no operator "<<" matches these operands [duplicate]

Question

No idea what's going on. I looked at other posts that are similar to this issue but no solution helped so far. Here's the code with comments by the parts giving errors. At one point it says that != doesn't work and in the rest of the code it's saying that << isn't working.

#include <iostream>
#include <algorithm>
#include <vector>
#include <ctime>
#include <cstdlib>
#include <cctype>

using namespace std;
//Hangman

int main()
{
    //setup
    vector<string> words;
    words.push_back("GUITAR");
    words.push_back("VIRGINIA");
    words.push_back("LAPTOP");
    words.push_back("WIFEY");
    words.push_back("IPHONE");

    srand(static_cast<unsigned int>(time(0)));   //randomly select a word
    random_shuffle(words.begin(), words.end());
    const string THE_WORD = words[0];
    const int MAX_WRONG = 8;                    //initialize wrong guesses
    int wrong = 0;
    string soFar(THE_WORD.size(), '-');         //initalize the word so far with dashes
    string used = " ";                          //initalize letters used


    cout << "Welcome to Hangman. Good luck!/n";

    //game loop
    //continues until a player guesses the word or gets too many wrong guesses
    while ((wrong < MAX_WRONG) && (soFar != THE_WORD)) //ERROR on the "!="
    {
        cout << "\n\nYou have " << (MAX_WRONG - wrong) << " incorrect guesses left.\n";
        cout << "\nYou've used the following letters:\n" << used << endl; //ERROR on "<<" between the string and used
        cout << "\nSo far, the word is:\n" << soFar << endl; //ERROR on "<<" between the string and soFar

    //recieve the player's guess
        char guess;
        cout << "\n\nEnter your guess: ";
        cin >> guess;
        guess = toupper(guess); //makes the guess uppercase since the secret word is uppercase
        while (used.find(guess) != string::npos)
        {
            cout << "\nYou've already guessed " << guess << endl;
            cout << "Enter your guess: ";
            cin >> guess;
            guess = toupper(guess);
        }

        used += guess;

        if (THE_WORD.find(guess) != string::npos)
        {
            cout << "That's right! " << guess << " is in the word.\n";

            //updated soFar to include newly guessed letter
            for (int i=0; i < THE_WORD.length(); ++i)
            {
                if (THE_WORD[i] == guess)
                {
                    soFar[i] = guess;
                }
            }
        }
        else
        {
            cout << "Sorry, " << guess << " isn't in the word.\n";
            ++wrong;
        }
    }
    //shut down
    if (wrong == MAX_WRONG)
    {
        cout << "\nYou've been hanged!";
    }
    else
    {
        cout << "\nYou guessed it!";
    }

    cout << "\nThe word was " << THE_WORD << endl; //ERROR on "<<" between the string and THE_WORD


    int pause;
    cin >> pause; //this is here just so my compiler will stay open so I can see what's going on
    return 0;
}

Answer 1

If you want to use std::string reliably, you must #include <string>.