On Friday, Jun 20, 2003, at 18:29 US/Pacific, Tanaka Akira wrote:

> In my view, this problem is "how to generate arbitrary graph
> structure".  Since "- &a [*a, *a]" denotes cyclic structure, it is
> clearly not possible to generate it in bottom-up or top-down.  Some
> destructive update is required.

This exact discussion is going on in the little languages mailing list. 
Guy Steele and others are talking about self referencing s-exprs. 
Apparently scheme has had this ability for some time. eg:

	#1=(a . #1#)

creates a list with 'a' and a reference back to the list. #1 is a 
marker, and #1# refers to it. Given that the implementation of scheme 
is so tiny, maybe it would be worthwhile to go sniff through a scheme 
implementation and see what they do.