Friend Function
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Friend Function
In object-oriented programming, a friend function, that is a "friend" of a given class, is a function that is given the same access as methods to private and protected data. A friend function is declared by the class that is granting access, so friend functions are part of the class interface, like methods. Friend functions allow alternative syntax to use objects, for instance f(x) instead of x.f(), or g(x,y) instead of x.g(y). Friend functions have the same implications on encapsulation as methods. A similar concept is that of friend class. Use cases This approach may be used in friendly function when a function needs to access private data in objects from two different classes. This may be accomplished in two similar ways *a function of global or namespace scope may be declared as friend of both classes *a member function of one class may be declared as friend of another one. #include using namespace std; class Foo; // Forward declaration of class Foo in order for exam ...
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Object-oriented Programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of procedures (often known as ''methods''). A common feature of objects is that procedures (or methods) are attached to them and can access and modify the object's data fields. In this brand of OOP, there is usually a special name such as or used to refer to the current object. In OOP, computer programs are designed by making them out of objects that interact with one another. OOP languages are diverse, but the most popular ones are class-based, meaning that objects are instances of classes, which also determine their types. Many of the most widely used programming languages (such as C++, Java, Python, etc.) are multi-paradigm and they support object-oriented programming to a greater or lesser degree, typically in combination with imper ...
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Class (computer Science)
In object-oriented programming, a class is an extensible program-code-template for creating objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods). In many languages, the class name is used as the name for the class (the template itself), the name for the default constructor of the class (a subroutine that creates objects), and as the type of objects generated by instantiating the class; these distinct concepts are easily conflated. Although, to the point of conflation, one could argue that is a feature inherent in a language because of its polymorphic nature and why these languages are so powerful, dynamic and adaptable for use compared to languages without polymorphism present. Thus they can model dynamic systems (i.e. the real world, machine learning, AI) more easily. When an object is created by a constructor of the class, the resulting object is called an instance of the class, and the member variabl ...
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Data
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpreted. A datum is an individual value in a collection of data. Data is usually organized into structures such as tables that provide additional context and meaning, and which may themselves be used as data in larger structures. Data may be used as variables in a computational process. Data may represent abstract ideas or concrete measurements. Data is commonly used in scientific research, economics, and in virtually every other form of human organizational activity. Examples of data sets include price indices (such as consumer price index), unemployment rates, literacy rates, and census data. In this context, data represents the raw facts and figures which can be used in such a manner in order to capture the useful information out of it. ...
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Separation Of Concerns
In computer science, separation of concerns is a design principle for separating a computer program into distinct sections. Each section addresses a separate '' concern'', a set of information that affects the code of a computer program. A concern can be as general as "the details of the hardware for an application", or as specific as "the name of which class to instantiate". A program that embodies SoC well is called a modular program. Modularity, and hence separation of concerns, is achieved by encapsulating information inside a section of code that has a well-defined interface. Encapsulation is a means of information hiding. Layered designs in information systems are another embodiment of separation of concerns (e.g., presentation layer, business logic layer, data access layer, persistence layer). Separation of concerns results in more degrees of freedom for some aspect of the program's design, deployment, or usage. Common among these is increased freedom for simplification and ...
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Friend Class
A friend class in C++ can access the private and protected members of the class in which it is declared as a friend. A significant use of a friend class is for a part of a data structure, represented by a class, to provide access to the main class representing that data structure. The friend class mechanism allows to extend the storage and access to the parts, while retaining proper encapsulation as seen by the users of the data structure. Similar to a friend class, a friend function is a function that is given access to the private and protected members of the class in which it is declared as a friend. Example The following example demonstrates the use of a friend-class for a graph data structure, where the graph is represented by the main class Graph, and the graph's vertices are represented by the class Vertex. #include #include #include #include class Graph; class Vertex ; class Graph ; Encapsulation A proper use of friend classes increases encapsulation, becaus ...
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Namespace
In computing, a namespace is a set of signs (''names'') that are used to identify and refer to objects of various kinds. A namespace ensures that all of a given set of objects have unique names so that they can be easily identified. Namespaces are commonly structured as hierarchies to allow reuse of names in different contexts. As an analogy, consider a system of naming of people where each person has a given name, as well as a family name shared with their relatives. If the first names of family members are unique only within each family, then each person can be uniquely identified by the combination of first name and family name; there is only one Jane Doe, though there may be many Janes. Within the namespace of the Doe family, just "Jane" suffices to unambiguously designate this person, while within the "global" namespace of all people, the full name must be used. Prominent examples for namespaces include file systems, which assign names to files. Some programming languages ...
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The C++ Programming Language
''The C++ Programming Language'' is a computer programming book first published in October 1985. It was the first book to describe the C++ programming language, written by the language's creator, Bjarne Stroustrup. In the absence of an official standard, the book served for several years as the ''de facto'' documentation for the evolving C++ language, until the release of the ''ISO/IEC 14882:1998: Programming Language C++'' standard on 1 September 1998. As the standard further evolved with the standardization of language and library extensions and with the publication of technical corrigenda, later editions of the book were updated to incorporate the new changes. History The first edition of ''The C++ Programming Language'' was published in 1985. As C++ evolved, a second edition was published in July 1991, reflecting the changes made. The third edition of the book was first published on 30 June 1997; a hardcover version of the third edition, with two new appendices, was later pub ...
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Bjarne Stroustrup
Bjarne Stroustrup (; ; born 30 December 1950) is a Danish computer scientist, most notable for the invention and development of the C++ programming language. As of July 2022, Stroustrup is a professor of Computer Science at Columbia University. Early life and education Stroustrup was born in Aarhus, Denmark. His family was working class, and he went to the local schools. He attended Aarhus University 1969–1975 and graduated with a master's degree in mathematics and computer science. His interests focused on microprogramming and machine architecture. He learned the fundamentals of object-oriented programming from its inventor, Kristen Nygaard, who frequently visited Aarhus. In 1979, he received a PhD in computer science from the University of Cambridge, where he was supervised by David Wheeler. His thesis concerned communication in distributed computer systems. Career In 1979, Stroustrup began his career as a member of technical staff in the Computer Science Research Ce ...
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Method (computer Programming)
A method in object-oriented programming (OOP) is a procedure associated with a message and an object. An object consists of ''state data'' and ''behavior''; these compose an ''interface'', which specifies how the object may be utilized by any of its various consumers. A method is a behavior of an object parametrized by a consumer. Data is represented as properties of the object, and behaviors are represented as methods. For example, a Window object could have methods such as open and close, while its state (whether it is open or closed at any given point in time) would be a property. In class-based programming, methods are defined within a class, and objects are instances of a given class. One of the most important capabilities that a method provides is ''method overriding'' - the same name (e.g., area) can be used for multiple different kinds of classes. This allows the sending objects to invoke behaviors and to delegate the implementation of those behaviors to the receiving o ...
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