public class mathNode
{
	mathNode left, right, parent;
	String op;
	public mathNode(String Operator)
	{
		op = Operator;
		left = null;
		right = null;
		parent = null;
	}
	public mathNode insertUp(mathNode newParent, mathNode tree)
	{
		if (parent != null)
		{
			if (parent.left == this)
			{
				parent.left = newParent;
			}
			else if (parent.right == this)
			{
				parent.right = newParent;
			}
		}
		newParent.left = this;
		newParent.parent = this.parent;
		this.parent = newParent;
		if (tree == this)
			return newParent;
		return tree;
	}
	public float eval()
	{
		if (op.equals("+"))
		{
			return (left.eval() + right.eval());
		}
		else if (op.equals("-"))
		{
			return (left.eval() - right.eval());
		}
		else if (op.equals("x"))
		{
			System.out.println(left.op+":"+op);
			System.out.println(op+":"+right.op);
			return (left.eval() * right.eval());
		}
		else if (op.equals("/"))
		{
			return (left.eval() / right.eval());
		}
		else
		{
			try
			{
//				System.out.println(op);
				return (Float.parseFloat(op));
			} catch (NumberFormatException e)
			{
				System.out.println("I don't understand this number: " + op+",\nso I can't parse this expression.");
				System.exit(0);
				return 0f;
			}
		}
	}
}