std::plus in C++ with examples

In this article, we will learn about std::plus in C++ with examples. It is a function object of the C++ standard library for performing addition. The object class whose call returns the result of adding its two arguments (as returned by operator + ).

std::plus in C++ with examples

It is defined in <functional> header.

template< class T >
struct plus;
(until C++14)
template< class T = void >
struct plus;
(since C++14)

Specializations:

The standard library provides a specialization of std::plus when T is not mentioned, which leaves the parameter types and return type to be deduced.
<plus>&lt;void>-which implement sum and return type.

Member types and definition:

• result_type-T
• first_argument_type-T
• second_argument_type -T

Member functions:

operator() which returns the sum of two arguments.

std::plus::operator()

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

It returns the sum of lhs and rhs.
The possible implementation of this function-

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

Example:

#include<iostream>
#include<functional>

using namespace std;
int main(){
    cout<<plus<>{}(5,9);
}

Output:14