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</pre><pre class="rust"><code><span class="kw">use crate</span>::{IsoWeek, Weekday};
<span class="doccomment">/// The common set of methods for date component.
///
/// Methods such as [`year`], [`month`], [`day`] and [`weekday`] can be used to get basic
/// information about the date.
///
/// The `with_*` methods can change the date.
///
/// # Warning
///
/// The `with_*` methods can be convenient to change a single component of a date, but they must be
/// used with some care. Examples to watch out for:
///
/// - [`with_year`] changes the year component of a year-month-day value. Don't use this method if
/// you want the ordinal to stay the same after changing the year, of if you want the week and
/// weekday values to stay the same.
/// - Don't combine two `with_*` methods to change two components of the date. For example to
/// change both the year and month components of a date. This could fail because an intermediate
/// value does not exist, while the final date would be valid.
///
/// For more complex changes to a date, it is best to use the methods on [`NaiveDate`] to create a
/// new value instead of altering an existing date.
///
/// [`year`]: Datelike::year
/// [`month`]: Datelike::month
/// [`day`]: Datelike::day
/// [`weekday`]: Datelike::weekday
/// [`with_year`]: Datelike::with_year
/// [`NaiveDate`]: crate::NaiveDate
</span><span class="kw">pub trait </span>Datelike: Sized {
<span class="doccomment">/// Returns the year number in the [calendar date](./naive/struct.NaiveDate.html#calendar-date).
</span><span class="kw">fn </span>year(<span class="kw-2">&</span><span class="self">self</span>) -> i32;
<span class="doccomment">/// Returns the absolute year number starting from 1 with a boolean flag,
/// which is false when the year predates the epoch (BCE/BC) and true otherwise (CE/AD).
</span><span class="attr">#[inline]
</span><span class="kw">fn </span>year_ce(<span class="kw-2">&</span><span class="self">self</span>) -> (bool, u32) {
<span class="kw">let </span>year = <span class="self">self</span>.year();
<span class="kw">if </span>year < <span class="number">1 </span>{
(<span class="bool-val">false</span>, (<span class="number">1 </span>- year) <span class="kw">as </span>u32)
} <span class="kw">else </span>{
(<span class="bool-val">true</span>, year <span class="kw">as </span>u32)
}
}
<span class="doccomment">/// Returns the month number starting from 1.
///
/// The return value ranges from 1 to 12.
</span><span class="kw">fn </span>month(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the month number starting from 0.
///
/// The return value ranges from 0 to 11.
</span><span class="kw">fn </span>month0(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the day of month starting from 1.
///
/// The return value ranges from 1 to 31. (The last day of month differs by months.)
</span><span class="kw">fn </span>day(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the day of month starting from 0.
///
/// The return value ranges from 0 to 30. (The last day of month differs by months.)
</span><span class="kw">fn </span>day0(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the day of year starting from 1.
///
/// The return value ranges from 1 to 366. (The last day of year differs by years.)
</span><span class="kw">fn </span>ordinal(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the day of year starting from 0.
///
/// The return value ranges from 0 to 365. (The last day of year differs by years.)
</span><span class="kw">fn </span>ordinal0(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the day of week.
</span><span class="kw">fn </span>weekday(<span class="kw-2">&</span><span class="self">self</span>) -> Weekday;
<span class="doccomment">/// Returns the ISO week.
</span><span class="kw">fn </span>iso_week(<span class="kw-2">&</span><span class="self">self</span>) -> IsoWeek;
<span class="doccomment">/// Makes a new value with the year number changed, while keeping the same month and day.
///
/// This method assumes you want to work on the date as a year-month-day value. Don't use it if
/// you want the ordinal to stay the same after changing the year, of if you want the week and
/// weekday values to stay the same.
///
/// # Errors
///
/// Returns `None` when:
///
/// - The resulting date does not exist (February 29 in a non-leap year).
/// - The year is out of range for [`NaiveDate`].
/// - In case of [`DateTime<Tz>`] if the resulting date and time fall within a timezone
/// transition such as from DST to standard time.
///
/// [`NaiveDate`]: crate::NaiveDate
/// [`DateTime<Tz>`]: crate::DateTime
///
/// # Examples
///
/// ```
/// use chrono::{NaiveDate, Datelike};
///
/// assert_eq!(
/// NaiveDate::from_ymd_opt(2020, 5, 13).unwrap().with_year(2023).unwrap(),
/// NaiveDate::from_ymd_opt(2023, 5, 13).unwrap()
/// );
/// // Resulting date 2023-02-29 does not exist:
/// assert!(NaiveDate::from_ymd_opt(2020, 2, 29).unwrap().with_year(2023).is_none());
///
/// // Don't use `with_year` if you want the ordinal date to stay the same:
/// assert_ne!(
/// NaiveDate::from_yo_opt(2020, 100).unwrap().with_year(2023).unwrap(),
/// NaiveDate::from_yo_opt(2023, 100).unwrap() // result is 2023-101
/// );
/// ```
</span><span class="kw">fn </span>with_year(<span class="kw-2">&</span><span class="self">self</span>, year: i32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the month number (starting from 1) changed.
