std::complex now satisfies the tuple protocol. Specializations of std::tuple_size, std::tuple_element, and overloads of std::get() are provided for std::complex<T>. tuple_size is 2, tuple_element yields T for both indices, and get<0> / get<1> return references to the real and imaginary parts respectively. This enables structured bindings for std::complex.

Accessing the real and imaginary parts of a std::complex required calling the .real() and .imag() member functions. Structured bindings and generic tuple-based algorithms did not work with std::complex. The tuple protocol makes std::complex usable in contexts that operate on tuple-like types, including structured bindings and std::apply().

#include <complex>
#include <print>
#include <tuple>

template<typename T>
void print_components(const T& tuple_like) {
    std::println("first: {}, second: {}",
        std::get<0>(tuple_like),
        std::get<1>(tuple_like));
}

int main() {
    auto z = std::complex<double>(3.0, 4.0);

    auto [re, im] = z;
    std::println("real: {}, imag: {}", re, im);  // real: 3, imag: 4

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

    print_components(z);  // first: 3, second: 4
}