220 35136 article Path: news.gmane.org!.POSTED!not-for-mail From: antanubis@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Add .emplace() method to std::unique_ptr and std::shared_ptr like it is in std::optional. Date: Mon, 30 Oct 2017 09:05:15 -0700 (PDT) Lines: 101 Approved: news@gmane.org Message-ID: References: <58eb77f6-2c2d-4ec1-85f8-08dcfe25a23e@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_6589_877696603.1509379515759" X-Trace: blaine.gmane.org 1509379526 4541 195.159.176.226 (30 Oct 2017 16:05:26 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 30 Oct 2017 16:05:26 +0000 (UTC) Cc: antanubis@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCJLPT5ZVQHBBPE33XHQKGQEPAI6AAI@isocpp.org Mon Oct 30 17:05:19 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f199.google.com ([209.85.217.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1e9CYo-00004y-CS for gclcip-std-proposals@m.gmane.org; Mon, 30 Oct 2017 17:05:10 +0100 Original-Received: by mail-ua0-f199.google.com with SMTP id b11sf10037680uae.0 for ; Mon, 30 Oct 2017 09:05:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc: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=wFxWaElvaJgLHaGz2Kh0yOs6X3C5XoSL5r7sdkh89Oc=; b=YIbQv3D+oM/35T+q2r79+JsiliD9qHhRDLP8Wvcj1kyRDORTneeeOEPY7pZ1LLmbAF nCJrcGMKixRbkjiOI1Gwc59s3Pkx6F6W8NIE2r7mdJe3zYkzxfxoIFlR0ResjdMByDOu fJ7jReKoYdFs0xUDyd/AUdXKnly5UygTlZ4T2SwTv8r/lcYWHtaGjow497kUNxUMi0DY 1q/rCvg3jV6/t09u3A7jWL7Mwchg6cldfEFGnw2MOsG+qmSWh6R7cwJQmlSjLgHrNk4Y 6tHRP+jm/aTpN5dYKoxWvfqY/5lEFlc1Hy/Ba37V1NCDGC9hctHmJuBJ70fLZ0WMYyEh O4Zw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc: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=wFxWaElvaJgLHaGz2Kh0yOs6X3C5XoSL5r7sdkh89Oc=; b=WT1+HmcBgTh+SDlIJ7ZcPVx6z1lldZxaEOQoxgM5zv1cEeapTFgOJq/jzBzCwmkmVU bv9iK2v4tUUuOgjpsRScWN6aDgMmY/8dbJcpBQjl6w9q5qJfgi5gU0BmdZo4Tchkobqs eEmdq4sqoU8IVqzwV0h8CTekx4lf+NauJswAFmZzPrX282PRxaJf+lMfh1ui4ku/i9ig iwDOISC7V6GJ0X8VbPGgDFU1GG180W6Vrk+JZOShYmKphDH2RBp61DxKgbo3QKrVFN2q T3VwWfsXaeNgUOmNOwmWh6azmRhh00sjABuBK/i3FILCOH7rvedotQA7SpGyGjDPDNfc brog== 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:cc: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=wFxWaElvaJgLHaGz2Kh0yOs6X3C5XoSL5r7sdkh89Oc=; b=VkI/HxmbO0j8f/eCO4btuoRCoyygRV+x87kbaK9tYi5ALkcrCfYzM1JeHlGT5qeN3S wjX87zAxbadEOouQqAGiYVCSMu9kTOBXEKR5RhAGHxaRd6nDOdf0nY5hJITkDjvVRfrn 5kEgXcku43OgWxEJaHgVYuoWIM307oU3S+XFnKWBU6iq+UEbBqJFHTffnpELQXJeX86i TOSOJGwN5fDQPypu7+hvA8mMgbqbvugdDsDoOUjdk1vWvRsaXhf9ISKW9rAwSxuJExC9 SxXFxo6YQiQWuZv73PhLg/FwSM3IebLQ+OlPGSW4SKrNHE3JSihhsKuhXHZNUHpq+rA8 iAIw== X-Gm-Message-State: AMCzsaV95SGNgWK0CaP6Dx/UAx8jCmUegupmTtmFLJhPON9biCKMydIr 5LPpENNxUxYU8ZjCHgScL0L2VA== X-Google-Smtp-Source: ABhQp+Tp206ynkHclfBMdhNLfTJQADaO9g1oy68Tqtq5gWZakMhz6aOtY9cs5cwRjpYThFpJ3eBtxw== X-Received: by 10.31.137.131 with SMTP id l125mr8725179vkd.98.1509379517638; Mon, 30 Oct 2017 09:05:17 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.159.53.238 with SMTP id u43ls4296849uad.11.gmail; Mon, 30 Oct 2017 09:05:16 -0700 (PDT) X-Received: by 10.31.142.13 with SMTP id q13mr1655480vkd.1.1509379516173; Mon, 30 Oct 2017 09:05:16 -0700 (PDT) In-Reply-To: <58eb77f6-2c2d-4ec1-85f8-08dcfe25a23e@isocpp.org> X-Original-Sender: antanubis@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:35136 Archived-At: ------=_Part_6589_877696603.1509379515759 Content-Type: multipart/alternative; boundary="----=_Part_6590_1388151577.1509379515759" ------=_Part_6590_1388151577.1509379515759 Content-Type: text/plain; charset="UTF-8" Perhaps being a nice substitution for "= make_...(...)" the return type should be the reference to smart pointer and the return value should be *this. On Monday, October 30, 2017 at 8:01:25 PM UTC+4, anta...@gmail.com wrote: > > I've found really helpful in my own smart pointer classes to have > something like .create(Args &&..args) method that creates an object for an > owning shared pointer without the necessity for repeating the type in the > make_* non-member function. > > It's a shame that standard smart pointers don't have such method, so in > order to create a value you always need to repeat the type name, while it > is contained in the pointer type itself. > > After that I realized, that std::optional<> has such method named > .emplace() together with a free function make_optional<>. In some way > std::optional<> is a lot like "in-place std::unique_ptr<>" with > deep-copying by default. > > So I thought that proposing a member function "ptr.emplace(Args&&... > args)" for both std::unique_ptr and std::shared_ptr will be a really good > idea, it will also fit well with std::optional. The naive (but working) > implementation would be just: > > void(?) unique_ptr::emplace(Args &&... args) { *this = > make_unique(std::forward(args)...); } > void(?) shared_ptr::emplace(Args &&... args) { *this = > make_shared(std::forward(args)...); } > > What do you think? Are there reasons not to add such methods? Or was this > discussed / proposed already? > > Vasilii Babich. > -- 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/db8aed18-d3b3-4df6-8e15-15f8c50e4bed%40isocpp.org. ------=_Part_6590_1388151577.1509379515759 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Perhaps being a nice substitution for "=3D make_...&l= t;T>(...)" the return type should be the reference to smart pointer= and the return value should be *this.

