建立一個由整陣列成的引數包

std::integer_sequence 本身就是儲存一個整數序列，可以將其轉換為引數包。它的主要價值是可以建立建立這些序列的工廠類别範本：

#include <iostream>
#include <initializer_list>
#include <utility>

template <typename T, T... I>
void print_sequence(std::integer_sequence<T, I...>) {
    std::initializer_list<bool>{ bool(std::cout << I << ' ')... };
    std::cout << '\n';
}

template <int Offset, typename T, T... I>
void print_offset_sequence(std::integer_sequence<T, I...>) {
    print_sequence(std::integer_sequence<T, T(I + Offset)...>());
}

int main() {
    // explicitly specify sequences:
    print_sequence(std::integer_sequence<int, 1, 2, 3>());
    print_sequence(std::integer_sequence<char, 'f', 'o', 'o'>());

    // generate sequences:
    print_sequence(std::make_index_sequence<10>());
    print_sequence(std::make_integer_sequence<short, 10>());
    print_offset_sequence<'A'>(std::make_integer_sequence<char, 26>());
}

print_sequence() 函式模板在擴充套件整數序列時使用 std::initializer_list<bool> 以保證評估順序而不建立未使用的[array]變數。