Description : This function is used to extend list by inserting new element at a given position.
Example :
// declaration of list
std::list< std::pair<int,char> > mylist;
// using emplace() function to
// insert new element at the
// beginning of the list
mylist.emplace ( mylist.begin(), 100, 'x' );
mylist.emplace ( mylist.begin(), 200, 'y' );
// printing the list
// after inserting the value
// at the beginning
std::cout << "mylist contains:";
for (auto& x: mylist)
std::cout << " (" << x.first << "," << x.second << ")";
std::cout << '\n';
}