std::plus - cppreference.com

From cppreference.com

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

Function object for performing addition. Effectively calls operator+ on two instances of type T.

Specializations

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

function object implementing x + y 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`
`first_argument_type` (deprecated in C++17)(removed in C++20)	`T`
`second_argument_type` (deprecated in C++17)(removed in C++20)	`T`

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

(until C++11)

Member functions

std::plus::operator()

`T operator()( const T& lhs, const T& rhs ) const;`		(constexpr since C++14)

Returns the sum of lhs and rhs.

Parameters

Return value

The result of lhs + rhs.

Exceptions

May throw implementation-defined exceptions.

Possible implementation

constexpr T operator()(const T& lhs, const T& rhs) const 
{
    return lhs + rhs;
}