Header and prototype for function taking a reference to vector as argument in c++

vector_reference_prototype.txt

==== my_main.cpp ====
#include <iostream>
#include "my_vector.hpp"
using namespace std;
int main()
{
    vector<int> myvec = {1, 2, 3};
    add_to_vector(myvec, 4);
    for(int elem : myvec){
           cout << elem << endl;
    }
    return 0;
}


==== my_vector.hpp ====
#include <vector>
#ifndef MY_VECTOR
#define MY_VECTOR
void add_to_vector(std::vector<int>&, int);
#endif


==== my_vector.cpp ====
#include "my_vector.hpp"
void add_to_vector(std::vector<int> &myvector, int mynum){
    myvector.push_back(mynum);
}


=== Instructions ===
- Compile with > g++ *.cpp *.hpp -o my_main
- Run with > ./my_main