|
Zipper (data Structure)
A zipper is a technique of representing an aggregate data structure so that it is convenient for writing programs that traverse the structure arbitrarily and update its contents, especially in purely functional programming languages. The zipper was described by Gérard Huet in 1997. It includes and generalizes the gap buffer technique sometimes used with arrays. The zipper technique is general in the sense that it can be adapted to List (computing), lists, Tree (data structure), trees, and other Recursive data type, recursively defined data structures. Such modified data structures are usually referred to as "a tree with zipper" or "a list with zipper" to emphasize that the structure is conceptually a tree or list, while the zipper is a detail of the implementation. A layperson's explanation for a tree with zipper would be an ordinary computer file system with operations to go to parent (often cd (command), cd ..), and to go downwards (cd subdirectory). The zipper is the pointer t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Structure
In computer science, a data structure is a data organization and storage format that is usually chosen for Efficiency, efficient Data access, access to data. More precisely, a data structure is a collection of data values, the relationships among them, and the Function (computer programming), functions or Operator (computer programming), operations that can be applied to the data, i.e., it is an algebraic structure about data. Usage Data structures serve as the basis for abstract data types (ADT). The ADT defines the logical form of the data type. The data structure implements the physical form of the data type. Different types of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks. For example, Relational database, relational databases commonly use B-tree indexes for data retrieval, while compiler Implementation, implementations usually use hash tables to look up Identifier (computer languages), identifiers. Data s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sum Type
In computer science, a tagged union, also called a variant, variant record, choice type, discriminated union, disjoint union, sum type, or coproduct, is a data structure used to hold a value that could take on several different, but fixed, types. Only one of the types can be in use at any one time, and a tag field explicitly indicates which type is in use. It can be thought of as a type that has several "cases", each of which should be handled correctly when that type is manipulated. This is critical in defining recursive datatypes, in which some component of a value may have the same type as that value, for example in defining a type for representing trees, where it is necessary to distinguish multi-node subtrees and leaves. Like ordinary unions, tagged unions can save storage by overlapping storage areas for each type, since only one is in use at a time. Description Tagged unions are most important in functional programming languages such as ML and Haskell, where they are called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clojure
Clojure (, like ''closure'') is a dynamic programming language, dynamic and functional programming, functional dialect (computing), dialect of the programming language Lisp (programming language), Lisp on the Java (software platform), Java platform. Like most other Lisps, Clojure's Syntax (programming languages), syntax is built on S-expressions that are first Parsing, parsed into data structures by a Lisp reader before being Compiler, compiled. Clojure's reader supports literal syntax for hash table, maps, sets, and Array (data structure), vectors along with lists, and these are compiled to the mentioned structures directly. Clojure treats Homoiconicity, code as data and has a Lisp macro system. Clojure is a Lisp-1 and is not intended to be code-compatible with other dialects of Lisp, since it uses its own set of data structures incompatible with other Lisps. Clojure advocates immutable object, immutability and persistent data structure, immutable data structures and encourages ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haskell (programming Language)
Haskell () is a General-purpose programming language, general-purpose, static typing, statically typed, purely functional programming, purely functional programming language with type inference and lazy evaluation. Designed for teaching, research, and industrial applications, Haskell pioneered several programming language #Features, features such as type classes, which enable type safety, type-safe operator overloading, and Monad (functional programming), monadic input/output (IO). It is named after logician Haskell Curry. Haskell's main implementation is the Glasgow Haskell Compiler (GHC). Haskell's Semantics (computer science), semantics are historically based on those of the Miranda (programming language), Miranda programming language, which served to focus the efforts of the initial Haskell working group. The last formal specification of the language was made in July 2010, while the development of GHC continues to expand Haskell via language extensions. Haskell is used in a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automated Theorem Prover
Automated theorem proving (also known as ATP or automated deduction) is a subfield of automated reasoning and mathematical logic dealing with proving mathematical theorems by computer programs. Automated reasoning over mathematical proof was a major motivating factor for the development of computer science. Logical foundations While the roots of formalized logic go back to Aristotle, the end of the 19th and early 20th centuries saw the development of modern logic and formalized mathematics. Frege's ''Begriffsschrift'' (1879) introduced both a complete propositional calculus and what is essentially modern predicate logic. His '' Foundations of Arithmetic'', published in 1884, expressed (parts of) mathematics in formal logic. This approach was continued by Russell and Whitehead in their influential ''Principia Mathematica'', first published 1910–1913, and with a revised second edition in 1927. Russell and Whitehead thought they could derive all mathematical truth using axioms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structural Editor
