In programming languages, type erasure is the load-time process by which explicit type annotations are removed from a program, before it is executed at run-time. Operational semantics not requiring programs to be accompanied by types are named type-erasure semantics, in contrast with type-passing semantics. Type-erasure semantics is an abstraction principle, ensuring that the run-time execution of a program doesn't depend on type information. In the context of generic programming, the opposite of type erasure is named reification. [1]
The reverse operation is named type inference. Though type erasure can be an easy way to define typing over implicitly typed languages (an implicitly typed term is well-typed if and only if it is the erasure of a well-typed explicitly typed lambda term), it doesn't provide Rule of inference for this definition.
A programming language is a system of notation for writing computer programs.
Java and C++ are two prominent object-oriented programming languages. By many language popularity metrics, the two languages have dominated object-oriented and high-performance software development for much of the 21st century, and are often directly compared and contrasted. Java's syntax was based on C/C++.
Generic programming is a style of computer programming in which algorithms are written in terms of data types to-be-specified-later that are then instantiated when needed for specific types provided as parameters. This approach, pioneered by the ML programming language in 1973, permits writing common functions or types that differ only in the set of types on which they operate when used, thus reducing duplicate code.
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. Usually the terms are various language 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.
In programming language theory, subtyping is a form of type polymorphism. A subtype is a datatype that is related to another datatype by some notion of substitutability, meaning that program elements, written to operate on elements of the supertype, can also operate on elements of the subtype.
Reification is the process by which an abstract idea about a computer program is turned into an explicit data model or other object created in a programming language. A computable/addressable object—a resource—is created in a system as a proxy for a non computable/addressable object. By means of reification, something that was previously implicit, unexpressed, and possibly inexpressible is explicitly formulated and made available to conceptual manipulation. Informally, reification is often referred to as "making something a first-class citizen" within the scope of a particular system. Some aspect of a system can be reified at language design time, which is related to reflection in programming languages. It can be applied as a stepwise refinement at system design time. Reification is one of the most frequently used techniques of conceptual analysis and knowledge representation.
In programming language theory and type theory, polymorphism is the use of a single symbol to represent multiple different types.
Type inference refers to the automatic detection of the type of an expression in a formal language. These include programming languages and mathematical type systems, but also natural languages in some branches of computer science and linguistics.
In computer programming, a parameter or a formal argument is a special kind of variable used in a subroutine to refer to one of the pieces of data provided as input to the subroutine. These pieces of data are the values of the arguments with which the subroutine is going to be called/invoked. An ordered list of parameters is usually included in the definition of a subroutine, so that, each time the subroutine is called, its arguments for that call are evaluated, and the resulting values can be assigned to the corresponding parameters.
In programming languages, ad hoc polymorphism is a kind of polymorphism in which polymorphic functions can be applied to arguments of different types, because a polymorphic function can denote a number of distinct and potentially heterogeneous implementations depending on the type of argument(s) to which it is applied. When applied to object-oriented or procedural concepts, it is also known as function overloading or operator overloading. The term ad hoc in this context is not intended to be pejorative; it refers simply to the fact that this type of polymorphism is not a fundamental feature of the type system. This is in contrast to parametric polymorphism, in which polymorphic functions are written without mention of any specific type, and can thus apply a single abstract implementation to any number of types in a transparent way. This classification was introduced by Christopher Strachey in 1967.
In computer science, type safety and type soundness are the extent to which a programming language discourages or prevents type errors. Type safety is sometimes alternatively considered to be a property of facilities of a computer language; that is, some facilities are type-safe and their usage will not result in type errors, while other facilities in the same language may be type-unsafe and a program using them may encounter type errors. The behaviors classified as type errors by a given programming language are usually those that result from attempts to perform operations on values that are not of the appropriate data type, e.g., adding a string to an integer when there's no definition on how to handle this case. This classification is partly based on opinion.
This article compares two programming languages: C# with Java. While the focus of this article is mainly the languages and their features, such a comparison will necessarily also consider some features of platforms and libraries. For a more detailed comparison of the platforms, see Comparison of the Java and .NET platforms.
In programming languages and type theory, parametric polymorphism allows a single piece of code to be given a "generic" type, using variables in place of actual types, and then instantiated with particular types as needed. Parametrically polymorphic functions and data types are sometimes called generic functions and generic datatypes, respectively, and they form the basis of generic programming.
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
.
Haxe is a high-level cross-platform programming language and compiler that can produce applications and source code for many different computing platforms from one code-base. It is free and open-source software, released under the MIT License. The compiler, written in OCaml, is released under the GNU General Public License (GPL) version 2.
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.
In generic programming, a concept is a description of supported operations on a type, including syntax and semantics. In this way, concepts are related to abstract types but concepts do not require a subtype relationship.
In computer science, manifest typing is explicit identification by the software programmer of the type of each variable being declared. For example: if variable X is going to store integers then its type must be declared as integer. The term "manifest typing" is often used with the term latent typing to describe the difference between the static, compile-time type membership of the object and its run-time type identity.
Go is a statically typed, compiled high-level programming language designed at Google by Robert Griesemer, Rob Pike, and Ken Thompson. It is syntactically similar to C, but also has memory safety, garbage collection, structural typing, and CSP-style concurrency. It is often referred to as Golang because of its former domain name, golang.org
, but its proper name is Go.
In computer programming, one of the many ways that programming languages are colloquially classified is whether the language's type system makes it strongly typed or weakly typed. However, there is no precise technical definition of what the terms mean and different authors disagree about the implied meaning of the terms and the relative rankings of the "strength" of the type systems of mainstream programming languages. For this reason, writers who wish to write unambiguously about type systems often eschew the terms "strong typing" and "weak typing" in favor of specific expressions such as "type safety".