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Re: Alternatives languages on the JVM: which one or is there no alternative?

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On 02.12.2013 16:26, Silvio wrote:
> On 12/02/2013 03:50 PM, Silvio wrote:
>> On 12/02/2013 03:33 PM, Robert Klemme wrote:
>>>
>>> The problem with "real" closures (i.e. the ones you can write to) is
>>> that they require a dramtic change in the underlying mechanics: you
>>> need to keep stack frames around for longer than a method call.
>>> Having that in Java would be really nice but the potential for impact
>>> on the huge basis of existing code is severe.  I personally like the
>>> simplified anonymous classes approach because it is a pragmatic step
>>> forward: you get to use anonymous functions with far less visual
>>> overhead than before.

>> Not necessarily. Local variables that are written to from closures in
>> their scope can also be given an extra level of indirection by mutably
>> wrapping them in an object. All access to the variable is then done
>> through the wrappers which can be copied into closures just like values
>> are copied in the read-only scenario.

Yes, true.  That's an approach I had not thought of.  The only downside 
I can see immediately is that you may pay the overhead for the 
additional indirection even if the closure is not used (e.g. because it 
is not in the branch of code actually executed).  One can even optimize 
the approach by creating a single instance carrying the local state so 
there is not one object per referred local variable but one per closure 
creation.  But I guess that overhead is as acceptable as this:

> BTW: that is how Scala does it so it is not a very experimental approach
> anymore. To many Java purists the thought that a primitive might become
> a full object may seem horrendous but if you think about it autoboxing
> does the same thing, even at the risk of repeatedly boxing the same
> primirive over and over...

Another thing which might not be that nice is that instance variables 
will be accessed differently, i.e. through 'this'.  So there is one 
access path for local variables introducing a synthetic indirection and 
another one going through 'this'.

Still, I don't see any hard reasons that speak against doing real 
closures.  Maybe it's just the pragmatic way, i.e. not enough resources 
to do the full thing (think of the delays of Java 8 we have seen 
already) and also that gives them the chance to learn how people use the 
new feature and maybe improve it before going full circle.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-25 03:09 -0800
  Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-25 12:46 +0100
    Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-25 05:20 -0800
    Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-25 22:10 +0100
      Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-25 14:34 -0800
      Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-26 08:54 +0100
        Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-26 00:29 -0800
          Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-26 15:29 +0100
            Re: Alternatives languages on the JVM: which one or is there no alternative? Arne Vajhøj <arne@vajhoej.dk> - 2013-11-26 21:55 -0500
              Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-27 08:59 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Joerg Meier <joergmmeier@arcor.de> - 2013-11-27 10:41 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-28 12:48 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? leif.roar@invalid.com (Leif Roar Moldskred) - 2013-11-28 16:28 -0600
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 00:03 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-29 00:41 -0800
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 12:05 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-11-29 03:51 -0800
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 16:44 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-11-29 16:48 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-02 06:33 -0800
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-02 15:50 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-02 16:26 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-02 21:07 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-02 23:33 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? markspace <markspace@nospam.nospam> - 2013-12-02 18:07 -0800
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-03 08:59 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-12-03 00:14 -0800
                Re: Alternatives languages on the JVM: which one or is there no alternative? Silvio <silvio@internet.com> - 2013-12-03 09:42 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-12-03 02:58 -0800
                Re: Alternatives languages on the JVM: which one or is there no alternative? Martin Gregorie <martin@address-in-sig.invalid> - 2013-12-03 20:55 +0000
                Re: Alternatives languages on the JVM: which one or is there no alternative? Saxo <jeti789@web.de> - 2013-12-04 00:12 -0800
                Re: Alternatives languages on the JVM: which one or is there no alternative? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-12-14 03:31 -0400
                Re: Alternatives languages on the JVM: which one or is there no alternative? Martin Gregorie <martin@address-in-sig.invalid> - 2013-12-14 10:11 +0000
                Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-14 17:39 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-12-14 16:52 +0000
                Re: Alternatives languages on the JVM: which one or is there no alternative? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-12-14 13:47 -0400
                Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-12-14 23:55 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Sebastian <news@seyweiler.dyndns.org> - 2013-12-04 10:39 +0100
                Re: Alternatives languages on the JVM: which one or is there no alternative? Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-12-14 03:56 -0400
  Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-26 21:28 +0000
    Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-26 23:29 +0100
      Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-27 05:13 +0000
        Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-27 22:57 +0100
          Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-29 23:22 +0000
            Re: Alternatives languages on the JVM: which one or is there no alternative? Robert Klemme <shortcutter@googlemail.com> - 2013-11-30 14:41 +0100
            Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-30 16:49 -0600
        Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-27 23:07 -0600
          Re: Alternatives languages on the JVM: which one or is there no alternative? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-11-28 23:41 +0000
            Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-29 00:08 -0600
              Re: Alternatives languages on the JVM: which one or is there no alternative? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-11-29 16:49 +0000
                Re: Alternatives languages on the JVM: which one or is there no alternative? Joshua Cranmer 🐧 <Pidgeot18@verizon.invalid> - 2013-11-30 16:46 -0600
                Re: Alternatives languages on the JVM: which one or is there no alternative? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2014-02-14 15:36 +0000
          Re: Alternatives languages on the JVM: which one or is there no alternative? v_borchert@despammed.com (Volker Borchert) - 2013-11-29 23:37 +0000
  Re: Alternatives languages on the JVM: which one or is there no alternative? Roedy Green <see_website@mindprod.com.invalid> - 2013-11-28 12:50 -0800

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