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# std::negation

From cppreference.com
< cpp‎ | types

Defined in header `<type_traits>` |  |
template<class B> struct negation; | (1) | (since C++17)

Forms the logical negation of the type trait `B`.

The type std::negation<B> is a `UnaryTypeTrait` with a BaseCharacteristic of std::integral_constant<bool, !B::value>.

### [edit] Template parameters

B | - | any type such that B::value is convertible to bool

### [edit] Helper variable template

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

[edit]

## Inherited from std::integral_constant

### Member constants

value [static] | true if `B` has a member `::value` that is false , false otherwise (public static member constant)

### Member functions

operator bool | converts the object to bool, returns `value` (public member function)
operator() (C++14) | returns `value` (public member function)

### Member types

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

### [edit] Possible implementation

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

### [edit] Example

| This section is incomplete Reason: no example

### [edit] See also

conjunction (C++17) | variadic logical AND metafunction (class template) [edit]
disjunction (C++17) | variadic logical OR metafunction (class template) [edit]

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