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Hash Cons
In computer science, particularly in functional programming, hash consing is a technique used to share values that are structurally equal. When a value is constructed, such as a cons cell, the technique checks if such a value has been constructed before, and if so reuses the previous value, avoiding a new memory allocation. A useful property of hash consing is that two structures can be tested for equality in constant time via pointer equality, which in turn can improve efficiency of Divide and conquer algorithms, divide and conquer algorithms when data sets contain overlapping blocks. Hash consing has been shown to give dramatic performance improvements—both space and time—for symbolic computation, symbolic and dynamic programming algorithms. Hash consing is most commonly implemented with hash tables storing weak references that may be garbage collection (computer science), garbage-collected when the data stored therein contains no reference (computer science), referenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, applied disciplines (including the design and implementation of Computer architecture, hardware and Software engineering, software). Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheme (programming Language)
Scheme is a dialect of the Lisp family of programming languages. Scheme was created during the 1970s at the MIT Computer Science and Artificial Intelligence Laboratory (MIT CSAIL) and released by its developers, Guy L. Steele and Gerald Jay Sussman, via a series of memos now known as the Lambda Papers. It was the first dialect of Lisp to choose lexical scope and the first to require implementations to perform tail-call optimization, giving stronger support for functional programming and associated techniques such as recursive algorithms. It was also one of the first programming languages to support first-class continuations. It had a significant influence on the effort that led to the development of Common Lisp.Common LISP: The Language, 2nd Ed., Guy L. Steele Jr. Digital Press; 1981. . "Common Lisp is a new dialect of Lisp, a successor to MacLisp, influenced strongly by ZetaLisp and to some extent by Scheme and InterLisp." The Scheme language is standardized in the offic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Implementation Of Functional Programming Languages
Implementation is the realization of an application, execution of a plan, idea, model, design, specification, standard, algorithm, policy, or the administration or management of a process or objective. Industry-specific definitions Information technology In the information technology industry, implementation refers to the post-sales process of guiding a client from purchase to use of the software or hardware that was purchased. This includes requirements analysis, scope analysis, customizations, systems integrations, user policies, user training and delivery. These steps are often overseen by a project manager using project management methodologies. Software Implementations involve several professionals that are relatively new to the knowledge based economy such as business analysts, software implementation specialists, solutions architects, and project managers. To implement a system successfully, many inter-related tasks need to be carried out in an appropriate sequence. U ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Communications Of The ACM
''Communications of the ACM'' (''CACM'') is the monthly journal of the Association for Computing Machinery (ACM). History It was established in 1958, with Saul Rosen as its first managing editor. It is sent to all ACM members. Articles are intended for readers with backgrounds in all areas of computer science and information systems. The focus is on the practical implications of advances in information technology and associated management issues; ACM also publishes a variety of more theoretical journals. The magazine straddles the boundary of a science magazine, trade magazine, and a scientific journal. While the content is subject to peer review, the articles published are often summaries of research that may also be published elsewhere. Material published must be accessible and relevant to a broad readership. From 1960 onward, ''CACM'' also published algorithms, expressed in ALGOL. The collection of algorithms later became known as the Collected Algorithms of the ACM. CA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interning (computer Science)
In computer science, interning is re-using objects of equal value on-demand instead of creating new objects. This creational pattern is frequently used for numbers and strings in different programming languages. In many object-oriented languages such as Python, even primitive types such as integer numbers are objects. To avoid the overhead of constructing a large number of integer objects, these objects get reused through interning. For interning to work the interned objects must be immutable, since state is shared between multiple variables. String interning is a common application of interning, where many strings with identical values are needed in the same program. History Lisp introduced the notion of interned strings for its symbols. The LISP 1.5 Programmers Manual describes a function called intern which either evaluates to an existing symbol of the supplied name, or if none exists, creates a new symbol of that name. This idea of interned symbols persists in more recen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hashlife
