inline operator overloading

[Fransje]

Hi all,
this is my Vector class:

class Vector {
    public:
        int X;
        int Y;

        Vector( int x = 0, int y = 0 );

        inline void operator = ( Vector& vec );
        inline void operator += ( Vector& vec );
};

And this is the implementation of the += operator:

inline void Vector::operator += ( Vector& vec ) {
	X += vec.X;
	Y += vec.Y;
}

In the main() function I use them like this:

Vector vec;
Vector vec2( 1, 1 );
vec += vec2;

And Code::Blocks gives an error on line 3:

main.cpp|7|undefined reference to `Vector::operator+=(Vector&)'|

Can somebody explain why this is apparently wrong?

PS: when I remove the inline keywords, everything works just fine.

[Moeljbcp]

the = and += operators should return a reference to the left hand side object after it's done. This is so you can do silly things like a = b = 1; and have it work just fine, as expected. (Both a and b will be equal to 1) Also, methods in classes should not be declared as inline.

E.g.

Vector& operator = (const Vector& vec);
Vector& operator += (const Vector & vec);

then implement it as

Vector& Vector::operator+= (const Vector & vec)
{
	this->X += vec.X;  // this is a pointer to the current object.
	this->Y += vec.Y;  // Optional but slightly more clear.
	return *this;
}

e: I made an error, I apologize; It is fixed now.

[vlad from moscow]

It seems that the linker does not see the object module where the operator is defined provided that the definition is in a separate module.