public member function
<list>

std::list::front

      reference front();
const_reference front() const;
Access first element
Returns a reference to the first element in the list container.

Unlike member list::begin, which returns an iterator to this same 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 first element in the list container.

If the list 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 list member types).

Example

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// list::front
#include <iostream>
#include <list>

int main ()
{
  std::list<int> mylist;

  mylist.push_back(77);
  mylist.push_back(22);

  // now front equals 77, and back 22

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

  std::cout << "mylist.front() is now " << mylist.front() << '\n';

  return 0;
}


Output:
mylist.front() is now 55

Complexity

Constant.

Iterator validity

No changes.

Data races

The container is accessed (neither the const nor the non-const versions modify the container).
The first 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

  • 1793521592 2018-02-23
  • 2864591591 2018-02-23
  • 6167231590 2018-02-23
  • 3669201589 2018-02-23
  • 7946381588 2018-02-23
  • 8957701587 2018-02-23
  • 3891941586 2018-02-23
  • 6039851585 2018-02-23
  • 2573991584 2018-02-23
  • 7728781583 2018-02-23
  • 3731582 2018-02-23
  • 1007451581 2018-02-22
  • 8908121580 2018-02-22
  • 141161579 2018-02-22
  • 9421578 2018-02-22
  • 2826901577 2018-02-22
  • 3647361576 2018-02-22
  • 5717551575 2018-02-22
  • 523811574 2018-02-22
  • 6439871573 2018-02-22