//============================================================================
// Name        : Calculator Program
// Author      : Phuc Peter Hoang
//				 RedID: 821516560
// Data		   : 9/15/2019
// Version     :
// Copyright   : Your copyright notice
// Description : Calculator Program with Anonymous Variables. A simple calculator program that repeatedly allows the user
//				 to select +,-,*,/ from a menu of operations on real values and then enter the two operands which then
//				 computes the result of applying the selected operation to those operands.
//============================================================================

#include <iostream>
#include <limits>
using namespace std;

int add (int *a, int *b);      //addition function prototype
int subtract (int *c, int *d); //subtraction function prototype
int multiply (int *e, int *f); //multiplication function prototype
int divide (int *g, int *h);   //division function prototype
int mod (int *x, int *y);      //module function prototype

int main() {

	    char *op = new (nothrow) char;  	  //anonymous variable operand user enter
	    char *choice = new (nothrow) char;    //anonymous variable ask user if they want to continue
	    int *num1 = new (nothrow) int;        //anonymous variable first number user enter
		int *num2 = new (nothrow )int;        //anonymous variable second number user enter
do
{

	    cout << "\nWelcome to the Calculator Program!\n";
	    cout << "\nEnter the first number:";
	    cin >> *num1;  						  //input first number

		while (cin.fail())                    //validating user input if they don't enter an integer number
		{
				cout <<"Error! Please enter an integer value:" <<endl;
				cin.clear();                  //clear the user's error input
				while (cin.get() != '\n');    //ignore the rest of the line after the first instance of user's error
				cin >> *num1;                 //letting user input a true input
		}
	    cout << "\nPlease enter the second number:";
	    cin >> *num2;

	    while (cin.fail())
	    {
	    		cout <<"Error! Please enter an integer value:" <<endl;
	    		cin.clear();			  	  //clear the user's error input
	   			while (cin.get() != '\n');    //ignore the rest of the line after the first instance of user's error
	 			cin >> *num2;         		  //letting user input a true input
	    }
	    cout << "\nPlease enter the operator you like to perform\n (+, -, *, /): ";
	    cin >> *op;							  //input operand

	    while (*op != '+' && *op != '-' && *op != '*' && *op != '/')
	    {
	    	cout <<"Error! Please enter the four operators: +, -, *, /"<< endl;
	    	cin.clear(); 					  //clear the user's error input
	    	while (cin.get () != '\n'); 	  //ignore the rest of the line after the first instance of user's error
	    	cin >> *op; 					  //letting user input a true input
	    }

	    	if (*op == '+')                   //addition condition
	    		cout << " " << *num1 << " + " << *num2 << " = " << add (num1, num2) << endl;
	    	else if (*op == '-')			  //subtraction condition
	    		cout << " " << *num1 << " - " << *num2 << " = " << subtract (num1, num2) << endl;
	    	else if (*op == '*')		      //multiplication condition
	    		cout << " " << *num1 << " * " << *num2 << " = " << multiply (num1, num2) << endl;
	    	else
	    	{
	    goback:		if (*num2 == 0)           //if user input a zero when dividing
	    		{
	    			cout <<"Error! Cannot divide by zero. Please enter a different integer." << endl;
	    			cin.clear ();             //clear the user's error input
	    			while (cin.get() != '\n');  //ignore the rest of the line after the first instance of user's error
	    			cin >> *num2;             //let user input a non-zero integer value
	    			goto goback;			  //jumping back to the goback variable so the user can input second number
	    		}
	    		cout << " " << *num1 << " / " << *num2 << " = " << divide (num1, num2) << endl << " Remainder = " << mod (num1, num2) << endl;
	    	}

	    	cout <<"\nDo you want to continue? ('y' to continue | 'n' to exit)\n";
	    	cin >> *choice;                   //user input options of continuing the program or exiting it
}
		while  (*choice == 'y');                      //condition to rerun the program
		cout <<"\nEnding Program...";

}
int add (int *a, int *b)					  //addition function
{
	int total = 0;
	total = *a + *b;
	return (total);
}

int subtract (int *c, int *d)  				 //subtraction function
{
	int total = 0;
	total = *c - *d;
	return (total);
}

int multiply (int *e, int *f)  				 //multiplication function
{
	int total = 0;
	total = *e * *f;
	return (total);
}

int divide (int *g, int *h) 				 //division function
{
	int total = 0;
	total = *g / *h;
	return (total);

}

int mod (int *x, int *y) 					  //remainder function
{
	int total = 0;
	total = *x % *y;
	return (total);

}