std::queue::back

      value_type& back();const value_type& back() const;

      reference& back();const_reference& back() const;

Access last element

Returns a reference to the last element in the queue. This is the "newest" element in the queue (i.e. the last element pushed into the queue).

This member function effectively calls member back of the underlying container object.

Parameters

none

Return value

A reference to the last element in the queue.

Member type value_type is the type of the elements in the container (defined as an alias of the first class template parameter, T).

Member types reference and const_reference are aliases of the underlying containers's types with the same name.

Example

// queue::back
#include <iostream>       // std::cout
#include <queue>          // std::queue

int main ()
{
  std::queue<int> myqueue;

  myqueue.push(12);
  myqueue.push(75);   // this is now the back

  myqueue.back() -= myqueue.front();

  std::cout << "myqueue.back() is now " << myqueue.back() << '\n';

  return 0;
}

Output:

Complexity

Constant (calling back on the underlying container).

Data races

The container is accessed (neither the const nor the non-const versions modify the container).
The reference returned can be used to access or modify the last element.

Exception safety

Provides the same level of guarantees as the operation performed on the container (no-throw guarantee for standard non-empty containers).