std::is_structural

Defined in header `<type_traits>`
template< class T > struct is_structural;		(since C++26)

std::is_structural is a UnaryTypeTrait.

If T is a structural type, provides the member constant value equal true. For any other type, value is false.

If the program adds specializations for std::is_structural or std::is_structural_v, the behavior is undefined.

Template parameters

a type to check

Helper variable template

template< class T >
constexpr bool is_structural_v = is_structural<T>::value;

(since C++26)

Inherited from std::integral_constant

Member constants

value

[static]

true if T is a structural type, false otherwise
(public static member constant)

Member functions

operator bool	converts the object to bool, returns `value` (public member function)
operator() (C++14)	returns `value` (public member function)

Member types

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

Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_is_structural`	`202603L`	(C++26)	`std::is_structural`

Example

#include <type_traits>

struct S { int x; };
class Bad1 { int x; };
struct Bad2 { mutable int x; };
struct A { int a[2][3]; };
struct B : public S {}; // OK: public base of structural type
struct C : private S {}; // not structural: private base
auto L = [](int n){ return -n; }; // captureless lambda

static_assert( std::is_structural_v<int>);   // scalar 
static_assert( std::is_structural_v<int&>);  // lvalue ref
static_assert(!std::is_structural_v<int&&>); // rvalue ref
static_assert( std::is_structural_v<S>);
static_assert(!std::is_structural_v<Bad1>);
static_assert(!std::is_structural_v<Bad2>);
static_assert( std::is_structural_v<A>);
static_assert( std::is_structural_v<B>);
static_assert(!std::is_structural_v<C>);
static_assert( std::is_structural_v<decltype(L)>);

int main() { }