Re: hash tables and GC

[Jeff Dalton <jeff%aiai.edinburgh.ac.uk@NSS.Cs.Ucl.AC.UK>]

> Specifically, I was thinking it would be nice to be
> able to attach a property list to arbitrary objects, and not just to
> symbols.  (Two objects that are EQ would have the same property list.)
> 
> As far as what it would allow you to do, this functionality is actually
> pretty close to what is being proposed with the GC'able hash tables, and
> I think it has some advantages. First, it would allow more freedom of
> implementation; off the top of my head, I can think of at least two
> approaches to doing it.  And, it avoids some of the strangenesses that
> would result from forcing GC'able hash tables into the same mold as
> ordinary hash tables (like not allowing EQUAL as the :TEST, and MAPHASH
> finding different sets of objects in the hash table depending on when
> the last GC was).

As you may recall, my original message took the idea from "temporary
properties" in Pop11.  So, the notion of "property" is OK with me.  But,
I'm not so happy with property *list*, which implies (1) linear search,
(2) the existence of an actual list, and (3) a format for the list (an
alternating sequence of property names and property values).

-- Jeff