template<std::size_t N>
using u16string = sprout::basic_string<char16_t, N>;
#include <type_traits>
#include <sprout/string.hpp>
using namespace sprout;
using type = u16string<8>;
static_assert(std::is_same<type::value_type, char16_t>::value, "element type of u16string is char16_t.");