220 41505 article Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: =?UTF-8?B?R2HFoXBlciBBxb5tYW4=?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Should names used in the initializer of an object of scoped enumeration type be looked up in the scope of the enum? 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[209.85.220.41]) by mx.google.com with SMTPS id v18sor7191686ljc.35.2019.02.26.06.44.42 for (Google Transport Security); Tue, 26 Feb 2019 06:44:42 -0800 (PST) Received-SPF: pass (google.com: domain of gasper.azman@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:a2e:6501:: with SMTP id z1mr13685058ljb.101.1551192281646; Tue, 26 Feb 2019 06:44:41 -0800 (PST) In-Reply-To: X-Original-Sender: gasper.azman@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=HGZU51cS; spf=pass (google.com: domain of gasper.azman@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=gasper.azman@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:41505 Archived-At: --000000000000ed10bd0582cd1890 Content-Type: text/plain; charset="UTF-8" That's not how lookup works :). You need to figure out what type your arguments are *before* you resolve the call. However, as a partial fix to your predicament, my paper "Using Enum" made it to C++20. http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1099r3.html On Tue, Feb 26, 2019 at 2:17 PM wrote: > I use enums quite a bit in my code as it is nice to have strongly typed > values used for passing to functions and switching. > > I'd like to propose the following as the name of such code: > Argument Dependent Name Lookup for Strongly Typed Enums > > ADNL is already used for variables and methods within the current scope > such as inside the same class or namespace, > but enums are still a case where the scope strongly suggests that the > value should be a member of an enum, yet must still be fully qualified. > > Let me give a few examples: > > enum class SpacialUnit { > Inch, > Millimeter, > Point, > Pixel, > }; > > > // assignment to a variable cannot be anything other than the type of the > variable > SpacialUnit unit = Inch; > > > // passing to a function that requires that type > Translate(10, Inch); > // where Translate is declared: > void Translate(int, SpacialUnit); > > > // returning from a function that declares that type > SpacialUnit GetUnit() { > return Inch; > } > > > // switching on a variable of that type > SpacialUnit unit; > switch (unit) { > case Inch: break; > case Millimeter: break; > } > > > // passing as a constexpr value to a template that declares argument type > template > class Rectangle { > ... > }; > > Rectangle saeRect; > > > In every single one of those cases mentioned above, there is no other > possible value besides a member of the enum that can be accepted without > explicit casting. > So why should we be required to qualify the enum name in these cases? > > -- > You received this message because you are subscribed to the Google Groups > "ISO C++ Standard - Future Proposals" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to std-proposals+unsubscribe@isocpp.org. > To post to this group, send email to std-proposals@isocpp.org. > To view this discussion on the web visit > https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/f2442186-7637-487d-ba01-919b6ef9f3e7%40isocpp.org > > . > -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAANG%3DkXAZbiVoBQMQZd2g1nbVnk%2BFnYMetjrNcEwpS3Pph4SBQ%40mail.gmail.com. --000000000000ed10bd0582cd1890 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
That's not how lookup works :). You n= eed to figure out what type your arguments are *before* you resolve the cal= l.

However, as a partial fix to your predicament, my pap= er "Using Enum" made it to C++20. http://www.open-std.org/j= tc1/sc22/wg21/docs/papers/2019/p1099r3.html

On Tue, Feb 26, = 2019 at 2:17 PM <mobile.schew= e@gmail.com> wrote:
I use enums quite a bit in my code as it is nic= e to have strongly typed values used for passing to functions and switching= ..

I'd like to propose the following as the name of s= uch code:
Argument Dependent Name Lookup for Strongly Typed Enums=

ADNL is already used for variables and method= s within the current scope such as inside the same class or namespace,
but enums are still a case where the scope strongly suggests that the= value should be a member of an enum, yet must still be fully qualified.

Let me give a few examples:

enu= m class= SpacialUnit=C2=A0{
=C2=A0 =C2=A0 Inch,
=C2=A0 = =C2=A0 Millimeter,
=C2=A0 =C2=A0 Point,
=C2=A0 =C2=A0 Pixel,
};


// assignment to a variable cannot be anything other= than the type of the variable
SpacialUnit unit =3D Inch;


// = passing to a function that requires that type
Translate(10, Inch);
//= where Translate is declared:
void Translate(int, SpacialUnit);

<= br>// returning from a function that declares that type
SpacialUnit GetU= nit() {
=C2=A0 =C2=A0 return Inch;
}


// switching on a var= iable of that type
SpacialUnit unit;
switch (unit) {
=C2=A0 =C2=A0= case Inch: break;
=C2=A0 =C2=A0 case Millimeter: break;
}

// passing as a constexpr value to a template that declares argument type<= br>template <SpacialUnit unit>
class Rectangle {
=C2=A0 =C2=A0 = ....
};

Rectangle<Inch> saeRect;

=

In every single one of those cases mentioned above, there is no o= ther possible value besides a member of the enum that can be accepted witho= ut explicit casting.
So why should we be required to qualify the = enum name in these cases?

--
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To view this discussion on the web visit = https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/f2442186-7637-= 487d-ba01-919b6ef9f3e7%40isocpp.org.

--
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To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAANG%3DkXAZb= iVoBQMQZd2g1nbVnk%2BFnYMetjrNcEwpS3Pph4SBQ%40mail.gmail.com.
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