220 29247 article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: explicit conversion from enum class to its underlying type Date: Sat, 29 Oct 2016 17:31:15 -0700 (PDT) Lines: 81 Approved: news@gmane.org Message-ID: References: <4afed494-4fc5-4b06-b3e7-255aa293068e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1448_120075116.1477787476050" X-Trace: blaine.gmane.org 1477787486 10295 195.159.176.226 (30 Oct 2016 00:31:26 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 30 Oct 2016 00:31:26 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBVH62TAAKGQEWVX5ULI@isocpp.org Sun Oct 30 02:31:22 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f199.google.com ([209.85.161.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1c0e1r-0001MT-0o for gclcip-std-proposals@m.gmane.org; Sun, 30 Oct 2016 02:31:15 +0200 Original-Received: by mail-yw0-f199.google.com with SMTP id w3sf173264205ywg.1 for ; Sat, 29 Oct 2016 17:31:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to: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=oKuDs604lDDiSz8PixasMKkw4xz8Q5iPnKTtWjxpfO4=; b=bDAuKPN6pc42hDkvb9fqufHBjBIGBDeg4wruwEYazbOaj3puyprpdLK5WYKjFBy5xr QSnBwHN8HtZz0xHfch7yBxqOIjv0WEWXYRCjWK2KSNLY5PhqmOHEn3w4Sr/huvZlraZc /KFp841Zh+rELC2bfxfqLNVSJXoTzOmApKudatSYpP2PIoIvxL5Wf4WrrbK9qQJKG3Xq B0nLoSneUUPiGDAqO+UWs2dRvZhrbPRW/qDJqGrhrCdwRxcbqL1tJCfswuoLD68q9d0a 7nCRF+8lahYjk2sMq/e4tORtBXDSOZSAKNNMEPTHKaoH+tghBe1XhDbUa0RtoTwGJVJy PY/A== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to: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=oKuDs604lDDiSz8PixasMKkw4xz8Q5iPnKTtWjxpfO4=; b=YAL+goq60zHMZaW3H8gjyIx+hzvktVUIGb+ENsB6kTePha+1VwzxbMOmbqcFrvyC1+ RZZTgm5K1mk9GLeFof9durqW5UbZnAFp55UUP02+b95xVkXKqB5MhpSCScYGCSgACOqA 9u1Q9ewR2GjzM0zexr5B5AcN88hPOFJgHFdM+ZWdSNPZwzrn05DWVxb/tLzoM7JFuaTI dndLX+K8KxNkREyKbmoYrrcuEIBek+YnrT0gH0cRDiFDn9TKQQrrJfCg02XMB1+gLtgs JayILy9eluHMuBl/UEtlqubcR/WqB1AAtRSnRWM4osevXMZtRRyP3FhgtzBwsm89DlsJ Fksg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to: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=oKuDs604lDDiSz8PixasMKkw4xz8Q5iPnKTtWjxpfO4=; b=ilRpYrLDqiY44egBZUP4opVH6ZwuP7S+H7qkGSk8f4/jifQCZCta6YSQqmEx0aYRkO vc7HuC3v0yme68Uym4/+QoFZSkSBxSN80ea1LgvZrqQd6rHaNgwYeo7T8KQA/6/86ze1 cWl7mPWpnBE9qQm8JFc6k0STjPP4KQxT9ucIEifw4IQHvIb7N2Ws2rvfJk4c+SFbLcGm Y7UrjBbsdHzyTU5k+5g4yhOSdpDr5h/IK5wfm0Twu446aTwf9wZQdZrDbC/pZOwc2EN6 4xT0r30S7SYFNFY1iXUojgCegmXYxlZdIJ/+x85xW+FNkp5hfE5T+hOjItW58fbQrECG XIMQ== X-Gm-Message-State: ABUngvfoSxsKr2qFLM+NWXR1IjBi1sWOFA6UZmLsdjrtaCG85VX78BOCrS6YJB/GYAaKjA== X-Received: by 10.129.117.70 with SMTP id q67mr7823216ywc.45.1477787477455; Sat, 29 Oct 2016 17:31:17 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.11.110 with SMTP id p43ls9675980otd.40.gmail; Sat, 29 Oct 2016 17:31:16 -0700 (PDT) X-Received: by 10.157.33.166 with SMTP id s35mr2410735otb.10.1477787476533; Sat, 29 Oct 2016 17:31:16 -0700 (PDT) In-Reply-To: <4afed494-4fc5-4b06-b3e7-255aa293068e@isocpp.org> 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:29247 Archived-At: ------=_Part_1448_120075116.1477787476050 Content-Type: multipart/alternative; boundary="----=_Part_1449_1965648314.1477787476050" ------=_Part_1449_1965648314.1477787476050 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Saturday, October 29, 2016 at 5:51:12 PM UTC-4, Andrzej Krzemie=C5=84ski= =20 wrote: > > Hi All, > > One of the nice safety features of enum classes is that they cannot be=20 > implicitly converted to their underlying type. However, do you think we= =20 > would lose this safety feature if we allowed an explicit conversion to th= e=20 > underlying type? > > I do not know of any practical use of explicit conversion operators excep= t=20 > for the contextual conversion to bool. And it is only this conversion tha= t=20 > I am interested in. > So, what you're asking for is if the underlying type of a strong enum is=20 `bool`, then that type can be contextually converted to `bool`. I don't=20 think it's worth adding a language feature for such an incredibly narrow=20 corner case. --=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/c1b30ec0-cf34-4244-9fb5-028458f5d659%40isocpp.or= g. ------=_Part_1449_1965648314.1477787476050 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Saturday, October 29, 2016 at 5:51:12 PM UTC-4, Andrzej= Krzemie=C5=84ski wrote:
Hi All,

One of the nice safety features of enum classes i= s that they cannot be implicitly converted to their underlying type. Howeve= r, do you think we would lose this safety feature if we allowed an explicit= conversion to the underlying type?

I do not know of any practical u= se of explicit conversion operators except for the contextual conversion to= bool. And it is only this conversion that I am interested in.

So, what you're asking for is if the underlying type= of a strong enum is `bool`, then that type can be contextually converted t= o `bool`. I don't think it's worth adding a language feature for su= ch an incredibly narrow corner case.

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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/c1b30ec0-cf34-4244-9fb5-028458f5d659= %40isocpp.org.
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