Accessing table entries with iterators

["Henderson, Michael D" <michael.d.henderson@...>]

The PIL says, "With proper iterators, we can traverse almost anything,
and do it in a readable fashion." I guess that I'm just not
understanding iterators.

If I have an entry like the following

entry = { timestamp = "2006/01/16 132155"
        , { "cpu" , 42.3  }
        , { "fan" , 5823  }
        , { "aaa" , "bbb" }
        };

How would I iterate through the table to print out something like the
following?

	timestamp is '2006/01/16 132155'
	resource #1
		type is 'cpu'
		value is (number) 42.3
	resource #2
		type is 'fan'
		value is (integer) 5823
	resource #3
		type is 'aaa'
		value is (string) 'bbb'

If I use pairs(entry), I don't get the resources in the order that they
were created.
	1
	2
	3
	timestamp

I can get pretty close by using the iterator from PIL 7.1:

	function list_iter (t)
	  local i = 0
	  local n = table.getn(t)
	  return function ()
	           i = i + 1
	           if i <= n then return t[i] end
	         end
	end

	if entry.timestamp then
		print(entry.timestamp)
	end
	for k in list_iter(entry) do
		print(k)
		for kk in pairs(k) do
			print("\t" .. kk)
			print("\t\t" .. k[kk])
		end
	end

	2006/01/16 132155
	table: 42f10
	        1
	                cpu
	        2
	                42.3
	table: 47f20
	        1
	                fan
	        2
	                5823
	table: 47f70
	        1
	                aaa
	        2
	                bbb

That's nice, but I want an iterator that throws an error if the
timestamp is missing or the values are missing. And I want to return the
two entries as two entries, not as a table. Would I do that by adding a
check prior to the return t[i] to verify that table.getn(t[i]) is 2? If
so, can I then just return t[i][1], t[i][2]? I guess that if I did that,
it would look like.

	function tbl_iter (t)
	  if not t.timestamp then
	    error("missing timestamp")
	  end;
	  local i = 0
	  local n = table.getn(t)
	  return function ()
           i = i + 1
           if i <= n then
             if table.getn(t[i]) == 2 then
               return t[i][1] , t[i][2]
             else
               error("missing entries")
             end
           end
         end
	end

	if entry.timestamp then
		print(entry.timestamp)
	end

	for k1, k2 in tbl_iter(entry) do
		print("type is " .. k1 .. " value is " .. k2 )
	done

	2006/01/16 132155
	type cpu value 42.3
	type fan value 5823
	type aaa value bbb

That seems to solve my problem. Man, this list is great!

Which leads me to another question. Is there a better way to write this?
This will run only a couple of hundred times a day and always against a
small table (maybe 30 entries), so performance isn't an issue, but I'd
like to make sure that I'm really understanding the right way to do
iterators.

Thanks,
Mike Henderson