# 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><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

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