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Uniqueness Type
In computing, a unique type guarantees that an object is used in a single-threaded way, with at most a single reference to it. If a value has a unique type, a function applied to it can be optimized to update the value in-place in the object code. Such in-place updates improve the efficiency of functional languages while maintaining referential transparency. Unique types can also be used to integrate functional and imperative programming. Introduction Uniqueness typing is best explained using an example. Consider a function readLine that reads the next line of text from a given file: function readLine(File f) returns String return line where String line = doImperativeReadLineSystemCall(f) end end Now doImperativeReadLineSystemCall reads the next line from the file using an OS-level system call which has the side effect of changing the current position in the file. But this violates referential transparency because calling it multiple times with the same argu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and software. Computing has scientific, engineering, mathematical, technological, and social aspects. Major computing disciplines include computer engineering, computer science, cybersecurity, data science, information systems, information technology, and software engineering. The term ''computing'' is also synonymous with counting and calculation, calculating. In earlier times, it was used in reference to the action performed by Mechanical computer, mechanical computing machines, and before that, to Computer (occupation), human computers. History The history of computing is longer than the history of computing hardware and includes the history of methods intended for pen and paper (or for chalk and slate) with or without the aid of tables. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mercury (programming Language)
Mercury is a functional logic programming language made for real-world uses. The first version was developed at the University of Melbourne, Computer Science department, by Fergus Henderson, Thomas Conway, and Zoltan Somogyi, under Somogyi's supervision, and released on April 8, 1995. Mercury is a purely declarative logic programming language. It is related to both Prolog and Haskell. It features a strong, static, polymorphic type system, and a strong mode and determinism system. The official implementation, the Melbourne Mercury Compiler, is available for most Unix and Unix-like platforms, including Linux, macOS, and for Windows. Overview Mercury is based on the logic programming language Prolog. It has the same syntax and the same basic concepts such as the selective linear definite clause resolution (SLD) algorithm. It can be viewed as a pure subset of Prolog with strong types and modes. As such, it is often compared to its predecessor in features and run-time e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linear Type
Substructural type systems are a family of type systems analogous to substructural logics where one or more of the structural rules are absent or only allowed under controlled circumstances. Such systems can constrain access to system resources such as files, locks, and memory by keeping track of changes of state and prohibiting invalid states. Different substructural type systems Several type systems have emerged by discarding some of the structural rules of exchange, weakening, and contraction: *''Ordered type systems'' (discard exchange, weakening and contraction): Every variable is used exactly once in the order it was introduced. *''Linear type systems'' (allow exchange, but neither weakening nor contraction): Every variable is used exactly once. *''Affine type systems'' (allow exchange and weakening, but not contraction): Every variable is used at most once. *''Relevant type systems'' (allow exchange and contraction, but not weakening): Every variable is used at least ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type Casting (computer Programming)
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, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linear Type
Substructural type systems are a family of type systems analogous to substructural logics where one or more of the structural rules are absent or only allowed under controlled circumstances. Such systems can constrain access to system resources such as files, locks, and memory by keeping track of changes of state and prohibiting invalid states. Different substructural type systems Several type systems have emerged by discarding some of the structural rules of exchange, weakening, and contraction: *''Ordered type systems'' (discard exchange, weakening and contraction): Every variable is used exactly once in the order it was introduced. *''Linear type systems'' (allow exchange, but neither weakening nor contraction): Every variable is used exactly once. *''Affine type systems'' (allow exchange and weakening, but not contraction): Every variable is used at most once. *''Relevant type systems'' (allow exchange and contraction, but not weakening): Every variable is used at least ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scala (programming Language)
Scala ( ) is a strongly statically typed high-level general-purpose programming language that supports both object-oriented programming and functional programming. Designed to be concise, many of Scala's design decisions are intended to address criticisms of Java. Scala source code can be compiled to Java bytecode and run on a Java virtual machine (JVM). Scala can also be transpiled to JavaScript to run in a browser, or compiled directly to a native executable. When running on the JVM, Scala provides language interoperability with Java so that libraries written in either language may be referenced directly in Scala or Java code. Like Java, Scala is object-oriented, and uses a syntax termed '' curly-brace'' which is similar to the language C. Since Scala 3, there is also an option to use the off-side rule (indenting) to structure blocks, and its use is advised. Martin Odersky has said that this turned out to be the most productive change introduced in Scala 3. Unlike J ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monads In Functional Programming
