#include <iostream>
#include <ostream>
#include <vector>
 
using namespace std;
 
class foo {
public:
	int bar;
};
 
template <typename T>
std::ostream& operator<< (std::ostream& out, const std::vector<T>& v) {
  if ( !v.empty() ) {
    out << '[';
 
    for (auto i = v.begin(); i < v.end(); i++)
    	out << *i << ", ";
    out << "]";
  }
  return out;
}
 
 
int main() {
	vector<foo> x {{1},{2}};
	vector<int> f {1,2,3};
	cout << f;
	return 0;
}

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