std::chrono::operator+, std::chrono::operator- (std::chrono::day)

< cpp‎ | chrono‎ | day
Utilities library
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Library feature-test macros (C++20)
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Formatting library (C++20)
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Defined in header <chrono>
constexpr std::chrono::day operator+( const std::chrono::day&  d,
                                      const std::chrono::days& ds ) noexcept;
(1) (since C++20)
constexpr std::chrono::day operator+( const std::chrono::days& ds,
                                      const std::chrono::day&  d ) noexcept;
(2) (since C++20)
constexpr std::chrono::day operator-( const std::chrono::day&  d,
                                      const std::chrono::days& ds ) noexcept;
(3) (since C++20)
constexpr std::chrono::days operator-( const std::chrono::day& x,
                                       const std::chrono::day& y ) noexcept;
(4) (since C++20)
1,2) Adds ds.count() days to d.
3) Subtracts ds.count() days from d.
4) Calculate the difference, in days, between two day x and y.


[edit] Return value

1,2) std::chrono::day(unsigned(d) + ds.count())
3) std::chrono::day(unsigned(d) - ds.count())
4) std::chrono::days(int(unsigned(x)) - int(unsigned(y)))

[edit] Notes

1-3) If the result would be outside the range [0255], the actual stored value is unspecified.

[edit] Example

#include <cassert>
#include <chrono>
int main()
    std::chrono::day d{15};
    d = d + std::chrono::days(2);
    assert(d == std::chrono::day(17));
    d = d - std::chrono::days(3);
    assert(d == std::chrono::day(14));
    constexpr std::chrono::days ds = std::chrono::day(16) - std::chrono::day(14);
    static_assert(ds == std::chrono::days(2));

[edit] See also

increments or decrements the day
(public member function) [edit]
adds or subtracts a number of days
(public member function) [edit]