Variable Templates

Collaboration diagram for Variable Templates:

Variables
template<typename _Tp, typename _Up>
constexpr strong_ordering	std::type_order_v
template<typename _Tp, typename _Up>
constexpr bool	std::is_layout_compatible_v
template<typename _Base, typename _Derived>
constexpr bool	std::is_pointer_interconvertible_base_of_v

Detailed Description

Since

C++17

Each trait in <type_traits> that has a value static data member is also available as a variable template, using the same name with a _v suffix. For example, std::is_integral_v<T> is a bool constant with the same value as std::is_integral<T>::value.

In some cases, using the variable template instead of the value member avoids instantiating the class template for the trait. This gives the compiler less work to do and can make your code compile a little faster.

Variable Documentation

is_layout_compatible_v

template<typename _Tp, typename _Up>

bool std::is_layout_compatible_v

constexpr

Since

C++20

Definition at line 4047 of file type_traits.

is_pointer_interconvertible_base_of_v

template<typename _Base, typename _Derived>

bool std::is_pointer_interconvertible_base_of_v

constexpr

Since

C++20

Definition at line 4075 of file type_traits.

type_order_v

template<typename _Tp, typename _Up>

strong_ordering std::type_order_v

inlineconstexpr

Since

C++26

Definition at line 1279 of file compare.