220 41202 article Path: news.gmane.org!.POSTED!not-for-mail From: Lawrence Emke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: Extensions of Scoped Enumerations Date: Sun, 2 Dec 2018 14:12:32 -0600 Lines: 240 Approved: news@gmane.org Message-ID: References: <506ba0a8-2d6b-4a4d-8fe8-b5e94d232365@isocpp.org> <82c331a0-fb81-4b67-8a7e-c5a6b8929e00@isocpp.org> <43b3f4ec-fd19-4144-bf24-067ce587e071@isocpp.org> <9e3bba78-04c2-42d5-b522-2712932c1659@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="0000000000003f51ac057c0fa94d" X-Trace: blaine.gmane.org 1543781465 5319 195.159.176.226 (2 Dec 2018 20:11:05 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 2 Dec 2018 20:11:05 +0000 (UTC) Cc: philipgins@gmail.com To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCGL5F7MUMNRBVXZSDQAKGQEVNGFXGA@isocpp.org Sun Dec 02 21:11:01 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi1-f198.google.com ([209.85.167.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gTY4y-0001Du-Q6 for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id a5sor5874708oif.39.2018.12.02.12.13.10 for (Google Transport Security); Sun, 02 Dec 2018 12:13:10 -0800 (PST) Received-SPF: pass (google.com: domain of lawrence.emke@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:aca:4ed8:: with SMTP id c207mr8663627oib.276.1543781589404; Sun, 02 Dec 2018 12:13:09 -0800 (PST) In-Reply-To: <9e3bba78-04c2-42d5-b522-2712932c1659@isocpp.org> X-Original-Sender: lawrence.emke@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=H14CtFAD; spf=pass (google.com: domain of lawrence.emke@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=lawrence.emke@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-Spam-Checked-In-Group: std-proposals@isocpp.org 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:41202 Archived-At: --0000000000003f51ac057c0fa94d Content-Type: text/plain; charset="UTF-8" I do not follow every item put forth in this conversation completely. My two cents (worth nothing) is: What is the underlying purpose of an enum? My answer: there seems to be two different purposes! The enum object came out of the need to provide a simple way for code users to communicate which options are being used when a function is called. This arose because before enums you had to remember and use the correct code to specify the option value. Codes changed, as functions were expanded and modified. There were two different uses: 1) the simple code, where the user specified a value (usually an integer) that represented the option being selected. 2) an exact value like 2048. or 4096, etc.. The specified value was actually used. This was more difficult because not all values were valid. So an easy way to provide this value was by using constants or a list of constants. By using numbers simple code and the constants added additional attributes to the object, namely the numerical ordering and the arithmetic operations. Programmers took advantage of these additional attributes (being numbers). Along comes object oriented programming, with homeomorphism, multiple inheritance. and operator overloading. In an effort to handle the problems that enums proposed in this new environment, again the two use cases were lumped into one implementation, where the referencing of the enum value required to state the enum type (or class) value with each reference. Going back to the original case situation, there are really two different objects being involved. The simple code value does not in itself require the additional attributes that are associated with numbers. The name/value case of constants may or may not require numeric attributes. The two uses can and should be separated, for good design requirements. It has been my experience that using one thing for two purposes usually leads to conflicts, as is the case with enums. The simple code case does not require a numeric value. It only requires a unique identifier. The only attributes needed in the code environment is equal and unequal, valid or not valid. The name/value case may or may not need a numerical ordering, and numeric operations. In the case of the simple code, any value for the code can be set, as long as it is not equal to any other enum value (i.e. unique within all possible enum code values within the environment.) The exact value for each enum value can be determined at execution time. Many enum lists can use the same enum value without concern of its use by another function. It has only one meaning. The case of name/value enums is different. In this situation the actual value is very important. can be used for calculation purposes. Its value is dependent on the local scope in which it is used. In this situation the naming of the scope is required. As far as return types. The scoped enum definition should return the name of the scope as the type value. For code enums the ENUM type should be returned. By using the different type values the two cases are identified as different. If an enum value is used without the scope type, it should be assumed to be of type "ENUM", then if a function requires a specific type of enum, it can detect that the wrong type of enum is being used. The reverse is also true. These are just some worthless thoughts about the ENUM subject. They cost nothing and have that value On Sat, Dec 1, 2018 at 7:44 AM wrote: > Hi Bengt, > > That's an interesting detail to fill in, thanks. I will add something > about that to the pdf as well. I think it should absolutely be the integer > and not the base enum, just as you suggest. > > Best, > Philip > > -- > 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/9e3bba78-04c2-42d5-b522-2712932c1659%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/CA%2BAqvO1Tdn-2NyEUBVMVJnuQw%2Bfsxym0gKVv1F5Q3sq3h5rLGw%40mail.gmail.com. --0000000000003f51ac057c0fa94d Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I do not follow every item put forth in this conversation = completely.

