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Quick Q: Does [=] capture all variables in scope? -- StackOverflow

By Blog Staff | May 2, 2013 04:45 AM | Tags: basics

Quick A: No.

A simple but important question:

C++11 lambda capture semantics

When I use [=] to indicate that I would like all local variables to be captured by value in a lambda, will that result in all local variables in the function being copied, or just all local variables that are used by the lambda?

So, for example, if I have:

vector<int> my_huge_vector(100000);
int my_measly_int;
some_function([=](int i){ return my_measly_int + i; });

Will my_huge_vector be copied, even though I don't use it in the lambda?

Quick Q: static constexpr variable vs. constexpr function? -- StackOverflow

By Blog Staff | May 1, 2013 04:39 PM | Tags: intermediate basics

With a nice Quick A by Morwenn that not only gives the right answer as of today, but is current with a feature voted into C++14 just two weeks ago that lets you drop the ()'s:

static constexpr variable vs. function

Is there a difference between declaring floating point constant as a static constexpr variable and a function as in example below, or is it just a matter of style?

class MY_PI
{
public:
    static constexpr float MY_PI_VAR = 3.14f;
    static constexpr float MY_PI_FUN() { return 3.14f; }
}

Functional Patterns in C++ -- Bartosz Milewski

By Blog Staff | May 1, 2013 12:11 PM | Tags: advanced

bartosz-milewski-functional.pngIf you're familiar with functional language styles and you want an advanced look at how your favorite functional styles are supported in modern C++, with a dash of Haskell, check out these three videos by Bartosz Milewski:

Functional Patterns in C++ (slides)

by Bartosz Milewski

Part 1, Functors: First the introduction to some common functional patterns like Functor, which, surprisingly pops up everywhere. I'll show the example of a unique_ptr and a vector as Functors. Of course, this is only in preparation for asynchronous functors.

Part 2, Currying, Applicative: A little digression to Haskell and the Maybe functor and the explanation of currying. Then I'll show you the Applicative Functor pattern. This is, of course, in preparation for for the asynchronous applicative functor pattern.

Part 3, Asynchronous API, Monoid, Monad: The encapsulation of asynchronous API that doesn't lead to inversion of control and spaghetti code. Very natural example of a Monad Pattern.

Slides (parts 1-3)

Interestingly, Bartosz' talk ends with a plea for (essentially) future.then and a C#-style await... both of which are under active consideration in the C++ standards committee as part of a potential near-term C++ technical specification on concurrency and parallelism.

Advanced Developer Conference C++

By MichaelWong | Apr 30, 2013 11:45 AM | Tags: None

adc.PNGThere's still time to go to:

Advanced Developers C++ 2013

May 7-8, 2013

Bad Aibling, Germany

Sessions are presented in either English or German. While the conference has many Windows-focused topics, a number of the sessions are of general interest to C++ developers.

Here are highlights from the Sessions page:

Trends and Future of C++ Standard and ISOCPP.org
Transactional Memory in C++
Michael Wong, IBM, and subgroup chair of ISO C++ SG5 (Transactional Memory)

Keynote: Building Modern Device Apps with C++ 
Building and Consuming Cloud Services with C++
Steve Teixeira, Microsoft

Warum wird Code so wie er ist? [Why does code get the way it does?]
Holger Kolb, DEVCOL

Einfacheres C++ mit C++11 [Simpler C++ with C++11]
Peter Sommerlad, FHO HSR Hochschule für Technik

Sicher sein oder sicher fühlen? -- Sicheren C++ Code schreiben [Be secure or feel secure? -- Writing secure C++ code]
Oliver Niehus, Microsoft

Performance-Optimierung für parallelen C++ Code auf Windows [Performance optimizing parallel C++ code on Windows]
Programmieren und Optimieren auf Xeon Phi [Programming and Optimizing for Xeon Phi]
Michael Steyer, Intel

Continue reading more sessions...

Trip Report: ISO C++ Spring 2013 Meeting, Part 3 -- Michael Wong

By Blog Staff | Apr 30, 2013 07:38 AM | Tags: None

iconNoCommunityPhoto155.pngPart 3 of Michael Wong's trip report:

The view from C++ Standard meeting April 2013 Part 3

by Michael Wong

In this series that looks at C++14 content, we looked at features from Language and Library for C++14. Now we will look at Concurrency which is the other group that contributed features for C++14. In reality, some of the features from Language and Library also came from Concurrency. ...

