C++ Papers for Issaquah - Concepts, Database and Evolution

By Meeting C++ | Feb 6, 2014 04:33 PM | Tags: standardization issaquah intermediate experimental evolution database concepts advanced

This is the second part of my series about the papers for the next C++ committee meeting in Issaquah:

C++ Papers for Issaquah - Concepts, Database & Evolution

by Jens Weller

From the article:

This is the second part about the papers for the C++ committee meeting in February in Issaquah. This time featuring papers from the subgroups of concept, database and evolution. Again, most papers in this series aim for a standard after C++14, most important for C++14 will be the national comments on the new standard. Also there are no new papers from the core working group, only the active issues, defects report and closed issues report are on this mailing.

Quick Q: Why does unique_ptr take two template parameters when shared_ptr only takes one? -- SO

By Blog Staff | Feb 6, 2014 05:39 AM | Tags: None

Recently on StackOverflow:

Why does unique_ptr take two template parameters when shared_ptr only takes one?

Both unique_ptr and shared_ptr accept a custom destructor to call on the object they own. But in the case of unique_ptr, the destructor is passed as a template parameter of the class, wherease the type of shared_ptr's custom destructor is to be specified as a template parameter of the constructor.

template <class T, class D = default_delete<T>>
class unique_ptr
{
    unique_ptr(T*, D&); //simplified
    ...
};

and

template<class T>
class shared_ptr
{
    template<typename D>
    shared_ptr(T*, D); //simplified
    ...
};

I can’t see why such difference. What requires that?

Quick Q: What do braces mean as a function argument? -- StackOverflow

By Blog Staff | Feb 5, 2014 03:12 AM | Tags: basics

Quick A: Something cool and convenient -- you can construct a temporary variable of the parameter type without having to repeat the type.

From SO:

C++ 11 Curly Braces

I haven't used C++ for a good few years, and have just come across this:

program.build({ default_device })

The definition is:

cl_int build(
    const VECTOR_CLASS<Device>& devices,
    const char* options = NULL,
    void (CL_CALLBACK * notifyFptr)(cl_program, void *) = NULL,
    void* data = NULL) const

What are the curly braces there for? I have never seen them used in a function call like this before. I assume it has something to do with the function pointer, but that seems optional?

Quick Q: Can a lambda refer to local variables? -- StackOverflow

By Blog Staff | Feb 4, 2014 11:32 AM | Tags: basics

Quick A: Using the [] capture list.

Yesterday on SO:

Is it possible in C++11 / 14 syntax to write an lambda function which will see parent variables?

In abstraction:

int i = 1;
auto go = [] () {
    return i;
};

Is it possible to make something like that in modern C++ syntax?

C++ Papers for Issaquah -- Concurrency

By Meeting C++ | Jan 29, 2014 07:47 AM | Tags: standardization performance intermediate experimental concurrency c++14 advanced

So I just started to read through the papers for the next C++ committee meeting in Issaquah in February, first part is about Concurrency:

C++ Papers for Issaquah -- Concurrency

by Jens Weller

From the article:

In february the C++ committee is going to meet for a week in Issaquah, it could be the final Meeting for C++14, the papers in this series will reflect both, C++14 and the standard that will come after it. Currently mostly known as C++1y. A lot of papers that are not part of C++14 will be formed into technical specifications, which some will then become C++1y later. Like the last series, I will again focus on the working groups, and post the papers sorted by the name of the working group, starting with concurrency.

Quick Q: How do I write string literals that contain special characters? -- StackOverflow

By Blog Staff | Jan 27, 2014 03:06 PM | Tags: None

Quick A: Use raw string literals! If your compiler doesn't have them yet, nag.

The original question on SO, but note the best answer is pepper_chico's rather than the selected answer:

Only Detect Text in Quotations (C++)

I'm not great at programming and recently started to read tutorials on C++.

I decided I would attempt to make a simple blackjack program. I tried to make a title with "big text" but C++ is preventing me from doing it because it is detecting other things inside the text.

    //Start Screen Begin
cout << " ____  _            _     _            _        ";
cout << "| __ )| | __ _  ___| | __(_) __ _  ___| | __    ";
cout << "|  _ \| |/ _` |/ __| |/ /| |/ _` |/ __| |/ /    ";
cout << "| |_) | | (_| | (__|   < | | (_| | (__|   <     ";
cout << "|____/|_|\__,_|\___|_|\_\/ |\__,_|\___|_|\_\    ";
cout << "                       |__/                     ";
    //Start Screen End

This is what I am trying to display, yet keep getting the following error:

undefined reference to​ 'WinMain@16'

I am asking if there is a way to tell C++ I only want it to read and display the text, and not use any functions.

C++ in 2014 -- Jens Weller

By Blog Staff | Jan 24, 2014 01:01 PM | Tags: None

From new C++ user groups springing up across Europe and upcoming conferences, to the Boost refactoring and (of course) C++14, Jens Weller has a nice piece previewing some of the things to look forward to for C++ in 2014.

C++ in 2014

by Jens Weller

Note that Jens' list is not complete, but it gives a pretty good overview of what's coming up in the near term with a few more things to be added later.

A small teaser from the article:

I already know that there are new C++ User Groups in Aachen, Dortmund, Heidelberg and Munich in Germany, also a Russian C++ User Group is now meeting in St. Petersburg and Moscow. I think a few others will follow...

Quick Q: Should "property get" functions be noexcept? -- StackOverflow

By Blog Staff | Jan 24, 2014 09:32 AM | Tags: intermediate

Quick A: Maybe, but it generally commits you to exposing the internal type (can't change representation).

Recently on SO:

Should I use noexcept for getters always?

Should I use noexcept method modifier for getters always in C++11?

I mean simple getters here that just return members. At least in all my getters I have here an exception can't possibly be thrown. One downside is that a getter gets too verbose:

const std::string& getName() const noexcept{ return name; }

The good side as pointed out in Stroustrup's book is that the compiler might do some optimizations here and there.

GotW #95 Solution: Thread Safety and Synchronization -- Herb Sutter

By Blog Staff | Jan 15, 2014 10:26 AM | Tags: intermediate

The solution to the latest GotW problem is now available:

GotW #95 Solution: Thread Safety and Synchronization

by Herb Sutter

From the article:

This GotW was written to answer a set of related frequently asked questions. So here’s a mini-FAQ on "thread safety and synchronization in a nutshell," and the points we’ll cover apply to thread safety and synchronization in pretty much any mainstream language.

Using Regular Expressions with Modern C++ -- Kenny Kerr

By Blog Staff | Jan 14, 2014 08:49 AM | Tags: intermediate

In the current MSDN Magazine:

Using Regular Expressions with Modern C++

by Kenny Kerr

From the article:

C++11 introduced a long list of features that are in themselves quite exciting, but if all you see is a list of isolated features, then you’re missing out. The combination of these features makes C++ into the powerhouse that many have grown to appreciate. I’m going to illustrate this point by showing you how to use regular expressions with modern C++... the combination of C++ language and library features really turns C++ into a productive programming language.