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std::logical_not(3) C++ Standard Libary std::logical_not(3)


std::logical_not - std::logical_not


Defined in header <functional>
template< class T > (until C++14)
struct logical_not;
template< class T = void > (since C++14)
struct logical_not;

Function object for performing logical NOT (logical negation). Effectively calls
operator! for type T.


The standard library provides a specialization of std::logical_not
when T is not specified, which leaves the parameter types and return
type to be deduced.
(since C++14)
logical_not<void> function object implementing !x deducing argument
(C++14) and return types
(class template specialization)

Member types

Type Definition
result_type (deprecated in C++17)(removed in C++20) bool
argument_type (deprecated in C++17)(removed in C++20) T

These member types are obtained via publicly inheriting (until C++11)
std::unary_function<T, bool>.

Member functions

operator() returns the logical NOT of the argument
(public member function)


bool operator()( const T& arg ) const; (until C++14)
constexpr bool operator()( const T& arg ) const; (since C++14)

Returns the logical NOT of arg.


arg - value to compute logical NOT of

Return value

The result of !arg.


May throw implementation-defined exceptions.

Possible implementation

constexpr // since C++14
bool operator()(const T &arg) const
return !arg;