op_multiply.md

operator*

• chrono[meta header]
• std::chrono[meta namespace]
• function template[meta id-type]
• cpp11[meta cpp]

namespace std {
namespace chrono {
  // duration * N = duration
  template <class Rep1, class Period, class Rep2>
  duration<typename common_type<Rep1, Rep2>::type, Period>
    constexpr operator*(const duration<Rep1, Period>& d, const Rep2& s); // (1)

  // N * duration = duration
  template <class Rep1, class Rep2, class Period>
  duration<typename common_type<Rep1, Rep2>::type, Period>
    constexpr operator*(const Rep1& s, const duration<Rep2, Period>& d); // (2)
}}

• common_type[link /reference/type_traits/common_type.md]

概要

durationの乗算を行う

テンプレートパラメータ制約

• (1) : is_convertible_v<const Rep2&, common_type_t<Rep1, Rep2>>がtrueであること
• (2) : is_convertible_v<const Rep1&, common_type_t<Rep1, Rep2>>がtrueであること

戻り値

using cd = duration<typename common_type<Rep1, Rep2>::type, Period>;
return cd(cd(d).count() * s);

• common_type[link /reference/type_traits/common_type.md]
• count[link /reference/chrono/duration/count.md]

例

#include <iostream>
#include <chrono>

using namespace std::chrono;

int main()
{
  // duration * rep
  {
    seconds s = seconds(3) * 2;
    std::cout << s.count() << std::endl;

    milliseconds ms = milliseconds(2) * 3;
    std::cout << ms.count() << std::endl;
  }

  // rep * duration
  {
    seconds s = 2 * seconds(3);
    std::cout << s.count() << std::endl;

    milliseconds ms = 3 * milliseconds(2);
    std::cout << ms.count() << std::endl;
  }
}

• count()[link count.md]

出力

6
6
6
6

バージョン

言語

• C++11

処理系

• GCC: 4.6.1 [mark verified]
• Visual C++: 2012 [mark verified], 2013 [mark verified], 2015 [mark verified]

参照

• P2117R0 C++ Standard Library Issues Resolved Directly In Prague