///
/// # Errors
///
/// Returns `None` when:
///
/// - The resulting date does not exist (for example `month(4)` when day of the month is 31).
/// - In case of [`DateTime<Tz>`] if the resulting date and time fall within a timezone
/// transition such as from DST to standard time.
/// - The value for `month` is out of range.
///
/// [`DateTime<Tz>`]: crate::DateTime
///
/// # Examples
///
/// ```
/// use chrono::{NaiveDate, Datelike};
///
/// assert_eq!(
/// NaiveDate::from_ymd_opt(2023, 5, 12).unwrap().with_month(9).unwrap(),
/// NaiveDate::from_ymd_opt(2023, 9, 12).unwrap()
/// );
/// // Resulting date 2023-09-31 does not exist:
/// assert!(NaiveDate::from_ymd_opt(2023, 5, 31).unwrap().with_month(9).is_none());
/// ```
///
/// Don't combine multiple `Datelike::with_*` methods. The intermediate value may not exist.
/// ```
/// use chrono::{NaiveDate, Datelike};
///
/// fn with_year_month(date: NaiveDate, year: i32, month: u32) -> Option<NaiveDate> {
/// date.with_year(year)?.with_month(month)
/// }
/// let d = NaiveDate::from_ymd_opt(2020, 2, 29).unwrap();
/// assert!(with_year_month(d, 2019, 1).is_none()); // fails because of invalid intermediate value
///
/// // Correct version:
/// fn with_year_month_fixed(date: NaiveDate, year: i32, month: u32) -> Option<NaiveDate> {
/// NaiveDate::from_ymd_opt(year, month, date.day())
/// }
/// let d = NaiveDate::from_ymd_opt(2020, 2, 29).unwrap();
/// assert_eq!(with_year_month_fixed(d, 2019, 1), NaiveDate::from_ymd_opt(2019, 1, 29));
/// ```
</span><span class="kw">fn </span>with_month(<span class="kw-2">&</span><span class="self">self</span>, month: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the month number (starting from 0) changed.
///
/// # Errors
///
/// Returns `None` when:
///
/// - The resulting date does not exist (for example `month0(3)` when day of the month is 31).
/// - In case of [`DateTime<Tz>`] if the resulting date and time fall within a timezone
/// transition such as from DST to standard time.
/// - The value for `month0` is out of range.
///
/// [`DateTime<Tz>`]: crate::DateTime
</span><span class="kw">fn </span>with_month0(<span class="kw-2">&</span><span class="self">self</span>, month0: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the day of month (starting from 1) changed.
///
/// # Errors
///
/// Returns `None` when:
///
/// - The resulting date does not exist (for example `day(31)` in April).
/// - In case of [`DateTime<Tz>`] if the resulting date and time fall within a timezone
/// transition such as from DST to standard time.
/// - The value for `day` is out of range.
///
/// [`DateTime<Tz>`]: crate::DateTime
</span><span class="kw">fn </span>with_day(<span class="kw-2">&</span><span class="self">self</span>, day: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the day of month (starting from 0) changed.
///
/// # Errors
///
/// Returns `None` when:
///
/// - The resulting date does not exist (for example `day0(30)` in April).
/// - In case of [`DateTime<Tz>`] if the resulting date and time fall within a timezone
/// transition such as from DST to standard time.
/// - The value for `day0` is out of range.
///
/// [`DateTime<Tz>`]: crate::DateTime
</span><span class="kw">fn </span>with_day0(<span class="kw-2">&</span><span class="self">self</span>, day0: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the day of year (starting from 1) changed.
///
/// # Errors
///
/// Returns `None` when:
///
/// - The resulting date does not exist (`with_ordinal(366)` in a non-leap year).
/// - In case of [`DateTime<Tz>`] if the resulting date and time fall within a timezone
/// transition such as from DST to standard time.
/// - The value for `ordinal` is out of range.
///
/// [`DateTime<Tz>`]: crate::DateTime
</span><span class="kw">fn </span>with_ordinal(<span class="kw-2">&</span><span class="self">self</span>, ordinal: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the day of year (starting from 0) changed.
