code: function nodeCopy(a)
  {
  	var newA = {
  		ctor: '_Array',
  		height: a.height,
  		table: a.table.slice()
  	};
  	if (a.height > 0)
  	{
  		newA.lengths = a.lengths.slice();
  	}
  	return newA;
  }
docs: Copies a node for updating. Note that you should not use this if only updating only one of "table" or "lengths" for performance reasons.