C++ <forward_list> - operator=() Function

The C++ forward_list::operator= function is used to assign new content to the container by replacing the current content.

Syntax

C++11

//copy version - copies all elements
//of x into the container
forward_list& operator= (const forward_list& x);

//move version - moves elements of x
//into the container
forward_list& operator= (forward_list&& x);

//initializer forward_list version - copies all 
//elements of il into the container
forward_list& operator= (initializer_list<value_type> il);

Parameters

`x`	Specify a forward_list object of same type.
`il`	Specify an initializer_list object.

Return Value

Returns *this.

Time Complexity

Linear i.e, Θ(n).

Example: using copy version

In the example below, the forward_list::operator= function is used to assign new values to the given forward_list.

#include <iostream>
#include <forward_list>
using namespace std;
 
int main (){
  forward_list<int> flist1{10, 20, 30, 40, 50};
  forward_list<int>::iterator it;

  //copying all content of flist1 into flist2
  forward_list<int> flist2;
  flist2 = flist1;

  cout<<"flist1 contains:";
  for(it = flist1.begin(); it != flist1.end(); ++it)
    cout<<" "<<*it;

  cout<<"\nflist2 contains:";
  for(it = flist2.begin(); it != flist2.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

flist1 contains: 10 20 30 40 50
flist2 contains: 10 20 30 40 50

Example: using move version

Using the move version of operator=, the content of one forward_list can be moved to another forward_list. Consider the following example:

#include <iostream>
#include <forward_list>
using namespace std;
 
int main (){
  forward_list<int> flist1{10, 20, 30, 40, 50};
  forward_list<int>::iterator it;

  cout<<"flist1 contains:";
  for(it = flist1.begin(); it != flist1.end(); ++it)
    cout<<" "<<*it;

  //moving all content of flist1 into flist2
  forward_list<int> flist2;
  flist2 = move(flist1);

  cout<<"\nflist1 contains:";
  for(it = flist1.begin(); it != flist1.end(); ++it)
    cout<<" "<<*it;

  cout<<"\nflist2 contains:";
  for(it = flist2.begin(); it != flist2.end(); ++it)
    cout<<" "<<*it;

  return 0;
}

The output of the above code will be:

flist1 contains: 10 20 30 40 50
flist1 contains:
flist2 contains: 10 20 30 40 50

Example: using initializer forward_list version

The initializer forward_list can also be used to assign values into a forward_list container. Consider the example below:

#include <iostream>
#include <forward_list>
using namespace std;
 
int main (){
  //creating empty forward_list
  forward_list<int> flist;
  forward_list<int>::iterator it;

  //creating initializer forward_list
  initializer_list<int> ilist = {10, 20, 30, 40, 50};

  //assigning values of flist using ilist
  flist = ilist;

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

  return 0;
}

The output of the above code will be:

flist contains: 10 20 30 40 50

❮ C++ <forward_list> Library