220 30470 <24e58aad-ecbc-4c83-a21b-de56ea4c1db0@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: enum_cast proposal Date: Tue, 10 Jan 2017 11:30:40 -0800 (PST) Lines: 253 Approved: news@gmane.org Message-ID: <24e58aad-ecbc-4c83-a21b-de56ea4c1db0@isocpp.org> References: <57258435-5d82-48e7-8ed7-3c38682418fb@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_718_171003813.1484076640633" X-Trace: blaine.gmane.org 1484076658 8341 195.159.176.226 (10 Jan 2017 19:30:58 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 10 Jan 2017 19:30:58 +0000 (UTC) Cc: m.cencora@gmail.com, gmisocpp@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBYPM2TBQKGQETLMPVNQ@isocpp.org Tue Jan 10 20:30:52 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f198.google.com ([209.85.161.198]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cR27x-0000Kr-VP for gclcip-std-proposals@m.gmane.org; Tue, 10 Jan 2017 20:30:38 +0100 Original-Received: by mail-yw0-f198.google.com with SMTP id v73sf54883781ywg.2 for ; Tue, 10 Jan 2017 11:30:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=Mge03ACt51jir2JpRb9tZ0kSwUScWfaMOurGjcvnsII=; b=L1nuZPdbI/6t6U8GsHwnFmtevQj3rrfOFxlXWMJLjcYHmLMNgsCQLH8bMlEICWyUFa JmG9eOI9kojOWRC7+NHcv/0BcsZGOmfjq48dVc5xiQCNrO7p/eM3ShwS9uZtm4pWaI2U Hoh1wT+eWRrNnv0CTppjp4CQw08Txw1mmVr8RiKa/Pn6RW+PpauqD/Bicr4+ZcllQbvr v7HuLMY9WmEL/x3rjKWnL28eXes848IgUKO7v0B9gja6j5N0r8QQGrz7GUEzANgPsa+O xBeSjg/OzT3MQUsGO/UQb6IZ+VIwcUiZxrktCBYPud0kHnxGLYEbINKIHzrm7an5hn8J Girw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=Mge03ACt51jir2JpRb9tZ0kSwUScWfaMOurGjcvnsII=; b=ULHMskVxW59py5lyXbHaHQOV0oL1duvNKsxPRNb7KeUR78CwbgUHld/FMSaAUNXnWY njZ+4k26CdGLsjzvfRB7H5dBbfK7auF2MG5Hqrn1ynzT863WiTxsQDXty0b0yepwjA7A ytjF/FZ5vPcrLatNL5XjkJlR4rEsS3rltsjZzuIHrlhFrn6m84q6cVo2Uavd15z1gLlg /PE3NA9yHkgFWVa1taykHza3pbtuRWMsT/xyP4kfXdR0a1YUviG88e7gDI/ZWgEnKtlP qWUBMneNCI+Jk3Fpw55w6c1c4DCLhzSAI/eTLEar5h+WGhOMIEeO3wFsatSlZfzaImSh atXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:x-original-sender:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=Mge03ACt51jir2JpRb9tZ0kSwUScWfaMOurGjcvnsII=; b=IO1KEGwPEVN2yhBEwTsdW1qFhEFzHlomYUM3Vreht1dWzOKj7lOckzHcgWaTKLLRcP JZUcqbhhkOal2uxHPTy75moCqFMVEB/+yBnrX1DFBOk3ribgDA3PwI8Fa5bIHRuEwinO x599iwe4U/m/ck3DMZyAT3KgRmmxoA9YYYDCHZQxmJ7Es+s7DF50XOvReYEzCZ0YC7Yo q7iYFEpPqin9NV3mmS6z+Bwgr+VtMWhpBur3hvJ8b68jaJqVIIGzDDq1fIPw/94UgXxQ yGpbIlZ6ob+Vmm+n7W7reJgon0U0NR6Wfn5WQyU3pKYB/UJ4Qxx4AvoX4otM0ecDRhyv OeQw== X-Gm-Message-State: AIkVDXKVmUNMecqSp7F93g6WnRuXXxoPtZYBWxwdQc3LPPY7y9WsSalyq8Z0eQmcjojneg== X-Received: by 10.13.201.133 with SMTP id l127mr1497418ywd.70.1484076642016; Tue, 10 Jan 2017 11:30:42 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.36.109 with SMTP id p100ls2570770ota.10.gmail; Tue, 10 Jan 2017 11:30:41 -0800 (PST) X-Received: by 10.157.61.131 with SMTP id l3mr395053otc.18.1484076641272; Tue, 10 Jan 2017 11:30:41 -0800 (PST) In-Reply-To: X-Original-Sender: jmckesson@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:30470 Archived-At: ------=_Part_718_171003813.1484076640633 Content-Type: multipart/alternative; boundary="----=_Part_719_1784432563.1484076640633" ------=_Part_719_1784432563.1484076640633 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Tuesday, January 10, 2017 at 1:49:05 PM UTC-5, Vicente J. Botet Escriba= =20 wrote: > > Le 10/01/2017 =C3=A0 16:31, m.ce...@gmail.com a =C3=A9crit = : > > > W dniu wtorek, 10 stycznia 2017 13:49:00 UTC+1 u=C5=BCytkownik=20 > gmis...@gmail.com napisa=C5=82:=20 >> >> >> >> On Tuesday, January 3, 2017 at 10:56:05 PM UTC+13, m.ce...@gmail.com=20 >> wrote:=20 >>> >>> Hi,=20 >>> >>> > I'll try to create a first draft after I get some more comments w.r.t to= =20 > exceptions. > For sure baseline API must be exception-free. > Do we really want to additionally support API that throws on error? > I'm rather inclined to leave it out - similarly as in to_chars/from_chars= .. > =20 > >> >> I hope this post assists you with your proposal. My suggestions are for= =20 >> your proposal to look something like this: >> >> In I think add: >> >> bool template is_enum( V ev ) >> { >> // compiler magic: >> // Calling this routine causes the compiler to generate or a call a=20 >> routine >> // that returns true if the value ev matches one of the enum E's >> // values. otherwise false. >> } >> > > 'is_enum' name is already used in type_traits header. > Also is_enum seems redundant to me, since to_enum already reports > if convertion succeeded instead of: > if (is_enum(139)) > > you could write: > if (to_enum(139).is_valid) > > or even: > if (to_enum(139)) > if we add explicit bool convertion operator for to_enum_result. > > > I believe we need two checking functions: > * is_enumerator : checks if the explicit conversion from the integer is= =20 > one of the explicit enumerators > * is_in_enum_range: checks if the integer is in the range of valid values= ..=20 > This is the precondition of the static_cast. > > IIUC when the underlying type is explicit, the range of values are the=20 > range of the underlying type. However when the underlying type is implici= t=20 > the range goes from the min to the max of the values of the enumerators. > Right, but `is_enumerator` is a functional superset of `is_in_enum_range`.= =20 Do people really need to ask *only* if a value is in the range of an=20 enumerator? --=20 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 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/24e58aad-ecbc-4c83-a21b-de56ea4c1db0%40isocpp.or= g. ------=_Part_719_1784432563.1484076640633 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Tuesday, January 10, 2017 at 1:49:05 PM UTC-5, = Vicente J. Botet Escriba wrote:
=20 =20 =20
Le 10/01/2017 =C3=A0 16:31, m.ce...@gmail.com a =C3=A9crit=C2=A0:

