#include <iostream>
using namespace std;

// declaration
class vector {
    private:
        float x,y,z;

    public:
        vector(float a=0, float b=0, float c=0) {
            x=a;
            y=b;
            z=c;
        }// vector()
        ~vector() {} // nothing to do :)
        void prtVec();
        void getVec(float &a, float &b, float &c) {
            a=x;
            b=y;
            c=z;
        }// getVec()
};// class vector

// definitions
void vector::prtVec() {
    cout << x << ", " << y << ", " << z << endl;
}// prtVec()

// standalone fn
vector sum(vector& a, vector& b) {
    float x0,y0,z0,x1,y1,z1;

    a.getVec(x0,y0,z0);
    b.getVec(x1,y1,z1);

    return vector(x0+x1,y0+y1,z0+z1);
}// sum()

// standalone operator overloading, IDENTICAL to
// sum() above!
vector operator+(vector& a, vector& b) {
    float x0,y0,z0,x1,y1,z1;

    a.getVec(x0,y0,z0);
    b.getVec(x1,y1,z1);

    return vector(x0+x1,y0+y1,z0+z1);
}// operator+()

int main()
{
    vector v1(1,2,3); // constructed with 0,0,0
    v1.prtVec();

    vector v2(2,4,6);
    v2.prtVec();

    vector v3 = sum(v1,v2);
    v3.prtVec();

    vector v4(-2,-4,-6);
    v4.prtVec();

    vector v5 = v3+v4; // vector version of +, ie our overloaded op definition
    v5.prtVec();

    vector v6(3,6,9);
    v6.prtVec();

    vector v7 = operator+(v5,v6); // "operator+" is an invokable function!
    v7.prtVec();

    return 0;
}// main()