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Metaobject
In computer science, a metaobject is an object that manipulates, creates, describes, or implements objects (including itself). The object that the metaobject pertains to is called the base object. Some information that a metaobject might define includes the base object's type, interface, class, methods, attributes, parse tree, etc. Metaobjects are examples of the computer science concept of reflection, where a system has access (usually at run time) to its own internal structure. Reflection enables a system to essentially rewrite itself on the fly, to alter its own implementation as it executes. Metaobject protocol A metaobject protocol (MOP) provides the vocabulary (protocol) to access and manipulate the structure and behaviour of systems of objects. Typical functions of a metaobject protocol include: *Create or delete a new class *Create a new property or method *Cause a class to inherit from a different class ("change the class structure") *Generate or change the code defining ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Art Of The Metaobject Protocol
''The Art of the Metaobject Protocol'' (AMOP) is a 1991 book by Gregor Kiczales, Jim des Rivieres, and Daniel G. Bobrow (all three working for Xerox PARC) on the subject of metaobject protocol. Overview The book contains an explanation of what a metaobject protocol is, why it is desirable, and the ''de facto'' standard for the metaobject protocol supported by many Common Lisp implementations as an extension of the Common Lisp Object System, or CLOS. A more complete and portable implementation of CLOS and the metaobject protocol, as defined in this book, was provided by Xerox PARC as Portable Common Loops. The book presents a simplified CLOS implementation for Common Lisp called "Closette", which for the sake of pedagogical brevity does not include some of the more complex or exotic CLOS features such as forward-referencing of superclasses, full class and method redefinitions, advanced user-defined method combinations, and complete integration of CLOS classes with Common Lisp's typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aspect-oriented Programming
In computing, aspect-oriented programming (AOP) is a programming paradigm that aims to increase modularity by allowing the separation of cross-cutting concerns. It does so by adding behavior to existing code (an advice) ''without'' modifying the code itself, instead separately specifying which code is modified via a "pointcut" specification, such as "log all function calls when the function's name begins with 'set. This allows behaviors that are not central to the business logic (such as logging) to be added to a program without cluttering the code core to the functionality. AOP includes programming methods and tools that support the modularization of concerns at the level of the source code, while aspect-oriented software development refers to a whole engineering discipline. Aspect-oriented programming entails breaking down program logic into distinct parts (so-called ''concerns'', cohesive areas of functionality). Nearly all programming paradigms support some level of groupi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Object (computer Science)
In computer science, an object can be a variable, a data structure, a function, or a method. As regions of memory, they contain value and are referenced by identifiers. In the object-oriented programming paradigm, ''object'' can be a combination of variables, functions, and data structures; in particular in class-based variations of the paradigm it refers to a particular instance of a class. In the relational model of database management, an object can be a table or column, or an association between data and a database entity (such as relating a person's age to a specific person). Object-based languages An important distinction in programming languages is the difference between an object-oriented language and an object-based language. A language is usually considered object-based if it includes the basic capabilities for an object: identity, properties, and attributes. A language is considered object-oriented if it is object-based and also has the capability of polymorphism, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gregor Kiczales
Gregor Kiczales is an American computer scientist. He is currently a full time professor of computer science at the University of British Columbia in Vancouver, British Columbia, Canada. He is best known for developing the concept of aspect-oriented programming, and the AspectJ extension to the Java programming language, both of which he designed while working at Xerox PARC. He is also one of the co-authors of the specification for the Common Lisp Object System, and is the author of the book ''The Art of the Metaobject Protocol'', along with Jim Des Rivières and Daniel G. Bobrow. Most of Kiczales' work throughout the years has been focused on allowing software engineers to create programs that look as much as possible like their design, to reduce complexity and make code maintenance easier, ultimately improving software quality. Career After pursuing undergraduate studies at MIT, Kiczales started his research career in 1980 at the MIT Lab for Computer Science, where he stay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiple Inheritance
