Use of void pointers (void*) and templates
In C, the use of void pointers can be extremely useful. It can be used as a universally generic pointer that can point to any type. The limitation to this is that you must know the type that the void pointer was casted from in order to obtain data from it (which usually isn't that bad). Here's example using a simple list struct.
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void - type with an empty set of values. It is an incomplete type that cannot be completed (consequently, objects of type void are disallowed). There are no arrays of void, nor references to void. However, pointers to void and functions returning type void (procedures in other languages) are permitted.
A C++ programmer frequently come across pointer variables, pointer arguments to function and pointer template arguments. Let us take different cases to see how C++98 handles the situation where a pointer is set to nothing. When we write void *p = 0; or void *p = NULL; What do we do? We think that we are initializing the pointer to null pointer but actually we are initializing it with 0 or 0L depending upon the definition of NULL.
C++ generics provide a powerful way to create an extensible design with the help of templates. The primary motivation of any generic model of programming is that it enables the programmer to develop components that provide easy and seamless transition from the design to the application code. It also better expresses design intention and highly supports the reuse of design structure with minimal recoding. A sense of the generic pattern also can be achieved through other means, such as polymorphism and virtual classes, void objects, and so forth, which simulate a flavor of generics by providing multiple service with a single interface, but they are quite different from templates.
We are going to discuss pointers in this tutorial. Pointers are considered one of the trickiest concepts in the C++ programming. But don’t worry; we are going to explain it in a very lucid manner. I can assure that after completing this tutorial, you will be teaching pointers to your fellows around.
Smart pointers are objects that look and feel like pointers, but are smarter. What does this mean? To look and feel like pointers, smart pointers need to have the same interface that pointers do: they need to support pointer operations like dereferencing (operator *) and indirection (operator ->). An object that looks and feels like something else is called a proxy object, or just proxy. The proxy pattern and its many uses are described in the books Design Patterns and Pattern Oriented Software Architecture.
Pointers represent an important aspect of C++. Although, newbies often get confused with pointers, even those who know other programming languages.
Pointers and references look different enough (pointers use the *Â and ->Â operators, references use .), but they seem to do similar things. Both pointers and references let you refer to other objects indirectly. How, then, do you decide when to use one and not the other?
This article is intended to all programming enthusiasts on all levels who do wish to understand pointers in C++ language. All code presented here is not a compiler specific and all examples will be written in plain ANSI C++. Debate about pointers can stretch for miles, and you would need to go really far to master it all. If you really want to run that far, this article gives you a clear understanding of fundamental concepts about pointers and prepares you for that journey. However, those who are new to C++ programming make sure that you are able to write and run your own C++ “hello world” program, and also it is recommended that you have a basic understanding of C++ functions and classes.
Pointers to Member Functions are one of C++'s more rarely used features, and are often not well understood even by experienced developers. This is understandable, as their syntax is necessarily rather clumsy and obscure.
While they do not have wide applicability, sometimes member function pointers are useful to solve certain problems, and when they do apply they are often the perfect choice, both for improved performance and to make the code sensible.
Today's lesson goes more into details about pointers and their usage as function's arguments. Additional tutorial about stacks in C and C++ is provided. Be sure to read this lesson carefully in order to understand it, since pointers are most important part of C programming language.