220 31512 article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: compressed std::bitset Date: Wed, 8 Mar 2017 15:22:45 -0800 (PST) Lines: 257 Approved: news@gmane.org Message-ID: References: <32cfea0a-7df8-47cf-47fd-549985f12295@wanadoo.fr> <06e829ca-417b-470c-95ca-c661e8752f79@isocpp.org> <4238c4e6-51f5-4a2f-94c8-f61ca415e7e0@isocpp.org> <3c737844-0d92-3713-7b7d-06130959a877@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_507_675719803.1489015365692" X-Trace: blaine.gmane.org 1489015367 27032 195.159.176.226 (8 Mar 2017 23:22:47 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 8 Mar 2017 23:22:47 +0000 (UTC) Cc: 3dw4rd@verizon.net To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBRVEQLDAKGQETVU2PJI@isocpp.org Thu Mar 09 00:22:42 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pf0-f200.google.com ([209.85.192.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1clkun-0006JH-Fn for gclcip-std-proposals@m.gmane.org; Thu, 09 Mar 2017 00:22:41 +0100 Original-Received: by mail-pf0-f200.google.com with SMTP id l66sf83254089pfl.6 for ; Wed, 08 Mar 2017 15:22:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc: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=qylYIaEcaUsCvc9HeuYDVVt4Cuhg/sgmDbxqJufJGLE=; b=nPue4s7HxhrjhRfYTdlAttr2EMAnslvWvUdV1FDMvzStWcHffY79SnPtWW6FXq24yO D0M5aJQgiDwKI60rIf4VAl2MnssM0zjC7eO9mht//3UcvCumnuO/78ozT0UKTskFxYPC 4B8gc3OJGy6zSfXdJm+A6dIe6WdzUlePLDuimBxXq9zvaZZvksqmEzHsY22PyipIleZO jpC7xuRuO64JcVsZ0xoG1qKvvCI17CckexrBh2PvEIoWoglFNqkzh8CALSOsuQv8E5QH 4uaUUjicQG+F408fP5pPF6aLGOEyuAJ7tkJ98isdvucgH/UvHDYyXOyqR1kWCzB4V4Cx 0EQw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc: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=qylYIaEcaUsCvc9HeuYDVVt4Cuhg/sgmDbxqJufJGLE=; b=YJoNuBU41q6o7iW0Z4hdX/yB1Wwv6q4FZ+GPfQ9vqQ+UB/cwDTOS28/aysLGhWIZai t8tXKtTyPI9houD4ahlxXyGojtzFVniRKktuXoBm3Dtii0j2epHGxL99z9WnZLdj9hNK lj8nOMefAb+S2C7h/D5zo3ov19YdMuJFGp8h68Rqm2V8YEAicun7a2a+KvYr0DxlwX2w TOi/UjSzCtlEhF1elGsrXO/bV43GFQarDiV0wXa6hsppfzBgSSsGzppE9NmXKM5DVULe p7sXJtHXb9SdkTMWB+Y38huMwRWPZMzSs3cUBlVkDI/qePLIzUqayYC5SmhO0YKOhfu1 W9yw== 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:cc: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=qylYIaEcaUsCvc9HeuYDVVt4Cuhg/sgmDbxqJufJGLE=; b=UGoxkXO2/SmyTq15azxENQCIkAYWWJVyTIVuhL8UytOCc+wUchOwvru4KokeR0ijFt /dvgjmghebE26Bmsk2LqEf+c5MpQRRPprXG4htCY9LoRsFTRhOeni4Ic6YHNnmcHcunX lZh/jfhjPHIaSTv460qZ6k22gUGssgyM5P5lwVoj2874+xyTKOzVAoWgl7Kosnie75gt cdpTmEWwtX6MwVPIlX8BBwxGd/RuniDi08Br6xodAiErJyY3tErez3CKpJ6ggo5hbWv8 mbjLtzoHxhEGxmDXL7TjKaCRL5AWevHJtwvyIKgzYjodgsnRmgpl7Zrv9ZGsnkfDB60V uEOQ== X-Gm-Message-State: AMke39lX8PzNSiEke65ikNo+pORDP1zYg8d/Bhqp8qel9ce7+HjiHUxdZJB9Z88bGyDpqw== X-Received: by 10.99.64.129 with SMTP id n123mr4295397pga.61.1489015367243; Wed, 08 Mar 2017 15:22:47 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.62.1 with SMTP id a1ls4896773otd.37.gmail; Wed, 08 Mar 2017 15:22:46 -0800 (PST) X-Received: by 10.157.18.133 with SMTP id g5mr1335011otg.8.1489015366382; Wed, 08 Mar 2017 15:22:46 -0800 (PST) In-Reply-To: X-Original-Sender: jmckesson@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:31512 Archived-At: ------=_Part_507_675719803.1489015365692 Content-Type: multipart/alternative; boundary="----=_Part_508_416094480.1489015365692" ------=_Part_508_416094480.1489015365692 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wednesday, March 8, 2017 at 5:26:07 PM UTC-5, 3dw...@verizon.net wrote: > > > > On Wednesday, March 8, 2017 at 7:44:56 AM UTC-5, Vicente J. Botet Escriba= =20 > wrote: >> >> Le 08/03/2017 =C3=A0 06:23, 3dw...@verizon.net a =C3=A9crit : >> >> >> >> On Tuesday, February 21, 2017 at 3:40:00 PM UTC-5, ricky6565 wrote:=20 >>> >>> Hi Vicente,=20 >>> >>> I think the Bitset2 library by= =20 >>> Claas Bontus provides what you are looking for. It's like std::bitset b= ut=20 >>> with enhanced functionality. It let's you set the underlying integral t= ype=20 >>> of the bitset. In fact, it defaults to uint8_t, uint16_t, or uint32_t i= f=20 >>> N bits fit into those integers. I would like this functionality added= =20 >>> to std::bitset but, as you said, it would probably be a breaking change= .. >>> >>> Riccardo >>> >> >> I was just thinking something similar. Allow the user to specify the=20 >> bitset leaf-type: >> >> template> numeric_limits::digits> >> class bit_array >> { >> // pretty much like bitset except I would add >> using leaf_type =3D LeafTp; >> leaf_iterator lbegin() //=20 >> leaf_iterator lend(); //=20 >> }; >> >> >> This is flipped relative to Bitset2 in that leaf type comes first and th= e=20 >> template would decide how many leaves based on bits. >> >> So now you could get these small bitsets: >> using bitset16 =3D bit_array; >> etc. >> >> I believe that both orders could have have usage (see below), an alias= =20 >> templates should help here to have both. >> However I don't like the possibility to have bit_array<>. How many bits= =20 >> do we have? >> > > In this case bit_array<> is bit_array std::numeric_limits::digits> > so on my system, 64-bits. Perhaps we want a fixed size integral type as= =20 > the default type. > You can't use a type that implementations are not required to support. We could also not a a default type. > Um, why not? Really, what's wrong with `unsigned int`? There are plenty of= =20 people who don't care about what the "leaf" type is; they just want a=20 convenient class for doing bit manipulation with. Why make things=20 needlessly difficult for them? > --=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/dd7dfbe0-8a9e-4fe4-b37a-312c495f648f%40isocpp.or= g. ------=_Part_508_416094480.1489015365692 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Wednesday, March 8, 2017 at 5:26:07 PM UTC-5, 3= dw...@verizon.net wrote:


