N4008: SIMD Polymorphism -- Arch Robison, Pablo Halpern, and Robert Geva

By Blog Staff | May 24, 2014 02:18 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4008

Date: 2014-05-22

SIMD Polymorphism

by Arch Robison, Pablo Halpern, and Robert Geva

Excerpt:

N3831 [1], presented at the February 2014 Issaquah meeting, proposed (among other things) adding SIMD-enabled functions to C++. Although there was significant interest in this concept, members of the committee felt that the description in N3831 would be improved by better integrating SIMD-enabled functions with the C++ type system. This paper explores such an integration. We show that though these functions exhibit a form of polymorphism, it is best kept distinct from the existing features for polymorphism in C++. In particular, SIMD polymorphism is best not treated as C++ template instantiation or overload resolution. Instead, we propose extending the C++ type system.

N4002: Cleaning‐up noexcept in the Library -- Nicolai Josuttis

By Blog Staff | May 24, 2014 02:14 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4002

Date: 2014-05-21

Cleaning‐up noexcept in the Library

by Nicolai Josuttis

Excerpt:

With N3279 we introduced some guidelines for how to use noexcept in the C++ Standard Library. However, after some years of experience, we learned that we have to

• Improve these guidelines
• Fix places where we agree that according to the old and new guidelines things are, or may be a problem
• Discuss and decide whether (or not) to fix issues upon which we have no clear opinion

N3998: C++ Latches and Barriers (Revision 3) -- Alasdair Mackintosh and Olivier Giroux

By Blog Staff | May 24, 2014 02:11 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3998

Date: 2014-05-21

C++ Latches and Barriers (Revision 3)

by Alasdair Mackintosh and Olivier Giroux

Excerpt:

Revision History

... Add Concepts, simplify latch and barrier, add notifying_barrier

N4003-05: File System ITS ssues Lists -- Beman Dawes

By Blog Staff | May 24, 2014 01:53 PM | Tags: None

New WG21 papers are available. Copies are linked below, and the papers will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document numbers: N4003-04

Date: 2014-03-23

Filesystem TS Active Issues List (Revision R0)

Filesystem TS Closed Issues List (Revision R0)

Filesystem TS Defect Report List (Revision R0)

by Beman Dawes

N4035: Implicit Evaluation of auto Variables and Arguments -- J Falcou, P Gottschling, H Sutter

By Blog Staff | May 23, 2014 08:35 AM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4035

Date: 2014-05-23

Implicit Evaluation of auto Variables and Arguments (revision 1)

by Joel Falcou, Peter Gottschling, Herb Sutter

Excerpt:

Revision to N3748

1. Prioritized syntax changed.

2. Third alternative introduced.

3. Library-based disabling introduced.

4. Some type traits removed.

Altogether, the proposal is a clear simplication to its predecessor.

1 Motivation

Type detection for variables from expressions' return type:

auto x= expr;

has proven high usability. However, it fails to meet most users' expectations and preferences when
proxies or expression templates (ET) are involved, e.g.:

matrix A, B;
// setup A and B
auto C= A  B;

Many people would expect C to be of type matrix as well. Whether C is a matrix depends on the
implementation of operator*. ...

N4009: Uniform Container Erasure -- Stephan T. Lavavej

By Blog Staff | May 22, 2014 03:23 PM | Tags: None

[Ed.: Alternative title: "Finally! Let's please erase and remove the erase-remove idiom"...]

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4009

Date: 2014-05-22

Uniform Container Erasure

by Stephan T. Lavavej

Excerpt:

This is a proposal to add erase_if(container, pred), making it easier to eliminate unwanted elements correctly and efficiently.

II. The Problem

It's surprisingly difficult to eliminate unwanted elements from a container, given a predicate that distinguishes "bad" elements from "good" elements. ...

N3994: Range-Based For-Loops: The Next Generation (Revision 1) -- Stephan T. Lavavej

By Blog Staff | May 22, 2014 03:21 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3994

Date: 2014-05-22

Range-Based For-Loops: The Next Generation (Revision 1)

by Stephan T. Lavavej

Excerpt:

This updates N3853 (see [1]) which proposed the syntax "for (elem : range)", by adding support for attributes and answering additional questions. Please see the original proposal for the rationale behind this feature, which is not repeated here.

...

Q15. Has this been implemented?

A15. Yes!  David Vandevoorde and Jonathan Caves have reported that they were
able to implement N3853 in less than an hour each. ...

N3977: Resumable Functions -- Niklas Gustafsson

By Blog Staff | May 22, 2014 03:10 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3977

Date: 2014-05-22

Resumable Functions

by Niklas Gustafsson

Excerpt:

This document is directly related to N3970, the working draft for a Technical Specification focusing on concurrency. It proposes a number of additions to N3970.

In relation to the superseded document N3858, this paper drops all the background information and focuses on proposed edits to the Concurrency TS. For background information, the reader is referred to the superseded document.

It is hereby proposed that the following modifications to the standard be incorporated into the Concurrency Technical Specification, N3970. Section and paragraph numbers refer to the C++ standard working draft.

N4023: Working Draft, C++ Extensions for Library Fundamentals -- Jeffrey Yasskin

By Blog Staff | May 22, 2014 12:49 PM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N4023

Date: 2014-05-21

Working Draft, C++ Extensions for Library Fundamentals

by Jeffrey Yasskin

Excerpt:

This technical specification describes extensions to the C++ Standard Library (1.2). These extensions are classes and functions that are likely to be used widely within a program and/or on the interface boundaries between libraries written by different organizations. ...

The goal of this technical specification is to build more widespread existing practice for an expanded C++ standard library. It gives advice on extensions to those vendors who wish to provide them.

N3976: Multidimensional bounds, index and array_view, revision 2 -- Łukasz Mendakiewicz, Herb Sutter

By Blog Staff | May 22, 2014 09:17 AM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3976

Date: 2014-05-21

Multidimensional bounds, index and array_view, revision 2

by Łukasz Mendakiewicz and Herb Sutter

Excerpt:

The feedback we have received during the Issaquah meeting was to prepare the wording for the proposal as-is. Consequently, only the wording (with minor improvements) is provided in this version. Interested readers should find the rationale, background information and design discussion in the previous revision of the proposal, viz. N3851.