C++ base guide 7 (templates)

#include <iostream>
#include <algorithm>
#include <fstream>
#include <math.h>
#include <vector>
#include <string>
#include <sstream>
#include <map>
#include <set>

using namespace std;

template<typename First, typename Second>
ostream& operator<<(ostream& out, const pair<First, Second>& p);

template<typename Iter>
string print_it(Iter it) {
    stringstream st;
    bool flag = true;
    for (auto& x : it) {
        if (!flag) {
            st << " ";
        }
        flag = false;
        st << x;
    }

    string s;
    getline(st, s);

    return s;
}

template<typename T>
ostream& operator<<(ostream& out, const vector<T>& v) {
    out << "[ " << print_it(v) << " ]";
    return out;
}

template<typename First, typename Second>
ostream& operator<<(ostream& out, const map<First, Second>& v) {
    out << "( " << print_it(v) << " )";

    return out;
}

template<typename First, typename Second>
ostream& operator<<(ostream& out, const pair<First, Second>& p) {
    out << "{ " << p.first << "," << p.second << " }";
    return out;
}

template<typename T>
T Min(T a, T b) {
    if (a < b) {
        return a;
    }
    return b;
}

template<typename First, typename Second>
struct Pair{
    First first;
    Second second;
};

template<typename First, typename Second>
ostream& operator<<(ostream& out, const Pair<First, Second>& p) {
    out << "{ " << p.first << "," << p.second << " }";
    return out;
}

int main() {
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif //
    Pair<int, double> p;
    p.first = 3;
    p.second = 3.54;
    cout << p << endl;
    return 0;
}