On Wednesday, March 8, 2017 at 7:44:56 AM UTC-5, Vicente= J. Botet Escriba wrote:
=20 =20 =20
Le 08/03/2017 =C3=A0 06:23, 3dw...@verizon.net a =C3=A9crit=C2=A0:


On Tuesday, February 21, 2017 at 3:40:00 PM UTC-5, ricky6565 wrote:
Hi Vicente,

I think the Bitset2 library by Claas Bontus provide= s what you are looking for. It's like std::bitset but wit= h enhanced functionality. It let's you set the underlying integral type of the bitset. In fact, it=C2=A0defaults to uint8_t, uint16_t, or uint32_t=C2=A0if N=C2=A0bits fit = into those integers.=C2=A0I would like this functionality add= ed to std::bitset but, as you said, it would probably be a breaking change.

Riccardo

I was just thinking something similar.=C2=A0 Allow the user to specify the bitset leaf-type:

template<typename LeafTp =3D unsigned long long, std::size_t Bits =3D std::numeric_limits<LeafTp>::digits><= /span>
=C2=A0 class bit_array
=C2=A0 {
=C2=A0 =C2=A0 // pretty= much like bitset except I would add
=C2=A0 =C2=A0 using leaf_type =3D LeafTp;
=C2=A0 =C2=A0 leaf_iterator lbegin() //
=C2=A0 =C2=A0 leaf_iterator lend(); //
=C2=A0 };


This is flipped relative to Bitset2 in that leaf type comes first and the template would decide how many leaves based on bits.

So now you could get these small bitsets:
using bitset16 =3D bit_array<uint16_t>;
etc.

I believe that both orders could have have usage (see below), an alias templates should help here to have both.
However I don't like the possibility to have bit_array<>. How many bits do we have?

In this case bit_a= rray<> is bit_array<unsigned long long, std::numeric_limits<uns= igned long long>::digits>
so on my system, 64-bits.=C2=A0 Perhaps = we want a fixed size integral type as the default type.

You can't use a type that implementations are not req= uired to support.

We could also not a a default type.
<= /blockquote>

Um, why not? Really, what's wrong with `unsigned i= nt`? There are plenty of people who don't care about what the "lea= f" type is; they just want a convenient class for doing bit manipulati= on with. Why make things needlessly difficult for them?

--
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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/dd7dfbe0-8a9e-4fe4-b37a-312c495f648f= %40isocpp.org.
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