On Monday, October 30, 2017 a= t 8:01:25 PM UTC+4, anta...@gmail.com wrote:
I've found really helpful in my own= smart pointer classes to have something like .create(Args &&..args= ) method that creates an object for an owning shared pointer without the ne= cessity for repeating the type in the make_* non-member function.

It's a shame that standard smart pointers don't hav= e such method, so in order to create a value you always need to repeat the = type name, while it is contained in the pointer type itself.

=
After that I realized, that std::optional<> has such metho= d named .emplace() together with a free function make_optional<>. In = some way std::optional<> is a lot like "in-place std::unique_ptr= <>" with deep-copying by default.

So I = thought that proposing a member function "ptr.emplace(Args&&..= .. args)" for both std::unique_ptr and std::shared_ptr will be a really= good idea, it will also fit well with std::optional. The naive (but workin= g) implementation would be just:

void(?) unique_pt= r<T>::emplace(Args &&... args) { *this =3D make_unique<T&g= t;(std::forward<Args>(args)...); }
void(?) shared_ptr&= lt;T>::emplace(Args &&... args) { *this =3D make_shared<T>= (std::forward<Args>(args)...); }

What d= o you think? Are there reasons not to add such methods? Or was this discuss= ed / proposed already?

Vasilii Babich.
=

--
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To view this discussion on the web visit https://groups.google.= com/a/isocpp.org/d/msgid/std-proposals/db8aed18-d3b3-4df6-8e15-15f8c50e4bed= %40isocpp.org.
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