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Downcasting
In class-based programming, downcasting or type refinement is the act of casting a reference of a base class to one of its derived classes. In many programming languages, it is possible to check through type introspection to determine whether the type of the referenced object is indeed the one being cast to or a derived type of it, and thus issue an error if it is not the case. In other words, when a variable of the base class (parent class) has a value of the derived class ( child class), downcasting is possible. Some languages, such as OCaml, disallow downcasting. Examples Java public class Fruit // parent class public class Apple extends Fruit // child class public static void main(String args[]) C++ // Parent class: class Fruit ; // Child class: class Apple : public Fruit ; int main(int argc, const char** argv) Uses Downcasting is useful when the type of the value referenced by the Parent variable is known and often is used when passing a value as a parame ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Top Type
In mathematical logic and computer science, some type theories and type systems include a top type that is commonly denoted with top or the symbol ⊤. The top type is sometimes called also ''universal type'', or ''universal supertype'' as all other types in the type system of interest are subtypes of it, and in most cases, it contains every possible object of the type system. It is in contrast with the bottom type, or the ''universal subtype'', which every other type is supertype of and it is often that the type contains no members at all. Support in programming languages Several typed programming languages provide explicit support for the top type. In statically-typed languages, there are two different, often confused, concepts when discussing the top type. # A ''universal base class'' or other item at the top of a run time ''class hierarchy'' (often relevant in object-oriented programming) or ''type hierarchy''; it is often possible to create objects with this (run time) type, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Conversion
In computer science, type conversion, type casting, type coercion, and type juggling are different ways of changing an expression from one data type to another. An example would be the conversion of an integer value into a floating point value or its textual representation as a string, and vice versa. Type conversions can take advantage of certain features of type hierarchies or data representations. Two important aspects of a type conversion are whether it happens ''implicitly'' (automatically) or ''explicitly'', and whether the underlying data representation is converted from one representation into another, or a given representation is merely ''reinterpreted'' as the representation of another data type. In general, both primitive and compound data types can be converted. Each programming language has its own rules on how types can be converted. Languages with strong typing typically do little implicit conversion and discourage the reinterpretation of representations, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dynamic Cast
In computer programming, run-time type information or run-time type identification (RTTI) is a feature of some programming languages (such as C++, Object Pascal, and Ada) that exposes information about an object's data type at runtime. Run-time type information may be available for all types or only to types that explicitly have it (as is the case with Ada). Run-time type information is a specialization of a more general concept called type introspection. In the original C++ design, Bjarne Stroustrup did not include run-time type information, because he thought this mechanism was often misused. Overview In C++, RTTI can be used to do safe typecasts, using the dynamic_cast operator, and to manipulate type information at runtime, using the typeid operator and std::type_info class. In Object Pascal, RTTI can be used to perform safe type casts with the as operator, test the class to which an object belongs with the is operator, and manipulate type information at run time with classes c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Static Cast
In the C++ programming language, static_cast is an operator that performs an explicit type conversion. Syntax static_cast (object); The ''type'' parameter must be a data type to which ''object'' can be converted via a known method, whether it be a builtin or a cast. The type can be a reference or an enumerator. All types of conversions that are well-defined and allowed by the compiler are performed using static_cast. The static_cast operator can be used for operations such as: * converting a pointer of a base class to a pointer of a non-virtual derived class (downcasting); * converting numeric data types such as enums to ints or floats. Although static_cast conversions are checked at compile time to prevent obvious incompatibilities, no run-time type checking is performed that would prevent a cast between incompatible data types, such as pointers. A static_cast from a pointer to a class B to a pointer to a derived class D is ill-formed if B is an inaccessible or ambiguous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Class-based Programming
Class-based programming, or more commonly class-orientation, is a style of object-oriented programming (OOP) in which inheritance occurs via defining ''classes'' of objects, instead of inheritance occurring via the objects alone (compare prototype-based programming). The most popular and developed model of OOP is a class-based model, instead of an object-based model. In this model, objects are entities that combine ''state'' (i.e., data), '' behavior'' (i.e., procedures, or ''methods'') and ''identity'' (unique existence among all other objects). The structure and behavior of an object are defined by a class, which is a definition, or blueprint, of all objects of a specific type. An object must be explicitly created based on a class and an object thus created is considered to be an instance of that class. An object is similar to a structure, with the addition of method pointers, member access control, and an implicit data member which locates instances of the class (i.e., obje ... [...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] |
