220 13469 <63de9d71-e3b0-4242-9698-bea3a307b3c7@isocpp.org> article Path: news.gmane.org!not-for-mail From: Matthew Fioravante Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Proposal: Strongly Typed Bitset Date: Wed, 1 Oct 2014 18:26:11 -0700 (PDT) Lines: 257 Approved: news@gmane.org Message-ID: <63de9d71-e3b0-4242-9698-bea3a307b3c7@isocpp.org> References: <113390b2-9c74-47e2-a943-5d27dd48bdf1@isocpp.org> <41983d24-efb2-4255-b09b-f84cff7bf56d@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_6190_1238732653.1412213171801" X-Trace: ger.gmane.org 1412213179 7404 80.91.229.3 (2 Oct 2014 01:26:19 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 2 Oct 2014 01:26:19 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDELF54RTIGRBNGTWKQQKGQEW5XZJ4Y@isocpp.org Thu Oct 02 03:26:14 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pa0-f70.google.com ([209.85.220.70]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XZV9q-00059s-7o for gclcip-std-proposals@m.gmane.org; Thu, 02 Oct 2014 03:26:14 +0200 Original-Received: by mail-pa0-f70.google.com with SMTP id et14sf6602295pad.5 for ; Wed, 01 Oct 2014 18:26:13 -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=kg2xpYchjfBl339E0jswUhnZV6xgDuA3ORosW5ohi/w=; b=M1MsLyRXfgIWyZeQhPeXpabbwFezDK1n7bKTsZp5zCi2stTMsKRQjklZfo8Y6ReW4N oX6qFWl2uxdVrx4qmRdqA6Q9kYG6tuSI76n+B+XSKoc7194nbGmICQ5zJ0mswTbkm6jt JEFNmTVrpDGTHHDjg2jlXgI2mKQSGRGBAPCP+JWElKah1zmjk2ypf3enFHx8saBBREwE XZ7MSO15t+ohcTFjoHfgATkkJDPa9fmxuL1SWMldd6J/6RxLga+LPTfen/83MyXdkitx HLHkRLiuOBhNTxzhYQ1mZoN2ul/f4mnqcx2K6f21MiT4gu/4gvvExqOIhCQWqu8HlUr6 6iTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; 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:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=kg2xpYchjfBl339E0jswUhnZV6xgDuA3ORosW5ohi/w=; b=IW+4CTLY9m5urT9VeRmY/XPcce4M8ZqraAXo57fstftPl1QrCMMgrZHo7UngxHW+66 kB/sOAL1zEtIyxK35Zx489Y9Wx4UqnMvHB0B2R2h7sxvwVUb2qEFfPFARxEAmnYEL9qk 8XYGwie4o4XfwJetG+8Tz1DKnYWB+f2EdSeNpe/5AZsfdX+Ao/aJBlKpc6kQFHyS/fVr 9MefkqU/ZYu2tvyC+tQq9KI/8NdgS31qkA5VCPXrv8KOYsG5snn7JWsQrncULaAnThf1 WAS72wJTDarU2oKJ/XmXLo7x0WvuBqx+0SL67/T3a/ttKfMR81Z46Dwpyp85CuQFxy3B Z6HA== X-Gm-Message-State: ALoCoQn8IeMeYieNtYi9nb2bTPhdUixqngM1BchSZ0S+ScSqTBy2SQx4lOhFsM6uVuQgATBD1d6F X-Received: by 10.68.219.226 with SMTP id pr2mr48541660pbc.4.1412213173191; Wed, 01 Oct 2014 18:26:13 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.36.244 with SMTP id p107ls696730qgp.94.gmail; Wed, 01 Oct 2014 18:26:12 -0700 (PDT) X-Received: by 10.140.94.10 with SMTP id f10mr65025qge.11.1412213172452; Wed, 01 Oct 2014 18:26:12 -0700 (PDT) In-Reply-To: X-Original-Sender: fmatthew5876@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:13469 Archived-At: ------=_Part_6190_1238732653.1412213171801 Content-Type: text/plain; charset=UTF-8 I've updated the draft with fast_bitset and small_bitset. https://github.com/fmatthew5876/stdcxx-bitset I had some ideas for additional directions to go into. I've not put these in the paper. Some new public members: template class bitset { public: using underlying_type = T[N / (sizeof(T) * CHAR_BIT) + 1]; array get_underlying() const; void set_underlying(array a); get_underlying() would return an array of T whose bits are identical to the bits stored in the bitset. All of the bits > N would be 0. set_underlying(a) would set the internal bits to the values of the bits in a. All of the bits > N are ignored. Alternatively, instead of value semantics we could do reference semantics: template class bitset { public: using underlying_type = T[N / (sizeof(T) * CHAR_BIT) + 1]; array& rep(); const array& rep() const; This is more dangerous as bitset is a value type which can be freely copied, but it might be more efficient for large bitsets. With either of these options, we could deprecate bitset::to_ulong() and bitset::to_ullong(). Finally, (this might be a separate proposal) bitset::to_string() is really an inefficient design. It returns a std::string which will require a memory allocation. Instead of that, to_string() could return std::array, which holds a null terminated bitstring. -- --- 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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. ------=_Part_6190_1238732653.1412213171801 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
I've updated the draft with fast_bitset and small_bitset.<= div>
https://github.com/fmatthew5876/stdcxx-bitset
<= div>
I had some ideas for additional directions to go into. I= 've not put these in the paper.

Some new public me= mbers:

template<= span style=3D"color: #000;" class=3D"styled-by-prettify"> <size_t N, typename T> class bitset {
  public:  
    using underlying_type =3D T[N <= /span>/ (sizeof(T) *<= /span> CHAR_BIT) + 1];

    array<T,sizeof(underly= ing_type)<= /span> / sizeof= (T)> get_underlying() const;
    void set_underlying(array&= lt;T,s= izeof(underlying_typ= e)<= span style=3D"color: #000;" class=3D"styled-by-prettify"> / sizeof(T)> a);
&n= bsp;

get_underlying() would return an array o= f T whose bits are identical to the bits stored in the bitset. All of the b= its > N would be 0.
set_underlying(a) would set the internal b= its to the values of the bits in a. All of the bits > N are ignored.

Alternatively, instead of value semantics we could do= reference semantics:
template<= span style=3D"color: #000;" class=3D"styled-by-prettify"> <size_t N, typename T> class bitset {
  public:  
    using underlying_type =3D T[N <= /span>/ (sizeof(T) *<= /span> CHAR_BIT) + 1];

    array<T,sizeof(underly= ing_type)<= /span> / sizeof= (T)>& rep();
    const array<T,sizeof(und= erlying_type) / = sizeof(T)>& rep() const;


This is more dangerous = as bitset is a value type which can be freely copied, but it might be more = efficient for large bitsets.

With either of these = options, we could deprecate bitset::to_ulong() and bitset::to_ullong().

Finally, (this might be a separate proposal) bitset::= to_string() is really an inefficient design. It returns a std::string which= will require a memory allocation.

Instead of that= , to_string() could return std::array<char,N+1>, which holds a null t= erminated bitstring.

--

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