std::swap (非メンバ関数)(C++11)

namespace std {
  template <class T, class Allocator>
  void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y);
}

#include <iostream>
#include <forward_list>
#include <string>
#include <algorithm> // std::for_each

template <class T>
void print(const std::string& name, const std::forward_list<T>& ls)
{
  std::cout << name << " : {";
  std::for_each(ls.begin(), ls.end(), [](const T& x) { std::cout << x << " "; });
  std::cout << "}" << std::endl;
}

int main()
{
  std::forward_list<int> ls1 = {4, 5, 6};
  std::forward_list<int> ls2 = {1, 2, 3};

  std::swap(ls1, ls2);

  print("ls1", ls1);
  print("ls2", ls2);
}