Type Introspection
In computing, type introspection is the ability of a program to ''examine'' the Data type, type or properties of an Object (computer science), object at Run time (program lifecycle phase), runtime. Some programming languages possess this capability. Introspection should not be confused with reflection (computer programming), reflection, which goes a step further and is the ability for a program to ''manipulate'' the values, metadata, properties, and functions of an object at runtime. Some programming languages also possess that capability (e.g., Java (programming language), Java, Python (programming language), Python, Julia (programming language), Julia, and Go (programming_language), Go). Examples Ruby Type introspection is a core feature of Ruby (programming language), Ruby. In Ruby, the Object class (ancestor of every class) provides and methods for checking the instance's class. The latter returns true when the particular instance the message was sent to is an instance of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parent Class
In object-oriented programming, inheritance is the mechanism of basing an object or class upon another object ( prototype-based inheritance) or class ( class-based inheritance), retaining similar implementation. Also defined as deriving new classes ( sub classes) from existing ones such as super class or base class and then forming them into a hierarchy of classes. In most class-based object-oriented languages, an object created through inheritance, a "child object", acquires all the properties and behaviors of the "parent object" , with the exception of: constructors, destructor, overloaded operators and friend functions of the base class. Inheritance allows programmers to create classes that are built upon existing classes, to specify a new implementation while maintaining the same behaviors ( realizing an interface), to reuse code and to independently extend original software via public classes and interfaces. The relationships of objects or classes through inheritance give ris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subclass (computer Science)
In object-oriented programming, inheritance is the mechanism of basing an object or class upon another object ( prototype-based inheritance) or class ( class-based inheritance), retaining similar implementation. Also defined as deriving new classes ( sub classes) from existing ones such as super class or base class and then forming them into a hierarchy of classes. In most class-based object-oriented languages, an object created through inheritance, a "child object", acquires all the properties and behaviors of the "parent object" , with the exception of: constructors, destructor, overloaded operators and friend functions of the base class. Inheritance allows programmers to create classes that are built upon existing classes, to specify a new implementation while maintaining the same behaviors ( realizing an interface), to reuse code and to independently extend original software via public classes and interfaces. The relationships of objects or classes through inheritance give ris ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OCaml
OCaml ( , formerly Objective Caml) is a general-purpose programming language, general-purpose, multi-paradigm programming language which extends the Caml dialect of ML (programming language), ML with object-oriented programming, object-oriented features. OCaml was created in 1996 by Xavier Leroy, Jérôme Vouillon, Damien Doligez, Didier Rémy, Ascánder Suárez, and others. The OCaml toolchain includes an interactive top-level Interpreter (computing), interpreter, a bytecode compiler, an optimizing native code compiler, a reversible debugger, and a package manager (OPAM). OCaml was initially developed in the context of automated theorem proving, and has an outsize presence in static program analysis, static analysis and formal methods software. Beyond these areas, it has found serious use in systems programming, web development, and financial engineering, among other application domains. The acronym ''CAML'' originally stood for ''Categorical Abstract Machine Language'', but O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java (programming Language)
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers ''write once, run anywhere'' ( WORA), meaning that compiled Java code can run on all platforms that support Java without the need to recompile. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of the underlying computer architecture. The syntax of Java is similar to C and C++, but has fewer low-level facilities than either of them. The Java runtime provides dynamic capabilities (such as reflection and runtime code modification) that are typically not available in traditional compiled languages. , Java was one of the most popular programming languages in use according to GitHub, particularly for client–server web applications, with a reported 9 million developers. Java was originally developed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Java Generics
Generics are a facility of generic programming that were added to the Java programming language in 2004 within version J2SE 5.0. They were designed to extend Java's type system to allow "a type or method to operate on objects of various types while providing compile-time type safety". The aspect '' compile-time type safety'' was not fully achieved, since it was shown in 2016 that it is not guaranteed in all cases. The Java collections framework supports generics to specify the type of objects stored in a collection instance. In 1998, Gilad Bracha, Martin Odersky, David Stoutamire and Philip Wadler created Generic Java, an extension to the Java language to support generic types. Generic Java was incorporated in Java with the addition of wildcards. Hierarchy and classification According to ''Java Language Specification'': *A type variable is an unqualified identifier. Type variables are introduced by generic class declarations, generic interface declarations, generic method declar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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