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Metaprogramming library

From cppreference.com
< cpp
 
 
Metaprogramming library
Type traits
Type categories
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
Type properties
(C++11)
(C++11)
(C++14)
(C++11)
(C++11)(until C++20)
(C++11)(deprecated in C++20)
(C++11)
Type trait constants
Metafunctions
(C++17)
Supported operations
Relationships and property queries
Type modifications
(C++11)(C++11)(C++11)
Type transformations
(C++11)(deprecated in C++23)
(C++11)(deprecated in C++23)
(C++11)
(C++11)
(C++17)

(C++11)(until C++20)(C++17)
Compile-time rational arithmetic
Compile-time integer sequences
 

C++ provides metaprogramming facilities, such as type traits, compile-time rational arithmetic, and compile-time integer sequences.

Contents

[edit] Type property

These type traits define compile-time template-based interfaces to query the properties of types.

Attempting to specialize a template defined in the <type_traits> header and described in this section results in undefined behavior.

A template defined in the <type_traits> header may be instantiated with an incomplete type unless otherwise specified, notwithstanding the general prohibition against instantiating standard library templates with incomplete types.

Defined in header <type_traits>
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 an integral type
(class template) [edit]
checks if a type is a 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 a lvalue reference
(class template) [edit]
checks if a type is a 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 a fundamental type
(class template) [edit]
checks if a type is an arithmetic type
(class template) [edit]
(C++11)
checks if a type is a scalar type
(class template) [edit]
(C++11)
checks if a type is an object type
(class template) [edit]
checks if a type is a compound type
(class template) [edit]
checks if a type is either a lvalue reference or rvalue reference
(class template) [edit]
checks if a type is a pointer to an 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 a standard-layout type
(class template) [edit]
(C++11)(deprecated in C++20)
checks if a type is a plain-old data (POD) type
(class template) [edit]
(C++11)(deprecated in C++17)(removed in C++20)
checks if a type is a 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 a class (but not union) type and has no non-static data members
(class template) [edit]
checks if a type is a polymorphic class type
(class template) [edit]
checks if a type is an abstract class type
(class template) [edit]
(C++14)
checks if a type is a final class type
(class template) [edit]
checks if a type is an aggregate type
(class template) [edit]
(C++11)
checks if a type is a signed arithmetic type
(class template) [edit]
checks if a type is an unsigned arithmetic type
(class template) [edit]
checks if a type is an array type of known bound
(class template) [edit]
checks if a type is an array type of unknown bound
(class template) [edit]
checks if a type is a scoped enumeration 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]
checks if a reference is bound to a temporary in direct-initialization
(class template) [edit]
checks if a reference is bound to a temporary in copy-initialization
(class template) [edit]
checks if two types are layout-compatible
(class template) [edit]
checks if a type is a pointer-interconvertible (initial) base of another type
(class template) [edit]
checks if objects of a type are pointer-interconvertible with the specified subobject of that type
(function template) [edit]
checks if two specified members correspond to each other in the common initial subsequence of two specified types
(function template) [edit]

[edit] Operations on traits

Defined in header <type_traits>
variadic logical AND metafunction
(class template) [edit]
variadic logical OR metafunction
(class template) [edit]
(C++17)
logical NOT metafunction
(class template) [edit]

[edit] Base classes

Defined in header <type_traits>
compile-time constant of specified type with specified value
(class template) [edit]

Two specializations of std::integral_constant for the type bool are provided:

Defined in header <type_traits>
Specializations
Type Definition
true_type std::integral_constant<bool, true>
false_type std::integral_constant<bool, false>

[edit] Type modifications

These type traits apply modifications on a template parameter, and declare (sometimes conditionally) the type member typedef as the resulting type.

Attempting to specialize a template defined in the <type_traits> header and described in this section results in undefined behavior, except that std::common_type and std::basic_common_reference (since C++20) may be specialized as required in description.

A template defined in the <type_traits> header may be instantiated with an incomplete type unless otherwise specified, notwithstanding the general prohibition against instantiating standard library templates with incomplete types.

Defined in header <type_traits>
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 a reference from the given type
(class template) [edit]
adds a lvalue or rvalue reference to the given type
(class template) [edit]
Pointers
removes a pointer from the given type
(class template) [edit]
adds a 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]

[edit] Miscellaneous transformations

Defined in header <type_traits>
(C++11)(deprecated in C++23)
defines the type suitable for use as uninitialized storage for types of given size
(class template) [edit]
(C++11)(deprecated in C++23)
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]
combines std::remove_cv and std::remove_reference
(class template) [edit]
(C++11)
conditionally removes a function overload or template specialization from overload resolution
(class template) [edit]
chooses one type or another based on compile-time boolean
(class template) [edit]
determines the common type of a group of types
(class template) [edit]
determines the common reference type of a group of types
(class template) [edit]
obtains the underlying integer type for a given enumeration type
(class template) [edit]
(C++11)(removed in C++20)(C++17)
deduces the result type of invoking a callable object with a set of arguments
(class template) [edit]
(C++17)
void variadic alias template
(alias template) [edit]
returns the type argument unchanged
(class template) [edit]

[edit] Compile-time rational arithmetic

The header <ratio> provides types and functions for manipulating and storing compile-time ratios.

[edit] Compile-time integer sequences

Defined in header <utility>
implements compile-time sequence of integers
(class template) [edit]