Custom hash for unordered_set

custom-unordered-set.cpp

#include <concepts> // integral
#include <unordered_set>
#include <utility> // pair

template <std::integral First, std::integral Second>
struct std::hash<std::pair<First, Second>> {
  using argument_type = std::pair<First, Second>;
  using result_type = std::size_t;

  auto
  operator()(const std::pair<First, Second> &pair) const noexcept
      -> std::size_t {
    const std::size_t h1 = std::hash<First>()(pair.first);
    const std::size_t h2 = std::hash<Second>()(pair.second);

    return h1 ^ h2;
  }
};

auto main() -> int {
  std::unordered_set<std::pair<int, int>> set;
}