std::tuple_size<std::complex>

 

C++

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std::complex

Member functions
complex::complex complex::operator= complex::real complex::imag	complex::operator+=complex::operator-=complex::operator*=complex::operator/=
Non-member functions
operator+operator- operator+operator-operator*operator/ operator==operator!= (until C++20)   operator<<operator>> get(std::complex) (C++26)	real imag abs arg norm conj proj (C++11) polar operator""ioperator""ifoperator""il (C++14)(C++14)(C++14)
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log   log10   exp
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pow   sqrt
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sin   cos tan asin (C++11) acos (C++11) atan (C++11)
Hyperbolic functions
sinh   cosh tanh asinh (C++11) acosh (C++11) atanh (C++11)
Helper types
tuple_size<std::complex> (C++26)
tuple_element<std::complex> (C++26)

 

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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