public member function
<forward_list>

std::forward_list::front

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

Unlike member forward_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 container.

If the forward_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 forward_list container (see member types).

Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
 
// forward_list::front
#include <iostream>
#include <forward_list>

int main ()
{
  std::forward_list<int> mylist = {2, 16, 77};

  mylist.front() = 11;

  std::cout << "mylist now contains:";
  for ( int& x : mylist ) std::cout << ' ' << x;

  std::cout << '\n';

  return 0;
}


Output:
mylist now contains: 11 16 77

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

forward_list::begin
Return iterator to beginning (public member type )
forward_list::before_begin
Return iterator to before beginning (public member function )

C++