220 33257 article Path: news.gmane.org!.POSTED!not-for-mail From: Tony V E Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: A strong typedef syntax idea Date: Thu, 20 Jul 2017 15:28:51 -0400 Lines: 240 Approved: news@gmane.org Message-ID: References: <6718363e-3517-4af2-aa5f-9f0dd436c14b@isocpp.org> <95d6f9b7-2f4c-4b1e-6e29-477a9cb3a66d@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="f403045ceeec36fdca0554c4c28d" X-Trace: blaine.gmane.org 1500578935 13944 195.159.176.226 (20 Jul 2017 19:28:55 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 20 Jul 2017 19:28:55 +0000 (UTC) To: Standard Proposals Original-X-From: std-proposals+bncBCUZ5QWKNQIPLCGEZMCRUBDPKSAKK@isocpp.org Thu Jul 20 21:28:50 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f69.google.com ([209.85.215.69]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dYH7x-0003I6-1R for gclcip-std-proposals@m.gmane.org; Thu, 20 Jul 2017 21:28:49 +0200 Original-Received: by mail-lf0-f69.google.com with SMTP id o82sf8379500lfg.5 for ; Thu, 20 Jul 2017 12:28:54 -0700 (PDT) ARC-Seal: i=2; a=rsa-sha256; t=1500578934; cv=pass; d=google.com; s=arc-20160816; b=B2b8FMkJwyhDzpfxrfzjZwhh9AFonxrCjmIjDWDjXZxPLKRC1P+87KdX3pfzXh2OXL RCLfUAku9frTSwWu0nL8HyuhUvt787MbX66Sjyjq77ZwL8xdXhil3XiMTYgpOeaOzs7J n1SgSyhlIZy+m8yLsgyPXBVvNcyy5sO1cgKYe6A5L2MJvXf/XduUW5mn0zVRBPN6yF3V Rt6F5T61zYKjt/NXb0r2GOAgtdG8cWP62OKZki8LQzcXaoBLZ96ObuBOQG+HY1AgrweH mHvHiPy0X7Y04OoqrxrgZof2cukAukVg696HL2esuaNTNJgY0b4VOdsJwMsoAGeWRORV /nIg== ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-unsubscribe:list-subscribe:list-archive:list-help:list-post :list-id:mailing-list:precedence:reply-to:to:subject:message-id:date :from:references:in-reply-to:mime-version:arc-authentication-results :arc-message-signature:dkim-signature:arc-authentication-results; bh=Sf3LS/tfEfHihdgE732S41AZIkSEDDOrSTLE8kMqGzE=; b=NjwERopJtVR5OghGRQszkV3FLpLKDzNkqkmr3CEeQqcoTAmvozKHmEGTnj7N5RWuco XV/KRCD5FECgXT9kARyuwwAJmSExZXE37l7C/TZL15oD1I2WgbA3L+dOUOY33oUN51oE 5kN3spEdDOYWTLaVQKRVyyx8tEk+p/1u++E6pANXdtfO+tAFpszesh8RqYcsjA8QBhoe C2+cgl/+eYXbrtmYbG0ElF9O2uWF5TlhPZdulMbs6jKOczdDL6fKx/4yusHvoBJjYlTd sqhtqusdyVfDc3sONCsx1KLP1WV/YLvZBZuYIiehf5ANZsRDlImHhvsTJ6R0bd6mAjfD pcFg== ARC-Authentication-Results: i=2; mx.google.com; dkim=pass header.i=@gmail.com header.b=ew8uQGIo; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:400c:c0c::232 as permitted sender) smtp.mailfrom=tvaneerd@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=Sf3LS/tfEfHihdgE732S41AZIkSEDDOrSTLE8kMqGzE=; b=1SprQif2dmiKfdPyd/tX+f1Jm/s8VPQ7pr2Ag/lBQYbEqOT+uhLEwVFIsFGxxMm3Be 2xtV/Dzh0R+QGYX9X2CDSi6XiHMLz/MzJu0vckG9X6GQn3e6fkPm6ulJHKp41f6Dd0yB /0CQedWrsrMqQMVcca54SF+P2cZb2xFjOpCFU0NgZ1UeSvUSGtjVl0+2Tdz2k9HpSVFw AvEi8OKjOuSdeLVvkyaQkq7ODRPCHJXzaFQSqpsns6jd7+lRQilMLyKXCMoAOpVF/wcf 7ELk9hVmPyixmWO583VehS05zSWBcxS2exgJMKNx6qQbdRbmLU+61sWfFjCMe++5xdu8 4nUQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to: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=Sf3LS/tfEfHihdgE732S41AZIkSEDDOrSTLE8kMqGzE=; b=gGLY2GM6kSfdH5kQBBGdCpykTCNXH2Dx0PPRw9KGPU/x4vVZZK0wBNNBfKUln3lN4c clpKDLvrqqzghF5QomaApy6o3fM7hviR8obxyD3utCqAs5ebu8AAECMQThH+NC/QcTY1 KEw6mV/xWf3hqa+Ih71vPW5E6TSUhicwhb2LmPngk0Z+IiGf+rv8MrBkCF/ldUlNVxpu CatqEN87iBOeu912kI3Z6NBBxU+sUXJWbfzeJn8AGikHlgtcC877EuqZRSkhkQaqpoPh RX1R0y0qW+ZaqVC5SNB51Q637IoI/dEMpiHedYXLfv95hfGVVMyUgfPNt1cC19iRqeo5 DK+A== X-Gm-Message-State: AIVw112LOF/AeRAF8UNZlRQwyHf18EAefdK3xC+0TeJUmQGIHDgOeH9j Ydg4XnqRaYbkcLKX X-Received: by 10.46.83.86 with SMTP id t22mr858571ljd.33.1500578934805; Thu, 20 Jul 2017 12:28:54 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.28.21.14 with SMTP id 14ls404672wmv.3.canary-gmail; Thu, 20 Jul 2017 12:28:52 -0700 (PDT) X-Received: by 10.28.217.3 with SMTP id q3mr2859600wmg.115.1500578932740; Thu, 20 Jul 2017 12:28:52 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1500578932; cv=none; d=google.com; s=arc-20160816; b=KCGRTDRRE1tCx197B6wZT/63ptzw430KvC29VUUmD1G8DbbgRH+vInFvWmp5S+sWIL KXnOcgQdSO9sP1SIrSp8ZWXga3O8wSmMBx1VpRuz07M+Of8Hpe2/CcEhZIbu0W6Yzz+c cLBmm8tc5PKar0zO9ouCTfYuYOk9YnTwBbbdEBr1GJAM9J+5LYJWvhpu4L1Pw14zittJ rnDY7DOsWEjYjrkwKqDTcjkd3JO7BeYEBYFfrCerODm6ggmzKBFoP18CVIoZM58pkH/2 U6qusYyfj4gnoqBVuBKROud1uS1NEOF/aCoA2olV3evMt1Bgez5oSS3ICyp4pXQKY6lg tDSQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=to:subject:message-id:date:from:references:in-reply-to:mime-version :dkim-signature:arc-authentication-results; bh=TL4HIcgbpPLv030DU8hEkJNa5cjwWeu2NR5XoHiR/hk=; b=dw0av62FPPFaJB4mq46Vq90waMNxhqs+M1vdzlRhZ4F1o1OjcT2fCfbo8nO8VbpFts mgyuBt1MODt6fqz6j29vz5mEGO4+0Y3vWCaXFasI+YWVA3GFPr1HEVxUbeJQMbLYgkyI bZdHXbnHkQQ/qk+nWrfRpFRpUCtr2INGL82KfhZ0j6fxF5PTTS8Pos137ZJzRM+5Rlqe p897Q5A8QETr6TMMGXZAv09jYkTIhQcZmLaXbatDJx6jJ7qgWVScnMfQhadhgVMev5ob z1ABtOxLHGya98QSZXrsiIip1R6qT4URw5SNS5XA+f68nO+GwUwrYFBmKxd302sbij7g fe/w== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.b=ew8uQGIo; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:400c:c0c::232 as permitted sender) smtp.mailfrom=tvaneerd@gmail.