std::negation
Defined in header <type_traits> | | |
|---|---|---|
template<class B> struct negation; | (1) | (since C++17) |
形成类型特征的逻辑否定B...
类型std::negation<B>是UnaryTypeTrait基本特征std::bool_constant<!bool(B::value)>...
模板参数
B | - | any type such that B::value is convertible to bool |
|---|
辅助变量模板
template<class B> inline constexpr bool negation_v = negation<B>::value; | | (since C++17) |
|---|
继承自STD：积分[医]常量
成员常数
value static | true if B has a member ::value that is false when explicitly converted to bool , false otherwise (public static member constant) |
|---|
成员函数
operator bool | converts the object to bool, returns value (public member function) |
|---|---|
operator() (C++14) | returns value (public member function) |
成员类型
Type | Definition |
|---|---|
value_type | bool |
type | std::integral_constant<bool, value> |
可能的实施
模板<class B>结构否定：STD：：Bool[医]常数<%21B：：value>{}；
*。
例
二次
#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';
}二次
产出：
二次
false
true二次
另见
conjunction (C++17) | variadic logical AND metafunction (class template) |
|---|---|
disjunction (C++17) | variadic logical OR metafunction (class template) |
integral_constantbool_constant (C++11)(C++17) | compile-time constant of specified type with specified value (class template) |
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