#pragma once

#include "myStack.h"


class calculator
{
private:
	double value;
	stack history;

public:
	calculator()
	{
		value = 0;
	}

	void add(double x)
	{
		history.push(value);
		value = value + x;
	}

	void undo()
	{
		value = history.pop();
	}

	double display()
	{
		return value;
	}

};