///
/// # Errors
///
/// Returns `None` when:
///
/// - The resulting date does not exist (`with_ordinal0(365)` in a non-leap year).
/// - In case of [`DateTime<Tz>`] if the resulting date and time fall within a timezone
/// transition such as from DST to standard time.
/// - The value for `ordinal0` is out of range.
///
/// [`DateTime<Tz>`]: crate::DateTime
</span><span class="kw">fn </span>with_ordinal0(<span class="kw-2">&</span><span class="self">self</span>, ordinal0: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Counts the days in the proleptic Gregorian calendar, with January 1, Year 1 (CE) as day 1.
///
/// # Examples
///
/// ```
/// use chrono::{NaiveDate, Datelike};
///
/// assert_eq!(NaiveDate::from_ymd_opt(1970, 1, 1).unwrap().num_days_from_ce(), 719_163);
/// assert_eq!(NaiveDate::from_ymd_opt(2, 1, 1).unwrap().num_days_from_ce(), 366);
/// assert_eq!(NaiveDate::from_ymd_opt(1, 1, 1).unwrap().num_days_from_ce(), 1);
/// assert_eq!(NaiveDate::from_ymd_opt(0, 1, 1).unwrap().num_days_from_ce(), -365);
/// ```
</span><span class="kw">fn </span>num_days_from_ce(<span class="kw-2">&</span><span class="self">self</span>) -> i32 {
<span class="comment">// See test_num_days_from_ce_against_alternative_impl below for a more straightforward
// implementation.
// we know this wouldn't overflow since year is limited to 1/2^13 of i32's full range.
</span><span class="kw">let </span><span class="kw-2">mut </span>year = <span class="self">self</span>.year() - <span class="number">1</span>;
<span class="kw">let </span><span class="kw-2">mut </span>ndays = <span class="number">0</span>;
<span class="kw">if </span>year < <span class="number">0 </span>{
<span class="kw">let </span>excess = <span class="number">1 </span>+ (-year) / <span class="number">400</span>;
year += excess * <span class="number">400</span>;
ndays -= excess * <span class="number">146_097</span>;
}
<span class="kw">let </span>div_100 = year / <span class="number">100</span>;
ndays += ((year * <span class="number">1461</span>) >> <span class="number">2</span>) - div_100 + (div_100 >> <span class="number">2</span>);
ndays + <span class="self">self</span>.ordinal() <span class="kw">as </span>i32
}
}
<span class="doccomment">/// The common set of methods for time component.
</span><span class="kw">pub trait </span>Timelike: Sized {
<span class="doccomment">/// Returns the hour number from 0 to 23.
</span><span class="kw">fn </span>hour(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the hour number from 1 to 12 with a boolean flag,
/// which is false for AM and true for PM.
</span><span class="attr">#[inline]
</span><span class="kw">fn </span>hour12(<span class="kw-2">&</span><span class="self">self</span>) -> (bool, u32) {
<span class="kw">let </span>hour = <span class="self">self</span>.hour();
<span class="kw">let </span><span class="kw-2">mut </span>hour12 = hour % <span class="number">12</span>;
<span class="kw">if </span>hour12 == <span class="number">0 </span>{
hour12 = <span class="number">12</span>;
}
(hour >= <span class="number">12</span>, hour12)
}
<span class="doccomment">/// Returns the minute number from 0 to 59.
</span><span class="kw">fn </span>minute(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the second number from 0 to 59.
</span><span class="kw">fn </span>second(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Returns the number of nanoseconds since the whole non-leap second.
/// The range from 1,000,000,000 to 1,999,999,999 represents
/// the [leap second](./naive/struct.NaiveTime.html#leap-second-handling).
</span><span class="kw">fn </span>nanosecond(<span class="kw-2">&</span><span class="self">self</span>) -> u32;
<span class="doccomment">/// Makes a new value with the hour number changed.
///
/// Returns `None` when the resulting value would be invalid.
</span><span class="kw">fn </span>with_hour(<span class="kw-2">&</span><span class="self">self</span>, hour: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the minute number changed.
///
/// Returns `None` when the resulting value would be invalid.
</span><span class="kw">fn </span>with_minute(<span class="kw-2">&</span><span class="self">self</span>, min: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with the second number changed.
///
/// Returns `None` when the resulting value would be invalid.
/// As with the [`second`](#tymethod.second) method,
/// the input range is restricted to 0 through 59.
</span><span class="kw">fn </span>with_second(<span class="kw-2">&</span><span class="self">self</span>, sec: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Makes a new value with nanoseconds since the whole non-leap second changed.
///
/// Returns `None` when the resulting value would be invalid.
