std::chrono::duration<Rep,Period>::operator=
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std::chrono::duration
Member functions
duration::operator=
Non-member functions
(until C++20)(C++20)
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Helper classes
duration& operator=( const duration &other ) = default;
(since C++11)
Assigns the contents of one duration to another.
[edit] Parameters
other
-
duration to copy from
[edit] Example
Run this code
#include <chrono> #include <iostream> int main() { using namespace std::chrono_literals; std::chrono::hours z_hours{}; std::chrono::seconds z_seconds{}; z_hours = 2h; // ok, no conversion needed z_seconds = z_hours; // First, the converting ctor is used to create a temporary object of `lhs`s type. // This ctor implicitly invokes the casting function // chrono::duration_cast<std::seconds>(z_hours). The resulting `rhs` rvalue // has the same type as `lhs`, and the `operator=` finally performs the assignment. std::cout << "hours: " << z_hours.count() << '\n'; std::cout << "seconds: " << z_seconds.count() << '\n'; z_seconds -= 42s; // z_hours = z_seconds; // compile-time error (which is good): incompatible types. // The library avoids the implicit cast to prevent a potential precision loss. z_hours = std::chrono::duration_cast <std::chrono::hours >(z_seconds); // ok z_hours = std::chrono::duration_cast <decltype(z_hours)>(z_seconds); // ditto std::cout << "hours: " << z_hours.count() << '\n'; std::cout << "seconds: " << z_seconds.count() << '\n'; std::chrono::duration <double, std::ratio <3600>> z2_hours{}; z2_hours = z_seconds; // ok, no truncation, implicit cast std::cout << "hours: " << z2_hours.count() << '\n'; }
Output:
hours: 2 seconds: 7200 hours: 1 seconds: 7158 hours: 1.98833