Не работают функции

#include "pch.h"
#include <iostream>
#include <algorithm>
#include <ctime>
#include <cstdlib>
#include <string>
#include <vector>
 
using namespace std;
 
const int MAX_WRONG = 8;
vector<string> words = {"VECTOR","STRING","WORDS"};
const string THE_WORD = words[0];
int wrong = 0;
string soFar(THE_WORD.size(), '-');
string used = " ";
char guess;
 
void enter_guess()
{
    while (used.find(guess) != string::npos)
    {
        cout << "You entered this letter already\n";
        cin >> guess;
        guess = toupper(guess);
    }
}
void check_guess_true()
{
    cout << "That's right! " << guess << " is in the word\n";
    for (int i = 0; i < THE_WORD.length(); ++i)
    {
        if (THE_WORD[i] == guess)
        {
            soFar[i] = guess;
        }
    }
}
inline void check_guess_false()
{
    cout << "Sorry, " << guess << " isn't in the word\n";
    ++wrong;
}
 
int main()
{
    srand(static_cast<unsigned int>(time(0)));
    random_shuffle(words.begin(), words.end());
    cout << "Welcome to Hangman,good luck\n";
 
 
    while ((wrong < MAX_WRONG) && (soFar != THE_WORD))
    {
        cin >> guess;
        enter_guess();
        if (THE_WORD.find(guess) != string::npos)
        {
            check_guess_true();
        }
        else
        {
            check_guess_false();
        }
    }
 
    if (wrong == MAX_WRONG)
    {
        cout << "\nYou've been hanged";
    }
    else
    {
        cout << "\nYou guessed it";
    }
    cout << "\nThe word was " << THE_WORD << endl;
}