Issue: HASH-TABLE-GC (no proposal)

[gz@spt.entity.com (Gail Zacharias)]

   Date: Mon, 17 Oct 88 20:19:26 PDT
   From: Jon L White <jonl@lucid.com>

   Anyone else know of other "actual needs"?

We've implemented "weak" sets (populations?); the motivating "actual need" was
keeping track of buffer marks in the editor.  There are other uses, mostly of
the same form (i.e.  keep track of sets of objects which need to be updated
and kept in synch with some other data structure, provided they are otherwise
accessible).  We don't have any actual uses for weak hash tables so far, but
are considering using them for maintaining some auxillary debugging info.

None of this has been released to users yet, though we will almost certainly
have some form of user-accessible weak data structures (at least weak sets,
possibly weak hash tables) in a future release.  I think this is one of those
cases where a typical user might not even realize that such objects are
possible and just naturally structure his algorithms (possibly non-optimally)
in such a way as to not need them.  So in a way asking for "actual need"
before they are available is not entirely fair...