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Quick Q: When do you need to declare a variable constexpr? -- StackOverflow

By Blog Staff | Nov 27, 2013 01:44 PM | Tags: intermediate

Quick A: When you want to use the variable in a way that requires its value to be known at compile time.

Here's a short nugget that helps demonstrate the meaning of constexpr:

Why is constexpr required even though member function is constexpr?

The following does not compile unless I put constexpr before initializer_list:

constexpr std::initializer_list<int> il = {
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10
};
std::array<int, il.size()> a;

But initializer_list size is constexpr:

constexpr size_type size() const;

What are inline namespaces good for? -- StackOverflow

By Blog Staff | Nov 27, 2013 11:36 AM | Tags: intermediate

Quick A: For source-level library versioning.

A StackOverflow classic:

What are inline namespaces for?

C++11 allows inline namespaces, all members of which are also automatically in the enclosing namespace. I cannot think of any useful application of this -- can somebody please give a brief, succinct example of a situation where an inline namespace is needed and where it is the most idiomatic solution?

(Also, it is not clear to me what happens when a namespace is declared inline in one but not all declarations, which may live in different files. Isn't this begging for trouble?)

Quick Q: Why write "5 == myValue" instead of "myvalue == 5"? -- StackOverflow

By Blog Staff | Nov 26, 2013 03:31 PM | Tags: basics

Quick A: Because it catches most cases where you accidentally wrote = instead of ==.

From SO:

Reason for using '5 == myValue' in conditionals

I've come across some code that flips how a condition is checked and was wondering why this would be done aside from a weird personal quirk. I've never seen any text books use it nor have I seen any sample code done this way.

// why do it this way?
if (5 == myValue)
{
    // do something
}

// instead of:
if (myValue == 5)
{
    // do something
}

I've only seen this way for == operand but not for any other operands.

Deleted Functions in C++11 -- Fang Lu

By Blog Staff | Nov 26, 2013 01:05 PM | Tags: None

Here is a quick overview of =delete from the IBM Cafe's tour of C++ features.

Note: This summary article focuses on applying =delete to special member functions, which is a main use case. However, be aware that that's only part of the story, because =delete can also apply to regular member function and free function overloads to suppress specific overloads with nice compile-time errors. We invite authors to write about this aspect as well -- just write about it on your own blog and and send us a link to your post via 'Suggest an Article' at the top of this page (you must be logged in to isocpp.org to see this option).

Deleted functions in C++11

by Fang Lu

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

Concept Checking in C++11 -- Eric Niebler

By Blog Staff | Nov 25, 2013 01:14 PM | Tags: intermediate advanced

While we're waiting for Concepts Lite, Eric shows how we can already do quite a bit in C++11 while planning for a transition to language support when it's available.

Concept Checking in C++11

by Eric Niebler

From the article:

This post describes some utilities I’ve recently developed for doing concept checking in C++11. These utilities are part of an ongoing project to reimplement ranges, also for C++11, but I think the concept checking utilities are useful and interesting in their own right...

Basic Structure of C++ Program -- Prashant Sharma

By prashant0788 | Nov 22, 2013 12:44 PM | Tags: basics

[Ed.: This is a simple short "hello world" overview for someone starting to program in C++, and is basically correct. There are lots of expert-friendly articles, but we like and want to encourage the beginner- and intermediate-level articles as well for the benefit of the many recent newcomers to the language.]

Basic Structure of C++ Program

The easiest way to understand the basic structure of C++ program is by writing a program. The basic C++ program is as follows: ...

Quick Q: Why is std::vector contiguous? -- StackOverflow

By Blog Staff | Nov 20, 2013 02:15 PM | Tags: intermediate

Quick A: Because if you're serious about performance, you'll often (not always) use contiguous arrays.

From SO:

Why is std::vector contiguous?

Besides the fact that the standard defines it to be contiguous, why is std::vector contiguous?

If it runs out of space, it needs to reallocate a new block and copy the old block to the new one before continuing.

What if it wasn't contiguous? When the storage fills up, it would just allocate a new block and keep the old block. When accessing through an iterator, it would do simple >, < checks to see which block the index is in and return it. This way it doesnt need to copy the array every time it runs out of space.

Would this really work/be better? or am i missing something?

C++11 Annoyance Avoiders -- Tony DaSilva

By Blog Staff | Nov 19, 2013 02:57 PM | Tags: None

A useful short nugget: override FTW!

C++11 Annoyance Avoiders

by Tony DaSilva

From the article:

I’ve always been torn as to whether or not to annotate derived class member functions intended to override base class members as virtual...

Type Erasure, Part 1 -- Andrzej KrzemieĊ„ski

By Blog Staff | Nov 19, 2013 09:47 AM | Tags: intermediate

What is this "type erasure" thing you speak of? It's not something at the other end of a pencil (remember those?) but a way to hold an object without knowing its exact type. Andrzej explains:

Type Erasure, Part 1

by Andrzej Krzemieński

From the article:

Have you ever came across term type erasure in C++? This “pattern” or “technique” is growing more and more popular. In this post I will try to describe what it is. Note that it is something different than a similar term in Java.

What does type encode?

Let’s start with describing the opposite of type erasure. We could call such situation “type-full-ness”. Forget the term though, let me illustrate what I mean with an example. ...