Best way to use shared_ptr

[renamed]

Hi

While developing a Matrix class, I ran into a problem and I'd like your points of view.

I have an Add method, which is

	std::tr1::shared_ptr<Matrix> Add(const Matrix& other) const{
		if(this->nRows != other.nRows || this->nCols != other.nCols){
			throw "Number of elements must be equal in both matrixes";
		}
		Matrix * pResult = new Matrix(nRows, nCols);
		std::tr1::shared_ptr<Matrix> ptr(pResult);
		for(unsigned int i = 0; i < nRows; i++){
			for(unsigned int j = 0; j < nCols; j++){
				T aux = GetElement(i, j) + other.GetElement(i, j);
				pResult->SetElement(i, j, aux);
			}
		}
		return ptr;
	}

I'm returning a smart pointer to the method caller, forcing it to handle a shared_ptr object. Is this the best way of doing it? Should I return a Matrix object and comment that Matrix is dynamically allocated instead?

I do not use a Matrix parameter by reference because I want to overload the "+" operator.

std::tr1::shared_ptr<Matrix>  operator +  (const Matrix &a) const { return Add(a); }

Thanks.

[helios]

IMO, this whole scheme is wrong. Idiomatically, the prototype of an operator+() overload should be T T::operator+(const T &) const. Either use smart pointers throughout or not at all. The correct scheme would then be

class MatrixInternal;

class Matrix{
    //Opaque pointer (pimpl + smart pointer):
    shared_ptr<MatrixInternal> p;
    //No other data members.
public:
    //Your overloads here.
};