C++ helper to extract nth element from a range in a loop.

nth.h

#pragma once
#include <utility>
#include <iterator>

template <int N, typename Range>
class nth_range {
public:
    using RangeIterator = decltype(std::begin(std::declval<Range>()));

    constexpr explicit nth_range(Range& _range) noexcept : begin_{std::begin(_range)}, end_{std::end(_range)} {}

    struct iterator {
        RangeIterator current;
        constexpr auto& operator*() const noexcept { return std::get<N>(*current); };
        constexpr auto& operator++() noexcept { ++current; return *current; };
        constexpr auto& operator++(int) noexcept { ++current; return *current; };
        constexpr bool operator==(iterator const& _other) const noexcept { return current == _other.current; }
        constexpr bool operator!=(iterator const& _other) const noexcept { return !(*this == _other); }
    };

    constexpr auto begin() const { return iterator{begin_}; }
    constexpr auto end() const { return iterator{end_}; }

private:
    RangeIterator const begin_;
    RangeIterator const end_;
};

template <std::size_t N, typename Range>
auto nth(Range& _range) { return nth_range<N, Range>(_range); }

nth_example.cpp

#include "nth.h"
#include <iostream>
#include <utility>
#include <vector>

int main()
{
    using namespace std;

    auto vec = vector<pair<int, char>{{1, 'a'}, {2, 'b'}};
    for (auto const v : nth<1>(vec))
        cout << v << '\n';

    return 0;
}