220 8407 <775b0fd7-2b3a-4667-b776-d13efe0d2fdb@isocpp.org> article Path: news.gmane.org!not-for-mail From: Cassio Neri Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: [exception_ptr] exception_ptr_cast: cast to the stored exception a la any_cast Date: Mon, 6 Jan 2014 07:33:23 -0800 (PST) Lines: 90 Approved: news@gmane.org Message-ID: <775b0fd7-2b3a-4667-b776-d13efe0d2fdb@isocpp.org> References: <52C7F46C.3060702@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_97_26744951.1389022403263" X-Trace: ger.gmane.org 1389022416 24463 80.91.229.3 (6 Jan 2014 15:33:36 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 6 Jan 2014 15:33:36 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDEYBBEU2UGBBREZVOLAKGQE6F5L5KY@isocpp.org Mon Jan 06 16:33:44 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oa0-f69.google.com ([209.85.219.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1W0CBB-0003uO-Tb for gclcip-std-proposals@m.gmane.org; Mon, 06 Jan 2014 16:33:26 +0100 Original-Received: by mail-oa0-f69.google.com with SMTP id m1sf7813452oag.4 for ; Mon, 06 Jan 2014 07:33:24 -0800 (PST) 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 :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=zpcWa3UtWe0IK3RRJVXZzOem+UXQCVKDlFLlLd/mvXc=; b=TbLAfzQ9jbr2JuK7FpWWow9xwnSkSuAk01Ds/giyVb97e8yEtIHJXjZ9bEvzhnvk9J Bw2iFluDcEC5a/IboPJ/3ljow3olpjqVH+ZYHj5vwu6EjCXwVwyZT4p7Ufk3iu96SGco /CXwgB8+BJ4iRmaq6NWkrE4FnajiBuHQKbWIcTzGCXXaiY83h5nL1aUjXMPv5K1YA4ZF AxyWZo/XVkGBzKT+TrocoUrXxn5m37fluphoDNen/Z8fc7Q3W23XVs4Imz44CdZ4a7MB f6Zu+zUC+ce8beHlPqoOGgCp6sxCBtrqVSLJwIl5l4aC2R8VDUBk0lBAbSvLDjcUrQQ9 pctg== 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:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=zpcWa3UtWe0IK3RRJVXZzOem+UXQCVKDlFLlLd/mvXc=; b=hUqS9B+PbptHe8kmylWuLedaGl2gdo1YqS+xcI9JWLSNWrEyixcLWNJ6b1oGkTk6MF Td8Z2TcxwaVApXwmTS9az5DSHtIVKqtq7do+p8bzUeAcZZKF57zF1CS+yUF7eijMNav3 UJ+c+jAfuX1zCXpGHTacfCLcX/wKPas0t70m4YOsiOBAh/5M7LP34gZLvlYOKiINJ75e xQV7CLoNagfGVDcgPzHSsV0eREqSETcwn8HgeBqQX4hwv6eL13STSkoszIVXMkfyl4pi crSRyrBc96nf84mWTLwU0n7pc8mrJN+HjKQins5Q4ulUZN/RDwas2EqQHW+A+PY4yXTG kAKw== X-Gm-Message-State: ALoCoQl98p5p3YIv9M+QtuTbisj6D4Mv3GFSCTlycJXkYHXldSx5l8scGB7fYRadEMy24q7xwsT4 X-Received: by 10.43.161.202 with SMTP id mh10mr19381273icc.23.1389022404733; Mon, 06 Jan 2014 07:33:24 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.2.69 with SMTP id 5ls5942361qes.98.gmail; Mon, 06 Jan 2014 07:33:23 -0800 (PST) X-Received: by 10.49.35.107 with SMTP id g11mr1360336qej.5.1389022403941; Mon, 06 Jan 2014 07:33:23 -0800 (PST) In-Reply-To: <52C7F46C.3060702@wanadoo.fr> X-Original-Sender: cassio.neri@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:8407 Archived-At: ------=_Part_97_26744951.1389022403263 Content-Type: text/plain; charset=ISO-8859-1 On Saturday, January 4, 2014 11:45:48 AM UTC, Vicente J. Botet Escriba wrote: > > > I would like to define a dynamic cast that returns a pointer to the stored > exception it the type match > > template > const E* expected_cast(const expected*); > > if (auto ex = expected_cast(&y)) > { > std::cout <num <<"," <den< } > > I'm not sure but what about something along these lines? const E* expected_cast(const expected* y) { try { if (!y->valid()) std::rethrow_exception(y->exception_ptr()); } catch (const E& object) { return &obj; } catch (...) { } return nullptr; } Is there any lifetime issue here? What if a similar function was part of the exceptr_ptr interface? HTH Cassio. -- --- 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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. ------=_Part_97_26744951.1389022403263 Content-Type: text/html; charset=ISO-8859-1


On Saturday, January 4, 2014 11:45:48 AM UTC, Vicente J. Botet Escriba wrote:

I would like to define a dynamic cast that returns a pointer to the stored exception it the type match

template <class E, class T>
const E* expected_cast(const expected<T>*);

if (auto ex = expected_cast<NotDivisible*>(&y))
{
   std::cout <<ex->num <<"," <<ex->den<<std::endl;
}


I'm not sure but what about something along these lines?

const E* expected_cast(const expected<T>* y) {
  try {
    if (!y->valid())
        std::rethrow_exception(y->exception_ptr());
  } catch (const E& object) {
     return &obj;
  } catch (...) {
  }
  return nullptr;
}

Is there any lifetime issue here? What if a similar function was part of the exceptr_ptr interface?

HTH
Cassio.

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