Converting std::array to std::vector

Question

In the code below, the size of the function (foo) argument (std::vector) can be anything to make the function a generic one. However, sometimes the size container is known so std::array can be used. The problem is to convert the std::array to std::vector. What is the best way to solve this problem? Is it better to just use std::vector always in this case?

#include <iostream>
#include <array>
#include <vector>

using namespace std;

// generic function: size of the container can be anything
void foo (vector<int>& vec)
{
    // do something
}

int main()
{
   array<int,3> arr; // size is known. why use std::vector?
   foo (arr); // cannot convert std::array to std::vector

   return 0;
}

Answer 1

Given that you pass in an array, foo does not seem to resize the container it gets passed in (however, it does seem to modify the elements since vec is passed non-const). It therefore does not need to know anything about the underlying container other than how to access elements.

Then, you can pass a pair of iterators (and make the iterator type a template argument), as many STL algorithms do.