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Re: Is a union a kind of class?

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On 08/31/2013 03:12 AM, Seungbeom Kim wrote:
>
> In the taxonomy of C++ types, is a union a (kind of) class?
>
> 9[class]/5 clearly says, "A union is a class defined with the class-key
> union [...]". 5.1.2[expr.prim.lambda]/3 and 9[class]/10 also mention "a
> non-union class [type]", and 5.9[expr.rel]/2 "provided their class is
> not a union", all of which imply that a union is a class.
>
> On the other hand, 3.9.2[basic.compound]/1 lists classes and unions
> separately, which strongly implies that a union is not a class.

Except that what 3.9.2p1 says about unions is "unions, which are classes
...". Note that the word "union" is italicized, which indicates that
this sentence constitutes the official definition of a union.

> If a union is a class, I think 3.9.2/1 is confusing (at best) and should
> be considered a defect.
--
James Kuyper


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Thread

Is a union a kind of class? Seungbeom Kim <musiphil@bawi.org> - 2013-08-31 01:12 -0600
  Re: Is a union a kind of class? Daniel Krügler <daniel.kruegler@googlemail.com> - 2013-08-31 23:52 -0700
  Re: Is a union a kind of class? James Kuyper <jameskuyper@verizon.net> - 2013-08-31 23:52 -0700
  Re: Is a union a kind of class? johnolithicsoftware@googlemail.com - 2013-12-19 11:24 -0800
    Re: Is a union a kind of class? "news" <news@fx21.iad.highwinds-media.com> - 2013-12-22 19:27 -0600
      Re: Is a union a kind of class? James Kuyper <jameskuyper@verizon.net> - 2013-12-27 13:11 -0600
        Re: Is a union a kind of class? evansl <cppljevans@googlemail.com> - 2013-12-29 23:00 -0600
          Re: Is a union a kind of class? James Kuyper <jameskuyper@verizon.net> - 2013-12-31 17:45 -0600

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