#pragma once

namespace std {
  class mutex;
  class recursive_mutex;
  class timed_mutex;
  class recursive_timed_mutex;

  struct defer_lock_t {
    explicit defer_lock_t() = default;
  };
  inline constexpr defer_lock_t defer_lock {};

  struct try_to_lock_t {
    explicit try_to_lock_t() = default;
  };
  inline constexpr try_to_lock_t try_to_lock {};

  struct adopt_lock_t {
    explicit adopt_lock_t() = default;
  };
  inline constexpr adopt_lock_t adopt_lock {};

  template<class Mutex> class lock_guard;
  template<class Mutex> class unique_lock;

  struct once_flag;
}