A structure editor, also structured editor or projectional editor, is any document editor that is cognizant of the document's underlying structure. Structure editors can be used to edit hierarchical or marked up text, computer programs, diagrams, chemical formulas, and any other type of content with clear and well-defined structure. In contrast, a text editor is any document editor used for editing plain text files. Typically, the benefits of text and structure editing are combined in the user interface of a single hybrid tool. For example, Emacs is fundamentally a text editor, but supports the manipulation of words, sentences, and paragraphs as structures that are inferred from the text. Conversely, Dreamweaver is fundamentally a structure editor for marked up web documents, but supports the display and manipulation of raw HTML text as well. Similarly, molecule editors typically support both graphical and textual input. Structure editing predominates when content is graphical a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Window (computing)
In computing, a window is a Graphical widget, graphical control element. It consists of a visual area containing some of the graphical user interface of the program it belongs to and is framed by a #Window decoration, window decoration. It usually has a rectangular shape that can overlap with the area of other windows. It displays the ''output'' of and may allow ''input'' to one or more Process (computing), processes. Windows are primarily associated with graphical displays, where they can be manipulated with a Pointer (graphical user interfaces), pointer by employing some kind of pointing device. Text-only displays can also support windowing, as a way to maintain multiple independent display areas, such as multiple buffers in Emacs. Text windows are usually controlled by keyboard, though some also respond to the mouse. A graphical user interface (GUI) using windows as one of its main "Interface metaphor, metaphors" is called a windowing system, whose main components are the disp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xmonad
xmonad is a dynamic window manager ( tiling) for the X Window System, noted for being written in the functional programming language Haskell. Window manager Begun in March 2007, version 0.1 was announced in April 2007 as 500 lines of Haskell (which have since grown to 2000 lines). xmonad is a tiling window manager—akin to dwm, larswm, and StumpWM. It arranges windows in a non-overlapping pattern, and enables managing windows without using the mouse. xmonad is packaged and distributed on a wide range of Unix-like operating systems, such as a large number of Linux distributions, and Berkeley Software Distribution (BSD) systems. While originally a clone of dwm (derivative in areas such as default keybindings), xmonad now supports features not available to dwm users such as per-workspace layout, tiling reflection, state preservation, layout mirroring, GNOME support and per-screen status bars; it can be customised by modifying an external configuration file and 'reload ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Cursor
In computer science, a database cursor is a mechanism that enables traversal over the records in a database. Cursors facilitate processing in conjunction with the traversal, such as retrieval, addition and removal of database records. The database cursor characteristic of traversal makes cursors akin to the programming language concept of iterator. Cursors are used by database programmers to process individual rows returned by database system queries. Cursors enable manipulation of whole result sets at once. In this scenario, a cursor enables the sequential processing of rows in a result set. In SQL procedures, a cursor makes it possible to define a result set (a set of data rows) and perform complex logic on a row by row basis. By using the same mechanics, a SQL procedure can also define a result set and return it directly to the caller of the SQL procedure or to a client application. A cursor can be viewed as a pointer to one row in a set of rows. The cursor can only referenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Focus (computing)
In a computing graphical user interface (GUI), a component has focus when it is selected to receive input from the user by an event such as a mouse button click or keypress. Moving the focus away from a specific user interface element is known as a blur event in relation to this element. Typically, the focus is withdrawn from an element by giving another element the focus. This means that focus and blur Event (computing), events are virtually simultaneous in relation to different user interface elements, one that becomes focused and one that is "blurred" (in the computing, not visual, sense). The concept is similar to a Cursor (user interface), cursor in a text-based environment. However, when considering a graphical interface, there is also a mouse pointer involved. Moving the mouse will typically move the mouse pointer without changing the focus. The focus can usually be changed by clicking on a component that can receive focus with the mouse. Many Desktop environment, desktops al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unit Type
In the area of mathematical logic and computer science known as type theory, a unit type is a type that allows only one value (and thus can hold no information). The carrier (underlying set) associated with a unit type can be any singleton set. There is an isomorphism between any two such sets, so it is customary to talk about ''the'' unit type and ignore the details of its value. One may also regard the unit type as the type of 0- tuples, i.e. the product of no types. The unit type is the terminal object in the category of types and typed functions. It should not be confused with the ''zero'' or empty type, which allows ''no'' values and is the initial object in this category. Similarly, the Boolean is the type with ''two'' values. The unit type is implemented in most functional programming languages. The void type that is used in some imperative programming languages serves some of its functions, but because its carrier set is empty, it has some limitations (as detail ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
