Dimensional Data

The concurrency support library in modern C++ is designed to solve read and write data securely in thread operations that allow us to develop faster multi-thread apps. This library includes built-in support for threads (std::thread), atomic operations (std::atomic), mutual exclusion (std::mutex), condition variables (std::condition_variable), and many other features. In C++14, in addition to mutex, there is a shared mutex (std::shared_mutex) which is an instance of the class located in header. In this post, we explain a frequently asked mutex question in modern C++, what are the differences between mutex and shared_mutex? What is a mutex (std::shared_mutex) in C++? Mutual Exclusion is a property of concurrency control and in programming, the Mutual Exclusion is a data exclusion method to lock and unlock data that provides exclusive access to a resource. This is mostly needed when we use shared data in multi-thread and multi-task operations in parallel programming. In C++, we can use std::mutex to define mutex data variables to protect his shared data from being simultaneously accessed by multiple threads. Here is an example of how we can use std::mutex with its lock() and unlock() methods,   std::mutex mtx;   mtx.lock();   // do operations mtx.unlock();   Here are more details and examples about std::mutex. What is a shared mutex (std::shared_mutex) in C++? The shared mutex comes with C++14, it is an instance of the class located in header and used with the shared_mutex class name in mutual exclusion operations of threads. The shared_mutex class is a part of the thread support library. It is a synchronization primitive for the thread operations that can be used to protect shared data when multiple threads try to access. Here is a simple example about std::shared_mutex with its try_lock_shared() and unlock_shared() methods that comes with C++17.   std::shared_mutex sharedmutex;   // in a thread function sharedmutex.try_lock_shared(); // do operations sharedmutex.unlock_shared();   Here are more details and a full example about shared_mutex. ———- LINK TO Learn About Useful Shared Mutexes Locking In Modern C++ —————— What are the differences between std::mutex and std::shared_mutex? While the std::mutex guarantees exclusive access to some kind of critical resource, the shared_mutex class extends this feature by a shared and exclusive level of accesses. The shared_mutex can be used in exclusive access level to prevent access of any other thread from acquiring the mutex, as in std::mutex. No matter if the other thread is trying to acquire shared or exclusive access. The shared_mutex can be used in the shared access level to allow multiple threads to acquire the mutex, but all of them are only in shared mode. In thread operations, exclusive access is not granted until all of the previously shared holders have returned the mutex. As long as an exclusive request is waiting, new shared ones are queued to be granted after the exclusive access. For more information about shared mutex feature, please see https://open-std.org/JTC1/SC22/WG21/docs/papers/2013/n3659.html C++ Builder is the easiest and fastest C and C++ IDE for building simple or professional applications on the Windows, MacOS, iOS & Android operating systems. It is also easy for beginners to learn with its wide range of samples, tutorials, help files, and LSP support for code. RAD Studio’s C++ Builder version comes with the award-winning VCL framework for high-performance native Windows apps and the powerful FireMonkey (FMX) framework for cross-platform UIs. There is a free C++ Builder Community Edition for students, beginners, and startups; it can be downloaded from here. For professional developers, there are Professional, Architect, […]

Sometimes we want to preserve the string format especially when we use string in a string with /”. In C++14 and above, there is a std::quoted template that allows handling strings safely where they may contain spaces and special characters and it keeps their formatting intact. In this post, we explain std::quoted quoted strings in modern C++. What Is Quoted String In Modern C++? The std::quoted template is included in  header, and it is used to handle strings (i.e. “Let’s learn from ”LearnCPlusPlus.org!” “) safely where they may contain spaces and special characters and it keeps their formatting intact.  Here is the syntax,   std::quoted( )   Here are C++14 templates defined in where the string is used as input,   template quoted( const CharT* s, CharT delim = CharT(‘”‘), CharT escape = CharT(‘\’) );   or   template quoted(   const std::basic_string& s,   CharT delim = CharT(‘”‘), CharT escape = CharT(‘\’) );   Here is a C++14 template defined in where the string is used as output,   template quoted( std::basic_string& s, CharT delim=CharT(‘”‘), CharT escape=CharT(‘\’) );   Note that this feature is is using std::basic_string and it improved in C++17 by the  std::basic_string_view support. What Is std::quoted quoted string in modern C++? Here is an example that uses input string and outputs into a stringstream:   const std::string str  = “I say “LearnCPlusPlus!””; std::stringstream sstr; sstr std::quoted(str_out);  // output sstr to str_out   Is there a full example about std::quoted quoted string in modern C++? Here is a full example about std::quoted in modern C++. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31   #include #include #include   int main() { std::stringstream sstr; const std::string str  = “Let’s learn from “LearnCPlusPlus.org!” “; sstr

