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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 ...
Modern object-oriented languages, such as C++ and Java, support a form of abstract data types. When a class is used as a type, it is an abstract type that refers to a hidden representation. In this model, an ADT is typically implemented as a class, and each instance of the ADT is usually an object of that class.
The bridge pattern is a design pattern used in software engineering that is meant to "decouple an abstraction from its implementation so that the two can vary independently", introduced by the Gang of Four. [1]
In languages supporting multiple inheritance, such as C++, interfaces are implemented as abstract classes. In languages without explicit support, protocols are often still present as conventions. This is known as duck typing. For example, in Python, any class can implement an __iter__ method and be used as a collection. [3]
The abstract list type L with elements of some type E (a monomorphic list) is defined by the following functions: nil: → L cons: E × L → L first: L → E rest: L → L. with the axioms first (cons (e, l)) = e rest (cons (e, l)) = l. for any element e and any list l. It is implicit that cons (e, l) ≠ l cons (e, l) ≠ e
Instead the class browser allows to edit the class together with its metaclass at the same time. The names of classes in the metaclass hierarchy are easily confused with the concepts of the same name. For instance: Object is the base class that provides common methods for all objects; "an object" is an integer, or a widget, or a Car, etc.
For example, class UnicodeConversionMixin might provide a method unicode_to_ascii() when included in class FileReader and class WebPageScraper, which do not share a common parent. Abstract classes cannot be instantiated into objects; they exist only for inheritance into other "concrete" classes that can be instantiated.
The factory method design pattern solves problems such as: How can an object's subclasses redefine its subsequent and distinct implementation? The pattern involves creation of a factory method within the superclass that defers the object's creation to a subclass's factory method.