220 31770 article Path: news.gmane.org!.POSTED!not-for-mail From: Sean Middleditch Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Complexities caused by using unique_ptr and move semantics Date: Sun, 26 Mar 2017 20:59:56 -0700 Lines: 137 Approved: news@gmane.org Message-ID: References: <46a85060-631b-49e5-94f3-ab07429d8085@isocpp.org> <86aeb556-e0d7-4d68-b553-1b4163461473@isocpp.org> <136fc743-bc63-48c8-b1d5-dc4084dd13cf@isocpp.org> <0d3f5162-b2f9-4389-a0ec-4e3928492fa3@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=94eb2c060d025dda68054bae6056 X-Trace: blaine.gmane.org 1490587201 31307 195.159.176.226 (27 Mar 2017 04:00:01 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 27 Mar 2017 04:00:01 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCDODCNR2QPRBPM44LDAKGQE6435OGI@isocpp.org Mon Mar 27 05:59:54 2017 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 1csLou-0007Im-9y for gclcip-std-proposals@m.gmane.org; Mon, 27 Mar 2017 05:59:52 +0200 Original-Received: by mail-yw0-f199.google.com with SMTP id d191sf65484891ywe.7 for ; Sun, 26 Mar 2017 20:59:58 -0700 (PDT) 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:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=gJYFUFqyOaxOFRAHeMb6EedEOpGCEDKL4XtbHPGc9VI=; b=dhetqVI7OzXrDWgIN9EWhRJ8cXnKfnNNPs0ROMV6lByhRhwpIqBxq8SArGNoGH22q5 6Ap1CQqgEEjACdYI+lytJHcROUc5W3+/nCXVrOEyL9AxhxGi62ux1Lh7Zu6zvNPf5O/S Jlld1xoJ6bfesUUL9dPwgflfmoFheQtDv56aHdisMC8Wakl3gaD96tVSHg3K9Ud9yx12 VLTnCV9flrX7IfnzXXuC70lhSR3rGLjixZV0nEj2FRVzix1lbeeeJBtRSN9F1ROtkgeW rc479tJQkuIhNhMXNeiQFTQazJX4LxDZljPZzkRrPgHdMtUI1h5h7NnNwcxFbnhBZZkF 1rCg== 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=gJYFUFqyOaxOFRAHeMb6EedEOpGCEDKL4XtbHPGc9VI=; b=PpM8bSkYzhGAFVGrstf3GxeOW6h5Z4vauxazkrr2k0xXoehb4N1TzosQ3QFjM7FLeJ sfwZRuasOhyhy5JzdXWtknqbeOg3Ax1nUNbcQQjn1OTi8mnrmI3/4jwVCsYmZPsMpN7B DwZFqbT6isgnTCfcNuBM1KuSc2Q5YwBwOurCOr5DZQfhCCV7ogRrg+05xLYVF7xOzSfW bmOOHQ5LoM8sx7eAoib7yDzoE8mPPwo+WodUECBXSLHxTemTDVPEjIwq3PMZUZHrSstx lUHPg610C3/7DqNkSWYw4wzFjupW+wrMHMi6T70NqwnjWSjT8DP9rDjyM2vmeE5QI4+R kzaA== X-Gm-Message-State: AFeK/H0Tt8Pwj7wS2z2InogWENWhU33lG7L7zlBqHiSzkEKuJXSq/wpGsI99J9F35QeY2A== X-Received: by 10.129.55.195 with SMTP id e186mr5641198ywa.0.1490587197951; Sun, 26 Mar 2017 20:59:57 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.7.18 with SMTP id 18ls11410285ote.1.gmail; Sun, 26 Mar 2017 20:59:57 -0700 (PDT) X-Received: by 10.200.46.91 with SMTP id s27mr20789384qta.278.1490587197076; Sun, 26 Mar 2017 20:59:57 -0700 (PDT) Original-Received: from mail-qk0-x22d.google.com (mail-qk0-x22d.google.com. [2607:f8b0:400d:c09::22d]) by mx.google.com with ESMTPS id j63si2091761qte.41.2017.03.26.20.59.57 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 26 Mar 2017 20:59:57 -0700 (PDT) Received-SPF: pass (google.com: domain of sean.middleditch@gmail.com designates 2607:f8b0:400d:c09::22d as permitted sender) client-ip=2607:f8b0:400d:c09::22d; Original-Received: by mail-qk0-x22d.google.com with SMTP id p22so28611973qka.3 for ; Sun, 26 Mar 2017 20:59:57 -0700 (PDT) X-Received: by 10.55.176.198 with SMTP id z189mr17520094qke.14.1490587196707; Sun, 26 Mar 2017 20:59:56 -0700 (PDT) Original-Received: by 10.237.47.65 with HTTP; Sun, 26 Mar 2017 20:59:56 -0700 (PDT) Original-Received: