Enumerating Inherited Properties

["John Passaniti" <jpass@...>]

Here's something that's come up in some code I'm writing.

Let's say I have a table with some interesting data in it:

	Parent = {this=1, that=2}

Now let's use Lua 5.0's nifty "easy inheritance" and create a Child
table that inherits from the Parent:

	Child = {other=3}
	setmetatable(Child, {__index = Parent})

Which lets you do this:

	print(Child.this, Child.that, Child.other)

Giving the expected result:

	1		2		3

Now let's iterate over the keys in Child:

	table.foreach(Child, print)

We get:

	other		3

And that makes sense.  After all, the Child table does really only have
one key in it.  But what if that's not what you want?  What if you want
to iterate through both the real and inherited keys in Child without
regard to if they were in Child or Parent (or a parent of Parent, etc.)?

Does anyone have an elegant way to deal with this?  

(Maybe this suggests a new metamethod?  One way this could work is if
tables had a metamethod related to indexing a table.  Such a metamethod
would have application beyond this message's example.)