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Standard library header <type_traits>

From cppreference.com
< cpp‎ | header

This header is part of the type support library.

Contents

Classes

Helper Classes
compile-time constant of specified type with specified value
(class template) [edit]
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) [edit]
checks if a type is std::nullptr_t
(class template) [edit]
checks if a type is integral type
(class template) [edit]
checks if a type is floating-point type
(class template) [edit]
(C++11)
checks if a type is an array type
(class template) [edit]
(C++11)
checks if a type is an enumeration type
(class template) [edit]
(C++11)
checks if a type is an union type
(class template) [edit]
(C++11)
checks if a type is a non-union class type
(class template) [edit]
checks if a type is a function type
(class template) [edit]
checks if a type is a pointer type
(class template) [edit]
checks if a type is lvalue reference
(class template) [edit]
checks if a type is rvalue reference
(class template) [edit]
checks if a type is a pointer to a non-static member object
(class template) [edit]
checks if a type is a pointer to a non-static member function
(class template) [edit]
Composite type categories
checks if a type is fundamental type
(class template) [edit]
checks if a type is arithmetic type
(class template) [edit]
(C++11)
checks if a type is scalar type
(class template) [edit]
(C++11)
checks if a type is object type
(class template) [edit]
checks if a type is compound type
(class template) [edit]
checks if a type is either lvalue reference or rvalue reference
(class template) [edit]
checks if a type is a pointer to a non-static member function or object
(class template) [edit]
Type properties
(C++11)
checks if a type is const-qualified
(class template) [edit]
checks if a type is volatile-qualified
(class template) [edit]
checks if a type is trivial
(class template) [edit]
checks if a type is trivially copyable
(class template) [edit]
checks if a type is standard-layout type
(class template) [edit]
(C++11)
checks if a type is plain-old data (POD) type
(class template) [edit]
(C++11)(deprecated in C++17)
checks if a type is literal type
(class template) [edit]
checks if every bit in the type's object representation contributes to its value
(class template) [edit]
(C++11)
checks if a type is class (but not union) type and has no data
(class template) [edit]
checks if a type is polymorphic class type
(class template) [edit]
(C++14)
checks if a type is a final class type
(class template) [edit]
checks if a type is abstract class type
(class template) [edit]
(C++11)
checks if a type is signed arithmetic type
(class template) [edit]
checks if a type is unsigned arithmetic type
(class template) [edit]
Supported operations
checks if a type has a constructor for specific arguments
(class template) [edit]
checks if a type has a default constructor
(class template) [edit]
checks if a type has a copy constructor
(class template) [edit]
checks if a type can be constructed from an rvalue reference
(class template) [edit]
checks if a type has a assignment operator for a specific argument
(class template) [edit]
checks if a type has a copy assignment operator
(class template) [edit]
checks if a type has a move assignment operator
(class template) [edit]
checks if a type has a non-deleted destructor
(class template) [edit]
checks if a type has a virtual destructor
(class template) [edit]
checks if objects of a type can be swapped with objects of same or different type
(class template) [edit]
Property queries
obtains the type's alignment requirements
(class template) [edit]
(C++11)
obtains the number of dimensions of an array type
(class template) [edit]
(C++11)
obtains the size of an array type along a specified dimension
(class template) [edit]
Type relationships
(C++11)
checks if two types are the same
(class template) [edit]
checks if a type is derived from the other type
(class template) [edit]
checks if a type can be converted to the other type
(class template) [edit]
checks if a type can be invoked (as if by std::invoke) with the given argument types
(class template) [edit]
Const-volatility specifiers
removes const or/and volatile specifiers from the given type
(class template) [edit]
(C++11)(C++11)(C++11)
adds const or/and volatile specifiers to the given type
(class template) [edit]
References
removes reference from the given type
(class template) [edit]
adds lvalue or rvalue reference to the given type
(class template) [edit]
Pointers
removes pointer from the given type
(class template) [edit]
adds pointer to the given type
(class template) [edit]
Sign modifiers
makes the given integral type signed
(class template) [edit]
makes the given integral type unsigned
(class template) [edit]
Arrays
removes one extent from the given array type
(class template) [edit]
removes all extents from the given array type
(class template) [edit]
Miscellaneous transformations
defines the type suitable for use as uninitialized storage for types of given size
(class template) [edit]
defines the type suitable for use as uninitialized storage for all given types
(class template) [edit]
(C++11)
applies type transformations as when passing a function argument by value
(class template) [edit]
(C++11)
hides a function overload or template specialization based on compile-time boolean
(class template) [edit]
chooses one type or another based on compile-type boolean
(class template) [edit]
deduces the result type of a mixed-mode arithmetic expression
(class template) [edit]
obtains the underlying integer type for a given enumeration type
(class template) [edit]
(C++11)
deduces the return type of a function call expression
(class template) [edit]
(C++17)
void variadic alias template
(alias template) [edit]
Operations on traits
variadic logical AND metafunction
(class template) [edit]
variadic logical OR metafunction
(class template) [edit]
(C++17)
logical NOT metafunction
(class template) [edit]


