Advanced C++ - Anonymous namespaces

Anonymous namespace is kind of namespace with no specified name. Such kind of namespace is visible only within file where it is defined within. I allows define variables and functions which could be visible as global, but within one file only. Thanks to that such files are not global within whole program. It also allow avoids making global static variable. Let's see an example of defining and usage of anonymous namespace. Consider following main.cpp file:
In the above example we have anonymous namespace containing one int typed variable. This variable can be used as global variable withing this main.cpp file but will not be visible inside any other files. That is simple example of usage anonymous variables. If you would like to compile it and play with it (changing or adding some parts of code to check what happends than) you can download it from here: https://github.com/xmementoit/CppAdventureExamples/tree/master/advancedCpp/anonymousNamespace

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STL - count and count_if algorithms

One of the basic and most useful STL algorithms is algorithm which can be used to count number of elements within selected container according to specified criteria. In order to do that we can use std::count or std::count_if algorithm. std::count (firstElementIterator, lastElementIterator, elementForSearch) - is function which will go through container using firstElementIterator and lastElementIterator and return number of container elements which value is equal elementForSearch std::count_if (firstElementIterator, lastElementIterator, UnaryPredicateFunction) - is function which examine range from firstElementIterator to lastElementIterator and return number of container elements which fulfill UnaryPredicateFunction criteria. UnaryPredicateFunction is function having following signature: bool functionName(const Type& a) . So, count_if returns number of elements where UnaryPredicateFunction returns true for. For better understanding let's take a...

C++ Multithreading - Race conditions

In the previous C++ Multithreading article I presented you how to pass parameters between threads. Take a detail look on the output of that example once again: In the first line of that output you can notice that output text from two threads is mixed. You are probably wondering why it happens? It is because we are not protecting resources which are shared by two threads (in this example cout stream is shared in both threads) which causes multithreading's phenomenon called race condition . Because threads switching and accessing to shared resources are managed by operating system we do not know when std::cout stream will be accessed by main thread and when it will be accessed by second thread. Therefore in the previous article I mentioned that output of the example can be little different on your computer than my output example. What's more it is possible that this output will be different for few consecutive invoking of the example on the same machine. It is beca...

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