std::ostream & out) const = 0;

};

std::ostream& operator << (std::ostream & out, const expr_node & e)
{
    return e.print(out);
}

class int_node: public expr_node//derived
{
public:

    virtual ~int_node() {}

    std::ostream& print(std::ostream &out) const { out << "derived"; }
};

int main(int argc, char**argv)
{
    expr_node *me[4];

    for (int i = 0; i < 4; ++i)
        me[i] = new int_node;//creating pointer to derived type
    return 0;
}

[myk45]

Thanks for the reply gerard4143.

>>You can't create abstract objects, hence the term abstract. You can create a pointer to an abstract type but its must point to a derived object.

Well,

inputSource *irSources[4];
irSources[0] = new irSource();

Here, irSources is just an array of pointers, similar to me[4] in your example.
It is made to point to a derived object(irSource object). So, that should work right?

Please correct me if im wrong.

[gerard4143]

It should work if irSource is derived from inputSource and if irSource is not abstract.

[myk45]

class inputSource {
	protected:
			double xPos;
			double yPos;
			double zPos;

			double rawX; 
			double rawY;

	public:
			virtual double getIrX() = 0;	// Pure virtual functions
			virtual double getIrY() = 0;
			virtual double getIrZ() = 0;

			virtual double getRawX() = 0;
			virtual double getRawY() = 0;

			void setIrX(double);
			void setIrY(double);
			void setIrZ(double);

			virtual void calcXYZ() = 0;
};

class irSource : public inputSource {
	public:
			double getIrX();
			double getIrY();
			double getIrZ();

			double getRawX(); 
			double getRawY(); 
			
			void setRawX(double rawX);
			void setRawY(double rawY);
	
			void calcXYZ();
};

class keyboardSource : public inputSource {
	public:
			double getIrX();
			double getIrY();
			double getIrZ();
	
			void calcXYZ();
};

class cameraSource : public inputSource {
	public:
			cameraSource(); 
			~cameraSource();
			
			double getRawX(); 
			double getRawY(); 

			void setRawX(double rawX);
			void setRawY(double rawY);

			double getIrX();
			double getIrY();
			double getIrZ();
	
			void calcXYZ();
};

here are the classes. irSource is derived from inputSource, and is not abstract. So, this is fine right?

Thanks.