Operand::pointer_type RPNEvaluator::evaluate(TokenList const& rpnExpression) {
	Operand::pointer_type result;

	stack <Operand::pointer_type> operand_stack;

	if (rpnExpression.empty())
		throw exception("Error: insufficient operands");

	for (auto x : rpnExpression)
	{
		if (is<Operand>(x))
		{

			operand_stack.push(convert<Operand>(x));


		}
		else
		{

			auto opera = convert<Operation>(x);
			if (dynamic_pointer_cast<Operation>(x)->number_of_args() > operand_stack.size())
			{
				throw exception("Insufficient # operands for operation");
			}

			OperandList opList;
			unsigned size = opera->number_of_args();

			while (size != 0)
{
				opList.push_front(operand_stack.top());
				operand_stack.pop();
				--size;
			}
			//operand_stack.push(convert<Operand>(x));

			if (is<UnaryOperator>(opera))
			{
				if (is<Negation>(opera))
				{
					if (opList.size() == 1) {
						if (is<Integer>(opList[0])) {
							if (is<Integer>(opList[0])) {
								Integer::value_type temp = (dynamic_pointer_cast<Integer>(opList[0])->get_value()) * -1;
								operand_stack.push(dynamic_pointer_cast<Operand>(make<Integer>(temp)));
							}
						}
						else if (is<Real>(opList[0])) {
							Real::value_type temp = dynamic_pointer_cast<Real>(opList[0])->get_value() * -1;
							operand_stack.push(dynamic_pointer_cast<Operand>(make<Real>(temp)));
						}
					}
					else
					{
						throw invalid_argument("Operands Not Valid For Operation");
						operand_stack.push(dynamic_pointer_cast<Operand>(make<Integer>(0)));
					}
				}

				if (is<Identity>(opera))
				{
					if (opList.size() == 1)
					{
						Integer::value_type temp = dynamic_pointer_cast<Integer>(opList[0])->get_value();
						operand_stack.push(dynamic_pointer_cast<Operand>(make<Integer>(temp)));
					}


				}
				if (is<Factorial>(opera))
				{

					Integer::value_type temp = dynamic_pointer_cast<Integer>(opList[0])->get_value();
					temp = factorial(temp);
					operand_stack.push(dynamic_pointer_cast<Operand>(make<Integer>(temp)));
				}


			}


		}

	}



	if (operand_stack.size() > 1)
		throw exception("Error: too many operands");
	if (operand_stack.empty())
		throw exception("Too many operations for the number of operands");

	result = operand_stack.top();


	operand_stack.pop();


	//result = rpnExpression;

	return result; // replace this with the result.




}