Home » Blog » 2016 » February

February 2016

P0144R1 and P0217R0: Structured bindings (Sutter, Stroustrup, Dos Reis) and wording (Maurer)

By Blog Staff | Feb 10, 2016 05:28 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.

 

P0144R1: Structured bindings (Herb Sutter, Bjarne Stroustrup, Gabriel Dos Reis)

This paper proposes the ability to declare multiple variables initialized from a tuple or struct, along the lines of:

tuple f(/*...*/) { /*...*/ return {a,b,c}; } 

auto {x,y,z} = f(); // x has type T1, y has type T2, z has type T3

This addresses the requests for support of returning multiple values, which has become a popular request lately.

Proposed wording appears in a separate paper, P0217.

 

P0217R0: Proposed wording for structured bindings (Jens Maurer)

This paper presents the proposed wording to implement structured bindings as described by Herb Sutter, Bjarne Stroustrup, and Gabriel dos Reis in P0144R1.

 

P0221R0: Proposed wording for default comparisons, revision 2 -- Jens Maurer

By Blog Staff | Feb 10, 2016 09:59 AM | Tags: None

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

Document number: P0221R0

Date: 2016-02-10

Proposed wording for default comparisons, revision 2

by Jens Maurer

Excerpt:

This paper presents design rationale and proposed wording to implement default comparisons for class types. It is a revision of N4532 with additional updates from the Evolution Working Group session at the Kona meeting of WG21 and in-depth discussions with interested parties. Blue text in the proposed wording indicates changes compared to N4532.

This paper assumes that the reader is familar with N4475 "Default comparisons (R2)" by Bjarne Stroustrup. In particular, default comparisons are assumed to be implicit (i.e. require no extra syntax to be available). 

CppCast Episode 44: HPC and more with Bryce Lelbach

By robwirving | Feb 10, 2016 07:47 AM | Tags: None

Episode 44 of CppCast the only podcast for C++ developers by C++ developers. In this episode Rob and Jason are joined by Bryce Lelbach to discuss High Performance Computing and other C++ topics.

CppCast Episode 44: HPC and more with Bryce Lelbach

by Rob Irving and Jason Turner

About the interviewee:

Bryce Adelstein Lelbach is a researcher at Lawrence Berkeley National Laboratory (LBNL), a US Department of Energy research facility. Working alongside a team of mathematicians and physicists, he develops and analyzes new parallel programming models for exascale and post-Moore architectures. Bryce is one of the developers of the HPX C++ runtime system; he spent five years working on HPX while he was at Louisiana State University's Center for Computation and Technology. He also helped start the LLVMLinux initiative, and has occasionally contributed to the Boost C++ libraries. Bryce is an organizer for C++Now and CppCon conferences and he is passionate about C++ community development. He serves as LBNL's representative to the C++ standards committee.

C++ track at NDC Oslo 2016, June 6-10 (CFP ends Feb 15)

By Olve Maudal | Feb 9, 2016 03:59 PM | Tags: None

For the third year in a row we will set up a strong C++ track at the NDC conference in Oslo, June 6-10. 

   The Call for Paper ends February 15   

At NDC Oslo the typical crowd of 2000+ developers can choose from 9-10 parallel tracks over 3 long days (June 8-10). One of these tracks will be about C++, but there will be tracks on embedded programming, security and IoT just to mention a few. There are also many preconference 2-day tutorials/workshops (June 6-7) and several of these will be on C++ and C (stay tuned).

We have already signed up several solid C++ speakers. Anthony Williams, Mark Isaacson, Hubert Matthews, Dan Saks, Andrei Alexandrescu, will be there. Will you? We have a few more slots available. In particular we are looking for C++ gurus based in Europe. Feel free to also contact Olve Maudal directly if you are interested.

If you are curious about the NDC conference please take a look at the humorous promo video for last years event.

Sometimes you get things wrong--Marshall Clow

By Adrien Hamelin | Feb 8, 2016 06:11 AM | Tags: intermediate efficiency

What is the best thing to return?

Sometimes you get things wrong

by Marshall Clow

From the article:

A few years ago, Sean Parent challenged me to provide an implementation of Boyer-Moore searching in C++. I did that, first in boost and then, later as part of the proposed Library Fundamentals Technical Specification.

The idea here is that you have a searcher object, which encapsulates the actual searching. You construct it with the pattern that you want to search for, and then you call the searchers operator() with the corpus that you want to search, and it will return to you the start of the pattern in the corpus, if it exists, and the end of the corpus, if it does not (this is the same set of rules that std::search follows).

But this weekend I realized that this is not the right thing to return. The searcher (and std::search for that matter) should return a “range” (ok, a pair of iterators) denoting the beginning and end of the pattern in the corpus. (Yes, you can get the end of the pattern by incrementing the returned iterator by the length of the pattern, but that’s an O(N) operation if you only have forward iterators...

Fundamentals of Type-Dependent Code Reuse - Mark Isaacson - NDC Oslo 2015

By Mark | Feb 7, 2016 11:41 PM | Tags: advanced

From NDC Oslo 2015:

Fundamentals of Type-Dependent Code Reuse

by Mark Isaacson

About the video:

This talk surveys different code reuse problems that can be solved by leveraging type information. Mark talks about how you can optimize your algorithms so that certain types use a "fast path", all while hiding that complexity from your users. He also talks about various ways to create "opt-in" functions for your classes. The talk is accessible to novices but builds gradually to complex ideas, including a theoretical C++17 "Mixer" class that allows users to add arbitrary functions to any type, including ints, on an instance by instance granularity.

build2 — C++ Build Toolchain

By Boris Kolpackov | Feb 7, 2016 11:38 PM | Tags: repository package intermediate build

build2 is an open source, cross-platform toolchain for building and packaging C++ code. It includes a build system, package manager, and repository web interface. There is also cppget.org, a public repository of open source C++ packages.

build2 — C++ Build Toolchain

From the announcement:

This is the first alpha release and currently it is more of a technology preview rather than anything that is ready for production. It has been tested on various Linux'es, Mac OS, and FreeBSD. There is no Windows support yet (but cross-compilation is supported).

P0225: Why I want Concepts, and why I want them sooner rather than later -- Ville Voutilainen

By Blog Staff | Feb 7, 2016 09:05 AM | Tags: None

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

Document number: P0225R0

Date: 2016-02-05

Why I want Concepts, and why I want them sooner rather than later

by Ville Voutilainen

Excerpt:

This paper provides highly-opinionated statements, anecdotes and personal opinions explaining why the author thinks Concepts should go into C++17 even if no Conceptified standard library parts are included in C++17.

Raw loops vs STL algorithms

By Meeting C++ | Feb 4, 2016 10:00 AM | Tags: intermediate efficiency c++14 c++11 basics

A new post on the Meeting C++ blog, this time on <algorithm>

Raw loops vs. STL algorithms

by Jens Weller

From the article:

Since last week I am working on my CMS for static HTML pages again, and so the series about Building applications with Qt and boost continues. Today its about using STL algorithms, or how Sean Parent once said "no raw loops!". Now, I am not Sean Parent, and not event the implementers of the STL are perfect. Most code which I write is application code, which then powers Meeting C++. Also, I don't know all STL algorithms, and some times its just to tempting to write a little loop instead of searching the STL for the specific algorithm. Yesterday I had such a case.