Standard library header <type_traits> (C++11)
From cppreference.com
This header is part of the metaprogramming library.
Classes | |
Helper Classes | |
(C++11)(C++17) |
compile-time constant of specified type with specified value (class template) |
true_type
|
std::integral_constant<bool, true> |
false_type
|
std::integral_constant<bool, false> |
Primary type categories | |
(C++11) |
checks if a type is void (class template) |
(C++14) |
checks if a type is std::nullptr_t (class template) |
(C++11) |
checks if a type is an integral type (class template) |
(C++11) |
checks if a type is a floating-point type (class template) |
(C++11) |
checks if a type is an array type (class template) |
(C++11) |
checks if a type is an enumeration type (class template) |
(C++11) |
checks if a type is a union type (class template) |
(C++11) |
checks if a type is a non-union class type (class template) |
(C++11) |
checks if a type is a function type (class template) |
(C++11) |
checks if a type is a pointer type (class template) |
(C++11) |
checks if a type is an lvalue reference (class template) |
(C++11) |
checks if a type is an rvalue reference (class template) |
(C++11) |
checks if a type is a pointer to a non-static member object (class template) |
(C++11) |
checks if a type is a pointer to a non-static member function (class template) |
Composite type categories | |
(C++11) |
checks if a type is a fundamental type (class template) |
(C++11) |
checks if a type is an arithmetic type (class template) |
(C++11) |
checks if a type is a scalar type (class template) |
(C++11) |
checks if a type is an object type (class template) |
(C++11) |
checks if a type is a compound type (class template) |
(C++11) |
checks if a type is either an lvalue reference or rvalue reference (class template) |
(C++11) |
checks if a type is a pointer to a non-static member function or object (class template) |
Type properties | |
(C++11) |
checks if a type is const-qualified (class template) |
(C++11) |
checks if a type is volatile-qualified (class template) |
(C++11) |
checks if a type is trivial (class template) |
(C++11) |
checks if a type is trivially copyable (class template) |
(C++11) |
checks if a type is a standard-layout type (class template) |
(C++11)(deprecated in C++20) |
checks if a type is a plain-old data (POD) type (class template) |
(C++11)(deprecated in C++17)(removed in C++20) |
checks if a type is a literal type (class template) |
checks if every bit in the type's object representation contributes to its value (class template) | |
(C++11) |
checks if a type is a class (but not union) type and has no non-static data members (class template) |
(C++11) |
checks if a type is a polymorphic class type (class template) |
(C++11) |
checks if a type is an abstract class type (class template) |
(C++14) |
checks if a type is a final class type (class template) |
(C++17) |
checks if a type is an aggregate type (class template) |
(C++23) |
checks if a type is an implicit-lifetime type (class template) |
(C++11) |
checks if a type is a signed arithmetic type (class template) |
(C++11) |
checks if a type is an unsigned arithmetic type (class template) |
(C++20) |
checks if a type is an array type of known bound (class template) |
(C++20) |
checks if a type is an array type of unknown bound (class template) |
(C++23) |
checks if a type is a scoped enumeration type (class template) |
Supported operations | |
(C++11)(C++11)(C++11) |
checks if a type has a constructor for specific arguments (class template) |
checks if a type has a default constructor (class template) | |
(C++11)(C++11)(C++11) |
checks if a type has a copy constructor (class template) |
(C++11)(C++11)(C++11) |
checks if a type can be constructed from an rvalue reference (class template) |
(C++11)(C++11)(C++11) |
checks if a type has an assignment operator for a specific argument (class template) |
(C++11)(C++11)(C++11) |
checks if a type has a copy assignment operator (class template) |
(C++11)(C++11)(C++11) |
checks if a type has a move assignment operator (class template) |
(C++11)(C++11)(C++11) |
checks if a type has a non-deleted destructor (class template) |
(C++11) |
checks if a type has a virtual destructor (class template) |
