std::negate - cppreference.com

From cppreference.com

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

Function object for performing negation. Effectively calls operator- on an instance of type T.

Specializations

The standard library provides a specialization of std::negate when T is not specified, which leaves the parameter types and return type to be deduced.

function object implementing -x deducing parameter and return types
(class template specialization) [edit]

(since C++14)

Member types

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

These member types are obtained via publicly inheriting std::unary_function<T, T>.

(until C++11)

Member functions

returns the negation of the argument
(public member function)

std::negate::operator()

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

Returns the negation of arg.

Parameters

arg

value to compute negation of

Return value

The result of -arg.

Exceptions

May throw implementation-defined exceptions.

Possible implementation

constexpr T operator()(const T& arg) const 
{
    return -arg;
}