[armedbear-devel] SETF for JFEILDS

[dmiles at users.sourceforge.net]

> ----- 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 9:18 AM
> Subject: Re: [armedbear-devel] SETF for JFEILDS
>
>
> On Mon, Nov 23, 2009 at 5:57 PM,  <logicmoo at gmail.com> wrote:
>> Ok even Allegro uses T and NIL for the Booleans.. which is why
>>
>>> CL-USER(17): (jclass-of (jfield "java.lang.Boolean" "TRUE"))
>>> NIL
>>> NIL
>>
>> was still correct.. I think the closer we stick with Allegro the better.
>>
>>
>>
>> for future reference (to myself) to make a boolean one does:
>>
>>
>> CL-USER(21): (jnew (jconstructor "java.lang.Boolean" "java.lang.String") "True")
>> #<java.lang.Boolean true {44AC5E}>
>> CL-USER(22): (jclass-of (jnew (jconstructor "java.lang.Boolean" "java.lang.String") "True"))
>> "java.lang.Boolean"
>> "java.lang.Boolean"
>
> If you want a boolean (primitive type) I believe you can do
> (make-immediate-object T-or-NIL :boolean)

(make-immediate-object t :boolean)
#<java.lang.Boolean true {1C904F75}>

Neat, I hadn't known (or forgot) about Arg2 of #'make-immediate-object !
Thx

> If you want Boolean.TRUE or Boolean.FALSE the cleaner way would be to
> have a jfield-raw like jcall-raw, if I understand it correctly.

CL-USER(24): (jfield-raw "java.lang.Boolean" "TRUE")
#<java.lang.Boolean true {465098F9}>

Indeed.


>>
>>
>> If there is any action items out of all this:
>>
>> Perhaps: javaInstance() on Nil returns Boolean.FALSE?
>
> This would break a lot of existing code, I'm afraid. NIL is often used
> to mean null.

*nod* well either meaning is just as dubious.. but as you say
allot of existing code likes NIL to mean EMPTY which sounds more like a 'null' than a 'false'.

>
>> Then in Symbol.java
>>
>> Object javaInstance() {
>> if (this == T) return Boolean.TRUE;
>> return super.javaInstance();
>> }
>>
>
> I don't agree for consistency with NIL and for similar concerns on
> existing code. However, hold on...
>
>>
>> And in LispObject itself any thoughts on?
>>
>> LispObject.this.javaInstance(Class c) {
>> if (c.isInstance(this)) return this;
>> // widen and resubmit for subclasses
>> if (c==int.class) return javaInstance(Integer.class);
>> if (c==boolean.class) return javaInstance(Boolean.class);
>> // they requested a boolean.. give it to them
>> if (c==Boolean.class) return getBooleanValue();
>> .....
>> //hit the error logic
>> }
>
> Now for javaInstance(Class) I completely agree with you: it should
> mean - everywhere! - "convert this object to a Java object of the
> given class, if possible".
>
> So LispObject.javaInstance(Class c) should be like you said, and in
> some subclasses (Fixnum, AbstractString come to my mind) it should be
> overridden.

Good

> At that point we could even generify it:
>
> public <T> T javaInstance(Class<T> c)
>
> So users might write, e.g., String s = myLispObject.javaInstance(String.class);
>

I like the generics for it as well


> Just my €.02
>
> Alessio
>
>>
>>
>> ----- Original Message -----
>> From: <dmiles at users.sourceforge.net>
>> To: "Armed Bear" <armedbear-devel at common-lisp.net>
>> Sent: Monday, November 23, 2009 7:42 AM
>> Subject: Re: [armedbear-devel] SETF for JFEILDS
>>
>>
>>>
>>> These 3 look good
>>>
>>>
>>> CL-USER(2): (jclass-of (jfield "java.lang.System" "out"))
>>> "java.io.PrintStream"
>>> "java.io.PrintStream"
>>>
>>> CL-USER(4): (jclass-of 1)
>>> NIL
>>> NIL
>>>
>>> CL-USER(5): (jclass-of (make-immediate-object 1))
>>> "java.lang.Integer"
>>> "java.lang.Integer"
>>>
>>>
>>>
>>> But is this correct?
>>>
>>>
>>> CL-USER(17): (jclass-of (jfield "java.lang.Boolean" "TRUE"))
>>> NIL
>>> NIL
>>> CL-USER(18): (jclass-of (jfield "java.lang.Boolean" "FALSE"))
>>> NIL
>>> NIL
>>>
>>>
>>>
>>>
>>
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>
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