by 10.237.47.65 with HTTP; Sun, 26 Mar 2017 20:59:56 -0700 (PDT) In-Reply-To: <0d3f5162-b2f9-4389-a0ec-4e3928492fa3@isocpp.org> X-Original-Sender: Sean.Middleditch@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of sean.middleditch@gmail.com designates 2607:f8b0:400d:c09::22d as permitted sender) smtp.mailfrom=sean.middleditch@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:31770 Archived-At: --94eb2c060d025dda68054bae6056 Content-Type: text/plain; charset=UTF-8 On Mar 26, 2017 6:12 PM, "Nicol Bolas" wrote: On Sunday, March 26, 2017 at 6:11:08 PM UTC-4, Sean Middleditch wrote: > On Fri, Mar 24, 2017 at 3:25 PM, Nicol Bolas wrote: > >> >>> Basically, you want to write something like: >>> >>> iterable foo::get_things() { return make_iterable(_things, >>> [](auto& p){ return *p; }); } >>> >>> >> That's a really bad tradeoff: type-erasing performance plus the cost of >> filtering, all just to gain some increased genericity. >> > > Not at all, because that'd be a template that gets fully inlined and > result in identical machine code (assuming a suitably capable optimizer). > How? `iterable` doesn't specify the It's an expositional snippet. This might shock and surprise you, but it wasn't copied verbatim from a working "thingy" codebase I just had lying around. :) I expect that `Iterator` could be defined as a concept in C++2x. The C++14 template version should use `auto` as the return value, yes. My mistake. Thanks for the totally necessary lesson on runtime abstraction costs though. -- You received this message because you are subscribed to a topic in the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this topic, visit https://groups.google.com/a/ isocpp.org/d/topic/std-proposals/nc5Sj-LtKbA/unsubscribe. To unsubscribe from this group and all its topics, 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/0d3f5162-b2f9-4389- a0ec-4e3928492fa3%40isocpp.org .. -- 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/CALQmNFiye2%3D681BUYyrYXhhYd-ub0X%3DQu0LaOqoj-2YLApFCKQ%40mail.gmail.com. --94eb2c060d025dda68054bae6056 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Mar 26, 2017 6:12 PM, "Nicol Bolas" <jmckesson@gmail.com> wrote:


On Sunday, March 26, 2= 017 at 6:11:08 PM UTC-4, Sean Middleditch wrote:
=
On Fri, Mar 24, 2017 at 3:25 PM, Nicol Bolas <jmck...@gmail.com> wrote:

Basically, you want to wr= ite something like:

=C2=A0 iterable<T&> = foo::get_things() { return make_iterable(_things, [](auto& p){ return *= p; }); }

=
That's a really bad tradeoff: type-erasing performance plus the cos= t of filtering, all just to gain some increased genericity.

Not at all, because that'd be a templ= ate that gets fully inlined and result in identical machine code (assuming = a suitably capable optimizer).

How? `iterable` doesn't specify the

It's an exp= ositional snippet. This might shock and surprise you, but it wasn't cop= ied verbatim from a working "thingy" codebase I just had lying ar= ound. :)

I expect that `= Iterator` could be defined as a concept in C++2x. The C++14 template versio= n should use `auto` as the return value, yes. My mistake.

Thanks for the totally necessary lesson o= n runtime abstraction costs though.


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