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=gmail.com Original-Received: from mail-wr0-x232.google.com (mail-wr0-x232.google.com. [2a00:1450:400c:c0c::232]) by mx.google.com with ESMTPS id z16si2126568wmc.103.2017.07.20.12.28.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Jul 2017 12:28:52 -0700 (PDT) Received-SPF: pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:400c:c0c::232 as permitted sender) client-ip=2a00:1450:400c:c0c::232; Original-Received: by mail-wr0-x232.google.com with SMTP id y43so74520606wrd.3 for ; Thu, 20 Jul 2017 12:28:52 -0700 (PDT) X-Received: by 10.223.169.41 with SMTP id u38mr4143578wrc.286.1500578932256; Thu, 20 Jul 2017 12:28:52 -0700 (PDT) Original-Received: by 10.28.142.20 with HTTP; Thu, 20 Jul 2017 12:28:51 -0700 (PDT) In-Reply-To: X-Original-Sender: tvaneerd@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.b=ew8uQGIo; spf=pass (google.com: domain of tvaneerd@gmail.com designates 2a00:1450:400c:c0c::232 as permitted sender) smtp.mailfrom=tvaneerd@gmail.com; dmarc=pass (p=NONE sp=NONE 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:33257 Archived-At: --f403045ceeec36fdca0554c4c28d Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Here's some example code which may or may not be helped by some form of "strong typedef". https://github.com/tvaneerd/code/blob/master/StrongId.h It wraps a string or int or whatever, and makes it a unique type (based on a Tag template param). Since it is for IDs, it doesn't want arithmetic (or concatenation) operations, but it does want equality and less (et al). I suspect you always want to "inherit" =3D=3D and !=3D, and most likely relational ordering. On Thu, Jul 20, 2017 at 6:59 AM, John McFarlane wrote= : > On Thu, Jul 20, 2017 at 2:29 AM Jonathan M=C3=BCller < > jonathanmueller.dev@gmail.com> wrote: > >> On 20.07.2017 11:25, Alex Newlifer wrote: >> > Hello! >> > >> > I suggest to use `explicit` specifier for using-declaration to make >> strong >> > typedef (aka completely new type). >> > >> > Simple example: >> > ``` >> > using explicit my_int_t =3D int; >> > >> > /* Now we cannot pass into function foo int values without explicit >> cast. >> > */ >> > void foo(my_int_t val) >> > {} >> > >> > int val =3D 0; >> > >> > foo(val); // Error >> > foo(static_cast(val)); // Ok >> > foo(my_int_t(0)); // Ok >> > ``` >> > >> >> While this would be a great step forward, this is not useful for all >> cases. >> > > Yes, something like this could be helpful for improving type safety. > > In a strong typedef you'd want to keep certain functions like an >> `operator+` in your example, but not necessarily *all* operators, member >> functions. >> > > Perhaps removing the operators of a type should be separated from the > concern of removing implicit casting. If you don't want the full > complement of arithmetic, maybe you should not start with `int` at all, b= ut > instead 'explicitly alias' a type with only the operators you want. > (Something like `boost::operators` can make this a easier to achieve.) > > John > >> >> See my blog post about it for rationale: >> http://foonathan.net/blog/2016/10/19/strong-typedefs.html >> >> -- >> You received this message because you are subscribed to the Google Group= s >> "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this group and stop receiving emails from it, send a= n >> 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/95d6f9b7-2f4c-4b1e- >> 6e29-477a9cb3a66d%40gmail.com. >> > -- > 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/CABPJVnR1kzLAp3c- > oLZBStoAmSjODiCAeq9MzDooq%2BTkzsV9sA%40mail.gmail.com > > . > --=20 Be seeing you, Tony --=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/CAOHCbit4n0oyoGp0ymu70APJg_UuNYyxd%2Bt1FQoU96DMm= h8JKw%40mail.gmail.com. --f403045ceeec36fdca0554c4c28d Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Here's some example code which may or may not be helpe= d by some form of "strong typedef".