In functional programming, monads are a way to structure computations as a sequence of steps, where each step not only produces a value but also some extra information about the computation, such as a potential failure, non-determinism, or side effect. More formally, a monad is a type constructor M equipped with two operations, which lifts a value into the monadic context, and which chains monadic computations. In simpler terms, monads can be thought of as interfaces implemented on type constructors, that allow for functions to abstract over various type constructor variants that implement monad (e.g. , , etc.). Both the concept of a monad and the term originally come from category theory, where a monad is defined as an endofunctor with additional structure. Research beginning in the late 1980s and early 1990s established that monads could bring seemingly disparate computer-science problems under a unified, functional model. Category theory also provides a few formal requiremen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Idris (programming Language)
Idris is a purely-functional programming language with dependent types, optional lazy evaluation, and features such as a totality checker. Idris may be used as a proof assistant, but is designed to be a general-purpose programming language similar to Haskell. The Idris type system is similar to Agda's, and proofs are similar to Coq's, including tactics (theorem proving functions/procedures) via elaborator reflection. Compared to Agda and Coq, Idris prioritizes management of side effects and support for embedded domain-specific languages. Idris compiles to C (relying on a custom copying garbage collector using Cheney's algorithm) and JavaScript (both browser- and Node.js-based). There are third-party code generators for other platforms, including Java virtual machine (JVM), Common Intermediate Language (CIL), and LLVM. Idris is named after a singing dragon from the 1970s UK children's television program '' Ivor the Engine''. Features Idris combines a number of featu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SAC Programming Language
SAC (Single Assignment C) is a strict purely functional programming language whose design is focused on the needs of numerical applications. Emphasis is laid on efficient support for array processing via data parallelism. Efficiency concerns are essentially twofold. On the one hand, efficiency in program development is to be improved by the opportunity to specify array operations on a high level of abstraction. On the other hand, efficiency in program execution, i.e. the runtime performance of programs, in time and memory consumption, is still to be achieved by sophisticated compilation schemes. Only as far as the latter succeeds, the high-level style of specifications can actually be called useful. To facilitate compiling to efficiently executable code, certain functional language features which are not considered essential for numerical applications, e.g. higher-order functions, polymorphism, or lazy evaluation, are not (yet) supported by SAC. These may be found in general-p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clean (programming Language)
Clean is a general-purpose purely functional programming language. Originally called the Concurrent Clean System or the Clean System, it has been developed by a group of researchers from the Radboud University in Nijmegen since 1987. Although development of the language has slowed, some researchers are still working in the language. In 2018, a spin-off company was founded that uses Clean. Features Clean shares many properties and syntax with a younger sibling language, Haskell: referential transparency, list comprehension, guards, garbage collection, higher order functions, currying, and lazy evaluation. However, Clean deals with mutable state and input/output (I/O) through a uniqueness type system, in contrast to Haskell's use of monads. The compiler takes advantage of the uniqueness type system to generate more efficient code, because it knows that at any point during the execution of the program, only one reference can exist to a value with a unique type. Therefore, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-threaded
In computer science, a thread of execution is the smallest sequence of programmed instructions that can be managed independently by a scheduler, which is typically a part of the operating system. In many cases, a thread is a component of a process. The multiple threads of a given process may be executed concurrently (via multithreading capabilities), sharing resources such as memory, while different processes do not share these resources. In particular, the threads of a process share its executable code and the values of its dynamically allocated variables and non- thread-local global variables at any given time. The implementation of threads and processes differs between operating systems. History Threads made an early appearance under the name of "tasks" in IBM's batch processing operating system, OS/360, in 1967. It provided users with three available configurations of the OS/360 control system, of which Multiprogramming with a Variable Number of Tasks (MVT) was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type System
In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a ''type'' (for example, integer, floating point, string) to every '' term'' (a word, phrase, or other set of symbols). 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 data types, such as "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 synta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
