template<typename First, typename Second>
struct std::pair< First, Second >
Adaptation of std::pair for Hana. 
Modeled concepts 
A std::pair models exactly the same concepts as a hana::pair. Please refer to the documentation of hana::pair for details.
constexpr auto pair = std::make_pair(1, 'x');
static_assert(
hana::less(pair, std::make_pair(3, 
'x')), 
"");
int main() { }