Standard library header <type_traits>
This header is part of the type support 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 an 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 a lvalue reference (class template) |
|
(C++11) | checks if a type is a 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 a lvalue reference or rvalue reference (class template) |
|
(C++11) | checks if a type is a pointer to an 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) |
|
(C++17) | 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++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) |
Supported operations |
|
|
(C++11)(C++11)(C++11) | checks if a type has a constructor for specific arguments (class template) |
|
(C++11)(C++11)(C++11) | 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 a 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) |
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 derived from the other type (class template) |
|
(C++11)(C++20) | checks if a type can be converted to the other type (class template) |
|
(C++17) | 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 or/and volatile specifiers from the given type (class template) |
|
(C++11)(C++11)(C++11) | adds const or/and 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 a 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) | makes the given integral type signed (class template) |
|
(C++11) | makes the given integral type unsigned (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) | defines the type suitable for use as uninitialized storage for types of given size (class template) |
|
(C++11) | 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) | hides a function overload or template specialization based on compile-time boolean (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) |
|
(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) |
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) |
Endian |
|
|
(C++20) | indicates the endianness of scalar types (enum) |
Constant evaluation context |
|
|
(C++20) | detects whether the call occurs within a constant-evaluated context (function) |
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_pod;
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, 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;
// 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 From, class To> struct is_convertible;
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 <size_t Len,
size_t Align = /*default-alignment*/ >
struct aligned_storage;
template <size_t Len, class... Types> struct aligned_union;
template <class T> struct decay;
template <class T> struct remove_cvref;
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> struct underlying_type;
template <class> class result_of; // not defined
template <class F, class... ArgTypes> class result_of<F(ArgTypes...)>;
template <class F, class... ArgTypes> class invoke_result;
template <size_t Len,
size_t Align = /*default-alignment*/ >
using aligned_storage_t = typename aligned_storage<Len, Align>::type;
template <size_t Len, class... Types>
using aligned_union_t = typename aligned_union<Len, Types...>::type;
template <class T>
using decay_t = typename decay<T>::type;
template <class T>
using remove_cvref_t = typename remove_cvref<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 underlying_type_t = typename underlying_type<T>::type;
template <class T>
using result_of_t = typename result_of<T>::type;
template <class F, class... ArgTypes>
using invoke_result_t = typename invoke_result<F, ArgTypes...>::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;
// endian
enum class endian {
little = /*implementation-defined*/,
big = /*implementation-defined*/,
native = /*implementation-defined*/
};
// 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_pod_v
= is_pod<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, 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;
// 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 From, class To> inline constexpr bool is_convertible_v
= is_convertible<From, To>::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;
// constant evaluation context
constexpr bool is_constant_evaluated() noexcept;
} // namespace stdClass 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; }
};
}
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/header/type_traits