Different way to manipulate/display a container

containers_display.cpp

#include <algorithm>
#include <iostream>
#include <iterator>
#include <map>
#include <numeric>
#include <sstream>
#include <utility>


template<class t_pair>
std::string to_string(const t_pair &pair) {
    auto ss = std::stringstream();
    ss << pair.first << ": " << pair.second;
    return ss.str();
}

template<class t_pair>
class pair_adaptor final {
private:
    const t_pair &pair_;

public:
    pair_adaptor(const t_pair &pair) : pair_(pair) {}

    friend std::ostream &operator<<(std::ostream &os, const pair_adaptor<t_pair> &pa) {
        return os << to_string(pa.pair_);
    }
};


int main() {
    auto m = std::map<int, int>{};

    {
        m.insert(std::make_pair<int, int>(0, 3));
        m.insert(std::make_pair<int, int>(4, 6));
        m.insert(std::make_pair<int, int>(8, 9));
    }

    {
        std::cout << "Iterator based iterations:" << std::endl;
        for (auto it = std::begin(m); it != std::end(m); ++it) {
            std::cout << to_string(*it) << "\n";
        }
    }

    {
        std::cout << "Range based iterations:" << std::endl;
        for (const auto &e: m) {
            std::cout << to_string(e) << "\n";
        }
    }

    {
        std::cout << "Copy:" << std::endl;
        std::copy(std::begin(m), std::end(m),
                  std::ostream_iterator<pair_adaptor<std::map<int, int>::value_type>>(std::cout, "\n"));
    }

    {
        std::cout << "For each:" << std::endl;
        std::for_each(std::begin(m), std::end(m),
                      [](const auto &p) {
                          std::cout << pair_adaptor<std::map<int, int>::value_type>(p) << "\n";
                      }
        );
    }

    {
        std::cout << "Transformation:" << std::endl;
        std::transform(std::begin(m), std::end(m), std::ostream_iterator<std::string>(std::cout, "\n"),
                       to_string<std::pair<int, int>>);
    }

    {
        std::cout << "Accumulate:" << std::endl;
        auto s = std::accumulate(std::next(std::begin(m)), std::end(m), to_string(*std::begin(m)),
                                 [=](std::string s, std::pair<int, int> p) {
                                     return std::move(s) + "\n" + to_string(p);
                                 });
        std::cout << s;
    }

    std::flush(std::cout);
}