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# std::literals::chrono_literals::operator""us

From cppreference.com
< cpp‎ | chrono

Defined in header `<chrono>` |  |
constexpr std::chrono::microseconds operator "" us(unsigned long long us); | (1) | (since C++14)
constexpr std::chrono::duration</*unspecified*/, std::micro> operator "" us(long double us); | (2) | (since C++14)

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

1) integer literal, returns exactly std::chrono::microseconds(us)
2) floating-point literal, returns a floating-point duration equivalent to std::chrono::microseconds

### [edit] Parameters

us | - | the number of microseconds

### [edit] Return value

The std::chrono::duration literal.

### [edit] Possible implementation

    constexpr std::chrono::microseconds operator ""us(unsigned long long us)
    {
        return std::chrono::microseconds(us);
    }
    constexpr std::chrono::duration<long double, std::micro> operator ""us(long double us)
    {
        return std::chrono::duration<long double, std::micro>(us);
    }

### [edit] 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.

### [edit] Example

Run this code

    #include <iostream>
    #include <chrono>

    int main()
    {
        using namespace std::chrono_literals;
        auto d1 = 250us;
        std::chrono::microseconds d2 = 1ms;
        std::cout << "250us = " << d1.count() << " microseconds\n"
                  << "1ms = " << d2.count() << " microseconds\n";
    }

Output:

    250us = 250 microseconds
    1ms = 1000 microseconds

### [edit] See also

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

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