Multiple inheritance is a feature of some object-oriented computer programming languages in which an object or class can inherit features from more than one parent object or parent class. It is distinct from single inheritance, where an object or class may only inherit from one particular object or class. Multiple inheritance has been a controversial issue for many years, with opponents pointing to its increased complexity and ambiguity in situations such as the "diamond problem", where it may be ambiguous as to which parent class a particular feature is inherited from if more than one parent class implements said feature. This can be addressed in various ways, including using virtual inheritance. Alternate methods of object composition not based on inheritance such as mixins and traits have also been proposed to address the ambiguity. Details In object-oriented programming (OOP), ''inheritance'' describes a relationship between two classes in which one class (the ''child'' class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Lisp Object System
The Common Lisp Object System (CLOS) is the facility for object-oriented programming which is part of ANSI Common Lisp. CLOS is a powerful dynamic object system which differs radically from the OOP facilities found in more static languages such as C++ or Java. CLOS was inspired by earlier Lisp object systems such as MIT Flavors and CommonLoops, although it is more general than either. Originally proposed as an add-on, CLOS was adopted as part of the ANSI standard for Common Lisp and has been adapted into other Lisp dialects such as EuLisp or Emacs Lisp. Features The basic building blocks of CLOS are methods, classes, instances of those classes, and generic functions. CLOS provides macros to define those: defclass, defmethod, and defgeneric. Instances are created with the method make-instance. Classes can have multiple superclasses, a list of slots (member variables in C++/Java parlance) and a special metaclass. Slots can be allocated by class (all instances of a class share th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single Dispatch
In computer science, dynamic dispatch is the process of selecting which implementation of a polymorphic operation (method or function) to call at run time. It is commonly employed in, and considered a prime characteristic of, object-oriented programming (OOP) languages and systems. Object-oriented systems model a problem as a set of interacting objects that enact operations referred to by name. Polymorphism is the phenomenon wherein somewhat interchangeable objects each expose an operation of the same name but possibly differing in behavior. As an example, a object and a object both have a method that can be used to write a personnel record to storage. Their implementations differ. A program holds a reference to an object which may be either a object or a object. Which it is may have been determined by a run-time setting, and at this stage, the program may not know or care which. When the program calls on the object, something needs to choose which behavior gets enacted. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Message Passing
In computer science, message passing is a technique for invoking behavior (i.e., running a program) on a computer. The invoking program sends a message to a process (which may be an actor or object) and relies on that process and its supporting infrastructure to then select and run some appropriate code. Message passing differs from conventional programming where a process, subroutine, or function is directly invoked by name. Message passing is key to some models of concurrency and object-oriented programming. Message passing is ubiquitous in modern computer software. It is used as a way for the objects that make up a program to work with each other and as a means for objects and systems running on different computers (e.g., the Internet) to interact. Message passing may be implemented by various mechanisms, including channels. Overview Message passing is a technique for invoking behavior (i.e., running a program) on a computer. In contrast to the traditional technique of callin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Generic Functions
In computer programming, a generic function is a function defined for Polymorphism (computer science), polymorphism. In statically typed languages In statically typed languages (such as C++ and Java (programming language), Java), the term ''generic functions'' refers to a mechanism for ''compile-time polymorphism'' (static dispatch), specifically parametric polymorphism. These are functions defined with TypeParameters, intended to be resolved with compile time type information. The compiler uses these types to instantiate suitable versions, resolving any function overloading appropriately. In Common Lisp Object System In some systems for object-oriented programming such as the Common Lisp Object System (CLOS) and Dylan (programming language), Dylan, a ''generic function'' is an entity made up of all methods having the same name. Typically a ''generic function'' is an instance of a class that Inheritance (object-oriented programming), inherits both from ''function'' and ''stand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiple Dispatch
Multiple dispatch or multimethods is a feature of some programming languages in which a function or method can be dynamically dispatched based on the run-time (dynamic) type or, in the more general case, some other attribute of more than one of its arguments. This is a generalization of single-dispatch polymorphism where a function or method call is dynamically dispatched based on the derived type of the object on which the method has been called. Multiple dispatch routes the dynamic dispatch to the implementing function or method using the combined characteristics of one or more arguments. Understanding dispatch Developers of computer software typically organize source code into named blocks variously called subroutines, procedures, subprograms, functions, or methods. The code in the function is executed by ''calling'' it – executing a piece of code that references its ''name''. This transfers control temporarily to the called function; when the function's execution has co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
