220 6151 <97c39adb-7f10-4bcc-a9c9-121356e2308c@isocpp.org> article Path: news.gmane.org!not-for-mail From: the.ultimate.koala@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: std::degenerate<> class template : primitive/enum types with a special "undefined" value Date: Wed, 4 Sep 2013 09:04:05 -0700 (PDT) Lines: 134 Approved: news@gmane.org Message-ID: <97c39adb-7f10-4bcc-a9c9-121356e2308c@isocpp.org> References: <18ab4801-260a-4228-8a7b-a71248b624e2@isocpp.org> <77a1bdf8-1e0d-4294-b528-d08ba5403c98@isocpp.org> <023111c2-c983-407d-918f-39be42aa2949@isocpp.org> <88ef15f1-6942-476e-b26c-6873ef6e6f0b@isocpp.org> <01900060-3aac-4645-a4a8-93b4e8760e42@isocpp.org> <5e63fe81-ab33-4bbb-ab4c-305f8b90140a@isocpp.org> <51a05a5a-ad56-4ffa-81d8-759953a93766@isocpp.org> <787f2f45-1fbc-4ce5-90fc-d8f0d8c2b8f4@isocpp.org> <6da8e8d3-7c26-4841-bc3f-40dd0715e92b@isocpp.org> <5226D6A4.4040707@wanadoo.fr> <90eb2850-ff75-47b6-979d-ac7400146b0b@isocpp.org> <208850a5-5c8f-46c4-abe0-2a5aaea09dfd@isocpp.org> <200f023a-8cf5-4325-bf3e-e3d1f4fa30c7@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_466_9070264.1378310645629" X-Trace: ger.gmane.org 1378310647 3242 80.91.229.3 (4 Sep 2013 16:04:07 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 4 Sep 2013 16:04:07 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDIODEPKWANBB5VTTWIQKGQEYDDCCCQ@isocpp.org Wed Sep 04 18:04:08 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ve0-f199.google.com ([209.85.128.199]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VHFYt-0001Yp-Fj for gclcip-std-proposals@m.gmane.org; Wed, 04 Sep 2013 18:04:07 +0200 Original-Received: by mail-ve0-f199.google.com with SMTP id m1sf522551ves.6 for ; Wed, 04 Sep 2013 09:04:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; 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 :content-type; bh=MCSB+hfC6Rhqt63z9GUhZjKa3/Brwa4Orknm73tZ3PM=; b=DorMRF4i/fED5kboxzOc3AT3vLOf9YhsQqQfiXIVTLxfO803d1QFIRO1pOfD4iWrsA vnYlTgfjbcszmkdfIGwGJ80Da4hGGpwLnV8AjCmIH64gc8Xaa7F4beqIxf1oUCADPTOA rirHsuFBhGkjEbUckCTWwPmeRdRky1uFZX2G+8G3fndpos/j6tjlSjPMHWgf2fpcRCcX Y/aXok/kvXuoPE681xzT6CK0BiW0mseFrglKdMhq9KRG5DrZsomEgSP3l/OKz+OijJ7Q IhhgalUpxyJq7PVYsYVi6xdbWAvn8rwXRGuK1S1zpJJUIf23UlNJ/eJ6n1EUlLfoYEi+ MWBg== X-Received: by 10.236.227.165 with SMTP id d35mr801984yhq.51.1378310646597; Wed, 04 Sep 2013 09:04:06 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.47.82 with SMTP id b18ls184424qen.53.gmail; Wed, 04 Sep 2013 09:04:05 -0700 (PDT) X-Received: by 10.49.3.134 with SMTP id c6mr154868qec.0.1378310645952; Wed, 04 Sep 2013 09:04:05 -0700 (PDT) In-Reply-To: X-Original-Sender: theultimatekoala@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:6151 Archived-At: ------=_Part_466_9070264.1378310645629 Content-Type: text/plain; charset=ISO-8859-1 > Please no, dense and sparse have mathematical meanings completely > different from this. Rational numbers over a bignum type could sort-of be > called dense in the mathematical sense. > Yes, although I am not a mathematician, I know that mathematics have, to my dismay, assigned precise meaning to a huge part of the dictionary. I just found these better than OhNoItsPacked and YessssssThereIsACornerThereFitItInFitItInQuick :-) If you agree with the idea, would you mind help me find better names? > >> - The concepts Sparse and Dense, >> >> What's the point of complementary concepts? Define "Dense" as "not > Sparse." > Of course. Implementation would also be complicated, with a need for enable_if as > Nicol mentioned. > Or Concepts Lite. (N3701) Sparse and !Sparse should cover a great deal of value semantics. I'm getting ahead of myself, I know. I'm imagining what an ideal implementation of optional would look like. > >> - The ability to get the underlying_type of a type T, whether Sparse >> or Dense, >> >> Maybe I'm confused. What could the underlying type of a Dense type be, > besides itself? > > enums and enum classes are Dense, but their underlying types are different. Using the semantics of Sparse and Dense as outlined above, I'd say >> Dense and Dense, although I don't know if there are any >> values left free by IEEE754. >> > There are as many distinct NaNs as there are numbers between 0.5 and 1, > but it's a bad idea to try to distinguish them. > So can we create a C++ type that can store doubles that are non-NaN? What would be the interface of such a type? -- --- 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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Please no, dense and sparse have mathematical meanings comple= tely different from this. Rational numbers over a bignum type could sort-of= be called dense in the mathematical sense.

Yes, although I am not a mathematician, I know that mathematics have,= to my dismay, assigned precise meaning to a huge part of the dictionary. I= just found these better than OhNoItsPacked<T> and YessssssThereIsACo= rnerThereFitItInFitItInQuick<T> :-)

If you agree with the idea= , would you mind help me find better names?
  • The concepts Sparse<T> = and Dense<T>,
What's the point= of complementary concepts? Define "Dense" as "not Sparse."

Of course.

Implementation would also be complicated= , with a need for enable_= if as Nicol mentioned.

Or Conce= pts Lite. (N3701) Sparse<T> and !Sparse<T> should cover a great= deal of value semantics.

I'm getting ahead of myself, I know. I'm i= magining what an ideal implementation of optional<T> would look like.
  • The ability t= o get the underlying_type of a type T, whether Sparse or Dense,
Maybe I'm confused. What could the underlyi= ng type of a Dense type be, besides itself?


enums = and enum classes= are Dense, but their underlying types are different.

Using the semantics of Spars= e<T> and Dense<T> as outlined above, I'd say Dense<double>= ; and Dense<float>, although I don't know if there are any values lef= t free by IEEE754.
There are as= many distinct NaNs as there are numbers between 0.5 and 1, but it's a bad = idea to try to distinguish them.
 So can we create a C++ type that can store doubles that are non-NaN? What = would be the interface of such a type?

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