C++ std::integer_sequence Create a parameter pack consisting of integers
Example
std::integer_sequence itself is about holding a sequence of integers which can be turned into a parameter pack. Its primary value is the possibility to create "factory" class templates creating these sequences:
#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>());
}
The print_sequence() function template uses an std::initializer_list<bool> when expanding the integer sequence to guarantee the order of evaluation and not creating an unused [array] variable.