It = wraps a string or int or whatever, and makes it a unique type (based on a T= ag template param).
Since it is for IDs, it doesn't want arit= hmetic (or concatenation) operations, but it does want equality and less (e= t al).

I suspect you always want to "inherit&= quot; =3D=3D and !=3D, and most likely relational ordering.

<= /div>

On Thu= , Jul 20, 2017 at 6:59 AM, John McFarlane <john@mcfarlane.name> wrote:
On Thu, Jul 20, 2017 at = 2:29 AM Jonathan M=C3=BCller <jonathanmueller.dev@gmail.com> wrote:<= br>
On 20.07.2017 11:25, Alex Newlifer = wrote:
> Hello!
>
> I suggest to use `explicit` specifier for using-declaration to make st= rong
> typedef (aka completely new type).
>
> Simple example:
> ```
> using explicit my_int_t =3D int;
>
> /* Now we cannot pass into function foo int values without explicit ca= st.
> */
> void foo(my_int_t val)
> {}
>
> int val =3D 0;
>
> foo(val); // Error
> foo(static_cast<my_int_t>(val)); // Ok
> foo(my_int_t(0)); // Ok
> ```
>

While this would be a great step forward, this is not useful for all cases.=

Yes, something like this could = be helpful for improving type safety.

In a strong typedef you'd want to keep certain functions like an
`operator+` in your example, but not necessarily *all* operators, member functions.

Perhaps removing the = operators of a type should be separated from the concern of removing implic= it casting.=C2=A0 If you don't want the full complement of arithmetic, = maybe you should not start with `int` at all, but instead 'explicitly a= lias' a type with only the operators you want.=C2=A0 (Something like `b= oost::operators` can make this a easier to achieve.)=C2=A0

John

See my blog post about it for rationale:
http://foonathan.net/blog/2016/10/19= /strong-typedefs.html

--
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/95d6f9b7-2f4c-4b1e-6e29-= 477a9cb3a66d%40gmail.com.

--
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/st= d-proposals/CABPJVnR1kzLAp3c-oLZBStoAmSjODiCAeq9MzDooq%2BTkz= sV9sA%40mail.gmail.com.



--
Be seeing you,
Tony

--
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 h= ttps://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAOHCbit4n0oyoG= p0ymu70APJg_UuNYyxd%2Bt1FQoU96DMmh8JKw%40mail.gmail.com.
--f403045ceeec36fdca0554c4c28d-- .