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std::negate<void>

From cppreference.com
< cpp‎ | utility‎ | functional
 
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
Function objects
Function invocation
(C++17)(C++23)
Identity function object
(C++20)
Transparent operator wrappers
(C++14)
(C++14)
negate<>
(C++14)
(C++14)  
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)

Old binders and adaptors
(until C++17*)
(until C++17*)
(until C++17*)
(until C++17*)  
(until C++17*)
(until C++17*)(until C++17*)(until C++17*)(until C++17*)
(until C++20*)
(until C++20*)
(until C++17*)(until C++17*)
(until C++17*)(until C++17*)

(until C++17*)
(until C++17*)(until C++17*)(until C++17*)(until C++17*)
(until C++20*)
(until C++20*)
 
Defined in header <functional>
template<>
class negate<void>;
(since C++14)

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

Contents

[edit] Member types

Type Definition
is_transparent unspecified

[edit] Member functions

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

std::negate<void>::operator()

template< class T >

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

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

Returns the result of negating arg.

Parameters

arg - value to negate

Return value

-std::forward<T>(arg).

[edit] Example

#include <complex>
#include <functional>
#include <iostream>
 
int main()
{
    auto complex_negate = std::negate<void>{}; // “void” can be omitted
    constexpr std::complex z(4, 2);
    std::cout << z << '\n';
    std::cout << -z << '\n';
    std::cout << complex_negate(z) << '\n';
}

Output:

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