# std::tuple_size<std::complex>

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< cpp‎ | numeric‎ | complex

Defined in header `<complex>` |  |
template< class T > struct tuple_size< std::complex <T>> : std::integral_constant < std::size_t, 2> {}; |  | (since C++26)

The partial specialization of `std::tuple_size` for std::complex provides a compile-time way to obtain the number of components of a `complex`, which is always 2, using tuple-like syntax. It is provided for structured binding support.

## Inherited from std::integral_constant

### Member constants

value [static] | the constant value 2 (public static member constant)

### Member functions

operator std::size_t | converts the object to std::size_t, returns value (public member function)
operator() (C++14) | returns value (public member function)

### Member types

Type | Definition
`value_type` | std::size_t
`type` | std::integral_constant < std::size_t, value>

### Notes

Feature-test macro | Value | Std | Feature
--- | --- | --- | ---
`__cpp_lib_tuple_like` | `202311L` | (C++26) | Add tuple protocol to std::complex

### Example

Run this code

    #include <complex>

    static_assert(std::tuple_size_v<std::complex<float>> == 2);

    static_assert([]
    {
        using namespace std::literals;
        auto [re, im] = -1.5 + 2.5i;
        return re == -1.5 && im == 2.5;
    }());

    static_assert([]
    {
        using namespace std::literals;
        auto z = std::complex<double>{};
        auto& [re, im] = z;
        re = 1.0;
        im = 2.0;
        return z == 1.0 + 2.0i;
    }());

    int main() {}

### See also

Structured binding (C++17) | binds the specified names to sub-objects or tuple elements of the initializer
tuple_size (C++11) | obtains the number of elements of a tuple-like type (class template)
std::tuple_element<std::complex> (C++26) | obtains the underlying real and imaginary number type of a std::complex (class template specialization)
get(std::complex) (C++26) | obtains a reference to real or imaginary part from a std::complex (function template)

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