std::is_structural

 

C++

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Type traits

Type traits (since C++11)

Type categories is_void is_null_pointer (DR*) is_reflection (C++26) is_array is_pointer is_enum is_union is_class is_function is_reference      is_object is_scalar is_compound is_integral is_floating_point      is_fundamental is_arithmetic is_lvalue_reference is_rvalue_reference is_member_pointer is_member_object_pointer is_member_function_pointer Type properties is_const is_volatile is_empty is_polymorphic is_final (C++14) is_abstract is_aggregate (C++17) is_structural (C++26) is_implicit_lifetime (C++23) is_trivial (deprecated in C++26) is_trivially_copyable is_standard_layout is_literal_type (until C++20*) is_pod (deprecated in C++20) is_signed is_unsigned is_bounded_array (C++20) is_unbounded_array (C++20) is_scoped_enum (C++23) has_unique_object_representations (C++17)     Type trait constants integral_constantbool_constanttrue_typefalse_type (C++17) Metafunctions conjunction (C++17) disjunction (C++17) negation (C++17)

Supported operations is_constructibleis_trivially_constructibleis_nothrow_constructible is_default_constructibleis_trivially_default_constructibleis_nothrow_default_constructible is_copy_constructibleis_trivially_copy_constructibleis_nothrow_copy_constructible is_move_constructibleis_trivially_move_constructibleis_nothrow_move_constructible is_assignableis_trivially_assignableis_nothrow_assignable is_copy_assignableis_trivially_copy_assignableis_nothrow_copy_assignable is_move_assignableis_trivially_move_assignableis_nothrow_move_assignable is_destructibleis_trivially_destructibleis_nothrow_destructible has_virtual_destructor is_swappable_withis_swappableis_nothrow_swappable_withis_nothrow_swappable (C++17)(C++17)(C++17)(C++17) Relationships and property queries is_same is_convertibleis_nothrow_convertible (C++20) is_layout_compatible (C++20) is_pointer_interconvertible_base_of (C++20) is_pointer_interconvertible_with_class (C++20)     is_corresponding_member (C++20) reference_constructs_from_temporary (C++23) reference_converts_from_temporary (C++23) is_base_of is_virtual_base_of (C++26) alignment_of rank extent is_invocableis_invocable_ris_nothrow_invocableis_nothrow_invocable_r (C++17)(C++17)(C++17)(C++17) Type modifications remove_cvremove_constremove_volatile add_cvadd_constadd_volatile make_signed make_unsigned remove_reference add_lvalue_referenceadd_rvalue_reference remove_pointer add_pointer remove_extent remove_all_extents Type transformations aligned_storage (deprecated in C++23) aligned_union (deprecated in C++23) decay remove_cvref (C++20) result_ofinvoke_result (until C++20*)(C++17) conditional common_type common_reference (C++20) underlying_type type_identity (C++20) enable_if void_t (C++17)

 

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

T

-

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

Run this code

#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() { }

See also

is_structural_type (C++26)

checks if reflected type is a structural type (function)