An Idiot's Guide to C++ Templates -- Ajay Vijayvargiya

By Blog Staff | Apr 30, 2013 06:18 AM | Tags: intermediate

A lot of people appreciated the information in this pair of articles, which cover the noted topics:

An Idiot's Guide to C++ Templates -- Part 1

The Syntax Drama

Function Templates

  • Pointers, References and Arrays with Templates
  • Multiple Types with Function Templates
  • Function Template -- Template Function
  • Explicit Template Argument Specification
  • Default Arguments with Function Templates

Class Templates

  • Multiple Types with Class Templates
  • Non-type Template Arguments
  • Template Class as Argument to Class Template
  • Default Template Arguments with Class Templates
  • Class' Methods as Function Templates

An Idiot's Guide to C++ Templates -- Part 2

Requirements from the Underlying Type

  • Requirements: Function Templates
  • Requirements: Class Templates

Separation of Declaration and Implementation

  • Separating Class Implementation

Templates and Other Aspects of C++

  • Class Templates, Friends
  • Class Templates, Operator Overloading
  • Class Templates, Inheritance
  • Function Pointers and Callbacks
  • Templates and Virtual Functions
  • Templates and Macros
  • Function Overloading

STL - An Introduction

Templates and Library Development

Explicit Instantiation

C++ on the Web: Run Your Big 3D Game in the Browser! -- Andre Weissflog

By Blog Staff | Apr 26, 2013 02:37 PM | Tags: intermediate

cpp-web.PNGBuilding C++ to target Javascript (e.g., asm.js) and execute C++ in the browser is becoming quite the popular indoor sport. Here's a current presentation and experience report:

C++ on the Web: Run your big 3D Game in the browser! (slides)

by Andre Weissflog
Head of Development, Berlin
Bigpoint GmbH

My presentation about porting large C/C++ code bases to the browser (emscripten, flascc, Google Native Client)

From the Wrap-up slide:

  • You can run big C/C++ code bases ("a million lines of code") in the browser.
  • Javascript is already fast enough for many types of games.
  • Massive performance improvements happening right now (better code generation, JS engines better at running generated code, asm.js...)
  • ...

Trip Report: ISO C++ Spring 2013 Meeting, Part 2 -- Michael Wong

By Blog Staff | Apr 26, 2013 01:21 PM | Tags: None

iconNoCommunityPhoto155.pngPart 2 of Michael Wong's trip report:

The view from C++ Standard meeting April 2013 Part 2

by Michael Wong

In part 1 of this trip report, I spoke about the general mood of the April C++ Std meeting in Bristol and the plan to release C++14 [Committee] Draft (CD) after the meeting. I also deep dived into the language feature set for C++14.

Now I will deep dive onto the library feature additions for C++14. As with the language features, some of these originated from other subgroups. As before, I will not talk about minor bug fixes, but also talk about proposals that did not pass as they are often the most controversial. ...

Trip Report: ISO C++ Spring 2013 Meeting -- Michael Wong

By Blog Staff | Apr 26, 2013 12:50 PM | Tags: None

iconNoCommunityPhoto155.pngA trip report from Michael Wong:

The view from C++ Standard meeting April 2013 Part 1

by Michael Wong

... Our goal was to triage all features that can enter C++14. This means C++14 is more than just bug fixes and is unlike a Technical Corrigendum like TC1 which bridged C++ 1998 to C++2003. As such it will have additional features beyond defect fixes that has been deemed to be small enough in scope and solution but significant enough in annoyance that it should be fixed immediately post C++11...

Here are the new language extensions voted in...

Quick Q: When should I use noexcept? -- StackOverflow

By Blog Staff | Apr 24, 2013 03:25 AM | Tags: basics

As C++11-compliant compilers start to roll out and be adopted, people want to know to best use new C++11 features, such as:

When Should I Really Use noexcept?

 

  1. There are many examples of functions that I know will never throw, but for which the compiler cannot determine so on its own. Should I append noexcept to the function declaration in all such cases? ... For which situations should I be more careful about the use of noexcept, and for which situations can I get away with the implied noexcept(false)?
  2. When can I realistically except to observe a performance improvement after using noexcept? ... Do modern compilers take advantage of noexcept in this way? If not, can I excect some of them to do so in the near future?