220 33551 <54580edb-4a76-4241-b5c8-19ccbc1a562e@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Arthur O'Dwyer Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Catch block for multiple exceptions Date: Wed, 2 Aug 2017 15:56:38 -0700 (PDT) Lines: 141 Approved: news@gmane.org Message-ID: <54580edb-4a76-4241-b5c8-19ccbc1a562e@isocpp.org> References: <4126837.jZlGhgVnua@tjmaciei-mobl1> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_6400_1396982999.1501714598251" X-Trace: blaine.gmane.org 1501714600 9615 195.159.176.226 (2 Aug 2017 22:56:40 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 2 Aug 2017 22:56:40 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDLZJYWNDQIKNMMJZQCRUBG5RJZQY@isocpp.org Thu Aug 03 00:56:34 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw0-f200.google.com ([209.85.161.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dd2Z8-0002Ab-8Z for gclcip-std-proposals@m.gmane.org; Thu, 03 Aug 2017 00:56:34 +0200 Original-Received: by mail-yw0-f200.google.com with SMTP id c13sf95466105ywa.2 for ; Wed, 02 Aug 2017 15:56:40 -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 :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=+qpqUmbVVh/wQo9E9Tle/t+oh++lHQxyr30EuipXSs8=; b=JwOutKZTzTaXjbjVxBYQqpUFx4U04BrV5qZjnvwM/baFyUMxOe2jO4oNuHz20Zz2tN xYORWfZUAkVyR3QpykyDUlqHKGQB+g3QjGgEQcHzGSw+PHYY3Hp4VLw09OPquiIhZY6o eY3pIBT4810jEHj12mEnenOVlwYC5ZNNzFfstKQ2Kthza/JvH/Fnal/krUzbryfOc9VM QAwB/cZleXQ0/XTtSgwIQsBv3sTXRjNXadt38OXGm2yPWHbZFrE9XVBvhfv/MLlm9uPb uNCaxkia2V29Dflz4xvk+kFEF2BzHGcbZMpy8ZMKdkvAfvrmfAManJggdkuNmQl/SMEt /DcQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=+qpqUmbVVh/wQo9E9Tle/t+oh++lHQxyr30EuipXSs8=; b=DaHiq45Ywuzc/50hViuzk1pxxYSU4cEW6Uglp9RVqz8F4Y2thLuOMF3lIRGiMzI52W DANb67PsexirKN854Gg+xlKHv2SikiJqQVGuxkZD2PbpnLiACNR5CwucO16EGAG0wE4/ CWy6X2SYee1H3qb5lfAn2CUkDnaz4ntkd9Zk/uaxqbA2Y2ZD3REXR/u3h7YCXb2ixbmV OdbYAxJhassbiyHgVHVJ27XKdZC8948Yv10e6gIYARBhhxedgeFo+DoJiJzTdTfh3bHk gW2HQ7QQ5HnQRyWGXK6yEaj9+CD1di4DJBCKggD8gdggNX/hzThFoeeE/tx9VH69rrDo nIlQ== 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: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=+qpqUmbVVh/wQo9E9Tle/t+oh++lHQxyr30EuipXSs8=; b=j6uzxV2ihBzfYGsc3pYfa4CwoIcuZhFZO/mbQprNMCo34b3HRh55alIfG0jLtnzAFy rmqzafFn9BuPZbjUDX5kY7TC0mds/evN5j5jQ3gzuDa6EkKPD3QLFM9lNT/8MiO1bnNK EvuUGzL/98NUXM5Kswy3X+6F9F+nQrn+t7QyAM8lxGq5ZTQQ4BC9qB1Qnf2JMe7jGtYU EUrDkulFQ6NzcVn/sL6CsKpXFpNeADh6OmYar2oNQd7s2fm1Fh8JNzDwNatsYZN+Y7Rw pqWyaxzwnpwxSGJDrCcJ+xd7p2PfrYO0cABlBTrx7awog3ChJaRYeS5FbURJFhhoQb50 37IA== X-Gm-Message-State: AIVw111Z/KpvkXeHaqO8TsI8fJO2mk2Pq2r1OU9yMysjRv0+M7f43pmD Lktw259bDxpW7R21 X-Received: by 10.13.203.20 with SMTP id n20mr18175335ywd.79.1501714600037; Wed, 02 Aug 2017 15:56:40 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.19.105 with SMTP id b102ls363699ioj.19.gmail; Wed, 02 Aug 2017 15:56:38 -0700 (PDT) X-Received: by 10.31.160.13 with SMTP id j13mr51526vke.25.1501714598735; Wed, 02 Aug 2017 15:56:38 -0700 (PDT) In-Reply-To: X-Original-Sender: arthur.j.odwyer@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:33551 Archived-At: ------=_Part_6400_1396982999.1501714598251 Content-Type: multipart/alternative; boundary="----=_Part_6401_1807263504.1501714598251" ------=_Part_6401_1807263504.1501714598251 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wednesday, August 2, 2017 at 11:40:35 AM UTC-7, Ville Voutilainen wrote: > > On 2 August 2017 at 21:05, Ricardo Fabiano de Andrade=20 > > wrote:=20 > > Hum, a template... bikeshedding an alternate syntax:=20 > >=20 > > catch(auto& e) {=20 > > ... do something=20 > > }=20 > > > Boo hiss. Let's just write a solution with the toys C++17 gives us. > FYI, this exact puzzle (variadic "catch") was discussed in the=20 #meta_programming Slack channel on June 30th; participants were Vittorio=20 Romeo, Barry Revzin, Eric Niebler, Peter Dimov, and myself (belatedly). My= =20 solution is here . Its punch= =20 line is: try { throw Derived(); // this is just a placeholder for some code= =20 that might throw } catch (...) { variant_catch([](auto&& e) { printf("caught %s (%s)\n", typeid(e).name(),=20 __PRETTY_FUNCTION__); }); } but with the caveat that this signature (also provided at the Wandbox link= =20 above) will be more performant (not that we care about the performance of= =20 the exceptional path, of course): variant_catch([&]() { throw Derived(); // this is just a placeholder for some code that= =20 might throw }, [](auto&& e) { printf("caught %s (%s)\n", typeid(e).name(), __PRETTY_FUNCTION__); }); HTH, =E2=80=93Arthur --=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/54580edb-4a76-4241-b5c8-19ccbc1a562e%40isocpp.or= g. ------=_Part_6401_1807263504.1501714598251 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Wednesday, August 2, 2017 at 11:40:35 AM UTC-7, Ville V= outilainen wrote:
On 2 August 2= 017 at 21:05, Ricardo Fabiano de Andrade
<ricardofabi...@gmail.com> wrote:
> Hum, a template... bikeshedding an alternate syntax:
>
> catch<exceptionA, exceptionB, exceptionC>(auto& e) {
> =C2=A0... do something
> }


