Std::negation (3) Linux Manual Page

std::negation – std::negation

Synopsis

Defined in header<type_traits>

    template <class B>
    (1)(since C++ 17)

        struct negation;

Forms the logical negation of the type trait B.
The type std::negation<B> is a UnaryTypeTrait with a BaseCharacteristic of std::bool_constant<!bool(B::value)>.

Template parameters

B – any type such that the expression bool(B::value) is a valid constant expression

Helper variable template

template<class B> (since C++17)
inline constexpr bool negation_v = negation<B>::value;

Inherited from std::integral_constant

Member constants

value true if B has a member ::value that is false when explicitly converted to bool , false otherwise
(public static member constant)
[static]

Member functions

converts the object to bool, returns value
operator bool (public member function)

operator() returns value
(public member function)
(C++14)

Member types

Type Definition
value_type bool
type std::integral_constant<bool, value>

Possible implementation

template<class B>
struct negation : std::bool_constant<!bool(B::value)> { };

Example

// Run this code

#include <iostream>

#include <type_traits>
static_assert(
    std::is_same<
        std::bool_constant<false>,
        typename std::negation<std::bool_constant<true>>::type>::value,
    "");

static_assert(
    std::is_same<
        std::bool_constant<true>,
        typename std::negation<std::bool_constant<false>>::type>::value,
    "");
int main()

{
    std::cout << std::boolalpha;
    std::cout << std::negation<std::bool_constant<true>>::value << '\n';
    std::cout << std::negation<std::bool_constant<false>>::value << '\n';
}

Output:

false
true

std::negation (3) Linux Manual Page