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934.duration is missingoperator%

Section: 30.5[time.duration]Status:C++11Submitter: Terry GolubiewskiOpened: 2008-11-30Last modified: 2016-01-28

Priority:Not Prioritized

View all otherissues in [time.duration].

View all issues withC++11 status.

Discussion:

Addresses US 81

duration is missingoperator%. This operator is convenientfor computing where in a time frame a givenduration lies. Amotivating example is converting aduration into a "broken-down"time duration such as hours::minutes::seconds:

class ClockTime{    typedef std::chrono::hours hours;    typedef std::chrono::minutes minutes;    typedef std::chrono::seconds seconds;public:    hours hours_;    minutes minutes_;    seconds seconds_;    template <class Rep, class Period>      explicit ClockTime(const std::chrono::duration<Rep, Period>& d)        : hours_  (std::chrono::duration_cast<hours>  (d)),          minutes_(std::chrono::duration_cast<minutes>(d % hours(1))),          seconds_(std::chrono::duration_cast<seconds>(d % minutes(1)))          {}};

[Summit:]

Agree except that there is a typo in the proposed resolution. The memberoperators should beoperator%=.

[Batavia (2009-05):]

We agree with the proposed resolution.Move to Tentatively Ready.

[2009-07 Frankfurt]

Moved from Tentatively Ready to Open only because the wording needs to beimproved for enable_if type constraining, possibly following Robert'sformula.

[2009-07 Frankfurt:]

Howard to open a separate issue (1177⁽ⁱ⁾) to handle the removal of memberfunctions from overload sets, provide wording, and possibly demonstratehow this can be implemented using enable_if (see947⁽ⁱ⁾).

Move to Ready.

Proposed resolution:

Add to the synopsis in 30[time]:

template <class Rep1, class Period, class Rep2>  duration<typename common_type<Rep1, Rep2>::type, Period>  operator%(const duration<Rep1, Period>& d, const Rep2& s);template <class Rep1, class Period1, class Rep2, class Period2>  typename common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type  operator%(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);

Add to the synopsis ofduration in 30.5[time.duration]:

template <class Rep, class Period = ratio<1>>class duration {public:  ...duration& operator%=(const rep& rhs);duration& operator%=(const duration& d);  ...};

Add to 30.5.4[time.duration.arithmetic]:

duration& operator%=(const rep& rhs);

Effects:rep_ %= rhs.

Returns:*this.

duration& operator%=(const duration& d);

Effects:rep_ %= d.count().

Returns:*this.

Add to 30.5.6[time.duration.nonmember]:

template <class Rep1, class Period, class Rep2>  duration<typename common_type<Rep1, Rep2>::type, Period>  operator%(const duration<Rep1, Period>& d, const Rep2& s);

Requires:Rep2 shall be implicitly convertible toCR(Rep1, Rep2) andRep2 shall not be an instantiation ofduration. Diagnostic required.

Returns:duration<CR, Period>(d) %= s.

template <class Rep1, class Period1, class Rep2, class Period2>  typename common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type  operator%(const duration<Rep1, Period1>& lhs, const duration<Rep2, Period2>& rhs);

Returns:common_type<duration<Rep1, Period1>, duration<Rep2, Period2>>::type(lhs) %= rhs.