#include <iostream>
#include <cmath>
#include <fstream>

#define ERROR_DIV_ZERO   "ERROR: can not be divided by zero.\n"
#define ERROR_CALC_PARAM   "ERROR: parameter was not calculated.\n"
#define ERROR_OPEN_FILE   "ERROR: the file can not be opened.\n"
#define ERROR_CREATE_FILE    "ERROR: the file can not be created.\n"
#define inputfile  "input.txt"
#define outputfile  "output.txt"

using namespace std;

class calculationObject{
    protected:

        double *calculatedParameter;

    public:

        virtual void set() = 0;
        virtual void calcParameter() = 0;
        virtual void get() = 0;
        virtual double getResult() = 0;
};
class Charge : virtual public calculationObject{
    private:

        double q1, q2, eps, r;

    public:

        Charge() : calculationObject(){
            q1 = q2 = eps = r = 0;
            calculatedParameter = NULL;
        }

        Charge(double _q1, double _q2, double _eps, double _r) : calculationObject(), q1(_q1), q2(_q2), eps(_eps), r(_r){}

        Charge(const Charge& x){
            q1 = x.q1;
            q2 = x.q2;
            eps = x.eps;
            r = x.r;
        }
        void set(){
            cout << " please, enter information about charge  " << endl;
            cout << " q1 = ";
            cin >> q1;
            cout << " q2 = ";
            cin >> q2;
            cout << " eps = ";
            cin >> eps;
            cout << " r = ";
            cin >> r;
            cout << endl;
        }
        void get(){
            cout << " information about charge  " << endl;
            cout << " q1 = " << q1 << endl;
            cout << " q2 = " << q2 << endl;
            cout << " eps = " << eps << endl;
            cout << " r = " << r << endl;
            cout << endl;
        }

        void calcParameter(){
            if(r == 0 || eps == 0) {
                cout << ERROR_DIV_ZERO;
                return;
            }
            calculatedParameter = new double;
            *calculatedParameter = (q1 * q2) / (eps * pow(2.,r)) ;
        }
        double getResult(){
            if(calculatedParameter == NULL) {
                cout << ERROR_CALC_PARAM << endl;
                return 0;
            }
            cout << " calculated parameter = " << *calculatedParameter << endl;
            return *calculatedParameter;
        }
        Charge& operator = (const Charge& x){
            q1 = x.q1;
            q2 = x.q2;
            eps = x.eps;
            r = x.r;
            return *this;
        }
    bool operator == (const Charge& x) {return (calculatedParameter == x.calculatedParameter);}
    bool operator != (const Charge& x) {return (calculatedParameter != x.calculatedParameter);}
    bool operator < (const Charge& x) {return (calculatedParameter < x.calculatedParameter);}
    bool operator <= (const Charge& x) {return (calculatedParameter <= x.calculatedParameter);}
    bool operator > (const Charge& x) {return (calculatedParameter > x.calculatedParameter);}
    bool operator >= (const Charge& x) {return (calculatedParameter >= x.calculatedParameter);}

    friend ifstream& operator >> (ifstream&, Charge&);
    friend ofstream& operator << (ofstream&, const Charge&);
    friend istream& operator >> (istream&, Charge&);
    friend ostream& operator << (ostream&, const Charge&);
};
ifstream& operator >> (ifstream& fin, Charge& x) {
        if(!fin.is_open()){
            cout << ERROR_OPEN_FILE;
            return fin;
        }
        fin >> x.q1 >> x.q2 >> x.eps >> x.r;
    return fin;
}
ofstream& operator << (ofstream& fout, const Charge& x) {
        if(!fout.is_open()){
            cout << ERROR_CREATE_FILE;
            return fout;
        }
        fout << " information about charge:  " << endl;
        fout << " q1 = " << x.q1 << endl;
        fout << " q2 = " << x.q2 << endl;
        fout << " eps = " << x.eps << endl;
        fout << " r = " << x.r << endl;
        fout << endl;
    return fout;
}
istream& operator >> (istream& in, Charge& x) {
        cout << " please, enter information about charge " << endl;
        cout << " q1 = ";
        in >> x.q1;
        cout << " q2 = ";
        in >> x.q2;
        cout << " eps = ";
        in >> x.eps;
        cout << " r = ";
        in >> x.r;
        cout << endl;
    return in;
}
ostream& operator << (ostream& out, const Charge& x) {
        out << " information about charge  " << endl;
        out << " q1 = " << x.q1 << endl;
        out << " q2 = " << x.q2 << endl;
        out << " eps = " << x.eps << endl;
        out << " r = " << x.r << endl;
        out << endl;
    return out;
}
int main(){

        Charge x;
        cout << endl << "Default constructor:" << endl;
        cout << x;

        Charge y(5.3, 2, 0.3, 7);
        cout << "Init constructor:" << endl;
        cout << y;

        Charge z = y;
        cout << " Copy constructor " << endl;
        cout << z;

        cout << " Set function " << endl;
        x.set();

        cout << " Get function " << endl;
        x.get();

        x.calcParameter();
        y.calcParameter();
        cout << " Result function " << endl;
        cout << " x ";
        x.getResult();

        cout << endl << endl;
        cout << " y ";
        y.getResult();
        cout << endl;
        cout << " Operator == for x, y returned " << (x == y) << endl << endl;
        cout << " Operator != for x, y returned " << (x != y) << endl << endl;
        cout << " Operator < for x, y returned " << (x < y) << endl << endl;
        cout << " Operator <= for x, y returned " << (x <= y) << endl << endl;
        cout << " Operator > for x, y returned " << (x > y) << endl << endl;
        cout << " Operator >= for x, y returned " << (x >= y) << endl << endl;

        cout << endl;
        cout << " Reading input file" << endl;

        Charge a;
        ifstream fin(inputfile);
        ofstream fout(outputfile);

        fin >> a;
        cout << a;
        fout << a;
        a.calcParameter();
        fout << "calculated parameter = " << a.getResult() << endl;

    return 0;
}