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std::tuple_size<std::complex>

From cppreference.com
< cpp‎ | numeric‎ | complex
 
C++
 
Numerics library
 
std::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.

Contents

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>

[edit] Notes

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

[edit] 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() {}

[edit] See also

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