public String infix()
	{
		if(child.size() > 0)
		{
			if(!isFunc)
			{
				String str = "";
				if(data.equals("-"))
					str = "-";
				for(int i =0; i<child.size()-1; i++)
				{
					if(child.get(i).child.size() > 0)
						str+="("+child.get(i).infix()+")"+data;
					else
						str+=child.get(i).infix()+data;
				}
				if(child.get(child.size()-1).child.size() > 0)
					str+="("+child.get(child.size()-1).infix()+")";
				else
					str+=child.get(child.size()-1).infix();
				return str;
			}
			else
			{
				String str = data+":(";
				for(int i= 0; i<child.size();i++)
				{
					str += child.get(i).infix();
					if(i<child.size()-1)
						str += ',';
				}
				str += ')';
				return str;
			}
		}
		else
			return data;
	}