std::chrono...:time_point)(3)

okay bestie, welcome to the C++ Standard Libary manual — page std::chrono...:time_point)(3). yes, that's how it spells “Libary”, I'm not fixing it, I'm just reporting it 💅.

🌸 NAME 🌸

• std::chrono::floor(std::chrono::time_point) — std::chrono::floor(std::chrono::time_point)

🦋 Synopsis 🦋

Defined in header <chrono> — and here's the synopsis exactly as the page lays it out (yes, the (since C++17) is just vibing in the middle, don't come for me 😭):

template< class ToDuration, class Clock, class Duration >

constexpr std::chrono::time_point<Clock, ToDuration>
(since C++17)

    floor( const std::chrono::time_point<Clock, Duration>& tp );

Returns the largest time point t representable in ToDuration that is smaller or equal to tp.

The function does not participate in the overload resolution unless ToDuration is a specialization of std::chrono::duration.

🎀 Parameters 🎀

• tp — time point to round down

💖 Return value 💖

tp rounded down to the next time point using duration of type ToDuration.

👑 Possible implementation 👑

bestie, here's the implementation from the page — tokens stay exactly as they are:

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 Clock, class FromDuration,
         class = std::enable_if_t<detail::is_duration_v<To>>>
constexpr std::chrono::time_point<Clock, To>
    floor(const std::chrono::time_point<Clock, FromDuration>& tp)
{
    return std::chrono::time_point<Clock, To>{
        std::chrono::floor<To>(tp.time_since_epoch())};
}

🍓 Example 🍓

// Run this code

#include <chrono>
#include <iostream>
#include <string>

template<typename TimePoint>
std::string to_string(const TimePoint& time_point)
{
    return std::to_string(time_point.time_since_epoch().count());
}

int main()
{
    using namespace std::literals::chrono_literals;
    using Sec = std::chrono::seconds;

    std::cout << "Time point\t" "Cast\t" "Floor\t" "Round\t" "Ceil\n";
    std::cout << "(ms)\t\t"     "(s)\t"  "(s)\t"   "(s)\t"   "(s)\n";
    for (const auto value_ms : {5432ms, 5678ms})
    {
        std::chrono::time_point<std::chrono::system_clock,
            std::chrono::milliseconds>
            time_point_ms(value_ms);

        std::cout
            << to_string(time_point_ms) << "\t\t"
            << to_string(std::chrono::time_point_cast<Sec>(time_point_ms)) << '\t'
            << to_string(std::chrono::floor<Sec>(time_point_ms)) << '\t'
            << to_string(std::chrono::round<Sec>(time_point_ms)) << '\t'
            << to_string(std::chrono::ceil<Sec>(time_point_ms)) << '\n';
    }
}

🌈 Output 🌈

Time point      Cast    Floor   Round   Ceil
(ms)            (s)     (s)     (s)     (s)
5432            5       5       5       6
5678            5       5       6       6

⭐ See also ⭐

• time_point_cast (C++11) — converts a time point to another time point on the same clock, with a different duration (function template)
• ceil(std::chrono::time_point) (C++17) — converts a time_point to another, rounding up (function template)
• round(std::chrono::time_point) (C++17) — converts a time_point to another, rounding to nearest, ties to even (function template)
• floor(std::chrono::duration) (C++17) — converts a duration to another, rounding down (function template)
• floor, floorf, floorl — nearest integer not greater than the given value (function); the page shows two (C++11) markers here

source/version: http://cppreference.com, date: 2024.06.10, page: std::chrono...:time_point)(3). okay bye bestie, go floor some time points 💅🫶