c++11 - C++ standard library forward_list issue -

i need solving exercise 9.28 c++ primer 5th edition. here task:

write function takes forward_list , 2 additional string arguments. function should find first string , insert second following first. if first string not found, insert second string @ end of list.

i can't idea written in book how forward_list works , why indeed need it, i'm asking help. below code wrote incomplete , need me finish it:

#include <iostream> #include <forward_list>  using namespace std;  void find_and_insert(forward_list<string>& flstr, const string& needle, const string& rplc) {      auto curr = flstr.begin();     auto last = flstr.end();     bool found = false;      while (curr != last) {          if (*curr == needle) {              found = true;             // put here?!             break;         }          // put here?!...          ++curr;     }      (const auto& elem : flstr) {          cout << elem << endl;     }      return; }  int main(int argc, char *argv[]) {      cout << endl;      forward_list<string> flstring = {"foo", "bar", "baz", "tomcat"};      find_and_insert(flstring, "bar", "insertion");      cout << endl;      return exit_success; } 

any suggestion refactor code welcome!

you can write function following way using member function before_begin

#include <iostream> #include <forward_list> #include <string>  void find_and_insert( std::forward_list<std::string> &lst,                        const std::string &src,                        const std::string &dest )  {     auto before = lst.before_begin();     auto first  = lst.begin();      while ( first != lst.end() && *first != src ) ++before, ++first;      lst.insert_after( first == lst.end() ? before : first, dest ); }  int main() {     std::forward_list<std::string> lst;      find_and_insert( lst, "one", "zero" );      ( const std::string &s : lst ) std::cout << s << ' ';     std::cout << std::endl;      find_and_insert( lst, "zero", "two");      ( const std::string &s : lst ) std::cout << s << ' ';     std::cout << std::endl;      find_and_insert( lst, "zero", "one");      ( const std::string &s : lst ) std::cout << s << ' ';     std::cout << std::endl;      find_and_insert( lst, "two", "three");      ( const std::string &s : lst ) std::cout << s << ' ';     std::cout << std::endl;      find_and_insert( lst, "four", "four");      ( const std::string &s : lst ) std::cout << s << ' ';     std::cout << std::endl; }     

the program output is

zero  0 2  0 1 2  0 1 2 3  0 1 2 3 4