public void delete (int i, int j)
	// delete the stone and note it
	{
		if (P.color(i, j) == 0) return;
		synchronized (Pos)
		{
			Node n = Pos.node();
			if (GF.getParameter("puresgf", true)
				&& (n.contains("B") || n.contains("W"))) n = newnode();
			String field = Field.string(i, j);
			if (n.contains("AB", field))
			{
				undonode();
				n.toggleaction(new Action("AB", field));
				setnode();
			}
			else if (n.contains("AW", field))
			{
				undonode();
				n.toggleaction(new Action("AW", field));
				setnode();
			}
			else if (n.contains("B", field))
			{
				undonode();
				n.toggleaction(new Action("B", field));
				setnode();
			}
			else if (n.contains("W", field))
			{
				undonode();
				n.toggleaction(new Action("W", field));
				setnode();
			}
			else
			{
				Action a = new Action("AE", field);
				n.expandaction(a);
				n.addchange(new Change(i, j, P.color(i, j)));
				P.color(i, j, 0);
				update(i, j);
			}
			showinformation();
			copy();
		}
	}