[armedbear-devel] SETF for JFEILDS

[logicmoo at gmail.com]

Thanks, you are right, much better to use the built-in key stuff

 (defun (setf jfield)  (newvalue class-ref-or-field field-or-instance
                         &optional ( instance nil instance-supplied-p) unused-value)
  (declare (ignore unused-value))
  (if instance-supplied-p
   (jfield class-ref-or-field field-or-instance instance newvalue)
   (jfield class-ref-or-field field-or-instance newvalue)))


----- Original Message ----- 
From: "Thomas Russ" <tar at ISI.EDU>
To: <dmiles at users.sourceforge.net>
Sent: Tuesday, November 24, 2009 9:24 AM
Subject: Re: [armedbear-devel] SETF for JFEILDS



On Nov 23, 2009, at 6:47 AM, logicmoo at gmail.com wrote:

> So actually
>
> (defun (setf jfield)  (newvalue class-ref-or-field field-or- 
> instance &optional ( instance :noinst) unusedvalue)
>  (if (eq instance :noinst)
>   (jfield class-ref-or-field field-or-instance newvalue)
>   (jfield class-ref-or-field field-or-instance instance newvalue)))
>
> Would be a little better.. good eye.

For what it's worth, I am not a fan of using special values to  
determine whether optional (or keyword) arguments are actually passed  
or not.  I prefer to use the predicate forms from the lambda list, so  
something more like

(defun (setf jfield)  (newvalue class-ref-or-field field-or-instance
                         &optional ( instance nil instance-supplied-p)  
unusedvalue)
  (declare (ignore unusedvalue))
  (if instance-supplied-p
   (jfield class-ref-or-field field-or-instance newvalue)
   (jfield class-ref-or-field field-or-instance instance newvalue)))




>
>
> ----- Original Message -----
> From: <dmiles at users.sourceforge.net>
> To: "Alessio Stalla" <alessiostalla at gmail.com>
> Cc: "Armed Bear" <armedbear-devel at common-lisp.net>
> Sent: Monday, November 23, 2009 6:27 AM
> Subject: Re: [armedbear-devel] SETF for JFEILDS
>
>
>>
>> ----- Original Message -----
>> From: "Alessio Stalla" <alessiostalla at gmail.com>
>> To: <dmiles at users.sourceforge.net>
>> Cc: "Armed Bear" <armedbear-devel at common-lisp.net>
>> Sent: Monday, November 23, 2009 5:42 AM
>> Subject: Re: [armedbear-devel] SETF for JFEILDS
>>
>>
>> On Mon, Nov 23, 2009 at 2:36 PM,  <logicmoo at gmail.com> wrote:
>>>> Does anyone object to adding this to java.lisp? If not could it  
>>>> be done?
>>>>
>>>> (defun (setf jfield)
>>>> (newvalue class-ref-or-field field-or-instance &optional  
>>>> ( instance :noinst) (value :novalue))
>>>> (if (eq instance :noinst)
>>>> (jfield class-ref-or-field field-or-instance newvalue)
>>>> (jfield class-ref-or-field field-or-instance instance newvalue)))
>>
>>> It seems a nice idea to me, but there are a couple of things that I
>>> don't understand:
>>
>> A>- why :noinst and not simply nil?
>>
>> JFIELD is defined as:   class-ref-or-field field-or-instance  
>> &optional instance value
>> The valid argument patterns for this operation are:
>> (class-ref  field-name): to retrieve the value of a static field.
>> (class-ref  field-name  instance-ref): to retrieve the value of a  
>> class field of the instance.
>> (class-ref  field-name  primitive-value:) to store primitive-value  
>> in a static field.
>> (class-ref  field-name  instance-ref  value): to store value in a  
>> class field of the instance.
>> (class-ref  field-name  nil  value): to store value in a static  
>> field (when value may be confused with an instance-ref).
>> (field-name  instance): to retrieve the value of a field of the  
>> instance. The class is derived from the instance.
>> (field-name  instance  value): to store value in a field of the  
>> instance. The class is derived from the instance.
>>
>> JFIELD doesn't distingusih between static and non static fields
>>
>> Also cases of  "class-ref  field-name  instance-ref   
>> value"  (accessing  superclass field)
>>
>> Depending on how the field is defined
>>
>> (setf (jfield  *MyClass* "someStaticBooleanField") NIL)
>>     it is distinguable from
>> (setf (jfield  *MySuperClass* "nonStaticBooleanField" *my- 
>> instance* ) NIL)
>>
>>
>> --------------------------------------------------------------------------------------------------------------------------
>> A>- value is not used, what's the point of it?
>>
>> correct the  "default :novalue" is not needed.
>> (I was debugging and trying to find corner cases with all those  
>> bizzare legal jfield signatures )
>>
>>
>>  but... "value" as an &optional was needed to match the signature  
>> of what is legal for jfield so things like this can work:
>>
>> (define-symbol-macro %iscold (jfield "org.armedbear.lisp.Lisp"  
>> "cold"))
>>   %iscold ;; ==> NIL
>>   (setq %iscold T) ;; ==> T
>>   %iscold ;; ==> T
>>   (setq %iscold NIL) ;; ==> NIL
>>
>>
>
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