(C++17)(C++17)(C++17)(C++17) |
checks if objects of a type can be swapped with objects of same or different type (class template) |
checks if a reference is bound to a temporary in copy-initialization (class template) | |
checks if a reference is bound to a temporary in direct-initialization (class template) |
Property queries | |
(C++11) |
obtains the type's alignment requirements (class template) |
(C++11) |
obtains the number of dimensions of an array type (class template) |
(C++11) |
obtains the size of an array type along a specified dimension (class template) |
Type relationships | |
(C++11) |
checks if two types are the same (class template) |
(C++11) |
checks if a type is a base of the other type (class template) |
(C++26) |
checks if a type is a virtual base of the other type (class template) |
(C++11)(C++20) |
checks if a type can be converted to the other type (class template) |
(C++20) |
checks if two types are layout-compatible (class template) |
checks if a type is a pointer-interconvertible (initial) base of another type (class template) | |
checks if a type can be invoked (as if by std::invoke) with the given argument types (class template) | |
Const-volatility specifiers | |
(C++11)(C++11)(C++11) |
removes const and/or volatile specifiers from the given type (class template) |
(C++11)(C++11)(C++11) |
adds const and/or volatile specifiers to the given type (class template) |
References | |
(C++11) |
removes a reference from the given type (class template) |
(C++11)(C++11) |
adds an lvalue or rvalue reference to the given type (class template) |
Pointers | |
(C++11) |
removes a pointer from the given type (class template) |
(C++11) |
adds a pointer to the given type (class template) |
Sign modifiers | |
(C++11) |
obtains the corresponding signed type for the given integral type (class template) |
(C++11) |
obtains the corresponding signed type for the given integral type (class template) |
Arrays | |
(C++11) |
removes one extent from the given array type (class template) |
(C++11) |
removes all extents from the given array type (class template) |
Miscellaneous transformations | |
(C++11)(deprecated in C++23) |
defines the type suitable for use as uninitialized storage for types of given size (class template) |
(C++11)(deprecated in C++23) |
defines the type suitable for use as uninitialized storage for all given types (class template) |
(C++11) |
applies type transformations as when passing a function argument by value (class template) |
(C++20) |
combines std::remove_cv and std::remove_reference (class template) |
(C++11) |
conditionally removes a function overload or template specialization from overload resolution (class template) |
(C++11) |
chooses one type or another based on compile-time boolean (class template) |
(C++11) |
determines the common type of a group of types (class template) |
determines the common reference type of a group of types (class template) | |
(C++11) |
obtains the underlying integer type for a given enumeration type (class template) |
(C++11)(removed in C++20)(C++17) |
deduces the result type of invoking a callable object with a set of arguments (class template) |
(C++17) |
void variadic alias template (alias template) |
(C++20) |
returns the type argument unchanged (class template) |
(C++20)(C++20) |
get the reference type wrapped in std::reference_wrapper (class template) |
Operations on traits | |
(C++17) |
variadic logical AND metafunction (class template) |
(C++17) |
variadic logical OR metafunction (class template) |
(C++17) |
logical NOT metafunction (class template) |
Functions | |
Member relationships | |
checks if objects of a type are pointer-interconvertible with the specified subobject of that type (function template) | |
(C++20) |
checks if two specified members correspond to each other in the common initial subsequence of two specified types (function template) |
Constant evaluation context | |
(C++20) |
detects whether the call occurs within a constant-evaluated context (function) |
(C++26) |
checks whether a pointer is within the object's lifetime at compile time (function) |
[edit] Synopsis
