public double add(int index, double delta) {
        magnitude -= vector[index] * vector[index];
        vector[index] += delta;
        magnitude += vector[index] * vector[index];
        return vector[index];
    }
public double add ( int index , double delta ) { magnitude -= vector [ index ] * vector [ index ] ; vector [ index ] += delta ; magnitude += vector [ index ] * vector [ index ] ; return vector [ index ] ; }
{@inheritDoc}