code: DevAttrHistory[] get_attr_history(int nb, int type)
  	{
  		DevAttrHistory[]	histo = new DevAttrHistory[nb];
  		int	start = size() - nb;
  		for(int i=start ; i<size() ; i++)
  		{
  			RingElt	record = (RingElt)elementAt(i);
  			boolean attr_failed;
  			AttributeValue value;
  			DevError[] errors;
  			value  = record.attr_value;
  			if (record.except==null)
  			{
  				attr_failed = false;
  				errors = new DevError[0];
  			}
  			else
  			{
  				attr_failed = true;
  				errors = record.except.errors;
  			}
  			histo[i-start] = new DevAttrHistory(attr_failed, value, errors);
  		}
  		return histo;
  	}
docs: ==========================================================================