std::chrono::duration::operator=(3)

NAME
std::chrono::duration::operator= - std::chrono::duration::operator=

Synopsis
   duration& operator=( const duration &other ) = default; (since C++11)
   Assigns the contents of one duration to another.

Parameters
   other - duration to copy from

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

See also
   constructor constructs new duration
                 (public member function)