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Modern C++ Features – User-Defined Literals--Arne Mertz

By Adrien Hamelin | Oct 27, 2016 11:56 AM | Tags: intermediate c++11

Learn more about litterals.

Modern C++ Features – User-Defined Literals

by Arne Mertz

From the article:

User-defined literals are a convenient feature added in C++11.

C++ always had a number of built-in ways to write literals: Pieces of source code that have a specific type and value. They are part of the basic building blocks of the language:

32 043 0x34   //integer literals, type int
4.27 5E1      //floating point literals, type double
'f', '\n'     //character literals, type char
"foo"         //string literal, type const char[4]
true, false   //boolean literals, type bool

These are only the most common ones, there are many more, including some newcomers in the newer standards. Other literals are nullptr and different kinds of prefixes for character and string literals. There also are suffixes we can use to change the type of a built-in numeric literal:

32u     //unsigned int
043l    //long
0x34ull //unsigned long long
4.27f   //float
5E1l    //long double

void foo(T& out) - How to fix output parameters--Jonathan Müller

By Adrien Hamelin | Oct 27, 2016 11:47 AM | Tags: c++11 advanced

Or how to improve readability and reduce errors.

void foo(T& out) - How to fix output parameters

by Jonathan Müller

From the article:

There are some cases where you need to return a value from a function but cannot use the return value. It happens, for example, in functions where you want to return multiple values at once. While you can pass multiple inputs to a function - the parameters, you cannot pass multiple return values in the same way.

C++ programmers tend to use a good old (lvalue) reference for that. You take a non-const reference as parameter and assign the output to that reference. The caller will pass a variable and upon function completion find the value of the variable changed.

Yet this approach has some problems: For starters, it is not obvious when just looking at the call that the variable is going to be changed. This is the reason that C++ style guides such as the one used by Google recommend using a pointer for that. The caller then has to explicitly pass in the address of the variable, making it explicit.

But with a pointer you can now pass in nullptr, you have to check for that in the function: A pointer where you really mean “reference” does not follow the guidelines I’ve been advocating for.

So is there not a universal solution?

There is, but first we need to understand the full scope of the problem.

Quick Q: Is std::vector so much slower than plain arrays?

By Adrien Hamelin | Oct 27, 2016 11:23 AM | Tags: performance intermediate

Quick A: A vector isn’t slower than an array when they do the same things. But it lets you do much more…

Some time ago on SO:

Is std::vector so much slower than plain arrays?

Using the following:

g++ -O3 Time.cpp -I <MyBoost>
./a.out
UseArray completed in 2.196 seconds
UseVector completed in 4.412 seconds
UseVectorPushBack completed in 8.017 seconds
The whole thing completed in 14.626 seconds


So array is twice as quick as vector.

But after looking at the code in more detail this is expected; as you run across the vector twice and the array only once. Note: when you resize() the vector you are not only allocating the memory but also running through the vector and calling the constructor on each member.

Re-Arranging the code slightly so that the vector only initializes each object once:

std::vector<Pixel>  pixels(dimensions * dimensions, Pixel(255,0,0));

Now doing the same timing again:

g++ -O3 Time.cpp -I <MyBoost>
./a.out
UseVector completed in 2.216 seconds


The vector now performance only slightly worse than the array. IMO this difference is insignificant and could be caused by a whole bunch of things not associated with the test.

I would also take into account that you are not correctly initializing/Destroying the Pixel object in the UseArrray() method as neither constructor/destructor is not called (this may not be an issue for this simple class but anything slightly more complex (ie with pointers or members with pointers) will cause problems.

Presenting Code

By Meeting C++ | Oct 27, 2016 06:46 AM | Tags: presenting community

How should we present code? - is the question.

Presenting Code

by Jens Weller

From the article:

At CppCon 2015 I decided to give a small lightning talk on how to present code in the coming year. This was a reflection on visiting many C++ related conferences and seeing many talks live and online...

Recommendations to speed C++ builds in Visual Studio--Sridhar Madhugiri

By Marco Arena | Oct 27, 2016 03:56 AM | Tags: visual studio

This post discusses features, techniques and tools you can use to reduce build time for C++ projects:

Recommendations to speed C++ builds in Visual Studio

by Sridhar Madhugiri

From the article:

Developers invoke build frequently while writing and debugging code, so improvements here can have a large impact on productivity. Many of the recommendations focus on this stage...

Announcing the lounge track for Meeting C++ 2016

By Meeting C++ | Oct 25, 2016 07:59 AM | Tags: community

Something new at Meeting C++ this year: a track dedicated to meetups!

Announcing the Lounge Track

by Jens Weller

From the Article:

If you look at the schedule, you might notice two changes. Most visible is that there is now a floor plan for the conference. The other one is very subtle: the breaks now have a hint for a 6th track.

ACCU 2017 Call for session -- ACCU

By Felix Petriconi | Oct 24, 2016 02:53 AM | Tags: community

The ACCU 2017 is now putting together its program, and they want you to speak on C++. The ACCU has a strong C++ track, though it is not a C++-only conference. If you have something to share, check out their

Call for Sessions

by the ACCU

From the article:

We have a long tradition of high quality sessions covering many aspects of software development, from programming languages (e.g. C, C++, D, C#, Go, Rust, Clojure, Erlang, Groovy, Haskell, Java, JavaScript, ECMAScript, Python, Ruby, Scala, etc.), and technologies (libraries, frameworks, databases, etc.) to subjects about the wider development environment such as testing, architecture and design, development process, analysis, patterns, project management, and softer aspects such as team building, communication and leadership. See the 2016 schedule for examples.

The Call for Sessions lasts 7 weeks and will close at midnight Friday 2016-12-02.

CppCast Episode 75: Robotics with Jackie Kay

By robwirving | Oct 21, 2016 06:57 AM | Tags: None

Episode 75 of CppCast the only podcast for C++ developers by C++ developers. In this episode Rob and Jason are joined by Jackie Kay from Marble to discuss the use of C++ in the Robotics industry and some of the unique challenges in Robotics development.

CppCast Episode 75: Robotics with Jackie Kay

by Rob Irving and Jason Turner

About the interviewee:

After spending her childhood wanting to become a novelist, Jackie switched over from writing stories to writing code during college. She graduated from Swarthmore College in 2014 with a Bachelor's in Computer Science and went on to work at the Open Source Robotics Foundation for two years, supporting Gazebo, a physics simulator for robotics R&D, and ROS, an open source application framework for robotics development. She recently started as an early employee at Marble in San Francisco, a startup working on autonomous delivery.

Jackie was a speaker at CppCon 2015 and 2016 and a volunteer at C++ Now 2016 and frequently attends the Bay Area ACCU meetups. Her hobbies include rock climbing, travelling, and reading (books, not just blog posts).