C++ <forward_list> - emplace_after() Function

The C++ forward_list::emplace_after function is used to insert new element at specified position in a forward_list. Each insertion of element increases the forward_list container size by one.

Syntax

C++11

template <class... Args>
iterator emplace_after (const_iterator position, Args&&... args);

Parameters

`position`	Specify the position in the forward_list where the new element need to be inserted.
`args`	Arguments forwarded to construct the new element.

Return Value

An iterator that points to the newly emplaced element.

Time Complexity

Constant i.e, Θ(1).

Example:

In the below example, the forward_list::emplace_after function is used to insert new element at specified position in a forward_list f_list.

#include <iostream>
#include <forward_list>
using namespace std;
 
int main (){
  forward_list<int> f_list{10, 20, 30, 40, 50};
  forward_list<int>::iterator it;

  //insert a new element at position = 3
  it = f_list.begin();
  advance(it, 2);
  f_list.emplace_after(it, 100);

  //insert a new element at position = 4
  f_list.emplace_after(it, 200);

  cout<<"f_list contains: ";
  cout<<"f_list contains: ";
  for(it = f_list.begin(); it != f_list.end(); it++)
   cout<<*it<<" ";   

  return 0;
}

The output of the above code will be:

f_list contains: 10 20 30 200 100 40 50

Example:

Lets see another example where the forward_list called f_list contains string values.

#include <iostream>
#include <forward_list>
using namespace std;
 
int main (){
  forward_list<string> f_list;
  forward_list<string>::iterator it;

  it = f_list.before_begin();
  //insert new element in the forward_list
  f_list.emplace_after(it, "JAN");
  f_list.emplace_after(it, "FEB");
  f_list.emplace_after(it, "MAR");
  f_list.emplace_after(it, "APR");
  f_list.emplace_after(it, "MAY");
  f_list.emplace_after(it, "JUN");

  cout<<"f_list contains: ";
  for(it = f_list.begin(); it != f_list.end(); it++)
  {
   cout<<*it<<" ";   
  }
  return 0;
}

The output of the above code will be:

f_list contains: JUN MAY APR MAR FEB JAN

❮ C++ <forward_list> Library