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Re: Self-updating relationship

Cross-posted to 2 groups.

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On 09/02/2015 07:43 PM, Stefan Ram wrote:
> James Kuyper <jameskuyper@verizon.net> writes:
>> formula freshly each time "spaces" is referred to. Is this a
>> characteristic of binding.NumberBinding, or some more general Java feature?
> 
>   It is a characteristics of a certain standard Java library
>   �JavaFX� that contains classes for "binding" properties to
>   other properties. Binding can establish a spreadsheet-like
>   relationship, so that one property can get updated when
>   another property is updated. But this is a feature of the
>   standard library, not of the language proper.
> 
>> In C++, the equivalent of the first form above would be simpler than the
>> equivalent of the second form, so it feels odd that the second form is
>> simpler in Java. I'll try to keep that in mind should I ever need to
>> program in Java again. It sounds like I've got a lot to learn before I
>> even get started.
> 
>   I am not aware of a similar means of binding in the standard
>   library of C++. But surely, one can implement it, if needed.

When I was talking about C++ equivalents, I was probably thinking of
something much simpler than what you're referring to as "binding". I
assumed that your original version worked something like the following:

struct Updating
{
    int height;
    int number;
    Updating(int _height, int _number) : height(_height),
	number(_number) {};
    int spaces(void) const { return height - number; }
};

And what I was wondering about is which part of your code made it behave
that way, rather than the way this struct would:

struct OneTime
{
    int height;
    int number;
    int spaces;
    OneTime(int _height, int _number) : height(_height),
        number(_number), spaces(_height - _number) {};
};

I'm not saying that OneTime is preferable to Updating, I was just
unclear about which features of your Java code caused it to behave more
like Updating than like OneTime. As I now understand it,
javafx.beans.binding.NumberBinding is that feature.
-- 
James Kuyper

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Re: Self-updating relationship James Kuyper <jameskuyper@verizon.net> - 2015-09-02 17:14 -0400
  Re: Self-updating relationship Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-09-02 17:46 -0400
    Re: Self-updating relationship Arne Vajhøj <arne@vajhoej.dk> - 2015-09-03 21:06 -0400
      Re: Self-updating relationship e.d.programmer@gmail.com - 2015-09-04 04:46 -0700
        Re: Self-updating relationship Arne Vajhøj <arne@vajhoej.dk> - 2015-09-04 19:43 -0400
    Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-04 11:49 -0400
      Re: Self-updating relationship Arne Vajhøj <arne@vajhoej.dk> - 2015-09-04 19:45 -0400
        Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-04 22:10 -0400
          Re: Self-updating relationship Arne Vajhøj <arne@vajhoej.dk> - 2015-09-04 22:31 -0400
            Re: Self-updating relationship Arne Vajhøj <arne@vajhoej.dk> - 2015-09-04 22:38 -0400
            Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-04 22:51 -0400
  Re: Self-updating relationship James Kuyper <jameskuyper@verizon.net> - 2015-09-02 18:49 -0400
    Re: Self-updating relationship James Kuyper <jameskuyper@verizon.net> - 2015-09-02 19:28 -0400
      Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-02 23:52 -0400
        Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-03 10:32 -0400
          Re: Self-updating relationship James Kuyper <jameskuyper@verizon.net> - 2015-09-03 10:53 -0400
            Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-03 11:31 -0400
              Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-03 11:35 -0400
              Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-03 11:49 -0400
              Re: Self-updating relationship James Kuyper <jameskuyper@verizon.net> - 2015-09-03 12:16 -0400
                Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-03 13:03 -0400
          Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-03 10:55 -0400
      Re: Self-updating relationship James Kuyper <jameskuyper@verizon.net> - 2015-09-03 00:06 -0400
    Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-02 23:38 -0400
      Re: Self-updating relationship Jeff Higgins <jeff@invalid.invalid> - 2015-09-03 01:22 -0400

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