220 24391 article Path: news.gmane.org!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: [tuple] extracting tuples out of a tuple Date: Mon, 15 Feb 2016 10:21:10 -0500 Lines: 54 Approved: news@gmane.org Message-ID: References: <1604CAB7-DF4D-45B4-A5F8-E21F70491CB7@gmail.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Trace: ger.gmane.org 1455549710 22730 80.91.229.3 (15 Feb 2016 15:21:50 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 15 Feb 2016 15:21:50 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC37LBFWUIFBB6GZQ63AKGQE5NZ27DI@isocpp.org Mon Feb 15 16:21:42 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lf0-f69.google.com ([209.85.215.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1aVKxu-0008Pg-7J for gclcip-std-proposals@m.gmane.org; Mon, 15 Feb 2016 16:21:30 +0100 Original-Received: by mail-lf0-f69.google.com with SMTP id 78sf50137253lfy.2 for ; Mon, 15 Feb 2016 07:21:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=to:from:subject:date:lines:message-id:references:mime-version :content-type:content-transfer-encoding:user-agent:in-reply-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=leJ8UtVLpkORFgdV0NA5iumP9yeVuNWRyrQso2oS1Mk=; b=0tfqc6XZQJ8faiyjvvONTAi4O2rxS3aQAa0s0AdKUO52MR8rc2+VJDrlCeSS0ubmI9 IARYi1zlEXNVEahWaapDG+hi8wVzsFKTFPjw12Ts9JycXWzQIUw3NpjNMSfEgw4cyUnh p4vD7T3ALM1TgyhqBZt/+0/07c64m1/r8/I0d5AjRqL9UIBvpIh8Xj9AoymsHpmxb++l nUXscpOjHrXweo8qy4JYHpjCBQ5Dk5XaJ/v8eVIcR8LF6PND2jZuypQ5Ih7NcKEOg3dF yhJtaHaKxVEFMCentgVXXojdqHvP3dvpK7muFhvJ0qQTuSzEvRNFXHQ X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:to:from:subject:date:lines:message-id:references :mime-version:content-type:content-transfer-encoding:user-agent :in-reply-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=leJ8UtVLpkORFgdV0NA5iumP9yeVuNWRyrQso2oS1Mk=; b=NbTPO5Cx1/BStyqS2EDqru5JOgOrwwey6KL9fgKGihh1pGjPm7EXCMSMMT5FHWIizA +Aqj2lK3DfnzGMynIrM0Zw0RqJ6YRZe1L6DeHlHH6tTFfaiz4t/BZ/PpT5AkPGYCqRUf Yctee+gpjwVc/wyB0bx7hpprtq5wWbWigHp7hFynVuZwxDavALEhP7YhliCgDkJJ7RT9 slS6ZHqDFvWCRxmNKs1p/Nk8LY7ly4dx5XOl8ZWhjtUrFLmDvVIOvd5PHqJf7X93Wxbp +Hs8k3qZG1Q49XxPPKT2m7GW8kaUI1rt7Yhj1XsVh2p3NWTw7pV X-Gm-Message-State: AG10YOTZfCwpVtHQoU5+TsLyXqtZn8kqXpuONqHr2E5PnvfRHyTG+gZbtXmwaUyOvFKX4Q== X-Received: by 10.194.172.40 with SMTP id az8mr1948500wjc.3.1455549689678; Mon, 15 Feb 2016 07:21:29 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.25.17.69 with SMTP id g66ls542727lfi.47.gmail; Mon, 15 Feb 2016 07:21:28 -0800 (PST) X-Received: by 10.25.23.220 with SMTP id 89mr7231037lfx.49.1455549688043; Mon, 15 Feb 2016 07:21:28 -0800 (PST) Original-Received: from plane.gmane.org (plane.gmane.org. [80.91.229.3]) by mx.google.com with ESMTPS id gj6si15252156lbc.110.2016.02.15.07.21.27 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 15 Feb 2016 07:21:28 -0800 (PST) Received-SPF: pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) client-ip=80.91.229.3; Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1aVKxm-0008JG-RS for std-proposals@isocpp.org; Mon, 15 Feb 2016 16:21:23 +0100 Original-Received: from tripoint.kitware.com ([66.194.253.20]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Feb 2016 16:21:22 +0100 Original-Received: from mwoehlke.floss by tripoint.kitware.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Feb 2016 16:21:22 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 42 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: tripoint.kitware.com User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 In-Reply-To: <1604CAB7-DF4D-45B4-A5F8-E21F70491CB7@gmail.com> X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of gclcip-std-proposals@m.gmane.org designates 80.91.229.3 as permitted sender) smtp.mailfrom=gclcip-std-proposals@m.gmane.org; dmarc=fail (p=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-Spam-Checked-In-Group: std-proposals@isocpp.org 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:24391 Archived-At: On 2016-02-13 05:03, David Krauss wrote: >> On 2016=E2=80=9302=E2=80=9313, at 12:30 AM, Oliver Kowalke wrote: >> >> I've had std::tie() in mind, >=20 > How about a function to get a pack of references from a tuple, Please, no; we already *have* std::tie, we don't need others (including split/splice): // David's tuple_ref std::tie([:]t...); // same as proposed std::split std::tie([:]tpl1..., [:]tpl2...) =3D std::make_tuple([:]tpl...); The RHS (second example) can of course be replaced with just `tpl` if `tpl` is already a std::tuple. Otherwise, this works for any *tuple-likes*, not just actual std::tuple's, provided that the LHS get(T&) returns a reference (as it does for e.g. std::tuple, and presumably would for aggregates when using the implicitly generated version a la P0197). > and a generic slice function, > [snip declaration] >=20 > tpl1 =3D tuple_slice< 0, 3 >( tpl ); > tpl2 =3D tuple_slice< 2, 2 >( tpl ); > std::tuple_cat( tuple_ref( tpl1 ), tuple_ref( tpl2 ) ) =3D tpl; I like that you're thinking along the lines of not creating a magical assignment operator (which is what the proposed head/tail would be; they necessarily would create a "magical" helper class with a templated assignment operator which consumes an *arbitrary* tuple of at least N elements and assigns the first N elements to the N elements of the LHS). I like less that you're still looking at a library solution that only handles std::tuple. Language unpacking/slicing handles *any tuple-like* (on the RHS, and any whose get returns a reference on the LHS). --=20 Matthew --=20 ---=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. Visit this group at https://groups.google.com/a/isocpp.org/group/std-propos= als/. .