template <template <class...> class Type_container, class... T1s, class... T2s>
constexpr auto concat(Type_container<T1s...>, Type_container<T2s...>) {
    return Type_container<T1s..., T2s...>{};
}
template <class Seq1, class Seq2, class... Seqs>
constexpr auto concat(Seq1 s1, Seq2 s2, Seqs... s) {
    return concat(s1, concat(s2, s...));
}
 
template <typename...>
struct Type_list{};
 
using list1 = Type_list<int>;
using list2 = Type_list<char>;
using list3 = Type_list<bool>;
 
#include <cstdio>
 
template <typename T>
void print_type(T) {
    puts(__PRETTY_FUNCTION__);
}
 
int main(){
	print_type(concat(list1{}, list2{}, list3{}));
}
 

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