[armedbear-devel] SLOT-VALUE and SLOT-VALUE-USING-CLASS with DEFSTRUCT

[Tobias C Rittweiler]

In article 
<AANLkTilR4sZL4IQ5sznTgw9nHHKCNq9-VtaYY20PmWBG at mail.gmail.com>,
 Alessio Stalla <alessiostalla at gmail.com> 
 wrote:

> On Mon, Jun 14, 2010 at 4:09 AM, William Wadsworth
> <will.wadsworth.10 at gmail.com> wrote:
> > Hi.
> >
> > The following transcript demonstrates the problem.
> >
> > --- BEGIN
> > Armed Bear Common Lisp 0.20.0
> > Java 1.6.0_20 Sun Microsystems Inc.
> > Java HotSpot(TM) Client VM
> > Low-level initialization completed in 0.667 seconds.
> > Startup completed in 4.849 seconds.
> > Type ":help" for a list of available commands.
> > CL-USER(1): (defstruct x a b c)
> > X
> > CL-USER(2): (slot-value (make-x :a 10) 'a)
> > #<THREAD "interpreter" {118958E}>: Debugger invoked on condition of
> > type UNDEFINED-FUNCTION
> >  The function SLOT-VALUE is undefined.
> > Restarts:
> >  0: CONTINUE     Try again.
> >  1: USE-VALUE    Specify a function to call instead.
> >  2: RETURN-VALUE Return one or more values from the call to SLOT-VALUE.
> >  3: TOP-LEVEL    Return to top level.
> > [1] CL-USER(3): :res
> > CL-USER(4): (slot-value (make-x :a 10) 'a)
> > #<THREAD "interpreter" {118958E}>: Debugger invoked on condition of
> > type SIMPLE-ERROR
> >  There is no applicable method for the generic function
> > #<STANDARD-GENERIC-FUNCTION MOP::SLOT-VALUE-USING-CLASS {932FE}
> >> when called with arguments (#<STRUCTURE-CLASS X {11EF443}> #<X {1184326}> 
> >> A).
> > Restarts:
> >  0: TOP-LEVEL Return to top level.
> > [1] CL-USER(5): :res
> > CL-USER(6):
> > --- END
> >
> > DEFCLASS seems to work fine, though I would like to keep using DEFSTRUCT.
> > I understand that the MOP is not really complete. However, Is there a 
> > workaround
> > that will not resort in using DEFCLASS?
> 
> At glance, what you ask is not there but can be implemented without
> too much effort. Structures already carry (on the Java side)
> information about their slots, which is used by the inspector. So,
> stay tuned ;)
> 
> Cheers,
> Alessio

I usually use WITH-SLOTS on structures, too, even though strictly,
it's not portable. Many implementations seem to support it just fine.
So yeah, go ahead and make it work on ABCL, too. :-)

  -T.