#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>

using namespace std;

class String
{
  friend ostream& operator << (ostream &out, String str);
  friend String operator + (String str1, string str2);
  friend string classToString(String str);
  friend String stringToClass(string str);
  friend bool operator == (String str1, string str2);
  friend bool operator != (String str1, string str2);
public:
    String(string defValue)
    {
        value = defValue;
    }
    String ()
    {

    }
    void setValue()
    {
        cout << "enter new value: " << endl;
        string newVal;
        cin >> newVal;
        cin.clear();
        cin.ignore(1000, '\n');
        this -> value = newVal;
    }
    void display()
    {
        cout << value << endl;
    }
    String operator = (String str2)
    {
      this -> value = str2.value;
      return *this;
    }
    char operator [](int i)
    {
      return (this -> value)[i];
    }
    String operator () (string newVal)
    {
      return this -> value = newVal;
    }
    String operator + (String str)
    {
      return this -> value + str.value;
    }
    bool operator == (String str)
    {
      return this -> value == str.value;
    }

    bool operator != (String str)
    {
      return this -> value != str.value;
    }

private:
    string value;

};

ostream& operator << (ostream &out, String str)
{
    out << str.value;
    return out;
}

String operator + (String str1, string str2)
{
    return str1.value + str2;
}

bool operator == (String str1, string str2)
{
  return str1.value == str2;
}

bool operator != (String str1, string str2)
{
  return str1.value != str2;
}

string classToString(String str)
{
    string res;
    res = str.value;
    return res;
}

String stringToClass(string str)
{
    String res("0");
    res.value = str;
    return res;
}

void compare(String str1, String str2)
{
    str1.setValue();
    str2.setValue();
    bool x = str1 == str2;
    if(x) cout << "strings are equal" << endl;
    else cout << "strings are different" << endl;
}

void compare1(String str1)
{
    str1.setValue();
    string temp;
    cout << "enter string to compare: " << endl;
    cin >> temp;
    cin.clear();
    cin.ignore(1000, '\n');
    bool x = str1 == temp;
    if(x) cout << "strings are equal" << endl;
    else cout << "strings are different" << endl;
}

int main()
{
    String str1;
    String str2;
    str1.setValue();
    str2.setValue();
    str1 = str2;
    cout << "the result of operation str1 = str2 is: " << endl;
    str1.display();
    int id;
    do
    {
      cout << "enter index: " << endl;
      cin >> id;
      cin.clear();
      cin.ignore(1000, '\n');
      if(id >= 0) break;
      else cout << "the index must be above 0" << endl;
    }while(true);
    cout << "the " << id << " simbol of a str1 is " << str1[id] << endl;
    string temp;
    cout << "enter new string: " << endl;
    cin >> temp;
    cin.clear();
    cin.ignore(1000, '\n');
    str2(temp);
    cout << "the result of operation () is: str2 = " << endl;
    str2.display();
    cout << "the result of operation str1 + str2 is " << str1 + str2 << endl;
    compare(str1, str2);
    cout << "enter string for addition: " << endl;
    cin >> temp;
    cin.clear();
    cin.ignore(1000, '\n');
    cout << "the result of addition string + String is ";
    (str1 + temp).display();
    compare1(str1);
    cout << "the result of << for str2 is: ";
    cout << str2 << endl;
    cout << "enter string for convertion to String: " << endl;
    cin >> temp;
    cin.clear();
    cin.ignore(1000, '\n');
    str1 = stringToClass(temp);
    str1.display();
    cout << "enter String for convertion to string: " << endl;
    str1.setValue();
    temp = classToString(str1);
    cout << temp;
    return 0;
}