Re: The nature of truth

[Jim White <jim at pagesmiths dot com>]

Chris Dean wrote:
> Per Bothner <per@bothner.com> wrote:
> > Chris Dean wrote: 
> > > because the Java method is returning new Boolean( "false" ) which is not
> > > the same object as the "interned" Boolean.FALSE object.
> ...
> > Why is the Java method doing something that silly?
> ...
> > My opinion: "don't do that".
>
> Fair enough ;-). I (and all right thinking people) wouldn't do that.
> But because those constructors exist, I can't really expect any third
> party code never to call new Boolean( ... ).

I concur that Kawa's treatment of java.lang.Boolean is (pretty much **) 
the correct interpretation for Scheme - there is only "one true #f".

The only problem is in going from general Java code which returns 
java.lang.Boolean (or perhaps even more generally, java.lang.Object).  I 
don't have any problem putting the onus on the Java code (or the Scheme 
application wrapper) to convert that result properly.

Note that this is not a problem for Boolean objects, not the boolean 
primitives.  Which does segue into where Kawa might do something 
slightly different.

**

Kawa is slightly inconsistent with #f:

(define-namespace bool "class:java.lang.Boolean")
(define fake-false (bool:new #f))
#f
(not #f)
fake-false
(not fake-false)
(bool:booleanValue fake-false)
(not (bool:booleanValue fake-false))

The issue being that non #f objects print as #f.

So while I don't think Kawa should necessarily call booleanValue on 
Boolean objects (aside from wasted overhead, it doesn't address Object), 
I wonder whether objects which are not eq? to #f should print as #f.

If they got toStringed, you'ld get:

(bool:toString fake-false)
false

Also perhaps only j.l.B.TRUE and j.l.B.FALSE should be boolean?  So 
(boolean? fake-false) would change from #t to #f (at which point it 
would be a "regular" object and print as "false").

Jim
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