[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_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_signed;
  template <class T> struct is_unsigned;
  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, class R = void> struct is_callable; // not defined
  template <class Fn, class... ArgTypes, class R>
  struct is_callable<Fn(ArgTypes...), R>;
  template <class, class R = void> struct is_nothrow_callable; // not defined
  template <class Fn, class... ArgTypes, class R>
  struct is_nothrow_callable<Fn(ArgTypes...), 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 <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 <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 <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...>
  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> constexpr bool is_void_v
  = is_void<T>::value;
  template <class T> constexpr bool is_null_pointer_v
  = is_null_pointer<T>::value;
  template <class T> constexpr bool is_integral_v
  = is_integral<T>::value;
  template <class T> constexpr bool is_floating_point_v
  = is_floating_point<T>::value;
  template <class T> constexpr bool is_array_v
  = is_array<T>::value;
  template <class T> constexpr bool is_pointer_v
  = is_pointer<T>::value;
  template <class T> constexpr bool is_lvalue_reference_v
  = is_lvalue_reference<T>::value;
  template <class T> constexpr bool is_rvalue_reference_v
  = is_rvalue_reference<T>::value;
  template <class T> constexpr bool is_member_object_pointer_v
  = is_member_object_pointer<T>::value;
  template <class T> constexpr bool is_member_function_pointer_v
  = is_member_function_pointer<T>::value;
  template <class T> constexpr bool is_enum_v
  = is_enum<T>::value;
  template <class T> constexpr bool is_union_v
  = is_union<T>::value;
  template <class T> constexpr bool is_class_v
  = is_class<T>::value;
  template <class T> constexpr bool is_function_v
  = is_function<T>::value;
 
  // composite type categories
  template <class T> constexpr bool is_reference_v
  = is_reference<T>::value;
  template <class T> constexpr bool is_arithmetic_v
  = is_arithmetic<T>::value;
  template <class T> constexpr bool is_fundamental_v
  = is_fundamental<T>::value;
  template <class T> constexpr bool is_object_v
  = is_object<T>::value;
  template <class T> constexpr bool is_scalar_v
  = is_scalar<T>::value;
  template <class T> constexpr bool is_compound_v
  = is_compound<T>::value;
  template <class T> constexpr bool is_member_pointer_v
  = is_member_pointer<T>::value;
 