/// As with the [`nanosecond`](#tymethod.nanosecond) method,
/// the input range can exceed 1,000,000,000 for leap seconds.
</span><span class="kw">fn </span>with_nanosecond(<span class="kw-2">&</span><span class="self">self</span>, nano: u32) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>>;
<span class="doccomment">/// Returns the number of non-leap seconds past the last midnight.
///
/// Every value in 00:00:00-23:59:59 maps to an integer in 0-86399.
///
/// This method is not intended to provide the real number of seconds since midnight on a given
/// day. It does not take things like DST transitions into account.
</span><span class="attr">#[inline]
</span><span class="kw">fn </span>num_seconds_from_midnight(<span class="kw-2">&</span><span class="self">self</span>) -> u32 {
<span class="self">self</span>.hour() * <span class="number">3600 </span>+ <span class="self">self</span>.minute() * <span class="number">60 </span>+ <span class="self">self</span>.second()
}
}
<span class="attr">#[cfg(test)]
</span><span class="kw">mod </span>tests {
<span class="kw">use </span><span class="kw">super</span>::Datelike;
<span class="kw">use crate</span>::{Duration, NaiveDate};
<span class="doccomment">/// Tests `Datelike::num_days_from_ce` against an alternative implementation.
///
/// The alternative implementation is not as short as the current one but it is simpler to
/// understand, with less unexplained magic constants.
</span><span class="attr">#[test]
</span><span class="kw">fn </span>test_num_days_from_ce_against_alternative_impl() {
<span class="doccomment">/// Returns the number of multiples of `div` in the range `start..end`.
///
/// If the range `start..end` is back-to-front, i.e. `start` is greater than `end`, the
/// behaviour is defined by the following equation:
/// `in_between(start, end, div) == - in_between(end, start, div)`.
///
/// When `div` is 1, this is equivalent to `end - start`, i.e. the length of `start..end`.
///
/// # Panics
///
/// Panics if `div` is not positive.
</span><span class="kw">fn </span>in_between(start: i32, end: i32, div: i32) -> i32 {
<span class="macro">assert!</span>(div > <span class="number">0</span>, <span class="string">"in_between: nonpositive div = {}"</span>, div);
<span class="kw">let </span>start = (start.div_euclid(div), start.rem_euclid(div));
<span class="kw">let </span>end = (end.div_euclid(div), end.rem_euclid(div));
<span class="comment">// The lowest multiple of `div` greater than or equal to `start`, divided.
</span><span class="kw">let </span>start = start.<span class="number">0 </span>+ (start.<span class="number">1 </span>!= <span class="number">0</span>) <span class="kw">as </span>i32;
<span class="comment">// The lowest multiple of `div` greater than or equal to `end`, divided.
</span><span class="kw">let </span>end = end.<span class="number">0 </span>+ (end.<span class="number">1 </span>!= <span class="number">0</span>) <span class="kw">as </span>i32;
end - start
}
<span class="doccomment">/// Alternative implementation to `Datelike::num_days_from_ce`
</span><span class="kw">fn </span>num_days_from_ce<Date: Datelike>(date: <span class="kw-2">&</span>Date) -> i32 {
<span class="kw">let </span>year = date.year();
<span class="kw">let </span>diff = <span class="kw">move </span>|div| in_between(<span class="number">1</span>, year, div);
<span class="comment">// 365 days a year, one more in leap years. In the gregorian calendar, leap years are all
// the multiples of 4 except multiples of 100 but including multiples of 400.
</span>date.ordinal() <span class="kw">as </span>i32 + <span class="number">365 </span>* diff(<span class="number">1</span>) + diff(<span class="number">4</span>) - diff(<span class="number">100</span>) + diff(<span class="number">400</span>)
}
<span class="kw">for </span>year <span class="kw">in </span>NaiveDate::MIN.year()..=NaiveDate::MAX.year() {
<span class="kw">let </span>jan1_year = NaiveDate::from_ymd_opt(year, <span class="number">1</span>, <span class="number">1</span>).unwrap();
<span class="macro">assert_eq!</span>(
jan1_year.num_days_from_ce(),
num_days_from_ce(<span class="kw-2">&</span>jan1_year),
<span class="string">"on {:?}"</span>,
jan1_year
);
<span class="kw">let </span>mid_year = jan1_year + Duration::days(<span class="number">133</span>);
<span class="macro">assert_eq!</span>(
mid_year.num_days_from_ce(),
num_days_from_ce(<span class="kw-2">&</span>mid_year),
<span class="string">"on {:?}"</span>,
mid_year
);
}
}
}
</code></pre></div>
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