vector resize() automatic fill

Question

I'm writing a class that holds a matrix (of double values), represented as vector<vector<double>>;

I want to implement the operator=, to re-fill my matrix with the details of a given sparse matrix. I'm writing the following code:

RegMatrix& RegMatrix::operator=(const SparseMatrix rhs){
    if(*this != rhs){
        _matrix.clear();
        _matrix.resize(rhs.getRow());
        int i;
        for(i=0;i<rhs.getRow();++i){
            _matrix.at(i).resize(rhs.getCol());
        }

        for(i=0;i<rhs.getSize();++i){
            Element e = rhs.getElement(i);
            _matrix[e._row][e._col] = e._val; 
        }
    }

    return *this;
}

Does the resize() method fill automatically the vector with zeros? Is my implementation ok?

Answer 1

New elements take the vector member's default value, or a specific value if you use the overload of resize with two parameters.

void resize(
   size_type _Newsize,
   Type _Val
);

In your case, the default will be an empty vector<double> - if that is not what you want, pass what you DO want to put there to the overload above.

Existing elements are not modified.