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

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< cpp‎ | chrono

Defined in header `<chrono>` |  |
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

Run this code

    #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

### See also

(constructor) | constructs new duration (public member function of `std::chrono::duration`)

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