Calculator

#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <sstream>
#include <string>
#include <cmath>
#include <vector>
#include <exception>
#include <ctime>
#include <ctype.h>

using std::cout;
using std::cin;
using std::endl;
using std::string;
using std::vector;
using std::stringstream;

void DrawLine (string Str, int Len = 80)
{
    int x = 0;
    cout << endl;
    for (int i = 0; i < Len;i++)
    {
        cout << Str[x];
        if (x == Str.size())
            x = 0;
    }
    if (Len != 80)
        cout << endl;
}

class Calculator
{
private:
    long double Num1;
    long double Num2;
public:
    void SetVal(int, int);

    long double Add ();
    long double Subtract();
    long double Multiply();
    long double Divide();
    int Mod();
    long double Expon();
}
calculator,
*Calc;

void Calculator::SetVal(int a, int b)
{
    Num1 = a;
    Num2 = b;
}

long double Calculator::Add()
{
    return Num1 + Num2;
}

long double Calculator::Subtract()
{
    return Num1-Num2;
}

long double Calculator::Multiply()
{
    return Num1*Num2;
}

long double Calculator::Divide ()
{
    return Num1/Num2;
}

int Calculator::Mod()
{
    return ((int(Num1))%(int(Num2)));
}

long double Calculator::Expon()
{
    long double X = 1;
    if (Num2 > 0)
    {
        for (int i = 0; i < int(Num2); i++)
        {
            X *= Num1;
        }
    return X;
    }

    else if (Num2 == 0)
        return 1;
    else if (Num2 < 0)
    {
        Num2 *= (-1);
        for (int i = 0; i < int(Num2); i++)
        {
            X *= Num1;
        }
    return (1/X);
    }
}

int main ()
{
    stringstream Ent1, Ent2, Oper, Sign1, Sign2;
    bool Check1 = true;
    bool Check2 = false;
    string Action;
    int x, y;
    string a , b;

    Calc =  &calculator;
    cout << "This calculator can calclulate a couple of thing that listed are in the Table shown below.";
    cout << "To tell the computer wha to calculate simply write the Expression.\n";
    cout << "NOTE: 1. Only one operator & two Numbers are allowed in the expression.\n";
    cout << "2. No variables are allowed.\n\n";
    cout << "3.The Sign of a number should only appear once.[i.e. No 1+ (---+1)]";

    cout << "\t--------------------------------------------------------------\n";
    cout << "\t|   Symbol       |       Operator             |" << endl;
    cout << "\t|-----------------------|------------------------------------|\n";
    cout << "\t|   +            |       Addition             |" << endl;
    cout << "\t|-----------------------|------------------------------------|\n";
    cout << "\t|   -            |       Subtraction          |" << endl;
    cout << "\t|-----------------------|------------------------------------|\n";
    cout << "\t|   *            |       Multiplication       |" << endl;
    cout << "\t|-----------------------|------------------------------------|\n";
    cout << "\t|   /            |       Divide               |" << endl;
    cout << "\t|-----------------------|------------------------------------|\n";
    cout << "\t|   %            |       Modulus*             |" << endl;
    cout << "\t|-----------------------|------------------------------------|\n";
    cout << "\t|   ^            |       Exponent             |" << endl;
    cout << "\t--------------------------------------------------------------\n";

    cout << endl << "* Modulus gives the remainder of a number divided by another.\n";
    bool LOOP = true;

    while (LOOP)
    {
        Check1 = true;
        Check2 = false;

        cout << endl << "What do you want to calculate:  ";
        getline (cin, Action);

        for (int i = 0; i < Action.size(); i++)
        {
            int Ax;

            if (Action[0] == '-')
                {
                    Sign1 << '-';
                }
            if (isdigit(Action[i]) && Check1)
            {
                Ent1 << Action[i];
            }

            if (!isalnum(Action[i]) && Check1 && i != 0)
            {
                Oper << Action[i];
                Check1 = false;
                Check2 = true;
                Ax = i;
                if (Action[Ax+1] == '-')
                {
                    Sign2 << '-';
                }
            }


            if (isdigit(Action[i]) && Check2)
            {
                Ent2 << Action[i];
            }
        }

        a = Ent1.str();
        b = Ent2.str();

        x = atoi(a.c_str());
        y = atoi(b.c_str());

        if (Sign1.str() == "-")
        {
            x = 0-x;
        }

        if (Sign2.str() == "-")
        {
            y = 0-y;
        }

        Calc -> SetVal(x,y);

        if (Oper.str() == "+")
        {
            cout << Calc -> Add();
        }

        else if (Oper.str() == "-")
        {
            cout << Calc -> Subtract();
        }

        else if (Oper.str() == "*")
        {
            cout << Calc -> Multiply();
        }

        else if (Oper.str() == "/")
        {
            cout << Calc -> Divide();
        }

        else if (Oper.str() == "%")
        {
            cout << Calc -> Mod();
        }

        else if (Oper.str() == "^")
        {
            cout << Calc -> Expon();
        }

        char x;
        cout << "\nDo you want to perform another calculation? [N -> Exit, Anything Else -> Restart]:  ";
        cin >> x;
        cin.sync();

        if (x == 'n' || x == 'N')
            LOOP = false;

        DrawLine ("_");
        Ent1.str("");
        Ent2.str("");
        Oper.str("");
        Sign1.str("");
        Sign2.str("");
    }

        ;cout << "\n\nPress Enter to exit . . .";
        cin.sync();
        cin.get();
        return 0;
}