Re: DEFSTRUCT and reclaimable storage

[BAK at MIT-AI (William A. Kornfeld)]

[This msg principally meant for Lisp machine users but may be of
 wider interest.]

There are a number of places in programs that I write in which I create
structures (ART-Q arrays) of specific types copiously and know when I am
finished with them.  As such, it would take a load off the garbage
collector if I could indicate that specific instances could be reused
for structure instances to be created in the future.(*)  The idea would
be that if the structure was defined as:

(DEFSTRUCT (FOO :RECLAIMABLE ...)
	...)

a function of one argument named RECLAIM-FOO would be defined.
(RECLAIM-FOO <structure>) will add <structure> to a linked chain of
structures bound to the variable FOO-FREE-CHAIN.  The linking is
accomplished by having a designated cell of the structure point to the
next instance.  The function MAKE-FOO will be defined to first check if
there is an instance sitting on FOO-FREE-CHAIN and if so use that one
rather than consing a new one.

Any Lispm system hacker interested in implementing this?  (I found
the code for DEFSTRUCT hard to grok.)



*
 I realize that some people have a philosophical objection to doing
this.  I don't want to get into a debate about it.  If you're curious
I'll send you descriptions of the applications I have in mind for which
it would be an extremely useful facility.