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From: pazzani@ics.uci.edu (Michael Pazzani)
Newsgroups: comp.lang.lisp
Subject: Re: STRUCTUREP
Message-ID: <2713DF17.555@ics.uci.edu>
Date: 11 Oct 90 02:55:18 GMT
References: <1990Oct10.091722.4495@hellgate.utah.edu> <1990Oct10.165312.29838@hellgate.utah.edu> <758@forsight.Jpl.Nasa.Gov>
Reply-To: pazzani@ics.uci.edu (Michael Pazzani)
Organization: UC Irvine Department of ICS
Lines: 27

In article <758@forsight.Jpl.Nasa.Gov> gat@robotics.Jpl.Nasa.Gov (Erann Gat) writes:
>That's actually not a bad solution to the puzzle:
>
>(defun structurep (thing)
>  (equal "#S" (subseq (format nil "~S" thing) 0 2)))
>
>This would work for any structure which did not have a :print-function
>defined.  (What a horrible hack, though!)
>
>E.

If you get to define the structures (rather than using a large existing
program), you could do this in a different way:

(defstruct struct) ;; It has no slots, but a struct-p is created

now just include struct in every structure you care about, and struct-p
will work on them.

(defstruct (pig (:include struct)) piglets)
(defstruct (goat (:include struct)) kids)
etc.

(struct-p (make-pig :piglets nil)) 


Mike