public member function

std:: forward_list::before_begin

<forward_list>
      iterator before_begin() noexcept;
const_iterator before_begin() const noexcept;
Return iterator to before beginning
Returns an iterator pointing to the position before the first element in the container.

The value returned shall not be dereferenced.

It is meant to be used as an argument for member functions emplace_after, insert_after, erase_after or splice_after, to especify the beginning of the sequence as the location on where to perform the action.

Parameters

none

Return Value

An iterator to the position before the beginning of the sequence.

Member types iterator and const_iterator are forward iterator types.

Example

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// forward_list::before_begin
#include <iostream>
#include <forward_list>

int main ()
{
  std::forward_list<int> mylist = {20, 30, 40, 50};

  mylist.insert_after ( mylist.before_begin(), 11 );

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

  return 0;
}


Output:
mylist contains: 11 20 30 40 50

Complexity

Constant.

Iterator validity

No changes.

See also