From Jason Turner

[time.cal.ymdlast]

C++17 → C++20 7.0 KB 239 lines
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tmp/tmp1xg5fxt_/{from.md → to.md} RENAMED
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+ ### Class `year_month_day_last` <a id="time.cal.ymdlast">[[time.cal.ymdlast]]</a>
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+
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+ #### Overview <a id="time.cal.ymdlast.overview">[[time.cal.ymdlast.overview]]</a>
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+
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+ ``` cpp
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+ namespace std::chrono {
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+ class year_month_day_last {
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+ chrono::year y_; // exposition only
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+ chrono::month_day_last mdl_; // exposition only
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+
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+ public:
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+ constexpr year_month_day_last(const chrono::year& y,
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+ const chrono::month_day_last& mdl) noexcept;
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+
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+ constexpr year_month_day_last& operator+=(const months& m) noexcept;
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+ constexpr year_month_day_last& operator-=(const months& m) noexcept;
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+ constexpr year_month_day_last& operator+=(const years& y) noexcept;
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+ constexpr year_month_day_last& operator-=(const years& y) noexcept;
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+
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+ constexpr chrono::year year() const noexcept;
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+ constexpr chrono::month month() const noexcept;
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+ constexpr chrono::month_day_last month_day_last() const noexcept;
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+ constexpr chrono::day day() const noexcept;
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+
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+ constexpr operator sys_days() const noexcept;
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+ constexpr explicit operator local_days() const noexcept;
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+ constexpr bool ok() const noexcept;
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+ };
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+ }
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+ ```
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+
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+ `year_month_day_last` represents the last day of a specific year and
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+ month. `year_month_day_last` is a field-based time point with a
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+ resolution of `days`, except that it is restricted to pointing to the
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+ last day of a year and month.
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+
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+ [*Note 1*: `year_month_day_last` supports `years`- and
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+ `months`-oriented arithmetic, but not `days`-oriented arithmetic. For
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+ the latter, there is a conversion to `sys_days`, which efficiently
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+ supports `days`-oriented arithmetic. — *end note*]
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+
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+ `year_month_day_last` meets the *Cpp17EqualityComparable* (
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+ [[cpp17.equalitycomparable]]) and *Cpp17LessThanComparable* (
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+ [[cpp17.lessthancomparable]]) requirements.
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+
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+ `year_month_day_last` is a trivially copyable and standard-layout class
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+ type.
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+
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+ #### Member functions <a id="time.cal.ymdlast.members">[[time.cal.ymdlast.members]]</a>
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+
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+ ``` cpp
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+ constexpr year_month_day_last(const chrono::year& y,
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+ const chrono::month_day_last& mdl) noexcept;
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+ ```
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+
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+ *Effects:* Initializes `y_` with `y` and `mdl_` with `mdl`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last& operator+=(const months& m) noexcept;
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+ ```
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+
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+ *Constraints:* If the argument supplied by the caller for the `months`
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+ parameter is convertible to `years`, its implicit conversion sequence to
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+ `years` is worse than its implicit conversion sequence to `months`
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+ [[over.ics.rank]].
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+
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+ *Effects:* `*this = *this + m`.
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+
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+ *Returns:* `*this`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last& operator-=(const months& m) noexcept;
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+ ```
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+
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+ *Constraints:* If the argument supplied by the caller for the `months`
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+ parameter is convertible to `years`, its implicit conversion sequence to
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+ `years` is worse than its implicit conversion sequence to `months`
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+ [[over.ics.rank]].
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+
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+ *Effects:* `*this = *this - m`.
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+
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+ *Returns:* `*this`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last& operator+=(const years& y) noexcept;
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+ ```
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+
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+ *Effects:* `*this = *this + y`.
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+
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+ *Returns:* `*this`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last& operator-=(const years& y) noexcept;
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+ ```
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+
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+ *Effects:* `*this = *this - y`.
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+
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+ *Returns:* `*this`.
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+
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+ ``` cpp
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+ constexpr chrono::year year() const noexcept;
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+ ```
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+
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+ *Returns:* `y_`.
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+
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+ ``` cpp
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+ constexpr chrono::month month() const noexcept;
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+ ```
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+
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+ *Returns:* `mdl_.month()`.
