NAME¶

std::negate - std::negate

Synopsis¶

Defined in header <functional>
template<> (since C++14)
class negate<void>;

std::negate<> is a specialization of std::negate with parameter and return type
deduced.

Member types¶

Member type Definition
is_transparent /* unspecified */

Member functions¶

operator() returns its negated argument
(public member function)

std::negate<>::operator()

template< class T >

constexpr auto operator()( T&& arg ) const

-> decltype(-std::forward<T>(arg));

Returns the result of negating arg (or whatever the unary operator- is overloaded to
do)

Parameters¶

arg - value to negate

Return value¶

The result of -arg.

Notes¶

The member type is_transparent indicates to the caller that this function object is
a transparent function object: it accepts arguments of arbitrary types and uses
perfect forwarding, which avoids unnecessary copying and conversion when the
function object is used in heterogeneous context, or with rvalue arguments. In
particular, template functions such as std::set::find and std::set::lower_bound make
use of this member type on their Compare types.

Example¶

// Run this code

#include <complex>
#include <functional>
#include <iostream>

int main()
{
constexpr std::complex z(4, 2);

std::cout << z << ' ' << -z << ' ' << std::negate{}(z) << '\n';
}

Output:¶

(4,2) (-4,-2) (-4,-2)