Hashlife is a memoized algorithm for computing the long-term fate of a given starting configuration in Conway's Game of Life and related cellular automata, much more quickly than would be possible using alternative algorithms that simulate each time step of each cell of the automaton. The algorithm was first described by Bill Gosper in the early 1980s while he was engaged in research at the Xerox Palo Alto Research Center. Hashlife was originally implemented on Symbolics Lisp machines with the aid of the Flavors extension. Hashlife Hashlife is designed to exploit large amounts of spatial and temporal redundancy in most Life rules. For example, in Conway's Life, many seemingly random patterns end up as collections of simple still lifes and oscillators. Hashlife does however not depend on patterns remaining in the same position; it is more about exploiting that large patterns tend to have subpatterns that appear in several places, possibly at different times. Representatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flyweight Pattern
In computer programming, the flyweight software design pattern refers to an Object (computer science), object that minimizes Computer memory, memory usage by sharing some of its data with other similar objects. The flyweight pattern is one of twenty-three well-known ''Design Patterns, GoF design patterns''. These patterns promote flexible object-oriented software design, which is easier to implement, change, test, and reuse. In other contexts, the idea of sharing data structures is called hash consing. The term was first coined, and the idea extensively explored, by Paul Calder and Mark Linton in 1990 to efficiently handle glyph information in a WYSIWYG, WYSIWYG document editor. Similar techniques were already used in other systems, however, as early as 1988. Overview The flyweight pattern is useful when dealing with a large number of objects that share simple repeated elements which would use a large amount of memory if they were individually embedded. It is common to hold sha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
String Interning
In computer science, string interning is a method of storing only one copy of each distinct string value, which must be immutable. Interning strings makes some string processing tasks more time-efficient or space-efficient at the cost of requiring more time when the string is created or interned. The distinct values are stored in a string intern pool. The single copy of each string is called its ''intern'' and is typically looked up by a method of the string class, for example String.intern() in Java. All compile-time constant strings in Java are automatically interned using this method. String interning is supported by some modern object-oriented programming languages, including Java, Python, PHP (since 5.4), Lua and .NET languages. Lisp, Scheme, Julia, Ruby and Smalltalk are among the languages with a symbol type that are basically interned strings. The library of the Standard ML of New Jersey contains an atom type that does the same thing. Objective-C's selectors, which a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Tokyo
The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era institutions, its direct precursors include the '' Tenmongata'', founded in 1684, and the Shōheizaka Institute. Although established under its current name, the university was renamed in 1886 and was further retitled to distinguish it from other Imperial Universities established later. It served under this name until the official dissolution of the Empire of Japan in 1947, when it reverted to its original name. Today, the university consists of 10 faculties, 15 graduate schools, and 11 affiliated research institutes. As of 2023, it has a total of 13,974 undergraduate students and 14,258 graduate students. The majority of the university's educational and research facilities are concentrated within its three main Tokyo campuses: Hongō, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xerox Palo Alto Research Center
Xerox Holdings Corporation (, ) is an American corporation that sells print and electronic document, digital document products and services in more than 160 countries. Xerox was the pioneer of the photocopier market, beginning with the introduction of the Xerox 914 in 1959, so much so that the word ''xerox'' is commonly used as a synonym for ''photocopy''. Xerox is headquartered in Norwalk, Connecticut, though it is incorporated in New York (state), New York with its largest group of employees based around Rochester, New York, the area in which the company was founded. As a large developed company, it is consistently placed in the list of Fortune 500 companies. The company purchased Affiliated Computer Services for $6.4 billion in early 2010. On December 31, 2016, Xerox separated its business process service operations, essentially those operations acquired with the purchase of Affiliated Computer Services, into a new publicly traded company, Conduent. Xerox focuses on its docu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lisp (programming Language)
Lisp (historically LISP, an abbreviation of "list processing") is a family of programming languages with a long history and a distinctive, fully parenthesized prefix notation. Originally specified in the late 1950s, it is the second-oldest high-level programming language still in common use, after Fortran. Lisp has changed since its early days, and many dialects have existed over its history. Today, the best-known general-purpose Lisp dialects are Common Lisp, Scheme, Racket, and Clojure. Lisp was originally created as a practical mathematical notation for computer programs, influenced by (though not originally derived from) the notation of Alonzo Church's lambda calculus. It quickly became a favored programming language for artificial intelligence (AI) research. As one of the earliest programming languages, Lisp pioneered many ideas in computer science, including tree data structures, automatic storage management, dynamic typing, conditionals, higher-order function ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
