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Groups > comp.lang.java.programmer > #11765

Re: Blocks for scope control

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On 1/20/2012 9:32 PM, Stefan Ram wrote:
> ram@zedat.fu-berlin.de (Stefan Ram) writes:
>> alpha();
>> { /* add a button to the frame */
>>   final Button button = new Button();
>>   frame.add( button ); }
>> beta();
>
>    I forgot to mention that there is an old software-engineering
>    principle: »The scope of every identifier should be as small
>    as possible.« Blocks help to realize this.
>
>    Or, let's look at code posted into some other thread recently:
>
> student<freenow12345@gmail.com>  writes:
>>         GOval g = makeCircle(centerX, centerY,radiusOuterCircle ,
>> Color.RED);
>>         add(g);
>>         g = makeCircle(centerX, centerY,radiusMiddleCircle ,
>> Color.WHITE);
>>         add(g);
>>         g = makeCircle(centerX, centerY,radiusInnerCircle ,
>> Color.RED);
>>         add(g);
>
>    With blocks, »g« can be made final:
>
> { final GOval g = makeCircle( centerX, centerY, radiusOuterCircle,  Color.RED   ); add( g ); }
> { final GOval g = makeCircle( centerX, centerY, radiusMiddleCircle, Color.WHITE ); add( g ); }
> { final GOval g = makeCircle( centerX, centerY, radiusInnerCircle,  Color.RED   ); add( g ); }
>
>    this also is more beautiful, because now there is more
>    symmetry between the the three actions, which then allows a
>    possible refactor to:
>
> { final CircleMaker circleMaker = new CircleMaker( g, centerX, centerY );
>    circleMaker.make( radiusOuterCircle,  Color.RED   );
>    circleMaker.make( radiusMiddleCircle, Color.WHITE );
>    circleMaker.make( radiusInnerCircle,  Color.RED   ); }
>
>    (this will probably not solve the actual problem of »student«).
>
>    Or, to tell the story from its end:
>
>    The most important principle is »DRY« - »Don't repeat
>    yourself!«. To do this, we abstract repetitions of the same
>    principle into a single code location using abstractions.
>    But to do this, in turn, we need to be able to see
>    repetitions of the same principle. And to be able to see
>    them, the code needs to be made as symmetric as possible,
>    that is, to do the same thing, the same wording should be
>    used.
>
>    Or in a single line:
>    First, make the repetition obvious, then abstract it.

The rule is OK.

But I consider it a 75% rule. Follow it in 75% of cases
and skip it when it does not make sense.

In this case I think the code became less readable, so I would
not do it.

And I would certainly not do that refactoring as it obfuscates
what the code is doing by hiding the adding to g.

Arne

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Thread

Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-15 11:50 -0400
  Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-15 17:10 +0100
  Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-15 17:32 +0100
    Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 11:21 -0800
    Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-16 07:59 +0100
  Re: Blocks for scope control markspace <-@.> - 2012-01-15 09:57 -0800
    Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 11:28 -0800
  Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 11:00 -0800
    Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-15 17:49 -0400
      Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-15 15:45 -0800
        Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-19 21:54 -0400
          Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-20 08:41 +0100
            Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-20 15:24 -0800
            Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-20 19:30 -0400
              Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-20 15:54 -0800
      Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-16 07:55 +0100
        Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-19 21:16 -0400
          Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-21 13:25 +0100
            Re: Blocks for scope control Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-01-21 10:41 -0400
              Re: Blocks for scope control Robert Klemme <shortcutter@googlemail.com> - 2012-01-22 13:03 +0100
  Re: Blocks for scope control Roedy Green <see_website@mindprod.com.invalid> - 2012-01-16 06:09 -0800
    Re: Blocks for scope control Henk van Voorthuijsen <voorth@xs4all.nl> - 2012-01-16 07:03 -0800
  Re: Blocks for scope control Arne Vajhøj <arne@vajhoej.dk> - 2012-01-17 18:43 -0500
  Re: Blocks for scope control Lew <noone@lewscanon.com> - 2012-01-20 11:05 -0800
  Re: Blocks for scope control Gene Wirchenko <genew@ocis.net> - 2012-01-20 12:11 -0800
  Re: Blocks for scope control Arne Vajhøj <arne@vajhoej.dk> - 2012-02-06 21:24 -0500

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