My two cents (worth nothing) is:
<= br>
What is the underlying purpose of an enum?

My answer: there seems to be two different purposes!
The e= num object came out of the need to provide a simple way for code users to
communicate which options are being used when a function is called= ..=C2=A0
This arose because before enums you had to remember and u= se the correct code
to specify the option value. Codes changed, a= s functions were expanded and modified.

There were= two different uses:
1) the simple code, where the user specified= a value (usually an integer) that represented
=C2=A0 =C2=A0the o= ption being selected.=C2=A0=C2=A0
2) an exact value like 2048. or= 4096, etc.. The specified value was actually used.
=C2=A0 =C2=A0= This was more difficult because not all values were valid. So an easy way t= o=C2=A0
=C2=A0 =C2=A0provide this value was by using constants or= a list of constants.=C2=A0=C2=A0

By using numbers= simple code and the constants added additional attributes to the=C2=A0
object, namely the numerical ordering and the arithmetic operations.= =C2=A0
Programmers took advantage of these additional attributes = (being numbers).

Along comes object oriented progr= amming, with homeomorphism, multiple inheritance. and
operator ov= erloading.=C2=A0=C2=A0

In an effort to handle the = problems that enums proposed in this new environment, again=C2=A0
the two use cases were lumped into one implementation, where the referenci= ng of
the enum value required to state the enum type (or class) v= alue with each reference.=C2=A0

Going back to the = original case situation, there are really two different objects being
=
involved.=C2=A0 =C2=A0The simple code value does not in itself require= the additional attributes
that are associated with numbers.=C2= =A0 The name/value case of constants may or may=C2=A0
not require= numeric attributes.=C2=A0

The two uses can and sh= ould be separated, for good design requirements.=C2=A0 It has been
my experience that using one thing for two purposes usually leads to conf= licts, as
is the case with enums.=C2=A0

= The simple code case does not require a numeric value. It only requires a u= nique identifier.
The only attributes needed in the code environm= ent is equal and unequal, valid or not valid.

The = name/value case may or may not need a numerical ordering, and numeric opera= tions.

In the case of the simple code, any value f= or the code can be set, as long as it is not equal
to any other e= num value (i.e. unique within all possible enum code values within the envi= ronment.)
The exact value for each enum value can be determined a= t execution time. Many enum lists
can use the same enum value wit= hout concern of its use by another function. It has only
one mean= ing.=C2=A0=C2=A0

The case of name/value enums is d= ifferent. In this situation the actual value is very important.
c= an be used for calculation purposes. Its value is dependent on the local sc= ope in which it
is used. In this situation the naming of the scop= e is required.=C2=A0

As far as return types.=C2=A0= The scoped enum definition should return the name of the scope
a= s the type value.=C2=A0 For code enums the ENUM type should be returned.=C2= =A0

By using the different type values the two cas= es are identified as different. If an enum
value is used without = the scope type, it should be assumed to be of type "ENUM", then
if a function requires a specific type of enum, it can detect that= the wrong type of enum
is being used. The reverse is also true.= =C2=A0

These are just some worthless thoughts abou= t the ENUM subject. They cost nothing
and have that value

=C2=A0


=C2=A0
=


On Sat, Dec 1, 2018 at 7:44 AM <philipgins@gmail.com> wrote:
<= blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px= #ccc solid;padding-left:1ex">
Hi Bengt,

That's an interesting detail to fill in, thanks. I will add something = about that to the pdf as well. I think it should absolutely be the integer = and not the base enum, just as you suggest.

Best,<= br>Philip

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail 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/9e3bba78-04c2-= 42d5-b522-2712932c1659%40isocpp.org.

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/CA%2BAqvO1Tdn= -2NyEUBVMVJnuQw%2Bfsxym0gKVv1F5Q3sq3h5rLGw%40mail.gmail.com.
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