Integral ranges with initializer_lists and parameter packs

int_range.cpp

#include <cstddef>
#include <iostream>
#include <type_traits>
#include <utility>

using namespace std;

template <typename T, T Start, T... Ts>
const auto& make_int_range_helper(std::integer_sequence<T, Ts...>) {
  static const initializer_list<int> il{ (Start+Ts)...};
  return il;
}

template <typename T = size_t, T Start = 0, T End,
          typename = std::enable_if_t<std::is_integral<T>::value>>
decltype(auto) make_int_range() {
  return make_int_range_helper<T, Start>(std::make_integer_sequence<T, End-Start>());
}

template <size_t N>
decltype(auto) make_index_range() {
  return make_int_range<size_t, 0, N>();
}

int main() {
  for (auto i : make_index_range<10>()) {
    cout << i << '\n';
  }
}