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Botet Escriba" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: enum_cast proposal Date: Tue, 10 Jan 2017 20:00:27 +0100 Lines: 69 Approved: news@gmane.org Message-ID: References: <57258435-5d82-48e7-8ed7-3c38682418fb@isocpp.org> <58750288.5080004@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1484074838 26481 195.159.176.226 (10 Jan 2017 19:00:38 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 10 Jan 2017 19:00:38 +0000 (UTC) User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:45.0) Gecko/20100101 Thunderbird/45.6.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDH67CONY4PBBTW62TBQKGQE4VPDM6I@isocpp.org Tue Jan 10 20:00:33 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f70.google.com ([209.85.215.70]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cR1em-0005t6-6V for gclcip-std-proposals@m.gmane.org; Tue, 10 Jan 2017 20:00:28 +0100 Original-Received: by mail-lf0-f70.google.com with SMTP id k86sf75397449lfi.4 for ; Tue, 10 Jan 2017 11:00:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-transfer-encoding:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=xe3I427El9CHNHg9ryT+ySNEl85PgDRp2acsrL0GS4w=; b=e8FJvZDgySBuWLO/VBG5xF0PDDwMGrhdyGxftRr/o2RjW2mINqpVvAgwO5Mlk8tNgI 63l/LZXf3IkvTL7tbIzEBOM9Kbsq0H4QsuZJZBfpMTkpSaVjk52y44RUr00xrycVLKaW D+rZTpil3w6orquW55uXIR/fvDs1QlgGRVewp5NAzl5ROs6OaOdYSzqcxbMPQe5A02f2 VOpIjM3Ce4azyu/qCOzOZWYZJpjXC4E1fSWTSaSV0tzeKetUvWdG9M95AsgtlU3r8uz9 f2aB4eBbfb+UXW2sKgIHKcnnQMNrvUWpR+QV7uIvPMnyg86pidxGyn3MFwyKdVQWVIKm X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=xe3I427El9CHNHg9ryT+ySNEl85PgDRp2acsrL0GS4w=; b=AwwCFZ845jruhpqaqChEqIEVnT2rD6iJhwifIm8jMavp4H94NKp8muX9HJe9OyMtqG X2pz94IAoyj7llAEtv97TPr2snJFGNJcBSfqYTuDl08FoMRH/DRA72H1oM+I4W4w8g8n xru8VfwdBMNNe6yS0527/QmLA40bcLX7uG3o3gFO2JB2e8PRoS/a1ceW02X0cm47gicT wt+PutIFot6GMNx7Li81iMV3sjUKhbdcPD16xYcxIzc7KESn0yCeWO9j/okPRuOvrcu1 SNvQoDmLZw1VMjopXugDlBotfdcQKpnHqLzQ1/UQWU3/NwTtTmCLJf7HBaFQq84Ognhm X-Gm-Message-State: AIkVDXLcOVTwNOkog5gha9IOTr73zPhyiVrdn25QfFZyTeCz6DRQLFo4cs6dsx0wx7Lehw== X-Received: by 10.46.76.17 with SMTP id z17mr390529lja.5.1484074831379; Tue, 10 Jan 2017 11:00:31 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.13.14 with SMTP id 14ls426561wmn.15.gmail; Tue, 10 Jan 2017 11:00:30 -0800 (PST) X-Received: by 10.194.191.133 with SMTP id gy5mr3185240wjc.56.1484074830116; Tue, 10 Jan 2017 11:00:30 -0800 (PST) Original-Received: from smtp.smtpout.orange.fr (smtp10.smtpout.orange.fr. [80.12.242.132]) by mx.google.com with ESMTPS id b1si2352753wjz.272.2017.01.10.11.00.30 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 10 Jan 2017 11:00:30 -0800 (PST) Received-SPF: neutral (google.com: 80.12.242.132 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) client-ip=80.12.242.132; Original-Received: from imac-de-vicente-botet-escriba.home ([2.11.64.156]) by mwinf5d20 with ME id Wj0U1u0053NGJZe03j0Vk3; Tue, 10 Jan 2017 20:00:29 +0100 X-ME-Helo: imac-de-vicente-botet-escriba.home X-ME-Auth: dmljZW50ZS5ib3RldEB3YW5hZG9vLmZy X-ME-Date: Tue, 10 Jan 2017 20:00:29 +0100 X-ME-IP: 2.11.64.156 In-Reply-To: X-Original-Sender: vicente.botet@wanadoo.fr X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 80.12.242.132 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) smtp.mailfrom=vicente.botet@wanadoo.fr 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:30468 Archived-At: Le 10/01/2017 =C3=A0 18:01, Peter Koch Larsen a =C3=A9crit : > Nicols proposal is very similar to mine, except that I do not have an > enum_cast_opt. And I do not really see a reason to have this option. > I believe that noone would use that option. Why write > > std::optional e =3D enum_opt_cast(x); Because optional is a monad and you can do much more than checking for=20 whether it is present? Anyway, all these functions could be defined in top of the checks. > if (e) > { > normal processing > } > else > { > handle conversion failure > } > > instead of > > if (is_enum(e)) > { > Enum e =3D to_enum(x); > normal processing > } > else > { > handle conversion failure > } > ? > Things to consider when implementing: > > What do you do if you have an enum with some same_valued elements > (enum E { ea =3D 0, eb =3D 0})? My implementation forbids this. What is the advantage to forbidding it. > It could also be useful to have an ordinal position: > > enum E > { > ea =3D 1000, > eb =3D -1000, > ec =3D 32 > }; > > static_assert(to_ordinal(ea) =3D=3D 0,"??"); > static_assert(to_ordinal(eb) =3D=3D 1,"??"); > static_assert(to_ordinal(ec) =3D=3D 2,"??"); I'm working on a proposal on ordinal types. We can consider that an enum=20 having all the enumerators different is an ordinal type if we consider=20 only these enumerators are valid. We could as well consider that any=20 Integral type is an ordinal type. This proposal will include also the value associated to a position and=20 on top of that ordinal_array, ordinal_set and ordinal_range. https://github.com/viboes/std-make/tree/master/include/experimental/fundame= ntal/v3/ordinal Vicente --=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/edb1413c-5a47-39ff-0c17-587a27ca86f8%40wanadoo.f= r. .