Sometimes You Must Violate an Abstraction to Maintain It -- Andrew Koenig

By Blog Staff | Jul 17, 2013 01:55 PM | Tags: basics

Koenig explains std::move as, well, just a bit of a fib, really:

Sometimes You Must Violate an Abstraction to Maintain It

by Andrew Koenig

From the article:

What std::move really does is to return its argument as an rvalue reference. In effect, every time we use std::move, we are telling a lie. In this case, by writing std::move(t.s), we are saying that we want to use t.s, but to do so in a way that treats t.s as an rvalue. It is acceptable for us to tell this lie for exactly the same reason that it is acceptable for us to cast t.s to string&& in the previous example: We know that t.s is a member of t, and t really refers to an rvalue in our caller's context.

We can tell such lies any time we are willing to take responsibility for the consequences. ...

How the C++ Compiler Decides to Move Objects -- Andrew Koenig

By Blog Staff | Jul 15, 2013 04:18 AM | Tags: basics

Recently at Dr. Dobb's:

How the C++ Compiler Decides to Move Objects

by Andrew Koenig

From the article:

After reading this post, you should be able to figure out what std::move does, although not necessarily how it does it...

C++11/14 Training Materials -- Scott Meyers

By Blog Staff | Jul 13, 2013 04:59 PM | Tags: intermediate basics

C++14 is still very much a draft -- it only became feature-complete in April and is now in its primary comment ballot. But interest in this new standard is high, with a restarted "Guru of the Week" series focusing on C++14 and now Scott Meyers has produced the first book-like materials that include significant coverage of C++14.

C++11 Training Materials Updated -- Now With C++14 Info!

For the seventh time since originally releasing them over three years ago, I've updated my annotated training materials for "The New C++". Until this update, "the new C++" referred to C++11, but with this revision, I'm including treatment of several features from draft C++14 that I believe will make it into the new new standard. As far as I know, this makes my training materials the first "book-like" publication that covers features in C++14.

What are “rvalue references for *this” for? -- StackOverflow

By Blog Staff | Jul 11, 2013 05:33 AM | Tags: intermediate

Readers ask:

What are “rvalue references for *this” for?

What are the most typical use cases of "rvalue references for *this" which the standard also calls reference qualifiers for member functions?

By the way, there is a really good explanation about this language feature here.

Optimizing C++ Code: Constant-Folding -- Jim Hogg

By Blog Staff | Jul 10, 2013 08:18 AM | Tags: optimization intermediate

The Visual C++ Team Blog has been publishing an article series about optimizations that C++ compilers perform for you under the covers to make your code more efficient. This short nugget answers a question people sometimes ask: "What's constant folding, and why do I care?"

Optimizing C++ Code: Constant-Folding

by Jim Hogg

From the article:

This post examines Constant-Folding -- one of the simplest optimizations performed by the VC++ compiler.  In this optimization, the compiler works out the result of an expression while it is compiling (at “compile-time”), and inserts the answer directly into the generated code.  This avoids the cost of performing those same calculations when the program runs (at “runtime”).

Here is an example...

Working with Dynamic Memory in C++ -- Stan Lippman, Josée Lajoie, Barbara Moo

By Blog Staff | Jul 9, 2013 09:57 AM | Tags: basics

A chapter worth reading on InformIT, excerpted from C++ Primer 5th Edition:

Working with Dynamic Memory in C++

by Stan Lippman, Josée Lajoie, Barbara Moo

C++ lets you allocate objects dynamically. The authors of C++ Primer discuss why properly freeing dynamic memory is a rich source of bugs, and how the new library defines smart pointers -- shared_ptr, unique_ptr, and weak_ptr -- that make managing dynamic memory much safer.

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?

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. ...