220 38460 article Path: news.gmane.org!.POSTED!not-for-mail From: Omer Rosler Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Concepts fragmentation problem Date: Sun, 3 Jun 2018 10:01:32 -0700 (PDT) Lines: 52 Approved: news@gmane.org Message-ID: References: <48f336e3-146b-4317-8a60-1a3acc16af4b@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_26135_692902384.1528045292855" X-Trace: blaine.gmane.org 1528045167 9539 195.159.176.226 (3 Jun 2018 16:59:27 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 3 Jun 2018 16:59:27 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBC2L3NWCRYJBB3N52DMAKGQEKWLD5HY@isocpp.org Sun Jun 03 18:59:23 2018 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 1fPWLj-0002Ny-E1 for gclcip-std-proposals@m.gmane.org; Sun, 03 Jun 2018 18:59:23 +0200 Original-Received: by mail-yw0-f199.google.com with SMTP id s12-v6sf21240847ywl.13 for ; Sun, 03 Jun 2018 10:01:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to: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=WTaO//VoeVaXj2ghQ9zu5h4JdDZHquIPdI4/Ps8A5KY=; b=TM3rAOAYXmwp1hU9OwgxttBMFQ7cNIlrrku2M+9aOjYDmvXvFRBE11Jbg/2wmm/+bX I09A0HKftaSVVM97qsij9T5UNmEgypu33MN8SbolzuOUbnq06qVnG3WbiiPINOka5TlT tSggMxL7HcA1OW1u9/m65ItbAk95mFmTTZ5JuliYu7f2c6XXCleMH4ISnm6bRC6SZn+n ebb58Qq7BPJl6igirQ1Hn297WrEOkA5uhDcqBwQvnEUvBeCP/IORtZ6vqunwVTpqgrsM LQ/TXe+oSW/wIC8Gd6A8YUcdzHpoChP9xx7zYDC2UNrhHHg2oX2JnRt3pIGzng0Cvcm3 zJRw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to: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=WTaO//VoeVaXj2ghQ9zu5h4JdDZHquIPdI4/Ps8A5KY=; b=aW6nfuGhkgWHtDu7WKIi9ajjTLPDJnBoLR7KLxYZrjq3XjS00pB8HhHX5tTHfwLDzd /VYRpCKc8szSABMQcynAtNR78mbEz81js6ZmFb2RN/0A7U57WvnnPU9pdyhpIeUbs+kP iVx/mL/IVC/sF+KtceWCdxuHKQD6jeZBFd7u0vwEMRpQK7ocVavx3XOLImocLDE1OOAn +8BcMyTQB/a+dPQ4at+mFQoVooHE2TmFcuwQQ69EaJBTuFsGrcBPhouOEOMENPRThWF7 Hkfl2Ip6Jr4fFBDYElGINz8l7hv4Lg1WXV2zpLok0QZbwsp+mO+0pfVwjv1w/jOSH2Hw wsMQ== 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: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=WTaO//VoeVaXj2ghQ9zu5h4JdDZHquIPdI4/Ps8A5KY=; b=bnPx06DVTeRe3x9/cNtFNZOYQN/tVLUXcW4tCWx9LrRmGsv63iCjVdjUAevm5Mziwg e2AeqEl0nM+gRIh2cRPhuN2ttaq63+ZiTSfThPuYKzA5kYGltSUJ6dkFh6cg206B8Ah+ /BghBmcvMw731Aaii8SyTpjfEDvSva+Zqt4zzKahhHyPvmBZkyluk/Ps91weN3l9GOY3 BXY5eQO3eEFqvykx/TCsSH1MFxRY0qxUKEXqe+BA6gPK61An1dG1y4MA+mO8ggon/PqE LDgUAnH4vHyJ11uZAydbO7LPK2NgYwIlBepyq/PRTP6MrgXvGhSuM4meiJPqJp4Uqln5 7EEA== X-Gm-Message-State: ALKqPwcXkrzQB5lb0vWWqUQW5yL1R6KeSiWrk9qPlAbrw5IjEvCl185z MnzGQml/7ULA7jl6IdifpeZRbA== X-Google-Smtp-Source: ADUXVKI8hucccCquhP8SmNnfNq+3twih8FPEyHP18j/VNnu5aNQWtIJbhRpwDXbnQKBrU1KNBEfAOg== X-Received: by 2002:a0d:c207:: with SMTP id e7-v6mr4815834ywd.192.1528045294301; Sun, 03 Jun 2018 10:01:34 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a81:f108:: with SMTP id h8-v6ls5280637ywm.10.gmail; Sun, 03 Jun 2018 10:01:33 -0700 (PDT) X-Received: by 2002:a0d:f606:: with SMTP id g6-v6mr756221ywf.3.1528045293276; Sun, 03 Jun 2018 10:01:33 -0700 (PDT) In-Reply-To: <48f336e3-146b-4317-8a60-1a3acc16af4b@isocpp.org> X-Original-Sender: omer.rosler@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:38460 Archived-At: ------=_Part_26135_692902384.1528045292855 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sunday, June 3, 2018 at 4:59:34 AM UTC+3, Nicol Bolas wrote: > On Saturday, June 2, 2018 at 7:57:30 PM UTC-4, Omer Rosler wrote: >=20 >=20 >=20 > The problem with second approach the user now has to remember two version= s of the same concepts: one to use and one to implement. >=20 >=20 > How many times have you used an iterator? I bet it's several orders of ma= gnitude more often than you've written one. >=20 >=20 > Yes, your library has two concepts. But they aren't two versions of the s= ame concept. There's the Iterator concept, and there's the ThingThatThisToo= lTurnsIntoAnIterator concept. Those aren't the same thing; indeed, more lik= ely than not, they are quite dissimilar. They have different interfaces and= different purposes. >=20 >=20 > Users don't have to remember the ThingThatThisToolTurnsIntoAnIterator con= cept, because they simply don't use it very often. When they need to use it= , they'll look up what it does and how it works. What they're going to reme= mber is Iterator, because that's what they're using most of the time. Well the iterator comparison for the ratio of uses/implementations is not f= air as this is not the case for every concept library out there.=20 There is a second problem with this separation into two concepts: Consider a customization point in the users' concepts that is given via a t= raits class. If that customization is not given by the ThingThatTurnsIntoMyConcept (then= this concept also has a traits class) then users and implementers use diff= erent customization points which costs the library in a lot more metaprogra= mming pain just because it uses concepts. --=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/e21d8a37-1e22-41b2-beef-b0d21f2886b6%40isocpp.or= g. ------=_Part_26135_692902384.1528045292855-- .