N4487: Constexpr Lambda -- Faisal Vali, Ville Voutilainen, Gabriel Dos Reis

By Blog Staff | Apr 29, 2015 09:10 AM | Tags: None

New WG21 papers are available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4487

Date: 2015-04-28

Constexpr Lambda

by Faisal Vali, Ville Voutilainen, Gabriel Dos Reis

Excerpt:

This proposal suggests allowing lambda-expressions in constant expressions, removing an existing restriction. The authors propose that certain lambda-expressions and operations on certain closure objects be allowed to appear within constant expressions. In doing so, we also propose that a closure type be considered a literal type if the type of each of its data-members is a literal type; and, that if the constexpr specifier is omitted within the lambda-declarator, that the generated function call operator be constexpr if it would satisfy the requirements of a constexpr function (similar to the constexpr inference that already occurs for implicitly defined constructors and the assignment operator functions).

Thoughts About C++17 -- Bjarne Stroustrup

By Blog Staff | Apr 29, 2015 08:34 AM | Tags: None

We normally wait until committee papers get "N" (permanent) numbers, but this one is an exception. It has also already been circulated to ISO C++ committee members in preparation for the next ISO C++ meeting that begins on Monday in Lenexa, Kansas, USA.

D4492: Thoughts About C++17

by Bjarne Stroustrup

From the paper:

This is a draft intended to focus a discussion at the Lexena committee meeting.

This is an extended version (based on feedback) of an internal committee standard reflector message that got so widely distributed and discussed that it would be a good idea to have it as a document. I have tried to remove distracting committee jargon. Thanks to people who took part in the reflector discussion or commented on the web. I have also added links. It is still a collection of thoughts aimed at stimulating a discussion, rather than a formal paper or a precise proposal.

The note was written for committee members, but “escaped into the wild.” Here are a few comments from the web: [Reddit] [The Register] [Hacker News]

As you see, people outside the committee also have strong opinions. Those opinions can depart radically from the ones I hear in the committee and from reality.

I am often asked “what will C++17 be?” and variations of “What will C++17 do for me?” ... [continue reading]

N4403: Draft wording for Resumable Functions -- Gor Nishanov

By Blog Staff | Apr 27, 2015 04:47 PM | Tags: None

New WG21 papers are available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4403

Date: 2015-04-10

Draft wording for Resumable Functions

by Gor Nishanov

N4402: Resumable Functions (revision 4) -- Gor Nishanov, Jim Radigan

By Blog Staff | Apr 27, 2015 04:42 PM | Tags: None

New WG21 papers are available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4402

Date: 2015-03-31

Resumable Functions (revision 4)

by Gor Nishanov, Jim Radigan

Excerpt:

Revisions and History

This document supersedes N4286. Changes relative to N4286 include:

• renaming customization points back to resumable_traits and resumable_handle as they were in N4134;
• changing requirements on the return type of initial_suspend() and final_suspend() to be lexically convertible to bool;
• changing requirements on the return type of yield_value() to be either of a void type or a type lexically convertible to bool;
• making a set_result member function optional in a promise type; the absence of a set_result indicates that resumable function does not support an eventual return value and using await operator or for-await statement is not allowed in resumable functions with such promise;
• altered cancellation mechanism in resumable functions; instead of using cancellation_requested() member function in a promise to indicate that on the next resume resumable function need to be cancelled, an explicit member function destroy() is added to the resumable_handle. A destroy() member function can be invoked to force resumption of coroutine to go on the cancel path;
• added resume(), destroy(), and done() member functions to resumable_handle;
• moved proposed wording into a separate document N4302;
• removed trivial awaitables suspend_always, suspend_never and suspend_if; switching yield_value, initial_suspend, and final_suspend to return bool eliminated the need for those;

Terms and Definitions

Coroutine

A generalized routine that in addition to traditional subroutine operations such as invoke and return supports suspend and resume operations.

...

2015-04 pre-Lenexa mailing available

By Blog Staff | Apr 14, 2015 09:02 AM | Tags: None

The 2015-04 mailing of new standards papers is now available.

NOTE: A number of these papers have already been publicized on this blog. This is the complete list including ones not previously publicized.

N4394: PL22.16/WG21 draft agenda: 4-9 May 2015, Lenexa KS/US -- Clark Nelson

By Blog Staff | Mar 20, 2015 12:53 PM | Tags: None

New WG21 papers are available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4394

Date: 2015-03-12

PL22.16/WG21 draft agenda: 4-9 May 2015, Lenexa KS/US

by Clark Nelson

Excerpt:

At this meeting we will address ballot comments on the Transactional Memory PDTS (N4302), and discuss whatever comments are available on the Concepts PDTS (N4377). We also aim to bring several projects to their next ballot stage, potentially including the following:

• Library Fundamentals 2 (prospective WD N4336)
• Concurrency (proposal N4313)
• Networking (proposal N4370)

N4388: A Proposal to Add a Const-Propagating Wrapper to the Standard Library -- J Coe, R Mill

By Blog Staff | Mar 3, 2015 01:29 PM | Tags: None

New WG21 papers are available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4388

Date: 2015-02-25

A Proposal to Add a Const-Propagating Wrapper to the Standard Library

by Jonathan Coe, Robert Mill

Excerpt:

We propose the introduction of a propagate_const wrapper class that propagates const-ness to pointer-like member variables. ... The behaviour of const member functions on objects with pointer-like data members is seen to be surprising by many experienced C++ developers. A const member function can call non-const functions on pointer-like data members and will do so by default without use of const_cast...

N4386: Unspecialized std::tuple_size should be defined -- Nevin Liber

By Blog Staff | Feb 27, 2015 07:33 AM | Tags: None

New WG21 papers are available. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4386

Date: 2015-02-24

Unspecialized std::tuple_size should be defined

by Nevin Liber

Excerpt:

This paper is wording for issue LWG 2446 / LEWG 42.

C++17 Library Papers for Cologne - Part II

By Meeting C++ | Feb 19, 2015 02:30 AM | Tags: None

The second and last part in my miniseries about the library papers for next weeks LWG Meeting:

C++17 Library Papers for Cologne - Part II

by Jens WEller

From the article:

This is the second part about the papers for the Library Working Group Meeting in Cologne next week. The last part already covered some interesting papers, and gives an impression on what will be included into the Standard Library for C++17...

2015-02 mid-meeting mailing available

By Blog Staff | Feb 11, 2015 09:49 AM | Tags: None

The 2015-02 mailing of new standards papers is now available.

NOTE: A number of these papers have already been publicized on this blog. This is the complete list including ones not previously publicized.