W dniu wtorek, 10 stycznia 2017 13:49:00 UTC+1 u=C5=BCytkownik gmis...@gmail.com napisa=C5=82:


On Tuesday, January 3, 2017 at 10:56:05 PM UTC+13, m.ce...@g= mail.com wrote:
Hi,


I'll try to create a first draft after I get some more comments w.r.t to exceptions.
For sure baseline API must be exception-free.
Do we really want to additionally support API that throws on error?
I'm rather inclined to leave it out - similarly as in to_chars/from_chars.
=C2=A0

I hope this post assists you with your proposal.=C2=A0My suggestions are for your proposal to look something like this:

In <utility> I think add:

bool template<typename E, typename V> is_enum( V ev )
{
=C2=A0// compiler=C2=A0magic:
=C2=A0// Calling this routine causes the compiler to generate or a call a routine
=C2=A0// that returns true if the value ev matches one of the enum E's
=C2=A0// values. otherwise false.
}

'is_enum' name is already used in type_traits header.<= br>
Also is_enum seems redundant to me, since to_enum already reports
if convertion succeeded instead of:
if (is_enum<MyEnum>(139))

you could write:
if (to_enum<MyEnum>(139).is_valid)

or even:
if (to_enum<MyEnum>(139))
if we add explicit bool convertion operator for to_enum_result.


I believe we need two checking functions:
* is_enumerator : checks if the explicit conversion from the integer is one of the explicit enumerators
* is_in_enum_range: checks if the integer is in the range of valid values. This is the precondition of the static_cast.

IIUC when the underlying type is explicit, the range of values are the range of the underlying type. However when the underlying type is implicit the range goes from the min to the max of the values of the enumerators.

Right, but `is_enumerat= or` is a functional superset of `is_in_enum_range`. Do people really need t= o ask only if a value is in the range of an enumerator?

--
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