std::logical_not

< cpp‎ | utility‎ | functional

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

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

Specializations

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.

logical_not<void>

(C++14)

function object implementing !x deducing argument and return types
(class template specialization)

(since C++14)

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 std::unary_function<T, bool>.

(until C++11)

Member functions

operator()

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

std::logical_not::operator()

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.

Parameters

arg

value to compute logical NOT of

Return value

The result of !arg.

Exceptions

May throw implementation-defined exceptions.

Possible implementation

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