220 27704 <57A8E703.5070402@gmail.com> article Path: news.gmane.org!.POSTED!not-for-mail From: Matthew Woehlke Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Extend the range-based for statement Date: Mon, 8 Aug 2016 16:09:39 -0400 Lines: 28 Approved: news@gmane.org Message-ID: <57A8E703.5070402@gmail.com> References: <152c8499-aa2f-4e23-aeec-cd055f06a6da@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-Trace: blaine.gmane.org 1470686987 26904 195.159.176.226 (8 Aug 2016 20:09:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 8 Aug 2016 20:09:47 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC37LBFWUIFBBBWOUO6QKGQEXASZ3GY@isocpp.org Mon Aug 08 22:09:43 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f200.google.com ([209.85.217.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bWqrm-0006qn-Rd for gclcip-std-proposals@m.gmane.org; Mon, 08 Aug 2016 22:09:42 +0200 Original-Received: by mail-ua0-f200.google.com with SMTP id u13sf85641987uau.2 for ; Mon, 08 Aug 2016 13:09:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :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=RL3I7BWKERNuv4ckKX2qadM1QkYbl5G2tf9NhwYMsNA=; b=wyquZEpRdJsB8PcNcj7C3AKpTgsTzSJP0RJ565hGRxrJJNQS58wSiZ83zoRVCsHefH pDIdZGtJ59FtxbivBiwQ79yU4GZURytv/8XBuovrAgIz9MJTWegP4xshl90byDrI7sf3 jY3e5/CSLEOvNlTj/0uor8N/3Yr3zNlsvKDE+rP+COND8yNet2fMf301aJ3ilEKTbWKu rTXW3ulnFhRQNRFnz0Gyvn2iLjE0SCkK6QLDyUZMFYExd14h5Edf+lgGkRB3pLeIdprS mIEjQFUY7gEnk+CKO3d1/RowTg/BUGNSxdArohbh0XjoRSt1KvpRkAXUuZIUvRc/yuwZ rBEw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version: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=RL3I7BWKERNuv4ckKX2qadM1QkYbl5G2tf9NhwYMsNA=; b=HBguUDEPdIyzYo59UkBDO+Z7MBE+LxB3MtKQ1AMHhWeQ0YF4I92pSH0ebfXhaQYb3j N046/lbGbruN75yJeDjE3qCtzq9T/GeIgCkYc6S/Kqbux1OWE3orSIok2t6WjRBKRohk L/PkgID2+/S+4LSiZYp+zJWRAYY8HJOZg59Q9P2IAP4+RY8hKMuPX2Osnlh+u+Lnxppk UWnr87MMgTdP12WbgWzBTVNUafJuwCDJs8LHDC0DeZbwDOuoQ73yy/yiVZ9mf7MCyOoO mWmKR1vXgU2DiypqP1jv4nrIYs+rGui4+h5aY1j38Ujfn1D7iJjERWFrdMWi3DQoEVAE 7btg== X-Gm-Message-State: AEkoouv0Z4qlUvEejPfLI4854vAbYNJaHD+p9pRvDZgdzduoPzSidrv11tlIKEkMYNDUDw== X-Received: by 10.237.44.38 with SMTP id f35mr81328119qtd.18.1470686982907; Mon, 08 Aug 2016 13:09:42 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.36.81 with SMTP id p75ls1292885ota.18.gmail; Mon, 08 Aug 2016 13:09:42 -0700 (PDT) X-Received: by 10.200.52.193 with SMTP id x1mr29379886qtb.65.1470686982157; Mon, 08 Aug 2016 13:09:42 -0700 (PDT) Original-Received: from mail-qk0-x22b.google.com (mail-qk0-x22b.google.com. 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[66.194.253.20]) by smtp.googlemail.com with ESMTPSA id j188sm15460070qke.22.2016.08.08.13.09.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 08 Aug 2016 13:09:41 -0700 (PDT) X-Enigmail-Draft-Status: N1110 In-Reply-To: <152c8499-aa2f-4e23-aeec-cd055f06a6da@isocpp.org> X-Original-Sender: mwoehlke.floss@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com; spf=pass (google.com: domain of mwoehlke.floss@gmail.com designates 2607:f8b0:400d:c09::22b as permitted sender) smtp.mailfrom=mwoehlke.floss@gmail.com; dmarc=pass (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-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:27704 Archived-At: On 2016-08-07 16:49, Antonio Perez wrote: > I propose that the range-based for statement is expanded to allow iteration > through multiple for-range-initializes simultaneously [...] Some general observations along the lines of the other replies... A std::zip needn't be too expensive. It doesn't need to fully construct a return object, and in fact probably *shouldn't*. At worst you have a little bit of local state. Another reason to go with something like std::zip is that you can combine it with other iterator adaptors to iterate over the longest list with 'filler' elements when the shorter runs out. Example: for(auto&& [x, y] : std::zip(long_list, std::pad(short_list, 0))) (...where std::pad is a hypothetical function that returns elements of the input list until it runs out, then returns the filler element forever.) -- Matthew -- 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. 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