other/semigroup_to_monoid.cpp

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• Last update: 2020-02-09 00:25:15+09:00

Required by

• other/min_assign_action.cpp

Verified with

• test/dual_segment_tree.test.cpp
• test/larsch.test.cpp

Code

#include <optional>
#include <utility>

template <class S> class semigroup_to_monoid {
  using T = std::optional<typename S::value_type>;

public:
  using value_type = T;
  static constexpr T operation(const T &l, const T &r) noexcept {
    if (!l)
      return r;
    if (!r)
      return l;
    return T(std::in_place, S::operation(*l, *r));
  }
  static constexpr T identity{std::nullopt};
};

#line 1 "other/semigroup_to_monoid.cpp"
#include <optional>
#include <utility>

template <class S> class semigroup_to_monoid {
  using T = std::optional<typename S::value_type>;

public:
  using value_type = T;
  static constexpr T operation(const T &l, const T &r) noexcept {
    if (!l)
      return r;
    if (!r)
      return l;
    return T(std::in_place, S::operation(*l, *r));
  }
  static constexpr T identity{std::nullopt};
};

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