29 Time library [time]

29.8 The civil calendar [time.cal]

29.8.17 Class year_month_weekday_last [time.cal.ymwdlast]

29.8.17.1 Overview [time.cal.ymwdlast.overview]

namespace std::chrono { class year_month_weekday_last { chrono::year y_; // exposition only chrono::month m_; // exposition only chrono::weekday_last wdl_; // exposition only public: constexpr year_month_weekday_last(const chrono::year& y, const chrono::month& m, const chrono::weekday_last& wdl) noexcept; constexpr year_month_weekday_last& operator+=(const months& m) noexcept; constexpr year_month_weekday_last& operator-=(const months& m) noexcept; constexpr year_month_weekday_last& operator+=(const years& y) noexcept; constexpr year_month_weekday_last& operator-=(const years& y) noexcept; constexpr chrono::year year() const noexcept; constexpr chrono::month month() const noexcept; constexpr chrono::weekday weekday() const noexcept; constexpr chrono::weekday_last weekday_last() const noexcept; constexpr operator sys_days() const noexcept; constexpr explicit operator local_days() const noexcept; constexpr bool ok() const noexcept; }; }
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year_month_weekday_last represents a specific year, month, and last weekday of the month.
year_month_weekday_last is a field-based time point with a resolution of days, except that it is restricted to pointing to the last weekday of a year and month.
[Note 1: 
year_month_weekday_last supports years- and months-oriented arithmetic, but not days-oriented arithmetic.
For the latter, there is a conversion to sys_days, which efficiently supports days-oriented arithmetic.
— end note]
year_month_weekday_last meets the Cpp17EqualityComparable (Table 28) requirements.
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year_month_weekday_last is a trivially copyable and standard-layout class type.

29.8.17.2 Member functions [time.cal.ymwdlast.members]

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constexpr year_month_weekday_last(const chrono::year& y, const chrono::month& m, const chrono::weekday_last& wdl) noexcept;
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Effects: Initializes y_ with y, m_ with m, and wdl_ with wdl.
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constexpr year_month_weekday_last& operator+=(const months& m) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Effects: *this = *this + m.
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Returns: *this.
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constexpr year_month_weekday_last& operator-=(const months& m) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Effects: *this = *this - m.
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Returns: *this.
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constexpr year_month_weekday_last& operator+=(const years& y) noexcept;
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Effects: *this = *this + y.
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Returns: *this.
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constexpr year_month_weekday_last& operator-=(const years& y) noexcept;
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Effects: *this = *this - y.
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Returns: *this.
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constexpr chrono::year year() const noexcept;
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Returns: y_.
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constexpr chrono::month month() const noexcept;
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Returns: m_.
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constexpr chrono::weekday weekday() const noexcept;
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Returns: wdl_.weekday().
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constexpr chrono::weekday_last weekday_last() const noexcept;
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Returns: wdl_.
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constexpr operator sys_days() const noexcept;
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Returns: If ok() == true, returns a sys_days that represents the last weekday() of year()/month().
Otherwise the returned value is unspecified.
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constexpr explicit operator local_days() const noexcept;
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Returns: local_days{sys_days{*this}.time_since_epoch()}.
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constexpr bool ok() const noexcept;
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Returns: y_.ok() && m_.ok() && wdl_.ok().

29.8.17.3 Non-member functions [time.cal.ymwdlast.nonmembers]

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constexpr bool operator==(const year_month_weekday_last& x, const year_month_weekday_last& y) noexcept;
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Returns: x.year() == y.year() && x.month() == y.month() && x.weekday_last() == y.weekday_last()
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constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Returns: (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last().
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constexpr year_month_weekday_last operator+(const months& dm, const year_month_weekday_last& ymwdl) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Returns: ymwdl + dm.
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constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const months& dm) noexcept;
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Constraints: If the argument supplied by the caller for the months parameter is convertible to years, its implicit conversion sequence to years is worse than its implicit conversion sequence to months ([over.ics.rank]).
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Returns: ymwdl + (-dm).
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constexpr year_month_weekday_last operator+(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
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Returns: {ymwdl.year()+dy, ymwdl.month(), ymwdl.weekday_last()}.
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constexpr year_month_weekday_last operator+(const years& dy, const year_month_weekday_last& ymwdl) noexcept;
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Returns: ymwdl + dy.
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constexpr year_month_weekday_last operator-(const year_month_weekday_last& ymwdl, const years& dy) noexcept;
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Returns: ymwdl + (-dy).
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template<class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& os, const year_month_weekday_last& ymwdl);
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Effects: Equivalent to: return os << format(os.getloc(), STATICALLY-WIDEN<charT>("{}/{:L}/{:L}"), ymwdl.year(), ymwdl.month(), ymwdl.weekday_last());