std::tuple_size<std::complex>

Since C++26

Header: <complex>

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.

# Declarations

template< class T >
struct tuple_size<std::complex<T>>
: std::integral_constant<std::size_t, 2> {};

(since C++26)

# Notes

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

# Example

#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