Taylor R Campbell wrote:
>    Date: Fri, 18 Sep 2009 08:21:51 -0400
>    From: David Van Horn <xxxxxx@cs.brandeis.edu>
>
>    In short, the space consumption has at worst a logarithmic overhead
>    compared to a plain ol' list.  Right?  I'm still not sure I'm answering
>    the question you're asking.
>
> Yes, you've answered my question.  I'm a little concerned now, though,
> that the representation you've chosen will cause problems if, for
> whatever reason, one tries to store a node as an element of a
> random-access list.  For example, suppose one has written a debugger
> that uses random-access lists, and one is trying to use that debugger
> to debug a routine internal to the random-access list library which
> has nodes as the values of local variables, which get stored in the
> debugger's random-access lists.  Code of the form (if (node? t) ... (f
> t)) makes me nervous.  But I still haven't read the implementation
> thoroughly; maybe this isn't an issue.

There would be problems if you stored a node as a leaf element of a
tree, that's correct.  But the node record type is not accessible
outside of the library implementation, so I'm not worried.  An
implementation that exposed the node type would be taking matters into
its own hands, but this is just the general problem of destroying
abstraction barriers.  I don't think it's worth coding defensively in
this case.

David