Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!gatech!udel!princeton!phoenix!eliot
From: eliot@phoenix.Princeton.EDU (Eliot Handelman)
Newsgroups: comp.lang.lisp
Subject: Re: conc-name in DEFSTRUCT
Message-ID: <7580@phoenix.Princeton.EDU>
Date: 4 Apr 89 21:52:32 GMT
References: <7564@phoenix.Princeton.EDU> <38532@think.UUCP>
Reply-To: eliot@phoenix.Princeton.EDU (Eliot Handelman)
Organization: Princeton University, NJ
Lines: 41

In article <38532@think.UUCP> barmar@kulla.think.com.UUCP (Barry Margolin) writes:
>In article <7564@phoenix.Princeton.EDU> eliot@phoenix.Princeton.EDU (Eliot Handelman) writes:
>>Ok, Should this or shouldn't it work?
>[Defines two different structures with the same (:conc-name common-) and same
>slot names.]

>What should it do?  Either COMMON-X and COMMON-Y take a FOO or a QUUX,
>and it is an error to call them with the wrong type of structure.  Be
>thankful you're using Lisp implementations that check at all
>(Symbolics CL never checks that structure accessors are given the
>correct type of structure).

Right, I wasn't sure if the accessors were required to do type-checking,
or if there was some way to ovverride that, or whether there should be
some way. 

>Perhaps you should be using the :include option if you want to allow
>one structure's accessors to be used with a similar structure.

:include has one undesirable side effect, though, in that the predicate
of the included structure is true for the second structure. In the 
implementations I'm using TYPE-OF returns the most specific type, but
I don't think that CL guarantees that behaviour. Anyhow :include suits
my purposes.

>Or
>maybe you want a real object-oriented programming facility, such as
>CLOS.

I had PCL going in Lucid on a vax-8700 and it was great, but it's really
too slow in KCl on a microvax II (our departmental machine). If somebody
wants to donate a Symbolics machine to a music department, it would be
put to fairly unusual use. You'll get mentioned in my thesis. You'll get
a tax rebate.

>>Also, can someone tell me what the depth argument to user-defined print
>>functions for structures is good for? How is it set, for example?

>It's used to implement *PRINT-DEPTH* abbreviation.

Thanks for the help.