std::chrono...o::duration)(3)

okay so bestie, welcome to the std::chrono...o::duration)(3) page from the C++ Standard Libary manual 💖 this is the std::chrono::floor(std::chrono::duration) page, and it’s literally about rounding a duration down. No cap, every deet is here, so let’s go 🎀

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🌸 NAME 🌸

std::chrono::floor(std::chrono::duration) — yes, that’s the name, and the page repeats it as std::chrono::floor(std::chrono::duration) too. It’s giving double-name main character energy 💅

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🦋 Synopsis 🦋

          Defined in header <chrono>
          template< class ToDuration, class Rep, class Period >
          constexpr ToDuration floor( const std::chrono::duration<Rep, Period>&
       (since C++17)
          d );

Okay so this function returns the greatest duration t representable in ToDuration that is less or equal to d. Periodt. 💜

And listen: the function does not participate in the overload resolution unless ToDuration is a specialization of std::chrono::duration. That’s the vibe check it has to pass, bestie ✨

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🎀 Parameters 🎀

• d — duration to convert

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🌈 Return value 🌈

d rounded down to a duration of type ToDuration. Slay, that’s it. 🫶

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🧚 Possible implementation 🧚

no cap, here’s a possible implementation:

          namespace detail
          {
              template<class> inline constexpr bool is_duration_v = false;
              template<class Rep, class Period> inline constexpr bool
       is_duration_v<
                  std::chrono::duration<Rep, Period>> = true;
          }

          template<class To, class Rep, class Period,
                   class = std::enable_if_t<detail::is_duration_v<To>>>
          constexpr To floor(const duration<Rep, Period>& d)
          {
              To t = std::chrono::duration_cast<To>(d);
              if (t > d)
                  return t - To{1};
              return t;
          }

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🍓 Example 🍓

okay here’s the example, run it if you want:

        // Run this code

        #include <chrono>
        #include <iomanip>
        #include <iostream>

        int main()
        {
            using namespace std::chrono_literals;
            std::cout << "Duration\tFloor\tRound\tCeil\n";
            for (using Sec = std::chrono::seconds;
                auto const d : {+4999ms, +5000ms, +5001ms, +5499ms, +5500ms,
       +5999ms,
                                -4999ms, -5000ms, -5001ms, -5499ms, -5500ms,
       -5999ms})
                std::cout << std::showpos << d << "\t\t"
                          << std::chrono::floor<Sec>(d) << '\t'
                          << std::chrono::round<Sec>(d) << '\t'
                          << std::chrono::ceil <Sec>(d) << '\n';
        }

Output

        Duration        Floor   Round   Ceil
        +4999ms         +4s     +5s     +5s
        +5000ms         +5s     +5s     +5s
        +5001ms         +5s     +5s     +6s
        +5499ms         +5s     +5s     +6s
        +5500ms         +5s     +6s     +6s
        +5999ms         +5s     +6s     +6s
        -4999ms         -5s     -5s     -4s
        -5000ms         -5s     -5s     -5s
        -5001ms         -6s     -5s     -5s
        -5499ms         -6s     -5s     -5s
        -5500ms         -6s     -6s     -5s
        -5999ms         -6s     -6s     -5s

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👑 See also 👑

the whole crew, bestie:

• duration_cast (C++11) — converts a duration to another, with a different tick interval (function template)
• ceil(std::chrono::duration) (C++17) — converts a duration to another, rounding up (function template)
• round(std::chrono::duration) (C++17) — converts a duration to another, rounding to nearest, ties to even (function template)
• floor(std::chrono::time_point) (C++17) — converts a time_point to another, rounding down (function template)
• floor, floorf, floorl — nearest integer not greater than the given value (function); the original listing has (C++11) and (C++11) chillin’ next to these

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mwah 💋 this lil page comes from http://cppreference.com, dated 2024.06.10, and it’s the std::chrono...o::duration)(3) page. Bye bestie, go round some durations down! 🎀✨