C++

Reference

<deque>

deque

public member function
<deque>

std::deque::back

      reference back();const_reference back() const;
Access last element
Returns a reference to the last element in the container.

Unlike member deque::end, which returns an iterator just past this element, this function returns a direct reference.

Calling this function on an empty container causes undefined behavior.

Parameters

none

Return value

A reference to the last element in the deque container.

If the deque object is const-qualified, the function returns a const_reference. Otherwise, it returns a reference.

Member types reference and const_reference are the reference types to the elements of the container (see deque member types).

Example

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// deque::back
#include <iostream>
#include <deque>

int main ()
{
  std::deque<int> mydeque;

  mydeque.push_back(10);

  while (mydeque.back() != 0)
    mydeque.push_back ( mydeque.back() -1 );

  std::cout << "mydeque contains:";

  for (std::deque<int>::iterator it = mydeque.begin(); it!=mydeque.end(); ++it)
    std::cout << ' ' << *it;

  std::cout << '\n';

  return 0;
}

Output:
mydeque contains: 10 9 8 7 6 5 4 3 2 1 0


Complexity

Constant.

Iterator validity

No changes.

Data races

The container is accessed (neither the const nor the non-const versions modify the container).
The last element is potentially accessed or modified by the caller. Concurrently accessing or modifying other elements is safe.

Exception safety

If the container is not empty, the function never throws exceptions (no-throw guarantee).
Otherwise, it causes undefined behavior.

See also

deque::front
Access first element (public member function)
deque::end
Return iterator to end (public member function)
deque::push_back
Add element at the end (public member function)
deque::pop_back
Delete last element (public member function)