namespace std { // helper class template<class T, T v> struct integral_constant; template<bool B> using bool_constant = integral_constant<bool, B>; using true_type = bool_constant<true>; using false_type = bool_constant<false>; // primary type categories template<class T> struct is_void; template<class T> struct is_null_pointer; template<class T> struct is_integral; template<class T> struct is_floating_point; template<class T> struct is_array; template<class T> struct is_pointer; template<class T> struct is_lvalue_reference; template<class T> struct is_rvalue_reference; template<class T> struct is_member_object_pointer; template<class T> struct is_member_function_pointer; template<class T> struct is_enum; template<class T> struct is_union; template<class T> struct is_class; template<class T> struct is_function; // composite type categories template<class T> struct is_reference; template<class T> struct is_arithmetic; template<class T> struct is_fundamental; template<class T> struct is_object; template<class T> struct is_scalar; template<class T> struct is_compound; template<class T> struct is_member_pointer; // type properties template<class T> struct is_const; template<class T> struct is_volatile; template<class T> struct is_trivial; template<class T> struct is_trivially_copyable; template<class T> struct is_standard_layout; template<class T> struct is_empty; template<class T> struct is_polymorphic; template<class T> struct is_abstract; template<class T> struct is_final; template<class T> struct is_aggregate; template<class T> struct is_signed; template<class T> struct is_unsigned; template<class T> struct is_bounded_array; template<class T> struct is_unbounded_array; template<class T> struct is_scoped_enum; template<class T, class... Args> struct is_constructible; template<class T> struct is_default_constructible; template<class T> struct is_copy_constructible; template<class T> struct is_move_constructible; template<class T, class U> struct is_assignable; template<class T> struct is_copy_assignable; template<class T> struct is_move_assignable; template<class T, class U> struct is_swappable_with; template<class T> struct is_swappable; template<class T> struct is_destructible; template<class T, class... Args> struct is_trivially_constructible; template<class T> struct is_trivially_default_constructible; template<class T> struct is_trivially_copy_constructible; template<class T> struct is_trivially_move_constructible; template<class T, class U> struct is_trivially_assignable; template<class T> struct is_trivially_copy_assignable; template<class T> struct is_trivially_move_assignable; template<class T> struct is_trivially_destructible; template<class T, class... Args> struct is_nothrow_constructible; template<class T> struct is_nothrow_default_constructible; template<class T> struct is_nothrow_copy_constructible; template<class T> struct is_nothrow_move_constructible; template<class T, class U> struct is_nothrow_assignable; template<class T> struct is_nothrow_copy_assignable; template<class T> struct is_nothrow_move_assignable; template<class T, class U> struct is_nothrow_swappable_with; template<class T> struct is_nothrow_swappable; template<class T> struct is_nothrow_destructible; template<class T> struct has_virtual_destructor; template<class T> struct has_unique_object_representations; template<class T, class U> struct reference_constructs_from_temporary; template<class T, class U> struct reference_converts_from_temporary; // type property queries template<class T> struct alignment_of; template<class T> struct rank; template<class T, unsigned I = 0> struct extent; // type relations template<class T, class U> struct is_same; template<class Base, class Derived> struct is_base_of; template<class Base, class Derived> struct is_virtual_base_of; template<class From, class To> struct is_convertible; template<class From, class To> struct is_nothrow_convertible; template<class T, class U> struct is_layout_compatible; template<class Base, class Derived> struct is_pointer_interconvertible_base_of; template<class Fn, class... ArgTypes> struct is_invocable; template<class R, class Fn, class... ArgTypes> struct is_invocable_r; template<class Fn, class... ArgTypes> struct is_nothrow_invocable; template<class R, class Fn, class... ArgTypes> struct is_nothrow_invocable_r; // const-volatile modifications