Re: Finding CLOS instances - Naggum cll archive

Subject: Re: Finding CLOS instances
From: Erik Naggum <erik@naggum.no>
Date: 1998/10/09
Newsgroups: comp.lang.lisp
Message-ID: <3116943851349974@naggum.no>

* "Bob Manjoney" <rjmct@acm.org>
| 1)  How does one find instances of a particular CLOS class for inspection?
| I'm coming from Smalltalk, where the expression:
| 
|     someClass allInstances.
| 
| would return a collection of all instances of someClass.  Is there anything
| comparable in CLOS?

  nothing in CLOS itself, but I needed this once, and discovered a function
  (present in Allegro CL 4.3, 4.3.1, and 5.0) that helps me get it:

(defun list-all-instances (class)
  (loop
    with instances = (excl::get-objects 12) ; standard-instance
    for index from 1 to (svref instances 0)
    for instance = (svref instances index)
    when (typep instance class)
    collect instance))

  (evaluate (print-type-counts) to learn that 12 is standard-instance.)

  hope this helps.

#:Erik