  // type properties
  template <class T> constexpr bool is_const_v
  = is_const<T>::value;
  template <class T> constexpr bool is_volatile_v
  = is_volatile<T>::value;
  template <class T> constexpr bool is_trivial_v
  = is_trivial<T>::value;
  template <class T> constexpr bool is_trivially_copyable_v
  = is_trivially_copyable<T>::value;
  template <class T> constexpr bool is_standard_layout_v
  = is_standard_layout<T>::value;
  template <class T> constexpr bool is_pod_v
  = is_pod<T>::value;
  template <class T> constexpr bool is_empty_v
  = is_empty<T>::value;
  template <class T> constexpr bool is_polymorphic_v
  = is_polymorphic<T>::value;
  template <class T> constexpr bool is_abstract_v
  = is_abstract<T>::value;
  template <class T> constexpr bool is_final_v
  = is_final<T>::value;
  template <class T> constexpr bool is_signed_v
  = is_signed<T>::value;
  template <class T> constexpr bool is_unsigned_v
  = is_unsigned<T>::value;
  template <class T, class... Args> constexpr bool is_constructible_v
  = is_constructible<T, Args...>::value;
  template <class T> constexpr bool is_default_constructible_v
  = is_default_constructible<T>::value;
  template <class T> constexpr bool is_copy_constructible_v
  = is_copy_constructible<T>::value;
  template <class T> constexpr bool is_move_constructible_v
  = is_move_constructible<T>::value;
  template <class T, class U> constexpr bool is_assignable_v
  = is_assignable<T, U>::value;
  template <class T> constexpr bool is_copy_assignable_v
  = is_copy_assignable<T>::value;
  template <class T> constexpr bool is_move_assignable_v
  = is_move_assignable<T>::value;
  template <class T, class U> constexpr bool is_swappable_with_v
  = is_swappable_with<T, U>::value;
  template <class T> constexpr bool is_swappable_v
  = is_swappable<T>::value;
  template <class T> constexpr bool is_destructible_v
  = is_destructible<T>::value;
  template <class T, class... Args> constexpr bool is_trivially_constructible_v
  = is_trivially_constructible<T, Args...>::value;
  template <class T> constexpr bool is_trivially_default_constructible_v
  = is_trivially_default_constructible<T>::value;
  template <class T> constexpr bool is_trivially_copy_constructible_v
  = is_trivially_copy_constructible<T>::value;
  template <class T> constexpr bool is_trivially_move_constructible_v
  = is_trivially_move_constructible<T>::value;
  template <class T, class U> constexpr bool is_trivially_assignable_v
  = is_trivially_assignable<T, U>::value;
  template <class T> constexpr bool is_trivially_copy_assignable_v
  = is_trivially_copy_assignable<T>::value;
  template <class T> constexpr bool is_trivially_move_assignable_v
  = is_trivially_move_assignable<T>::value;
  template <class T> constexpr bool is_trivially_destructible_v
  = is_trivially_destructible<T>::value;
  template <class T, class... Args> constexpr bool is_nothrow_constructible_v
  = is_nothrow_constructible<T, Args...>::value;
  template <class T> constexpr bool is_nothrow_default_constructible_v
  = is_nothrow_default_constructible<T>::value;
  template <class T> constexpr bool is_nothrow_copy_constructible_v
  = is_nothrow_copy_constructible<T>::value;
  template <class T> constexpr bool is_nothrow_move_constructible_v
  = is_nothrow_move_constructible<T>::value;
  template <class T, class U> constexpr bool is_nothrow_assignable_v
  = is_nothrow_assignable<T, U>::value;
  template <class T> constexpr bool is_nothrow_copy_assignable_v
  = is_nothrow_copy_assignable<T>::value;
  template <class T> constexpr bool is_nothrow_move_assignable_v
  = is_nothrow_move_assignable<T>::value;
  template <class T, class U> constexpr bool is_nothrow_swappable_with_v
  = is_nothrow_swappable_with<T, U>::value;
  template <class T> constexpr bool is_nothrow_swappable_v
  = is_nothrow_swappable<T>::value;
  template <class T> constexpr bool is_nothrow_destructible_v
  = is_nothrow_destructible<T>::value;
  template <class T> constexpr bool has_virtual_destructor_v
  = has_virtual_destructor<T>::value;
  template <class T> constexpr bool has_unique_object_representations_v
  = has_unique_object_representations<T>::value;
 
  // type property queries
  template <class T> constexpr size_t alignment_of_v
  = alignment_of<T>::value;
  template <class T> constexpr size_t rank_v
  = rank<T>::value;
  template <class T, unsigned I = 0> constexpr size_t extent_v
  = extent<T, I>::value;
 
  // type relations
  template <class T, class U> constexpr bool is_same_v
  = is_same<T, U>::value;
  template <class Base, class Derived> constexpr bool is_base_of_v
  = is_base_of<Base, Derived>::value;
  template <class From, class To> constexpr bool is_convertible_v
  = is_convertible<From, To>::value;
  template <class T, class R = void> constexpr bool is_callable_v
  = is_callable<T, R>::value;
  template <class T, class R = void> constexpr bool is_nothrow_callable_v
  = is_nothrow_callable<T, R>::value;
 
  // logical operator traits:
  template<class... B> constexpr bool conjunction_v = conjunction<B...>::value;
  template<class... B> constexpr bool disjunction_v = disjunction<B...>::value;
  template<class B> constexpr bool negation_v = negation<B>::value;
} // namespace std

[edit] Class 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; }
  };
}