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Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ?

From "R.Wieser" <address@not.available>
Newsgroups comp.lang.c++
Subject Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ?
Date 2022-08-18 09:58 +0200
Organization Aioe.org NNTP Server
Message-ID <tdkrg5$1t7d$1@gioia.aioe.org> (permalink)
References <tdkk90$1bt7$1@gioia.aioe.org> <slrntfrodf.cin.ike@sdf.org>

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Ike,

> First, == binds stronger than & in C and C++

Yep, thats the part that I missed.

>  flags & flagMask == flagMask
>
> is interpreted as
>
>  flags & (flagMask == flagMask)
>
> which can be simplified to
>
>  flags & 1
>
> which is true if the least significant bit of flags is set.

IOW, while that "superset" is technically true, its also confusing the
matter by being unspecific.

but even in that case, for flags = 1 and flagMask = 0,
> -->  flags is a superset of flagMask
> -->  flags != flagMask
> -->  ((flags & flagMask) == flagMask)  equals  ((1 & 0) == 0)
>                                       equals  (0 == 0)
>                                       equals  true

As far as I understood that was exactly what they where aiming for.

Thanks for the precedence heads-up.

Regards,
Rudy Wieser

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Thread

flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? "R.Wieser" <address@not.available> - 2022-08-18 07:55 +0200
  Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Ike Naar <ike@sdf.org> - 2022-08-18 06:52 +0000
    Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? "R.Wieser" <address@not.available> - 2022-08-18 09:58 +0200
      Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Muttley@dastardlyhq.com - 2022-08-18 14:50 +0000
        Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? "R.Wieser" <address@not.available> - 2022-08-18 17:12 +0200
        Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? scott@slp53.sl.home (Scott Lurndal) - 2022-08-18 15:29 +0000
          Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-08-18 16:43 +0100
            Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? scott@slp53.sl.home (Scott Lurndal) - 2022-08-18 16:10 +0000
            Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? David Brown <david.brown@hesbynett.no> - 2022-08-18 21:19 +0200
              Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Manfred <noname@add.invalid> - 2022-08-19 02:57 +0200
                Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? David Brown <david.brown@hesbynett.no> - 2022-08-19 08:29 +0200
            Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-19 08:12 -0700
          Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2022-08-18 16:47 +0100
            Re: flags & flagMask == flagMask can be true for flags != flagMask if Muttley@dastardlyhq.com - 2022-08-18 15:50 +0000
            Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-08-18 10:46 -0700
              Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-08-18 11:30 -0700
          Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Muttley@dastardlyhq.com - 2022-08-18 15:47 +0000
        Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-19 08:53 -0700
          Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? David Brown <david.brown@hesbynett.no> - 2022-08-19 18:00 +0200
          Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Muttley@dastardlyhq.com - 2022-08-19 16:10 +0000
            Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-08-19 16:45 -0700
    Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Juha Nieminen <nospam@thanks.invalid> - 2022-08-19 06:01 +0000
      Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-08-19 16:07 +0100
      Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2022-08-19 16:08 +0100
  Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Mike Terry <news.dead.person.stones@darjeeling.plus.com> - 2022-08-18 16:14 +0100
    Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? "R.Wieser" <address@not.available> - 2022-08-18 18:10 +0200
  Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-08-18 11:56 -0700
    Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? "R.Wieser" <address@not.available> - 2022-08-18 21:31 +0200
      Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-08-18 21:24 -0700
        Re: flags & flagMask == flagMask can be true for flags != flagMask if flags is a superset of flagMask ? "R.Wieser" <address@not.available> - 2022-08-19 09:36 +0200

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