[armedbear-devel] MQTT example using ABCL and Eclipse Paho

[Frederico Munoz]

Hi,

Alessio Stalla <alessiostalla at gmail.com> writes:
> Hi! This is very interesting - both the "how to use Eclipse Paho in
> Lisp" part, and the comparison with Clojure. Thanks for sharing!

You're too kind, thank you. I'm glad you found it worthwhile, my idea is
to share practical tidbits, even if code-wise they are hardly very elegant.

>>     CL-USER(4): (#"sleep" 'Thread 100)
>>     #<THREAD "interpreter" {19AA4D78}>: Debugger invoked on condition of type ERROR
>>       no such method
>>     Restarts:
>>       0: TOP-LEVEL Return to top level.
>
> I think this is because Thread.sleep takes an argument of type long,
> while 100 is an int, and ABCL isn't smart enough to search for
> applicable methods taking type conversions into account.

That was exactly my idea, which is why I tried:
(#"sleep" 'Thread (coerce 100 'long-float)), but now that you mention it
I went looking around and found jcoerce, which seems like a way to do it
without relying on any smartness. That being said it doesn't seem to
work:

(java::jcoerce 100 "java.lang.Long")
=>  The value 100 is not of type "java.lang.Long".
      [Condition of type TYPE-ERROR]

I found this link that points towards some conversion not being
implemented
(http://lists.common-lisp.net/pipermail/armedbear-devel/2012-July/002481.html),
so perhaps this is not doable right now.

> Creating Java classes in Lisp (known as "runtime-class" for historical
> reasons in ABCL) is a partially implemented feature at the moment, and
> documented quite messily (see
> <http://lisp.not.org/trac/armedbear/wiki/JavaFfi/RuntimeClass>; it is
> more of an idea dump than a proper reference). The key missing
> functionality is calling superclass constructors, which renders it not
> useful in a lot of cases. I worked on it a bit a while ago; if you're
> interested, I might start working on it again a bit - adding
> constructors is not a lot of work.

Yes, thank you, I remember you referring to this some months ago when I
wrote about the Swing examples. I'll take a look and perhaps present a
very simple use-case and why it does or doesn't work, just to identify
specific implementation improvements.

Best regards,

Frederico