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Abstract Type
In programming languages, an abstract type is a type in a nominative type system that cannot be instantiated directly; a type that is not abstract – which ''can'' be instantiated – is called a ''concrete type''. Every instance of an abstract type is an instance of some concrete subtype. Abstract types are also known as ''existential types''. An abstract type may provide no implementation, or an incomplete implementation. In some languages, abstract types with no implementation (rather than an incomplete implementation) are known as ''protocols'', ''interfaces'', ''signatures'', or ''class types''. In class-based object-oriented programming, abstract types are implemented as ''abstract classes'' (also known as ''abstract base classes''), and concrete types as ''concrete classes''. In generic programming, the analogous notion is a concept, which similarly specifies syntax and semantics, but does not require a subtype relationship: two unrelated types may satisfy the same conce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programming Languages
A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming language is usually split into the two components of syntax (form) and semantics (meaning), which are usually defined by a formal language. Some languages are defined by a specification document (for example, the C programming language is specified by an ISO Standard) while other languages (such as Perl) have a dominant implementation that is treated as a reference. Some languages have both, with the basic language defined by a standard and extensions taken from the dominant implementation being common. Programming language theory is the subfield of computer science that studies the design, implementation, analysis, characterization, and classification of programming languages. Definitions There are many considerations when defining w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abstract Method
A method in object-oriented programming (OOP) is a Procedure (computer science), procedure associated with a Message passing, message and an Object (computer science), object. An object consists of ''state data'' and ''behavior''; these compose an Interface (computing), ''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 Property (programming), 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 (computer science), class, and objects are Instance (computer science), 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Class
In computer science, a type class is a type system construct that supports ad hoc polymorphism. This is achieved by adding constraints to type variables in parametrically polymorphic types. Such a constraint typically involves a type class T and a type variable a, and means that a can only be instantiated to a type whose members support the overloaded operations associated with T. Type classes were first implemented in the Haskell programming language after first being proposed by Philip Wadler and Stephen Blott as an extension to "eqtypes" in Standard ML, and were originally conceived as a way of implementing overloaded arithmetic and equality operators in a principled fashion. In contrast with the "eqtypes" of Standard ML, overloading the equality operator through the use of type classes in Haskell does not require extensive modification of the compiler frontend or the underlying type system. Overview Type classes are defined by specifying a set of function or constant name ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Class (computer Programming)
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 variable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Template Method Pattern
In object-oriented programming, the template method is one of the behavioral design patterns identified by Gamma et al. in the book ''Design Patterns''. The template method is a method in a superclass, usually an abstract superclass, and defines the skeleton of an operation in terms of a number of high-level steps. These steps are themselves implemented by additional ''helper methods'' in the same class as the ''template method''. The ''helper methods'' may be either ''abstract methods'', in which case subclasses are required to provide concrete implementations, or '' hook methods,'' which have empty bodies in the superclass. Subclasses can (but are not required to) customize the operation by overriding the hook methods. The intent of the template method is to define the overall structure of the operation, while allowing subclasses to refine, or redefine, certain steps. Overview This pattern has two main parts: * The "template method" is implemented as a method in a base c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leaf Class (programming Language)
In class-based object-oriented programming languages, a leaf class is a class that should not be subclassed. This can be enforced either by convention, or by using a language feature such as the final keyword in C++, Dart, Java or PHP PHP is a general-purpose scripting language geared toward web development. It was originally created by Danish-Canadian programmer Rasmus Lerdorf in 1993 and released in 1995. The PHP reference implementation is now produced by The PHP Group ..., or the sealed keyword in C# or Scala. In Java, the Leaf node is an abstract class for all scene graph nodes that have no children. Leaf nodes specify lights, geometry, and sounds. They specify special linking and instancing capabilities for sharing scene graphs and provide a view platform for positioning and orienting a view in the virtual world. References Class (computer programming) {{Compu-lang-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trait (computer Programming)