template<class T> struct remove_const; template<class T> struct remove_volatile; template<class T> struct remove_cv; template<class T> struct add_const; template<class T> struct add_volatile; template<class T> struct add_cv; template<class T> using remove_const_t = typename remove_const<T>::type; template<class T> using remove_volatile_t = typename remove_volatile<T>::type; template<class T> using remove_cv_t = typename remove_cv<T>::type; template<class T> using add_const_t = typename add_const<T>::type; template<class T> using add_volatile_t = typename add_volatile<T>::type; template<class T> using add_cv_t = typename add_cv<T>::type; // reference modifications template<class T> struct remove_reference; template<class T> struct add_lvalue_reference; template<class T> struct add_rvalue_reference; template<class T> using remove_reference_t = typename remove_reference<T>::type; template<class T> using add_lvalue_reference_t = typename add_lvalue_reference<T>::type; template<class T> using add_rvalue_reference_t = typename add_rvalue_reference<T>::type; // sign modifications template<class T> struct make_signed; template<class T> struct make_unsigned; template<class T> using make_signed_t = typename make_signed<T>::type; template<class T> using make_unsigned_t = typename make_unsigned<T>::type; // array modifications template<class T> struct remove_extent; template<class T> struct remove_all_extents; template<class T> using remove_extent_t = typename remove_extent<T>::type; template<class T> using remove_all_extents_t = typename remove_all_extents<T>::type; // pointer modifications template<class T> struct remove_pointer; template<class T> struct add_pointer; template<class T> using remove_pointer_t = typename remove_pointer<T>::type; template<class T> using add_pointer_t = typename add_pointer<T>::type; // other transformations template<class T> struct type_identity; template<class T> struct remove_cvref; template<class T> struct decay; template<bool, class T = void> struct enable_if; template<bool, class T, class F> struct conditional; template<class... T> struct common_type; template<class T, class U, template<class> class TQual, template<class> class UQual> struct basic_common_reference { }; template<class... T> struct common_reference; template<class T> struct underlying_type; template<class Fn, class... ArgTypes> struct invoke_result; template<class T> struct unwrap_reference; template<class T> struct unwrap_ref_decay; template<class T> using type_identity_t = typename type_identity<T>::type; template<class T> using remove_cvref_t = typename remove_cvref<T>::type; template<class T> using decay_t = typename decay<T>::type; template<bool b, class T = void> using enable_if_t = typename enable_if<b, T>::type; template<bool b, class T, class F> using conditional_t = typename conditional<b, T, F>::type; template<class... T> using common_type_t = typename common_type<T...>::type; template<class... T> using common_reference_t = typename common_reference<T...>::type; template<class T> using underlying_type_t = typename underlying_type<T>::type; template<class Fn, class... ArgTypes> using invoke_result_t = typename invoke_result<Fn, ArgTypes...>::type; template<class T> using unwrap_reference_t = typename unwrap_reference<T>::type; template<class T> using unwrap_ref_decay_t = typename unwrap_ref_decay<T>::type; template<class...> using void_t = void; // logical operator traits template<class... B> struct conjunction; template<class... B> struct disjunction; template<class B> struct negation; // primary type categories template<class T> inline constexpr bool is_void_v = is_void<T>::value; template<class T> inline constexpr bool is_null_pointer_v = is_null_pointer<T>::value; template<class T> inline constexpr bool is_integral_v = is_integral<T>::value; template<class T> inline constexpr bool is_floating_point_v = is_floating_point<T>::value; template<class T> inline constexpr bool is_array_v = is_array<T>::value; template<class T> inline constexpr bool is_pointer_v = is_pointer<T>::value; template<class T> inline constexpr bool is_lvalue_reference_v = is_lvalue_reference<T>::value; template<class T> inline constexpr bool is_rvalue_reference_v = is_rvalue_reference<T>::value; template<class T> inline constexpr bool is_member_object_pointer_v = is_member_object_pointer<T>::value; template<class T> inline constexpr bool is_member_function_pointer_v = is_member_function_pointer<T>::value; template<class T> inline constexpr bool is_enum_v = is_enum<T>::value; template<class T> inline constexpr bool is_union_v = is_union<T>::value; template<class T> inline constexpr bool is_class_v = is_class<T>::value; template<class T> inline constexpr bool is_function_v = is_function<T>::value; // composite type categories template<class T> inline constexpr bool is_reference_v = is_reference<T>::value; template<class T> inline constexpr bool is_arithmetic_v = is_arithmetic<T>::value; template<class T> inline constexpr bool is_fundamental_v = is_fundamental<T>::value; template<class T> inline constexpr bool is_object_v = is_object<T>::value; template<class T> inline constexpr bool is_scalar_v = is_scalar<T>::value; template<class T> inline constexpr bool is_compound_v = is_compound<T>::value; template<class T> inline constexpr bool is_member_pointer_v = is_member_pointer<T>::value; // type properties template<class T> inline constexpr bool is_const_v = is_const<T>::value; template<class T> inline constexpr bool is_volatile_v = is_volatile<T>::value; template<class T> inline constexpr bool is_trivial_v = is_trivial<T>::value; template<class T> inline constexpr bool is_trivially_copyable_v = is_trivially_copyable<T>::value; template<class T> inline constexpr bool is_standard_layout_v = is_standard_layout<T>::value; template<class T> inline constexpr bool is_empty_v = is_empty<T>::value; template<class T> inline constexpr bool is_polymorphic_v = is_polymorphic<T>::value; template<class T> inline constexpr bool is_abstract_v = is_abstract<T>::value; template<class T> inline constexpr bool is_final_v = is_final<T>::value; template<class T> inline constexpr bool is_aggregate_v = is_aggregate<T>::value; template<class T> inline constexpr bool is_signed_v = is_signed<T>::value; template<class T> inline constexpr bool is_unsigned_v = is_unsigned<T>::value; template<class T> inline constexpr bool is_bounded_array_v = is_bounded_array<T>::value; template<class T> inline constexpr bool is_unbounded_array_v = is_unbounded_array<T>::value; template<class T> inline constexpr bool is_scoped_enum_v = is_scoped_enum<T>::value; template<class T, class... Args> inline constexpr bool is_constructible_v = is_constructible<T, Args...>::value; template<class T> inline constexpr bool is_default_constructible_v = is_default_constructible<T>::value; template<class T> inline constexpr bool is_copy_constructible_v = is_copy_constructible<T>::value; template<class T> inline constexpr bool is_move_constructible_v = is_move_constructible<T>::value; template<class T, class U> inline constexpr bool is_assignable_v = is_assignable<T, U>::value; template<class T> inline constexpr bool is_copy_assignable_v = is_copy_assignable<T>::value; template<class T> inline constexpr bool is_move_assignable_v = is_move_assignable<T>::value; template<class T, class U> inline constexpr bool is_swappable_with_v = is_swappable_with<T, U>::value; template<class T> inline constexpr bool is_swappable_v = is_swappable<T>::value; template<class T> inline constexpr bool is_destructible_v = is_destructible<T>::value; template<class T, class... Args> inline constexpr bool is_trivially_constructible_v = is_trivially_constructible<T, Args...>::value; template<class T> inline constexpr bool is_trivially_default_constructible_v = is_trivially_default_constructible<T>::value; template<class T> inline constexpr bool is_trivially_copy_constructible_v = is_trivially_copy_constructible<T>::value; template<class T> inline constexpr bool is_trivially_move_constructible_v = is_trivially_move_constructible<T>::value; template<class T, class U> inline constexpr bool is_trivially_assignable_v = is_trivially_assignable<T, U>::value; template<class T> inline constexpr bool is_trivially_copy_assignable_v = is_trivially_copy_assignable<T>::value; template<class T> inline constexpr bool is_trivially_move_assignable_v = is_trivially_move_assignable<T>::value; template<class T> inline constexpr bool is_trivially_destructible_v = is_trivially_destructible<T>::value; template<class T, class... Args> inline constexpr bool is_nothrow_constructible_v = is_nothrow_constructible<T, Args...