220 29090 <34f09dd5-e231-4a0b-a218-48c8eabe73c5@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: m.cencora@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Initializer list for move-only types Date: Wed, 26 Oct 2016 06:35:25 -0700 (PDT) Lines: 133 Approved: news@gmane.org Message-ID: <34f09dd5-e231-4a0b-a218-48c8eabe73c5@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2104_556885896.1477488925721" X-Trace: blaine.gmane.org 1477488951 26237 195.159.176.226 (26 Oct 2016 13:35:51 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 26 Oct 2016 13:35:51 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD7YFUMJRYMBBH7CYLAAKGQEEXB3WAI@isocpp.org Wed Oct 26 15:35:47 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qt0-f200.google.com ([209.85.216.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bzOMa-0004Gz-Dj for gclcip-std-proposals@m.gmane.org; Wed, 26 Oct 2016 15:35:28 +0200 Original-Received: by mail-qt0-f200.google.com with SMTP id g32sf2805439qta.2 for ; Wed, 26 Oct 2016 06:35:31 -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: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=adNaIO2IDBSxiOBjpPrjT42T2S/hLNRZ4rFz2lgnPyc=; b=usGO6K40rSCU+alpdhuu57SPYsOUT+XESRDl55YTMf7BA6VP9Zg9FZF/CVLZz89S7H xhCL6jqdELYU/EIWw3EnPen2zEvPAXwFIthESTsuUGwDoHpP8loJsxPKvGUkhvB9cDhS UOAy0mswVibPVqVIV9ROJ3Gt7mRoD5EpFQG80lsabzdST5peI+Z0es+nAbQxE24EdjAf u6BDmFmofGRqe6x1UmKCEKKG+9Xn/wrlhFkzKKZA79I95oEun2gTHVEx3nbyjmBFsxza 3WcffrAOiRwOSS5AyA0LSBEqfxZ2m3/R9Vcf3BnFXg3PfiDu7PnElbS42Y/x5LaRgh3k /OQA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id: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=adNaIO2IDBSxiOBjpPrjT42T2S/hLNRZ4rFz2lgnPyc=; b=LCTdjR8lYRW6Fdei+LgZXtkf4FMPflul8WPGK8HE5bFeGFlA0o3Zb+gQrnc7tv8QQU 5bRZMIljp95xw2iiRTE4mkM2CR1+mFFAWHeBg0VqVHv3c8I+atdmVAQksW4AtyS64F/G DFpqocTje88QSKfPh7S1x6mpB2/bXA3qyQAPG1M328Q7wZwPFd+VSBofNirAU1X4i1Ne 4dN3J0qbwy4+FjhndXwl+OwO2+oYTa7jQI4ttW/QkMIHrQHpbZHDJ7X9wv4O3nh+dNX/ 8MMbclJweTbm/Hfn2bYXA94Zs8w1d65xXW6pxUp7NjO4q4y6125szl+1kL2iXfxw7NTL Xeqw== 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: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=adNaIO2IDBSxiOBjpPrjT42T2S/hLNRZ4rFz2lgnPyc=; b=Y8bZIjANN1h54k2CCzNY79w6HuJqCyu2n8Mz04QGhsN+aaMzj6cEg3JOpE46jldpHm L8NNMra6NvNI/95NRo+V2vegGKVx+L8I0Wyvw5OCzDV1mJLLj9FyS9u/cnyHzhVPRXG3 qlAcsK/s0dKoOJDRkBnuaNkZkNTrkItDeH8HdwM037H82xsai1yZsDmkmBdrwG7OROA5 aywFSDcYRnwV/7vgTnasWwjmddNGc2wi44iqLovAR8cSFQc2/ZiB6SCOOfgLrZYsPza5 NCpYCpm+t4V53UnVHY6w+JFhcutVwBMxbCO2+ko8+eNUGD8knOTzYY+76J3KJ5RTA1Cq kNOQ== X-Gm-Message-State: ABUngvel6X6UJdZldTofiPRgWrX2gpqLwPYPIAoK4WmNPAc06lg6JcbULfRxoUMXhlBTsg== X-Received: by 10.200.40.189 with SMTP id i58mr509342qti.76.1477488930799; Wed, 26 Oct 2016 06:35:30 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.57.142 with SMTP id l136ls1883042ita.20.canary-gmail; Wed, 26 Oct 2016 06:35:26 -0700 (PDT) X-Received: by 10.36.53.9 with SMTP id k9mr520677ita.8.1477488926889; Wed, 26 Oct 2016 06:35:26 -0700 (PDT) X-Original-Sender: m.cencora@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:29090 Archived-At: ------=_Part_2104_556885896.1477488925721 Content-Type: multipart/alternative; boundary="----=_Part_2105_1204335180.1477488925721" ------=_Part_2105_1204335180.1477488925721 Content-Type: text/plain; charset=UTF-8 Hi, in C++14 we can construct std::array with a list of move-only objects (non-copyable) thanks to aggregate initialization. Unfortunately we cannot do the same for std::vector of move-only types, because initializer list points to const objects. While language experts know the reason of it, from pure user perspective it is inconsistent. #include #include #include struct MoveOnly { MoveOnly(MoveOnly&&) = default; MoveOnly& operator=(MoveOnly&&) = default; }; int main() { // works just fine std::array arr = {{ MoveOnly{}, MoveOnly{}, MoveOnly{}, MoveOnly{} }}; // does not compile std::vector vec = { MoveOnly{}, MoveOnly{}, MoveOnly{}, MoveOnly{} }; // workaround std::vector vec2(std::make_move_iterator(arr.begin()), std::make_move_iterator(arr.end())); } Can this be fixed? Regards, Maciej -- 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. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/34f09dd5-e231-4a0b-a218-48c8eabe73c5%40isocpp.org. ------=_Part_2105_1204335180.1477488925721 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Hi,