The auto keyword arrives with the new features of the C++11 and the standards above. In C++14, there is a new decltype that is used with auto keyword. In modern C++, the decltype(auto) type-specifier deduces return types while keeping their references and cv-qualifiers, while auto does not. In this post, we explain what decltype (auto) is in modern C++ and how to use it. What is auto in modern C++? The auto keyword is used to define variable types automatically, it is a placeholder type specifier (an auto-typed variable), or it can be used in a function declaration, or a structured binding declaration. If you want to learn more about auto keyword, here it is, What is decltype in modern C++? The decltype keyword and operator represents the type of a given entity or expression. This feature is one of the C++11 features added to compilers (including BCC32 and other CLANG compilers). In a way you are saying “I am declaring this variable to be the same type as this other variable“. Here are more details about how you can use it, How to use decltype (auto) in modern C++? In C++14, there is a new decltype feature that allows you to use with the auto keyword. In C++14 and standards above, the decltype(auto) type-specifier deduces return types while keeping their references and cv-qualifiers, while auto does not. Since C++14, here is the syntax,   type_constraint (optional) decltype ( auto )   In this syntax, the type is decltype(expr) and expr can be an initializer or a return statement. Here is a simple example how we can use it,   decltype(auto) x = i;   Are there some simple examples about decltype (auto) in modern C++? Here are some simple examples that shows difference between auto and decltype(auto), In C++14 and above, we can use decltype(auto) with const int values as below,   const int x = 4096; auto xa = x;    // xa : int decltype(auto) xb = x;  // xb : const int   In C++14 and above, we can use decltype(auto) with int& values as below,   int y = 2048; int& y0 = y;  // y_ : int auto ya = y0;  // yc2 : int decltype(auto) yb = y0;  // yb : int&   In C++14 and above, we can use decltype(auto) with int values as below,   int&& z = 1024; auto zm = std::move(z);   // zm : int decltype(auto) zm2 = std::move(z);  // zm2 : int&&   In C++11 and above, we can use auto for return types,   auto myf(const int& i) { return i; // auto return type : int }   In C++14 and above, we can use decltype(auto) for return types,   decltype(auto) myf2(const int& i) {    return i; // decltype(auto) return type : const int& }   Is there a full example about decltype (auto) in modern C++? Here is a full example that shows how you can use auto and decltype(auto) in different int types. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54   #include   auto myf(const int& i) { return i; // auto […]

The C++14 standard (and later), brings a lot of useful smart pointers and improvements on them. They help us to avoid the mistake of incorrectly freeing the memory addressed by pointers. In modern C++, we have the new and delete operators that are used to allocate and free objects from memory, and in this post, we explain how to use new and delete operators. Can we use new and delete elisions in modern C++ or is it obsolete? Allocating memory and freeing it safely is hard if you are programming a very big application. In Modern C++, there are smart pointers that help avoid the mistake of incorrectly freeing the memory addressed by pointers. Smart pointers make it easy to define pointers, they came with C++11. The most used types of C++ smart pointer are unique_ptr, auto_ptr, shared_ptr, and weak_ptr. Smart pointers are preferable to raw pointers in many different scenarios, but there is still a lot of need to use for the new and delete methods in C++14 and above. When we develop code that requires in-place construction, we need to use new and, possibly, delete operations. They are useful, in a memory pool, as an allocator, as a tagged variant, as a buffer, or as a binary message to a buffer. Sometimes we can use new and delete for some containers if we want to use raw pointers for storage. Modern C++ has a lot of modern choices for faster and safer memory operations. Generally, developers choose to use unique_ptr/make_unique and make_shared rather than raw calls to new and delete. Even though we have a lot of standard smart pointers and abilities, we still need new and/or delete operators. How can we use new and delete elisions in C++? What is the new operator in C++? The new operator in C++, denotes a request for memory allocation on the free memory. If there is sufficient memory, a new operator initializes the memory and returns the address of the newly allocated and initialized memory to the pointer variable.    = new ;   Here, the data_type could be any built-in data type, i.e. basic C / C++ types, array, or any class types i.e. class, structure, union.  Now, let’s see how we can use new operator. We can simply use auto and new to create a new pointer and space for its buffer as below,   auto *ptr = new long int;     or in old style still you can use its type in definition instead of auto as below,   long int *ptr = new long int;     one of the great feature of pointers is we don’t need to allocate them at the beginning, we can set them NULL, and we can allocate them in some steps as below,   long int *ptr = NULL; … ptr = new long int;     What is the delete operator in C++? The delete operator in C++ is used to free the dynamically allocated array pointed by pointer variable. Here is the syntax for the delete operator,   delete ;   we can use delete[] for the pointer_arrays, here is the syntax for them,   delete[] ;   here is how we can use delete to delete a pointer, and this is how we can delete pointer arrays,   int *arr […]