#include <iostream>
#include <string>
#include <Windows.h>
using namespace std;

enum mathType
{
	ADD = 0,
	SUB = 1,
	MUL = 2,
	DIV = 3
};

double calculate(mathType op, double num1, double num2);
mathType getSumType();

int main ()
{
	mathType type;
	double num1, num2;

	cout << "x, /, + or - : ";
	type = getSumType();

	cout << "Please enter number 1: ";
	cin  >> num1;
	cout << endl;

	cout << "Please enter number 2: ";
	cin >> num2;
	cout << endl;

	cout << calculate (type, num1, num2) << endl;

	system("PAUSE");
	return 0;

}

mathType getSumType()
{
	char input = NULL;
	mathType type;

	while(input != 'x' && input != '/' && input != '+' && input != '-')
	{
		cin >> input;

		switch(input)
		{
		case 'x':
			type = MUL;
			break;
		case '/':
			type = DIV;
			break;
		case '+':
			type = ADD;
			break;
		case '-':
			type = SUB;
			break;
		default:
			cout << endl << "Invalid command!" << endl;
			break;
		}
	}

	return type;
}

double calculate (mathType op, double num1, double num2)
{
	switch(op)
	{
	case MUL:
		return (num1*num2);
		break;
	case DIV:
		return (num1/num2);
		break;
	case ADD:
		return (num1+num2);
		break;
	case SUB:
		return (num1-num2);
		break;
	default:
		MessageBox(NULL, "Error, invalid type of primitive!", "Error!", NULL);
		return NULL;
		break;
	}
}