From Jason Turner

[time.hms.members]

C++17 → C++20 3.8 KB 122 lines
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+ ### Members <a id="time.hms.members">[[time.hms.members]]</a>
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+
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+ ``` cpp
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+ static constexpr unsigned fractional_width = see below;
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+ ```
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+
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+ `fractional_width` is the number of fractional decimal digits
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+ represented by `precision`. `fractional_width` has the value of the
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+ smallest possible integer in the range \[`0`, `18`\] such that
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+ `precision` will exactly represent all values of `Duration`. If no such
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+ value of `fractional_width` exists, then `fractional_width` is 6.
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+
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+ [*Example 1*:
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+
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+ See  [[time.hms.width]] for some durations, the resulting
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+ `fractional_width`, and the formatted fractional second output of
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+ `Duration{1}`.
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+
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+ **Table: Examples for `fractional_width`** <a id="time.hms.width">[time.hms.width]</a>
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+
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+ | | | |
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+ | --------------------------------- | --- | ------------- |
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+ | `hours`, `minutes`, and `seconds` | `0` | |
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+ | `milliseconds` | `3` | `0.001` |
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+ | `microseconds` | `6` | `0.000001` |
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+ | `nanoseconds` | `9` | `0.000000001` |
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+ | `duration<int, ratio<1, 2>>` | `1` | `0.5` |
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+ | `duration<int, ratio<1, 3>>` | `6` | `0.333333` |
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+ | `duration<int, ratio<1, 4>>` | `2` | `0.25` |
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+ | `duration<int, ratio<1, 5>>` | `1` | `0.2` |
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+ | `duration<int, ratio<1, 6>>` | `6` | `0.166666` |
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+ | `duration<int, ratio<1, 7>>` | `6` | `0.142857` |
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+ | `duration<int, ratio<1, 8>>` | `3` | `0.125` |
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+ | `duration<int, ratio<1, 9>>` | `6` | `0.111111` |
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+ | `duration<int, ratio<1, 10>>` | `1` | `0.1` |
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+ | `duration<int, ratio<756, 625>>` | `4` | `0.2096` |
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+
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+
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+ — *end example*]
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+
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+ ``` cpp
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+ using precision = see below;
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+ ```
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+
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+ `precision` is
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+
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+ ``` cpp
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+ duration<common_type_t<Duration::rep, seconds::rep>, ratio<1, $10^fractional_width$>>
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+ ```
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+
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+ ``` cpp
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+ constexpr explicit hh_mm_ss(Duration d);
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+ ```
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+
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+ *Effects:* Constructs an object of type `hh_mm_ss` which represents the
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+ `Duration d` with precision `precision`.
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+
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+ - Initializes `is_neg` with `d < Duration::zero()`.
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+ - Initializes `h` with `duration_cast<chrono::hours>(abs(d))`.
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+ - Initializes `m` with
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+ `duration_cast<chrono::minutes>(abs(d) - hours())`.
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+ - Initializes `s` with
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+ `duration_cast<chrono::seconds>(abs(d) - hours() - minutes())`.
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+ - If `treat_as_floating_point_v<precision::rep>` is `true`, initializes
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+ `ss` with `abs(d) - hours() - minutes() - seconds()`. Otherwise,
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+ initializes `ss` with
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+ `duration_cast<precision>(abs(d) - hours() - minutes() - seconds())`.
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+
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+ [*Note 1*: When `precision::rep` is integral and `precision::period` is
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+ `ratio<1>`, `subseconds()` always returns a value equal to
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+ `0s`. — *end note*]
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+
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+ *Ensures:* If `treat_as_floating_point_v<precision::rep>` is `true`,
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+ `to_duration()` returns `d`, otherwise `to_duration()` returns
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+ `duration_cast<precision>(d)`.
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+
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+ ``` cpp
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+ constexpr bool is_negative() const noexcept;
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+ ```
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+
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+ *Returns:* `is_neg`.
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+
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+ ``` cpp
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+ constexpr chrono::hours hours() const noexcept;
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+ ```
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+
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+ *Returns:* `h`.
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+
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+ ``` cpp
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+ constexpr chrono::minutes minutes() const noexcept;
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+ ```
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+
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+ *Returns:* `m`.
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+
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+ ``` cpp
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+ constexpr chrono::seconds seconds() const noexcept;
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+ ```
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+
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+ *Returns:* `s`.
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+
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+ ``` cpp
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+ constexpr precision subseconds() const noexcept;
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+ ```
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+
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+ *Returns:* `ss`.
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+
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+ ``` cpp
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+ constexpr precision to_duration() const noexcept;
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+ ```
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+
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+ *Returns:* If `is_neg`, returns `-(h + m + s + ss)`, otherwise returns
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+ `h + m + s + ss`.
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+
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+ ``` cpp
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+ constexpr explicit operator precision() const noexcept;
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+ ```
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+
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+ *Returns:* `to_duration()`.
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+