op_compare_3way.md

operator<=>

• chrono[meta header]
• std::chrono[meta namespace]
• function template[meta id-type]
• cpp20[meta cpp]

namespace std::chrono {
  template <class Clock, class Duration1,
    three_way_comparable_with<Duration1> Duration2>
  constexpr auto
    operator<=>(const time_point<Clock, Duration1>& lhs,
                const time_point<Clock, Duration2>& rhs); // (1) C++20
}

• time_point[link /reference/chrono/time_point.md]

概要

三方比較を行う

戻り値

return lhs.time_since_epoch() <=> rhs.time_since_poch();

• time_since_epoch[link /reference/chrono/time_point/time_since_epoch.md]

例

#include <cassert>
#include <chrono>

using namespace std::chrono;

int main()
{
  time_point<system_clock> tp1{ seconds{3} };
  time_point<system_clock> tp2{ seconds{3} };
  time_point<system_clock> tp3{ seconds{4} };

  assert((tp1 <=> tp2) == 0);
  assert((tp1 <=> tp3) != 0);
}

• system_clock[link /reference/chrono/system_clock.md]

出力

バージョン

言語

• C++20

処理系

• Clang:
• GCC: 10
• Visual C++: ??

参照

• P1614R2 The Mothership has Landed
  • C++20での三方比較演算子の追加と、関連する演算子の自動導出