Subject:
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Re: Why Java for Robots
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 17 Jan 2006 21:48:44 GMT
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Original-From:
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Juergen Stuber <juergen@&StopSpam&jstuber.net>
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Viewed:
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1951 times
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Hi Peter,
PeterBalch <PeterBalch@compuserve.com> writes:
> > Juergen Stuber wrote:
> > > it has no garbage collector, e.g.,
> > That is the top item on my list to add to Lejos,
> > and on NXT it is possible :-)
>
> Why? Full Java requires it but you're not trying to make a full Java
> implementation.
there are plenty of other languages, many in research,
that sit on top of a Java VM, and the interesting ones need
garbage collection (I've been explicitly asked this for Curry :-) ).
Also, other kinds of VMs are popular with Lisp and Smalltalk
and the like.
> Why can't all your data be statically allocated by the
> compiler (not allocated at run-time)?
Because that limits the programming style very much.
For example, I want to pass around messages.
> Sure, you'd have to tweak the language a little but so
> what? You're never aiming to run the code cross-platform.
Not yet, but maybe we should start now?
> > No, there would have to be a JSR for a tiny real time Java first.
>
> Let's hope it comes Real Soon.
Actually there is something called real-time Java.
Last time I looked I found it too complex for the RCX,
but for the NXT it might be feasible, though I'm not sure I like it.
> > But you need to be a better more disciplined programmer for C
> > than for Java, as it is much easier to mess things up.
>
> Examples please. Java is better than C but how much better?
>
> Anyone who does pointer arithmetic should be shot.
It depends what you are doing.
I'd rather say if you don't absolutely need to, don't.
If you do, be very careful not to shoot yourself in your foot.
> Bounds checking should be done at compile-time.
That's not so easy, in general it is not possible.
> What is a robot sitting on Mars to do if it gets an "out of memory" or
> "illegal pointer value" or "array bounds exceeded" error?
Log the error and reboot.
If it happens too often boot into an emergency system and
wait for humans to clean up the mess
(similar things have happened, though it was the file system overflowing).
Jürgen
--
Jürgen Stuber <juergen@jstuber.net>
http://www.jstuber.net/
gnupg key fingerprint = 2767 CA3C 5680 58BA 9A91 23D9 BED6 9A7A AF9E 68B4
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