std::literals::chrono_literals::operator""ns

Defined in header <chrono>

1	`constexpr std::chrono::nanoseconds operator` `""` `ns(unsigned` `long` `long` `nsec);`

(1)

(since C++14)

constexpr std::chrono::duration</*unspecified*/,
                           std::nano> operator "" ns(long double nsec);

(2)

(since C++14)

Forms a std::chrono::duration literal representing nanoseconds.

1) integer literal, returns exactly std::chrono::nanoseconds(nsec)

2) floating-point literal, returns a floating-point duration equivalent to std::chrono::nanoseconds

Parameters

nsec

the number of nanoseconds

Return value

The std::chrono::duration literal.

Possible implementation

constexpr std::chrono::nanoseconds operator ""ns(unsigned long long ns)
{
    return chrono::nanoseconds(ns);
}
constexpr std::chrono::duration<long double, std::nano> operator ""ns(long double ns)
{
    return std::chrono::duration<long double, std::nano>(ns);
}

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 duration classes, the duration literal operators become visible as well.

Example

#include <iostream>
#include <chrono>
  
int main()
{
    using namespace std::chrono_literals;
    auto d1 = 250ns;
    std::chrono::nanoseconds d2 = 1us;
    std::cout << "250ns = " << d1.count() << " nanoseconds\n"
              << "1us = " << d2.count() << " nanoseconds\n";
}

Output:

250ns = 250 nanoseconds
1us = 1000 nanoseconds

std::literals::chrono_literals::operator&quot;&quot;ns