When decltype meets auto -- Scott Meyers

By Blog Staff | Jul 8, 2013 03:58 PM | Tags: advanced

A fresh Scott Meyers post about a brand-new C++14 feature:

When decltype meets auto

by Scott Meyers

... C++14 is on the horizon, and one of the new features sure to stifle even the strongest of yawns is the ability to declare types using decltype(auto). This feature leads to two questions, only the first of which is rhetorical:

1. You can declare what?
2. During type deduction for decltype(auto), which type deduction rules are to be followed: those for auto or those for decltype? Or does decltype(auto) have its own set of type deduction rules?

Quick Q: How do I remove a unique_ptr from a queue? -- StackOverflow

By Blog Staff | Jul 8, 2013 11:39 AM | Tags: basics

Quick A: move(q.front()).

remove unique_ptr from queue

I'm trying to figure out how/if I can use unique_ptr in a queue.

// create queue
std::queue<std::unique_ptr<int>> q;

// add element
std::unique_ptr<int> p (new int{123});
q.push(std::move(p));

// try to grab the element
auto p2 = foo_queue.front();
q.pop();

I do understand why the code above doesn't work. Since the front & pop are 2 separate steps, the element cannot be moved. Is there a way to do this?

Living with Lambdas -- Alfons Haffmans

By Blog Staff | Jul 8, 2013 03:31 AM | Tags: advanced

We have such a powerful language, and what a powerful language it is.

Living with Lambdas

by Alfons Haffmans

From the article:

You can work in the functional programming paradigm in C++. And you may be surprised at how complete C++’s support for functional programming is.

... C++ has always been a multi-paradigm language. And while previous attempts to add practical functional programming features required significant effort, recent additions to the C++ standard, like lambdas, have improved the situation. This paper explores the out-of-box support for functional programming provided by the new standard. We’ll look at techniques typically found in introductory functional programming textbooks. This article assumes familiarity with C++, but not necessarily with basic functional programming.

The source code is available in github and is compiled using gcc 4.8 installed on Mac OSX using MacPorts.

Quick Q: What are move semantics? -- StackOverflow

By Blog Staff | Jul 6, 2013 05:22 AM | Tags: basics

One of the highest-ranked C++ questions (and answers) on StackOverflow is worth re-reading if you're new to the topic:

What are move semantics?

I just finished listening to the Software Engineering talk radio podcast interview with Scott Meyers regarding C++0x. Most of the new features made sense to me, and I am actually excited about C++0x now, with the exception of one. I still don't get move semantics... What are they exactly?

Moving an Object Does Not Destroy The Original -- Andrew Koenig

By Blog Staff | Jul 5, 2013 04:17 PM | Tags: basics

Andy's next on move semantics:

Moving an Object Does Not Destroy The Original

by Andrew Koenig

From the article:

Recall first that objects are generally moved instead of copied because the originals are about to go away. When I learned this fact, I thought at first that moving an object should destroy the original. ...

I was surprised to learn that that is not what happens. Instead, whenever a program moves an object, it must leave that object with a valid value so that it can be destroyed later. ...

Modern C++ Programming with Test-Driven Development -- Jeff Langr

By Tom Kirby-Green | Jul 3, 2013 04:16 AM | Tags: tdd intermediate

[Ed.: This upcoming book is currently in beta. Thanks Tom for pointing it out!]

I have nothing to do with this book other than I've bought the beta book and am enjoying it thus far. It fills a gap in the market very nicely.

Modern C++ Programming with Test-Driven Development: Code Better, Sleep Better

by Jeff Langr, edited by Michael Swaine

If you program in C++ you’ve been neglected. Test-driven development (TDD) is a modern software development practice that can dramatically reduce the number of defects in systems, produce more maintainable code, and give you the confidence to change your software to meet changing needs. But C++ programmers have been ignored by those promoting TDD -- until now. In this book, Jeff Langr gives you hands-on lessons in the challenges and rewards of doing TDD in C++.

Auto: A Necessary Evil? -- Roger Orr

By fbuontempo | Jul 2, 2013 02:05 PM | Tags: intermediate basics

Roger Orr has written about the history and use of auto in ACCU's Overload 115:

Auto -- A Necessary Evil?

by Roger Orr

From the article:

The keyword auto now lets you declare variables where the compiler provides the actual type and the programmer is either unwilling or unable to name the actual type. The keyword can also be used in function definitions to let you provide the return type after the rest of the function declaration, which is useful when the return type depends on the type of the arguments.

As with any new keyword there are questions about usage –- at two levels. First of all, where and how are programmers permitted to use the new feature. Secondly, what guidance is there to sensible adoption of the new feature. I intend to start with by answering the first question and then subsequently focus on the second.

Quick Q: Are there significant differences between boost::bind and std::bind? -- StackOverflow

By Blog Staff | Jul 1, 2013 01:58 PM | Tags: intermediate boost

A few minutes ago on SO:

Should I be seeing significant differences between std::bind and boost::bind?

I'm exploring the support for C++11 on the 4.7 branch of g++ (Ubuntu/Linaro 4.7.3-2ubuntu~12.04, to be specific) and I seem to be finding differences. In particular, if I comment out the #include of boost/bind.hpp and systematically replace occurrences of boost::bind with std::bind in the Boost ASIO async client example (taken from http://www.boost.org/doc/libs/1_45_0/doc/html/boost_asio/example/http/client/async_client.cpp), the program no longer compiles. Any explanation for this?

Quick Q: What type does auto use for containers? -- StackOverflow

By Blog Staff | Jun 28, 2013 10:43 AM | Tags: None

Quick A: std::initalizer_list. And did you know you can even do for(auto i: {1,2,3,4,5}) ?

What type does auto use for containers?

I can achieve identical output by using different containers in C++. For example . .

    std::array<int, 5> v = {1,2,3,4,5};
    for(auto i : v)
        std::cout << i << ", ";

or

    std::vector<int> v = {1,2,3,4,5};

or

    int v[] = {1,2,3,4,5};

etc.

So what container does auto use here?

    auto v = {1,2,3,4,5};
    for(auto i : v)
        std::cout << i << ", ";

Quick Q: Why does draft C++14 have both runtime-sized arrays and std::dynarray? -- StackOverflow

By Blog Staff | Jun 27, 2013 09:56 PM | Tags: c++14

Several people have asked:

Why both runtime-sized arrays and std::dynarray in C++14?

Draft C++14 includes both runtime-sized arrays and the std::dynarray container. From what I can tell, the only real difference between the two is that std::dynarray has an STL interface (e.g., begin, end, size, etc.), while runtime-sized arrays do not. So why does C++14 need them both?