220 31766 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 15:11:06 -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> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=001a113567bed6a331054ba980bf X-Trace: blaine.gmane.org 1490566270 2924 195.159.176.226 (26 Mar 2017 22:11:10 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 26 Mar 2017 22:11:10 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCDODCNR2QPRB67Y4DDAKGQEEHV2DII@isocpp.org Mon Mar 27 00:11:06 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qt0-f197.google.com ([209.85.216.197]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1csGNK-0008P0-LX for gclcip-std-proposals@m.gmane.org; Mon, 27 Mar 2017 00:11:02 +0200 Original-Received: by mail-qt0-f197.google.com with SMTP id h56sf33828986qtc.10 for ; Sun, 26 Mar 2017 15:11:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender: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=hpcPh1EzdPrwOBQ/IKiSYp1vHcHqCj+dlKalqShwbgM=; b=V+RDmqLU4OlBbh3+1h2fqgW2/D7Ohg3kohksnufZO/MDO+fTjEf0Z7coCeANNH5ARZ MBAPQ3oM5nqhGGcb2XT6qm8rJ/Z4LkBOU+1uJWWoz45xV26qSBg4+FLsTe2IXsJQ4wrH NyoQ5qJqZBQyDQTG1mn3sHfq4VnqE8nYUcYkvW88owpl5BcZ1/U4rZKp/dJp8T6BFv5N qJxI33qeAlmxdexb2p0MGXLLlNbgjMvvS8goYdydNBFKScmIDkvQAbeF1k3vKB6biTX4 USH6epT6dkagS2JZftFRuPt8HptwLM2w5U6/WY2fdIs3UG9wiwO+QIOPbAtuSRC6Ja+B fYXw== X-Gm-Message-State: AFeK/H1WOeaFTGD8Bkt6R1wF/HuTqSStvfmM6Vy+SMgCOzXtUM7wqJlW/1jptCKmZNaIMw== X-Received: by 10.200.50.241 with SMTP id a46mr6158113qtb.13.1490566268083; Sun, 26 Mar 2017 15:11:08 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.35.166 with SMTP id t35ls4641186otb.11.gmail; Sun, 26 Mar 2017 15:11:07 -0700 (PDT) X-Received: by 10.200.44.156 with SMTP id 28mr18499552qtw.48.1490566267149; Sun, 26 Mar 2017 15:11:07 -0700 (PDT) Original-Received: from mail-qt0-x22c.google.com (mail-qt0-x22c.google.com. [2607:f8b0:400d:c0d::22c]) by mx.google.com with ESMTPS id 202si8102611qkm.327.2017.03.26.15.11.07 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 26 Mar 2017 15:11:07 -0700 (PDT) Received-SPF: pass (google.com: domain of sean.middleditch@gmail.com designates 2607:f8b0:400d:c0d::22c as permitted sender) client-ip=2607:f8b0:400d:c0d::22c; Original-Received: by mail-qt0-x22c.google.com with SMTP id n21so24677950qta.1 for ; Sun, 26 Mar 2017 15:11:07 -0700 (PDT) X-Received: by 10.200.44.138 with SMTP id 10mr19350147qtw.12.1490566266657; Sun, 26 Mar 2017 15:11:06 -0700 (PDT) Original-Sender: sean.middleditch@gmail.com Original-Received: by 10.237.47.65 with HTTP; Sun, 26 Mar 2017 15:11:06 -0700 (PDT) In-Reply-To: <136fc743-bc63-48c8-b1d5-dc4084dd13cf@isocpp.org> X-Original-Sender: sean@middleditch.us 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:c0d::22c as permitted sender) smtp.mailfrom=sean.middleditch@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:31766 Archived-At: --001a113567bed6a331054ba980bf Content-Type: text/plain; charset=UTF-8 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). Again, that's all writeable _today_ if you put in the leg work (we have in our libraries), it's just not a standard pattern in the C++ libraries, and you don't get the niceties that concepts provides wrt errors and composition. Generators and mapped iterables aren't new here, just like C++ lambdas weren't new - they're just syntactic sugar for a well-established pattern. > > But Boost.Range already has something like this: `any_range > `, > coupled with transforming the input range by a function > > . > > -- > 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/136fc743-bc63-48c8- > b1d5-dc4084dd13cf%40isocpp.org > > . > -- Sean Middleditch http://seanmiddleditch.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/CALQmNFgAe4B2tiqjA7Mq1TWXWdt-OMAUD41AKzuxh_6_X%3DuRcQ%40mail.gmail.com. --001a113567bed6a331054ba980bf Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On F= ri, Mar 24, 2017 at 3:25 PM, Nicol Bolas <jmckesson@gmail.com> wrote:

Basically, you want to write 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 cost of filtering, all just to gain some incr= eased genericity.

Not at a= ll, because that'd be a template that gets fully inlined and result in = identical machine code (assuming a suitably capable optimizer). Again, that= 's all writeable _today_ if you put in the leg work (we have in our lib= raries), it's just not a standard pattern in the C++ libraries, and you= don't get the niceties that concepts provides wrt errors and compositi= on.

Generators and mapped iterables aren't new= here, just like C++ lambdas weren't new - they're just syntactic s= ugar for a well-established pattern.
=C2=A0

But Boost.Range already has someth= ing like this: `any_range= `, coupled with transforming the input range by a function.

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--
Sean Middleditchhttp://seanmiddle= ditch.com

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