std::literals::chrono_literals::operator""h (3) - Linux Manuals

std::literals::chrono_literals::operator""h: std::literals::chrono_literals::operator""h

NAME

std::literals::chrono_literals::operator""h - std::literals::chrono_literals::operator""h

Synopsis

Defined in header <chrono>
constexpr chrono::hours operator "" h(unsigned long long hrs); (1) (since C++14)
constexpr chrono::duration</*unspecified*/, std::ratio<3600,1>> (2) (since C++14)
operator "" h(long double hrs);

Forms a std::chrono::duration literal representing hours.
1) integer literal, returns exactly std::chrono::hours(hrs)
2) floating-point literal, returns a floating-point duration equivalent to std::chrono::hours

Parameters

hrs - the number of hours

Return value

The std::chrono::duration literal.

Possible implementation

  constexpr std::chrono::hours operator ""h(unsigned long long h)
  {
      return std::chrono::hours(h);
  }
  constexpr std::chrono::duration<long double, ratio<3600,1>> operator ""h(long double h)
  {
      return std::chrono::duration<long double, std::ratio<3600,1>>(h);
  }

Notes

These operators are declared in the namespace std::literals::chrono_literals, where both literals and chrono_literals are inline namespaces. Access to these operators can be gained with using namespace std::literals, using namespace std::chrono_literals, and using namespace std::literals::chrono_literals.
In addition, within the namespace std::chrono, the directive using namespace literals::chrono_literals; is provided by the standard library, so that if a programmer uses using namespace std::chrono; to gain access to the classes in the chrono library, the corresponding literal operators become visible as well.

Example

// Run this code

  #include <iostream>
  #include <chrono>

  int main()
  {
      using namespace std::chrono_literals;
      auto day = 24h;
      auto halfhour = 0.5h;
      std::cout << "one day is " << day.count() << " hours\n"
                << "half an hour is " << halfhour.count() << " hours\n";
  }

Output:

  one day is 24 hours
  half an hour is 0.5 hours