In computer programming, a trait is a concept used in object-oriented programming which represents a set of methods that can be used to extend the functionality of a class. Rationale In object-oriented programming, behavior is sometimes shared between classes which are not related to each other. For example, many unrelated classes may have methods to serialize objects to JSON. Historically, there have been several approaches to solve this without duplicating the code in every class needing the behavior. Other approaches include multiple inheritance and mixins, but these have drawbacks: the behavior of the code may unexpectedly change if the order in which the mixins are applied is altered, or if new methods are added to the parent classes or mixins. Traits solve these problems by allowing classes to use the trait and get the desired behavior. If a class uses more than one trait, the order in which the traits are used does not matter. The methods provided by the traits have dire ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duck Typing
Duck typing in computer programming is an application of the duck test—"If it walks like a duck and it quacks like a duck, then it must be a duck"—to determine whether an object can be used for a particular purpose. With nominative typing, an object is ''of a given type'' if it is declared to be (or if a type's association with the object is inferred through mechanisms such as object inheritance). In duck typing, an object is ''of a given type'' if it has all methods and properties required by that type. Duck typing can be viewed as a usage-based structural equivalence between a given object and the requirements of a type. See structural typing for a further explanation of structural type equivalence. Example This is a simple example in Python 3 that demonstrates how any object may be used in any context, up until it is used in a way that it does not support. class Duck: def swim(self): print("Duck swimming") def fly(self): print("Duck flyi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Typing
In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every "term" (a word, phrase, or other set of symbols). Usually the terms are various constructs of a computer program, such as variables, expressions, functions, or modules. A type system dictates the operations that can be performed on a term. For variables, the type system determines the allowed values of that term. Type systems formalize and enforce the otherwise implicit categories the programmer uses for algebraic data types, data structures, or other components (e.g. "string", "array of float", "function returning boolean"). Type systems are often specified as part of programming languages and built into interpreters and compilers, although the type system of a language can be extended by optional tools that perform added checks using the language's original type syntax and grammar. The main purpose of a type system in a programming language ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Typing
In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every "term" (a word, phrase, or other set of symbols). Usually the terms are various constructs of a computer program, such as variables, expressions, functions, or modules. A type system dictates the operations that can be performed on a term. For variables, the type system determines the allowed values of that term. Type systems formalize and enforce the otherwise implicit categories the programmer uses for algebraic data types, data structures, or other components (e.g. "string", "array of float", "function returning boolean"). Type systems are often specified as part of programming languages and built into interpreters and compilers, although the type system of a language can be extended by optional tools that perform added checks using the language's original type syntax and grammar. The main purpose of a type system in a programming language ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Objective-C
Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. Originally developed by Brad Cox and Tom Love in the early 1980s, it was selected by NeXT for its NeXTSTEP operating system. Due to Apple macOS’s direct lineage from NeXTSTEP, Objective-C was the standard programming language used, supported, and promoted by Apple for developing macOS and iOS applications (via their respective APIs, Cocoa and Cocoa Touch) until the introduction of the Swift programming language in 2014. Objective-C programs developed for non-Apple operating systems or that are not dependent on Apple's APIs may also be compiled for any platform supported by GNU GCC or LLVM/Clang. Objective-C source code 'messaging/implementation' program files usually have filename extensions, while Objective-C 'header/interface' files have extensions, the same as C header files. Objective-C++ files are denoted with a file extension. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
This (computer Science)
this, self, and Me are keywords used in some computer programming languages to refer to the object, class, or other entity of which the currently running code is a part. The entity referred to by these keywords thus depends on the execution context (such as which object is having its method called). Different programming languages use these keywords in slightly different ways. In languages where a keyword like "this" is mandatory, the keyword is the only way to access data and methods stored in the current object. Where optional, they can disambiguate variables and functions with the same name. Object-oriented programming In many object-oriented programming languages, this (also called self or Me) is a variable that is used in instance methods to refer to the object on which they are working. The first OO language, SIMULA 67, used this to explicitly reference the local object. C++ and languages which derive in style from it (such as Java, C#, D, and PHP) also generally use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
