Re: Virtual functions: To const, or not to const?

From	Paavo Helde <eesnimi@osa.pri.ee>
Newsgroups	comp.lang.c++
Subject	Re: Virtual functions: To const, or not to const?
Date	2022-10-10 15:13 +0300
Organization	A noiseless patient Spider
Message-ID	<ti129g$qa0t$3@dont-email.me> (permalink)
References	<thosit$6fp$1@gioia.aioe.org> <thp091$3lkbh$1@dont-email.me> <ti0djb$1ghm$1@gioia.aioe.org>

Show all headers | View raw

10.10.2022 09:20 Juha Nieminen kirjutas:
> David Brown <david.brown@hesbynett.no> wrote:
>> Shouldn't it be a matter of deciding whether the function logically
>> changes the object or not?  If it clearly changes the object, it must be
>> non-const.  But if it leaves the object with the same publicly visible
>> state, make it const.  Any later bits that might need changing should be
>> mutable.
>>
>> A virtual function is an interface, not implementation detail.  It
>> doesn't make sense to me to have a virtual function that is logically
>> const in a base class, but logically non-const in a derived class.
> 
> There are situations where the base class function is *so* abstract that
> it doesn't even express if the derived class implementations should be
> mutable or const. Some derived classes might want to implement as a
> non-const function, other derived classes as a const function (so that
> it can be called with const objects/references).

If that's really so, then it looks like you have got two different class 
hierarchies or at least two interfaces, not one.

Maybe the part(s) of the inheritance tree which you want to call over 
const references should be cut off and converted into a separate tree 
having a const interface.

Thread

Virtual functions: To const, or not to const? Juha Nieminen <nospam@thanks.invalid> - 2022-10-07 09:47 +0000
  Re: Virtual functions: To const, or not to const? David Brown <david.brown@hesbynett.no> - 2022-10-07 12:50 +0200
    Re: Virtual functions: To const, or not to const? Juha Nieminen <nospam@thanks.invalid> - 2022-10-10 06:20 +0000
      Re: Virtual functions: To const, or not to const? Richard Damon <Richard@Damon-Family.org> - 2022-10-10 07:38 -0400
        Re: Virtual functions: To const, or not to const? Juha Nieminen <nospam@thanks.invalid> - 2022-10-10 12:08 +0000
          Re: Virtual functions: To const, or not to const? Richard Damon <Richard@Damon-Family.org> - 2022-10-10 20:47 -0400
      Re: Virtual functions: To const, or not to const? Paavo Helde <eesnimi@osa.pri.ee> - 2022-10-10 15:13 +0300
        Re: Virtual functions: To const, or not to const? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-10-10 09:43 -0700
      Re: Virtual functions: To const, or not to const? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-10-10 09:26 -0700
  Re: Virtual functions: To const, or not to const? Paavo Helde <eesnimi@osa.pri.ee> - 2022-10-07 14:00 +0300
  Re: Virtual functions: To const, or not to const? Richard Damon <Richard@Damon-Family.org> - 2022-10-07 07:29 -0400
  Re: Virtual functions: To const, or not to const? Öö Tiib <ootiib@hot.ee> - 2022-10-07 05:55 -0700
  Re: Virtual functions: To const, or not to const? "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2022-10-08 14:56 +0200
  Re: Virtual functions: To const, or not to const? Bonita Montero <Bonita.Montero@gmail.com> - 2022-10-08 16:35 +0200
    Re: Virtual functions: To const, or not to const? Michael S <already5chosen@yahoo.com> - 2022-10-08 11:03 -0700
      Re: Virtual functions: To const, or not to const? Bonita Montero <Bonita.Montero@gmail.com> - 2022-10-08 20:36 +0200
      Re: Virtual functions: To const, or not to const? Mr Flibble <flibble@reddwarf.jmc.corp> - 2022-10-08 20:19 +0100
        Re: Virtual functions: To const, or not to const? Bonita Montero <Bonita.Montero@gmail.com> - 2022-10-10 17:58 +0200
      Re: Virtual functions: To const, or not to const? Muttley@dastardlyhq.com - 2022-10-09 09:19 +0000
  Re: Virtual functions: To const, or not to const? Manfred <noname@add.invalid> - 2022-10-08 21:42 +0200

csiph-web