Scott Meyers in Oslo: Friday, June 14

By Blog Staff | Jun 4, 2013 04:46 PM | Tags: intermediate

On Friday, June 14, Scott Meyers will be giving a talk open to the public at the Oslo C++ Users Group.

From Scott's announcement:

Lambdas vs. std::bind in C++11 and C++14

Scott Meyers

 

C++ developers have long had a need to bind functions and arguments together for a later call. This is what makes it possible to invoke member functions on objects inside STL algorithms. The same technology can be used to create custom callback functions and to adapt function interfaces to different calling contexts.

In C++98, such binding was accomplished via std::bind1st and std::bind2nd. TR1 added std::tr1::bind, which was promoted to std::bind in C++11. But C++11 also introduced lambda expressions, and they’re slated to become even more powerful in C++14. That means that there are now two mechanisms in C++ for binding functions to arguments for later calls: std::bind and lambda expressions. In this talk, Scott examines the pros and cons of each approach, comparing them in terms of expressiveness, clarity, and efficiency, and he comes to the conclusion that one should almost always be used instead of the other. But which one?

 

This presentation assumes a basic familiarity with std::bind and C++11 lambda expressions.

Trailing Return Types -- sumi_cj

By Blog Staff | Jun 4, 2013 11:08 AM | Tags: None

From the IBM C/C++ Cafe:

Introduction to the C++11 feature: trailing return types

by sumi_cj

From the article:

To solve this problem, C++11 introduced a feature called trailing return types. Using this feature, the previous program can be rewritten as follows:

template<class T>
auto mul(T a, T b) -> decltype(a*b){
    return a*b;
}

Quick Q: When should I use {} vs. () to initialize variables? -- StackOverflow

By Blog Staff | Jun 3, 2013 03:37 PM | Tags: basics

Quick A: In C++11, prefer to initialize using {} where possible, which is nearly always.

Uniform initialization syntax difference

What's the difference between doing

A a{ A() };

and,

 

A a( A{} );

to avoid the Most Vexing Parse? When should I use a particular one?

Quick Q: Should I return a const value? -- StackOverflow

By Blog Staff | Jun 3, 2013 12:47 PM | Tags: intermediate

Quick A: No.

Some authors wrote "Consider doing this" in C++98. The answer is now a definite "No" because it prevents move from returned values.

Isn't the const modifier here unnecessary?

The "Effective C++" Item 3 says "Use const whenever possible", and it gives an example like:

 

const Rational operator*(const Rational& lhs,
                            const Rational& rhs);

to prevent clients from being able to commit atrocities like this:

Rational a, b, c;
...
(a * b) = c;   // invoke operator= on the result of a*b!

But isn't the non-reference return value of functions allready a rvalue? So why bother doing this?

GotW #90 Solution: Factories -- Herb Sutter

By Blog Staff | May 31, 2013 02:50 PM | Tags: intermediate basics

The solution to the latest GotW problem is now available:

GotW #90 Solution: Factories (updated for C++11/14)

by Herb Sutter

From the article:

Guideline: A factory that produces a reference type should return a unique_ptr by default, or a shared_ptr if ownership is to be shared with the factory.

Guideline: A factory that produces a non-reference type should return a value by default, and throw an exception if it fails to create the object. If not creating the object can be a normal result, return an optional<> value.

Copying Container Elements From The C++ Library: It's Trickier Than It Looks -- Andrew Koenig

By Blog Staff | May 31, 2013 02:41 PM | Tags: None

New on DDJ:

Copying Container Elements From The C++ Library: It's Trickier Than It Looks

by Andrew Koenig

From the article:

Now consider this call:

 

v.push_back(v[0]);

GCC 4.8.1 released, C++11 feature complete

By seth | May 31, 2013 11:09 AM | Tags: None

The release of GCC 4.8.1 was announced today (31 May 2013) on the gcc mailing list. In addition to many bug fixes, GCC 4.8.1 adds support for C++11 ref-qualifiers, the final missing C++11 feature. This makes GCC the first C++11 [Ed.: language specification] feature complete compiler to be released.

Information on the full set of changes is available on the GCC 4.8 series page. 

Clang 3.3, also C++11 feature complete, is in release testing and the release is currently scheduled for June 5th. Within a week full C++11 support will be available from two major compilers and on numerous platforms supported by those compilers.

Forging ahead with support for the next C++ standard.

GotW #89 Solution: Smart Pointers -- Herb Sutter

By Blog Staff | May 30, 2013 02:36 PM | Tags: intermediate basics

The solution to GotW #89 is now available:

GotW #89 Solution: Smart Pointers (updated for C ++11/14)

by Herb Sutter

From the article:

So, why use make_shared (or, if you need a custom allocator, allocate_shared) whenever you can, which is nearly always? There are two main reasons: simplicity, and efficiency...

C++ auto and decltype Explained -- Thomas Becker

By Blog Staff | May 29, 2013 03:59 PM | Tags: None

Here's a nice detailed treatment of auto and decltype by longtime author Thomas Becker.

C++ auto and decltype Explained

by Thomas Becker

From the article:

A while later, sometime in 2012, I noticed that there was another feature, or rather, a pair of features, in C++11 that I had not fully understood, namely, the auto and decltype keywords. With auto and decltype, unlike rvalue references, the problem is not that they are difficult to grasp. On the contrary, the problem is that the idea is deceptively easy, yet there are hidden subtleties that can trip you up.

Let's start with a good look at the auto keyword...

Defaulted Functions in C++11 -- Fang Lu

By Blog Staff | May 29, 2013 10:22 AM | Tags: basics

New at the IBM DeveloperWorks C/C++ Cafe:

Defaulted functions in C++11

by Fang Lu

From the article:

The defaulted functions feature is newly introduced into the C++11 standard. In this article, I will explain this feature and provide some examples on how to use it.