std::chrono::month::operator+=, std::chrono::month::operator-=
From cppreference.com
constexpr std::chrono::month& operator+=( const std::chrono::months& m ) noexcept;
|
(1) | (since C++20) |
constexpr std::chrono::month& operator-=( const std::chrono::months& m ) noexcept;
|
(2) | (since C++20) |
Adds or subtracts m.count() from the month value, reducing the result modulo 12 to an integer in the range [1, 12].
1) Performs
*this = *this + m;.2) Performs
*this = *this - m;.Return value
A reference to this month after modification.
Notes
After a call to one of these functions, ok() is always true if no overflow occurred during the operation.
Example
Run this code
#include <chrono>
#include <iostream>
int main()
{
std::cout << std::boolalpha;
std::chrono::month m{6};
m += std::chrono::months(2);
std::cout << (m == std::chrono::month(8)) << ' '
<< (m == std::chrono::August) << ' ';
m -= std::chrono::months(3);
std::cout << (m == std::chrono::month(5)) << ' '
<< (m == std::chrono::May) << ' ';
m = std::chrono::October;
m += std::chrono::months{8}; // ((10 += 8 == 18) % 12) == 6;
std::cout << (m == std::chrono::June) << ' ';
m -= std::chrono::months{std::chrono::December - std::chrono::February}; // -= 10
// (6 -= 10) == -4; -4 % 12 == (12 - 4) == 8
std::cout << (m == std::chrono::August) << '\n';
}
Output:
true true true true true true