in C++14 we can construct std::arra= y with a list of move-only objects (non-copyable) thanks to aggregate initi= alization.
Unfortunately we cannot do the same for std::vector of= move-only types, because initializer list points to const objects.
While language experts know the reason of it, from pure user perspective= it is inconsistent.

#inclu= de <iterator>
#include <vector>
#include <array>

struct MoveOnly
{
=C2=A0 =C2=A0MoveOnly(MoveO= nly&&) =3D default;
=C2=A0 =C2=A0MoveOnly& operator=3D(MoveOnly&&= ;) =3D default;
};

int= main()
{=
=C2=A0 =C2=A0// works just fine
=C2=A0 =C2=A0std::array<MoveOnly, 4> arr = =3D {{
= =C2=A0 =C2=A0 =C2=A0 MoveOnly{},
= =C2=A0 =C2=A0 =C2=A0 MoveOnly{},
=C2=A0 =C2=A0 =C2=A0 MoveOn= ly{},
=C2= =A0 =C2=A0 =C2=A0 MoveOnly{}
=C2=A0 =C2=A0}};

=C2=A0 =C2=A0// does not compile
=C2=A0 =C2=A0std::v= ector<MoveOnly> vec =3D {
<= font color=3D"#660066">=C2=A0 =C2=A0 =C2=A0 MoveOnly{},
=C2=A0 =C2=A0 =C2=A0 MoveOnl= y{},
=C2= =A0 =C2=A0 =C2=A0 MoveOnly{},
=C2=A0 =C2=A0 =C2=A0 MoveOnly{}
=C2=A0 =C2=A0};

=C2=A0 /= / workaround
=C2=A0 std::vector<MoveOnl= y> vec2(std::make_move_iterator(arr.begin()),
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0std::make_move_iterator(arr.end()));<= /div>
}



Can this be= fixed?

Regards,
Maciej

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
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/34f09dd5-e231-4a0b-a218-48c8eabe73c5= %40isocpp.org.
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