Boo hiss. Let's just write a solution with the toys C++17 gives us.=

FYI, this exact puzzle (variadic "= ;catch") was discussed in the #meta_programming Slack channel on June = 30th; participants were Vittorio Romeo, Barry Revzin, Eric Niebler, Peter D= imov, and myself (belatedly). My solution is here. Its punch line is:

=C2=A0 =C2=A0 =C2=A0 =C2= =A0 try {
=C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 throw Derived();=C2=A0=C2=A0// this is just a placeho= lder for some code that might throw
=C2=A0 =C2=A0 =C2=A0 =C2=A0 } catch (...) {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 variant_catch<const Derived&, const Base&>([](auto&= ;& e) {
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 printf("caught %s (%s= )\n", typeid(e).name(), __PRETTY_FUNCTION__);
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 })= ;
=C2=A0 =C2=A0 = =C2=A0 =C2=A0 }

but with the caveat t= hat this signature (also provided at the Wandbox link above) will be more p= erformant (not that we care about the performance of the exceptional path, = of course):

=C2=A0 =C2=A0 variant_catch<const Derived&, const Base&>= ([&]() {
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 throw Derived(); =C2=A0// this is just a placeholder f= or some code that might throw
=C2=A0 =C2=A0 }, [](auto&& e) {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 printf("caug= ht %s (%s)\n", typeid(e).name(), __PRETTY_FUNCTION__);
=C2=A0 =C2=A0 });

HTH,
=E2=80=93Arthur

--
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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/54580edb-4a76-4241-b5c8-19ccbc1a562e= %40isocpp.org.
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