>::value; template<class T> inline constexpr bool is_nothrow_default_constructible_v = is_nothrow_default_constructible<T>::value; template<class T> inline constexpr bool is_nothrow_copy_constructible_v = is_nothrow_copy_constructible<T>::value; template<class T> inline constexpr bool is_nothrow_move_constructible_v = is_nothrow_move_constructible<T>::value; template<class T, class U> inline constexpr bool is_nothrow_assignable_v = is_nothrow_assignable<T, U>::value; template<class T> inline constexpr bool is_nothrow_copy_assignable_v = is_nothrow_copy_assignable<T>::value; template<class T> inline constexpr bool is_nothrow_move_assignable_v = is_nothrow_move_assignable<T>::value; template<class T, class U> inline constexpr bool is_nothrow_swappable_with_v = is_nothrow_swappable_with<T, U>::value; template<class T> inline constexpr bool is_nothrow_swappable_v = is_nothrow_swappable<T>::value; template<class T> inline constexpr bool is_nothrow_destructible_v = is_nothrow_destructible<T>::value; template<class T> inline constexpr bool has_virtual_destructor_v = has_virtual_destructor<T>::value; template<class T> inline constexpr bool has_unique_object_representations_v = has_unique_object_representations<T>::value; template<class T, class U> inline constexpr bool reference_constructs_from_temporary_v = reference_constructs_from_temporary<T, U>::value; template<class T, class U> inline constexpr bool reference_converts_from_temporary_v = reference_converts_from_temporary<T, U>::value; // type property queries template<class T> inline constexpr size_t alignment_of_v = alignment_of<T>::value; template<class T> inline constexpr size_t rank_v = rank<T>::value; template<class T, unsigned I = 0> inline constexpr size_t extent_v = extent<T, I>::value; // type relations template<class T, class U> inline constexpr bool is_same_v = is_same<T, U>::value; template<class Base, class Derived> inline constexpr bool is_base_of_v = is_base_of<Base, Derived>::value; template<class Base, class Derived> inline constexpr bool is_virtual_base_of_v = is_virtual_base_of<Base, Derived>::value; template<class From, class To> inline constexpr bool is_convertible_v = is_convertible<From, To>::value; template<class From, class To> inline constexpr bool is_nothrow_convertible_v = is_nothrow_convertible<From, To>::value; template<class T, class U> inline constexpr bool is_layout_compatible_v = is_layout_compatible<T, U>::value; template<class Base, class Derived> inline constexpr bool is_pointer_interconvertible_base_of_v = is_pointer_interconvertible_base_of<Base, Derived>::value; template<class Fn, class... ArgTypes> inline constexpr bool is_invocable_v = is_invocable<Fn, ArgTypes...>::value; template<class R, class Fn, class... ArgTypes> inline constexpr bool is_invocable_r_v = is_invocable_r<R, Fn, ArgTypes...>::value; template<class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_v = is_nothrow_invocable<Fn, ArgTypes...>::value; template<class R, class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_r_v = is_nothrow_invocable_r<R, Fn, ArgTypes...>::value; // logical operator traits template<class... B> inline constexpr bool conjunction_v = conjunction<B...>::value; template<class... B> inline constexpr bool disjunction_v = disjunction<B...>::value; template<class B> inline constexpr bool negation_v = negation<B>::value; // member relationships template<class S, class M> constexpr bool is_pointer_interconvertible_with_class(M S::*m) noexcept; template<class S1, class S2, class M1, class M2> constexpr bool is_corresponding_member(M1 S1::*m1, M2 S2::*m2) noexcept; // constant evaluation context constexpr bool is_constant_evaluated() noexcept; consteval bool is_within_lifetime(const auto*) noexcept; }
[edit] Class template std::integral_constant
namespace std { template <class T, T v> struct integral_constant { static constexpr T value = v; using value_type = T; using type = integral_constant<T, v>; constexpr operator value_type() const noexcept { return value; } constexpr value_type operator()() const noexcept { return value; } }; }