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+
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+ ``` cpp
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+ constexpr chrono::month_day_last month_day_last() const noexcept;
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+ ```
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+
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+ *Returns:* `mdl_`.
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+
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+ ``` cpp
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+ constexpr chrono::day day() const noexcept;
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+ ```
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+
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+ *Returns:* If `ok()` is `true`, returns a `day` representing the last
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+ day of the (`year`, `month`) pair represented by `*this`. Otherwise, the
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+ returned value is unspecified.
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+
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+ [*Note 1*: This value may be computed on demand. — *end note*]
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+
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+ ``` cpp
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+ constexpr operator sys_days() const noexcept;
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+ ```
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+
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+ *Returns:* `sys_days{year()/month()/day()}`.
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+
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+ ``` cpp
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+ constexpr explicit operator local_days() const noexcept;
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+ ```
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+
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+ *Returns:* `local_days{sys_days{*this}.time_since_epoch()}`.
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+
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+ ``` cpp
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+ constexpr bool ok() const noexcept;
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+ ```
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+
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+ *Returns:* `y_.ok() && mdl_.ok()`.
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+
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+ #### Non-member functions <a id="time.cal.ymdlast.nonmembers">[[time.cal.ymdlast.nonmembers]]</a>
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+
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+ ``` cpp
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+ constexpr bool operator==(const year_month_day_last& x, const year_month_day_last& y) noexcept;
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+ ```
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+
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+ *Returns:*
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+ `x.year() == y.year() && x.month_day_last() == y.month_day_last()`.
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+
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+ ``` cpp
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+ constexpr strong_ordering operator<=>(const year_month_day_last& x,
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+ const year_month_day_last& y) noexcept;
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+ ```
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+
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+ *Effects:* Equivalent to:
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+
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+ ``` cpp
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+ if (auto c = x.year() <=> y.year(); c != 0) return c;
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+ return x.month_day_last() <=> y.month_day_last();
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+ ```
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+
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+ ``` cpp
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+ constexpr year_month_day_last
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+ operator+(const year_month_day_last& ymdl, const months& dm) noexcept;
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+ ```
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+
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+ *Constraints:* If the argument supplied by the caller for the `months`
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+ parameter is convertible to `years`, its implicit conversion sequence to
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+ `years` is worse than its implicit conversion sequence to `months`
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+ [[over.ics.rank]].
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+
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+ *Returns:* `(ymdl.year() / ymdl.month() + dm) / last`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last
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+ operator+(const months& dm, const year_month_day_last& ymdl) noexcept;
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+ ```
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+
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+ *Constraints:* If the argument supplied by the caller for the `months`
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+ parameter is convertible to `years`, its implicit conversion sequence to
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+ `years` is worse than its implicit conversion sequence to `months`
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+ [[over.ics.rank]].
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+
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+ *Returns:* `ymdl + dm`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last
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+ operator-(const year_month_day_last& ymdl, const months& dm) noexcept;
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+ ```
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+
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+ *Constraints:* If the argument supplied by the caller for the `months`
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+ parameter is convertible to `years`, its implicit conversion sequence to
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+ `years` is worse than its implicit conversion sequence to `months`
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+ [[over.ics.rank]].
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+
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+ *Returns:* `ymdl + (-dm)`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last
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+ operator+(const year_month_day_last& ymdl, const years& dy) noexcept;
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+ ```
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+
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+ *Returns:* `{ymdl.year()+dy, ymdl.month_day_last()}`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last
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+ operator+(const years& dy, const year_month_day_last& ymdl) noexcept;
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+ ```
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+
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+ *Returns:* `ymdl + dy`.
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+
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+ ``` cpp
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+ constexpr year_month_day_last
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+ operator-(const year_month_day_last& ymdl, const years& dy) noexcept;
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+ ```
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+
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+ *Returns:* `ymdl + (-dy)`.
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+
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+ ``` cpp
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+ template<class charT, class traits>
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+ basic_ostream<charT, traits>&
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+ operator<<(basic_ostream<charT, traits>& os, const year_month_day_last& ymdl);
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+ ```
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+
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+ *Effects:* Equivalent to:
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+
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+ ``` cpp
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+ return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{}/{}"),
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+ ymdl.year(), ymdl.month_day_last());
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+ ```
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+