Are fold expressions a C++14 or a C++1z feature?

Question

https://isocpp.org/std/the-standard states that the working draft N4296

contains the C++14 standard plus minor editorial changes.

I noted that N4296 §5.1.3 contains a specification of "Fold expressions". I thought this to be a feature which did not make it to the official C++14 standard.

Are fold expressions part of C++14 or is this addition in N4296 one of those minor editorial changes?

c++17, but you'll find them supported in clang with -std=c++1z and supported with a warning with -std=c++14 — Richard Hodges, Apr 02 '16 at 18:31
5.1.3 is not in C++14. My recollection is that draft N3936 was what became the C++14 standard. — Michael Burr, Apr 02 '16 at 18:37
The addition of fold expressions does seem like quite a bit more than an editorial change (especially a 'minor' one). — Michael Burr, Apr 02 '16 at 18:51

T.C. · Accepted Answer · 2016-04-05T21:07:01.740

11

N3937 is the C++14 DIS (Draft International Standard). N3936 (no longer publicly available, but can be dug out from the github repo) is N3937 with a different cover.
N4141 is the C++14 IS; it's the DIS plus some editorial changes. It's not publicly available.
N4140 is the pre-Urbana working draft; it's N4141 plus more editorial changes.
N4296 is the post-Urbana working draft. It includes C++17 features voted in at the committee's Urbana meeting.

Fold expressions is a C++17 feature.

edited Apr 05 '16 at 21:07

answered Apr 03 '16 at 01:09

T.C.

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Why N4141 isn't publicly available ? – Destructor Apr 03 '16 at 04:22
The numbers are confusing. N4140 is N4141 plus more editorial changes (4140 < 4141)? Not like N39## something + editorial changes? – jotik Apr 03 '16 at 06:42
@jotik N3936 == N3937 (ignoring cover page). N4140 = N3936 + many editorial changes. N4141 = N3937 + a much smaller subset of those editorial changes. – T.C. Apr 03 '16 at 09:03
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Fold expressions seems to originate from [N4191](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4191.html) (dated 2014-10-07), so it clearly didn't make the standard on which the final ballot period closed in August 2014. – jotik Apr 03 '16 at 12:23
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@Destructor Because they don't want to have the *exact* text of an international standard freely available. In practice, it doesn't matter, I don't think; simply use whatever draft immediately predates the IS. – Kuba hasn't forgotten Monica Apr 05 '16 at 20:41
I thought the whole point of an IS is to be publicly available, usually for a hefty fee. – Toby Speight Apr 05 '16 at 21:05

Are fold expressions a C++14 or a C++1z feature?

1 Answers1