From: Jovdbroe
Subject: Question about symbols, slot-exists-p and find-symbol
Date: Fri, 02 Dec 2005 01:21:37 +0000
Message-ID: <VN2dndnDX7k_PBLenZ2dnUVZ8t2dnZ2d@scarlet.biz>

Hi,

I'm looking for some help,
I'm trying to access a slot of a CLOS object that has a certain name, 
coming from a string "name"
To make things clearer, why does cg-user(55) in the example work while 
cg-user(56) doesn't?

(defclass arena ()(longname map))
#<STANDARD-CLASS ARENA>
CG-USER(54): (defvar sth (make-instance 'arena))
STH
CG-USER(55): (slot-exists-p sth 'longname)
T
CG-USER(56): (slot-exists-p sth (find-symbol "longname" (package-name 
*package*)))
NIL

thanks,
Greetings,
Johan

• Re: Question about symbols, slot-exists-p and find-symbol Edi Weitz
  • Re: Question about symbols, slot-exists-p and find-symbol Jovdbroe
• Re: Question about symbols, slot-exists-p and find-symbol Thomas A. Russ

From: Edi Weitz
Subject: Re: Question about symbols, slot-exists-p and find-symbol
Date: Fri, 02 Dec 2005 01:30:38 +0000
Message-ID: <ud5kgnv41.fsf@agharta.de>

On Fri, 02 Dec 2005 02:21:37 +0100, Jovdbroe <········@vub.ac.be> wrote:

> I'm trying to access a slot of a CLOS object that has a certain
> name, coming from a string "name" To make things clearer, why does
> cg-user(55) in the example work while cg-user(56) doesn't?
>
> (defclass arena ()(longname map))
> #<STANDARD-CLASS ARENA>
> CG-USER(54): (defvar sth (make-instance 'arena))
> STH
> CG-USER(55): (slot-exists-p sth 'longname)
> T
> CG-USER(56): (slot-exists-p sth (find-symbol "longname" (package-name
> *package*)))
> NIL

Assuming that you're /not/ using AllegroCL's "modern" mode you should
try

  (find-symbol "LONGNAME" (package-name *package*))

instead.  Try

  (symbol-name 'longname)

And, by the way, why don't you use it like this?

  (find-symbol "LONGNAME" *package*)

Cheers,
Edi.

-- 

Lisp is not dead, it just smells funny.

Real email: (replace (subseq ·········@agharta.de" 5) "edi")

From: Jovdbroe
Subject: Re: Question about symbols, slot-exists-p and find-symbol
Date: Fri, 02 Dec 2005 01:57:21 +0000
Message-ID: <Tt2dndrsB7ucNxLenZ2dnUVZ8qqdnZ2d@scarlet.biz>

Thanks!

Worked like a charm.

Edi Weitz wrote:
> On Fri, 02 Dec 2005 02:21:37 +0100, Jovdbroe <········@vub.ac.be> wrote:
> 
> 
>>I'm trying to access a slot of a CLOS object that has a certain
>>name, coming from a string "name" To make things clearer, why does
>>cg-user(55) in the example work while cg-user(56) doesn't?
>>
>>(defclass arena ()(longname map))
>>#<STANDARD-CLASS ARENA>
>>CG-USER(54): (defvar sth (make-instance 'arena))
>>STH
>>CG-USER(55): (slot-exists-p sth 'longname)
>>T
>>CG-USER(56): (slot-exists-p sth (find-symbol "longname" (package-name
>>*package*)))
>>NIL
> 
> 
> Assuming that you're /not/ using AllegroCL's "modern" mode you should
> try
> 
>   (find-symbol "LONGNAME" (package-name *package*))
> 
> instead.  Try
> 
>   (symbol-name 'longname)
> 
> And, by the way, why don't you use it like this?
> 
>   (find-symbol "LONGNAME" *package*)
> 
> Cheers,
> Edi.
> 

From: Thomas A. Russ
Subject: Re: Question about symbols, slot-exists-p and find-symbol
Date: Mon, 05 Dec 2005 17:35:34 +0000
Message-ID: <ymizmnfo3a1.fsf@sevak.isi.edu>

Jovdbroe <········@vub.ac.be> writes:

> To make things clearer, why does cg-user(55) in the example work while 
> cg-user(56) doesn't?
> 
> (defclass arena ()(longname map))
> #<STANDARD-CLASS ARENA>
> CG-USER(54): (defvar sth (make-instance 'arena))
> STH
> CG-USER(55): (slot-exists-p sth 'longname)
> T
> CG-USER(56): (slot-exists-p sth (find-symbol "longname" (package-name 
> *package*)))
> NIL

Well, what does (find-symbol "longname" (package-name *package*))
return?

Are you surprised?

If so, look at    (symbol-name 'longname)
and use the result of that in FIND-SYMBOL.

-- 
Thomas A. Russ,  USC/Information Sciences Institute