Re: issues with std::variant

From	Christian Gollwitzer <auriocus@gmx.de>
Newsgroups	comp.lang.c++
Subject	Re: issues with std::variant
Date	2019-12-06 09:39 +0100
Organization	A noiseless patient Spider
Message-ID	<qsd446$hs1$1@dont-email.me> (permalink)
References	(4 earlier) <f0062225-f506-4306-9d48-1e15215f72d1@googlegroups.com> <qs991n$80l$1@dont-email.me> <374e069c-2c44-4b3e-bdaa-86d0488d90e4@googlegroups.com> <qsa04p$pa9$1@dont-email.me> <5ecddbd0-d352-47e7-967d-1378da2635c4@googlegroups.com>

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Am 05.12.19 um 18:59 schrieb Taylor:
> On Wednesday, December 4, 2019 at 8:13:24 PM UTC-8, Alf P. Steinbach wrote:
>> On 05.12.2019 01:18, Taylor wrote:
>> Re the problem you're asking about, it seems clear that there is some
>> commonality of the classes that has not been factored out / abstracted,
>> but that the rest of the code relies on.
> 
> If I were to use inheritance to factor out commonality, I would need to use multiple inheritance and it could get messy. So for example, there's the base class Node, then there might be ExposedNode, and ColorfulNode, LabeledNode.
> 
> Or I could use interfaces, such has HasExposedPosition, HasColor, HasLabel, etc. I did this before and it's much more code than the variant stuff.
> 

I'm far from understanding the problem, but factoring out common members 
does not mean you nead "class A: public B" inheritance. You could also 
have a "struct Node" and then stuff the things that vary into the 
variant, which is a member of "Node". This is done in C with unions very 
often e.g. for byte code interpreters, where all the values have a type 
tag, a reference count, an alternative representation, and then a union 
which contains the real data.

Christian

Thread

issues with std::variant wtholliday@gmail.com - 2019-12-04 08:37 -0800
  Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-04 10:26 -0800
    Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-04 11:07 -0800
      Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-04 12:31 -0800
        Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-04 13:09 -0800
          Re: issues with std::variant "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-12-04 22:39 +0100
            Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-04 16:18 -0800
              Re: issues with std::variant "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-12-05 05:13 +0100
                Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-05 09:59 -0800
                Re: issues with std::variant Christian Gollwitzer <auriocus@gmx.de> - 2019-12-06 09:39 +0100
                Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-06 09:12 -0800
          Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-04 14:46 -0800
            Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-04 16:28 -0800
              Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-05 00:00 -0800
                Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-05 00:48 -0800
                Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-05 08:17 -0800
                Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-05 09:44 -0800
                Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-05 11:14 -0800
                Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-05 12:37 -0800
                Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-05 13:20 -0800
                Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-05 13:42 -0800
                Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-05 15:41 -0800
                Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-06 09:44 -0800
                Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-07 04:43 -0800
                Re: issues with std::variant Manfred <noname@add.invalid> - 2019-12-07 18:17 +0100
                Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-07 11:45 -0800
                Re: issues with std::variant Christian Gollwitzer <auriocus@gmx.de> - 2019-12-06 09:58 +0100
                Re: issues with std::variant Öö Tiib <ootiib@hot.ee> - 2019-12-06 06:06 -0800
  Re: issues with std::variant David Brown <david.brown@hesbynett.no> - 2019-12-04 22:34 +0100
    Re: issues with std::variant Vir Campestris <vir.campestris@invalid.invalid> - 2019-12-05 15:07 +0000
      Re: issues with std::variant Taylor <wtholliday@gmail.com> - 2019-12-05 10:01 -0800
      Re: issues with std::variant David Brown <david.brown@hesbynett.no> - 2019-12-05 22:15 +0100

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