I have this error: variable std::stringstream ss has initializer but incomplete type stringstream ss(line); ^ I do not undetstand what I did wrong I appreciate Thank you in advance! And This is my code I have wrote: #include <iostream> #include <fstream> #include <vector> #include <algorithm> using namespace std; struct User { string ID; string First_Name; string Last_Name; string IP_Address; }; void read_users(vector<User>& users) { ifstream input_file("Users.csv"); string line; while (getline(input_file, line)) { User user; stringstream ss(line); getline(ss, user.ID, ','); getline(ss, user.First_Name, ','); getline(ss, user.Last_Name, ','); getline(ss, user.IP_Address, ','); users.push_back(user); } input_file.close(); } void write_users(const vector<User>& users) { ofstream output_file("sorted_users.csv"); for (const auto& user : users) { output_file << user.ID << ',' << user.First_Name << ',' << user.Last_Name << ',' << user.IP_Address << endl; } output_file.close(); } void bubble_sort(vector<User>& users) { int n = users.size(); for (int x = 0; x < n - 1; x++) { for (int y = 0; y < n - x - 1; y++) { if (users[y].Last_Name > users[y + 1].Last_Name) { swap(users[y], users[y + 1]); } } } } int main() { vector<User> users; read_users(users); bubble_sort(users); write_users(users); return 0; }.

1. I have this error: variable std::stringstream ss has initializer but incomplete type stringstream
ss(line);
^
I do not undetstand what I did wrong I appreciate Thank you in advance!
And This is my code I have wrote:
#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
using namespace std;
struct User {
string ID;
string First_Name;
string Last_Name;
string IP_Address;
};
void read_users(vector<User>& users) {
ifstream input_file("Users.csv");
string line;
while (getline(input_file, line)) {
User user;
stringstream ss(line);
getline(ss, user.ID, ',');
getline(ss, user.First_Name, ',');
getline(ss, user.Last_Name, ',');
getline(ss, user.IP_Address, ',');
users.push_back(user);
}
input_file.close();
}
void write_users(const vector<User>& users) {
ofstream output_file("sorted_users.csv");
for (const auto& user : users) {
output_file << user.ID << ',' << user.First_Name << ',' <<
user.Last_Name << ',' << user.IP_Address << endl;
}

2. output_file.close();
}
void bubble_sort(vector<User>& users) {
int n = users.size();
for (int x = 0; x < n - 1; x++) {
for (int y = 0; y < n - x - 1; y++) {
if (users[y].Last_Name > users[y + 1].Last_Name) {
swap(users[y], users[y + 1]);
}
}
}
}
int main() {
vector<User> users;
read_users(users);
bubble_sort(users);
write_users(users);
return 0;
}