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From: Vassilis Radis <rad...@gmail.com>
Newsgroups: comp.lang.lisp
Subject: Customization of evaluation for a specific custom type of object
Date: Thu, 2 Jun 2011 04:57:34 -0700 (PDT)
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I want to implement a kind of reference system like this:
Suppose that I have:

(defclass reference () ((host) (port) (file)))

and also I have:

(defun fetch-remote-value (reference) ...) which fetches and deserializes a=
 lisp object.

How could I intervene in the evaluation process so as whenever a reference =
object is being evaluated, the remote value gets fetched and re-evaluated a=
gain to produce the final result?

A more elaborate description of what I want to accomplish:

Using cl-store I serialize lisp objects and send them to a remote file(or d=
b or anything) to be saved. Upon successful storage I keep the host,port an=
d file in a reference object. I would like, whenever eval gets called on a =
reference object, to first retrieve the object, and then call eval on the r=
etrieved value. Since a reference can be also serialized in other (parent) =
objects or aggregate types, I can get free on-demand recursive remote refer=
ence resolution by modyfing eval so i dont have to traverse and resolve the=
 loaded object's child references myself which I suppose is a real PITA. An=
d Of course there is the option of whether , after resolution,  we should r=
eplace the value or not, thus having to resolve it once or every time respe=
ctively, but if we made it an option in the reference, it would be sweeet.