Topic: Computer science

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๐Ÿ”— Hy

๐Ÿ”— Computing ๐Ÿ”— Computer science ๐Ÿ”— Computing/Software

Hy (alternately, Hylang) is a programming language, a dialect of the language Lisp designed to interact with the language Python by translating expressions into Python's abstract syntax tree (AST). Hy was introduced at Python Conference (PyCon) 2013 by Paul Tagliamonte.

Similar to Kawa's and Clojure's mapping of s-expressions onto the Java virtual machine (JVM), Hy is meant to operate as a transparent Lisp front end to Python's abstract syntax. Lisp allows operating on code as data (metaprogramming). Thus, Hy can be used to write domain-specific languages. Hy also allows Python libraries, including the standard library, to be imported and accessed alongside Hy code with a compiling step converting the data structure of both into Python's AST.

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  • "Hy" | 2019-08-04 | 850 Upvotes 141 Comments
  • "Hy" | 2016-11-07 | 70 Upvotes 5 Comments

๐Ÿ”— Non-English-based programming languages

๐Ÿ”— Computing ๐Ÿ”— Computer science

Non-English-based programming languages are programming languages that do not use keywords taken from or inspired by English vocabulary.

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๐Ÿ”— Peter Naur has died

๐Ÿ”— Biography ๐Ÿ”— Computer science ๐Ÿ”— Biography/science and academia ๐Ÿ”— Denmark

Peter Naur (25 October 1928 โ€“ 3 January 2016) was a Danish computer science pioneer and Turing award winner. His last name is the "N" in the BNF notation (Backusโ€“Naur form), used in the description of the syntax for most programming languages. He contributed to the creation of the ALGOL 60 programming language.

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๐Ÿ”— Moravec's Paradox

๐Ÿ”— Computer science ๐Ÿ”— Philosophy ๐Ÿ”— Philosophy/Logic ๐Ÿ”— Philosophy/Philosophy of science ๐Ÿ”— Philosophy/Philosophy of mind

Moravec's paradox is the observation by artificial intelligence and robotics researchers that, contrary to traditional assumptions, reasoning (which is high-level in humans) requires very little computation, but sensorimotor skills (comparatively low-level in humans) require enormous computational resources. The principle was articulated by Hans Moravec, Rodney Brooks, Marvin Minsky and others in the 1980s. As Moravec writes, "it is comparatively easy to make computers exhibit adult level performance on intelligence tests or playing checkers, and difficult or impossible to give them the skills of a one-year-old when it comes to perception and mobility".

Similarly, Minsky emphasized that the most difficult human skills to reverse engineer are those that are unconscious. "In general, we're least aware of what our minds do best", he wrote, and added "we're more aware of simple processes that don't work well than of complex ones that work flawlessly".

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๐Ÿ”— Black Perl

๐Ÿ”— Computer science ๐Ÿ”— Poetry

"Black Perl" is a code poem written using the Perl programming language. It was posted anonymously to Usenet on April 1, 1990, and is popular among Perl programmers as a piece of Perl poetry. Written in Perl 3, the poem is able to be executed as a program.

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๐Ÿ”— Cyc

๐Ÿ”— Computing ๐Ÿ”— Computer science ๐Ÿ”— Cognitive science ๐Ÿ”— Software ๐Ÿ”— Software/Computing ๐Ÿ”— Databases ๐Ÿ”— Databases/Computer science

Cyc (pronounced SYKE, ) is a long-living artificial intelligence project that aims to assemble a comprehensive ontology and knowledge base that spans the basic concepts and rules about how the world works. Hoping to capture common sense knowledge, Cyc focuses on implicit knowledge that other AI platforms may take for granted. This is contrasted with facts one might find somewhere on the internet or retrieve via a search engine or Wikipedia. Cyc enables AI applications to perform human-like reasoning and be less "brittle" when confronted with novel situations.

Douglas Lenat began the project in July 1984 at MCC, where he was Principal Scientist 1984โ€“1994, and then, since January 1995, has been under active development by the Cycorp company, where he is the CEO.

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  • "Cyc" | 2022-09-28 | 24 Upvotes 2 Comments
  • "Cyc" | 2019-12-13 | 357 Upvotes 173 Comments

๐Ÿ”— Attempto Controlled English

๐Ÿ”— Computer science ๐Ÿ”— Linguistics ๐Ÿ”— Languages

Attempto Controlled English (ACE) is a controlled natural language, i.e. a subset of standard English with a restricted syntax and restricted semantics described by a small set of construction and interpretation rules. It has been under development at the University of Zurich since 1995. In 2013, ACE version 6.7 was announced.

ACE can serve as knowledge representation, specification, and query language, and is intended for professionals who want to use formal notations and formal methods, but may not be familiar with them. Though ACE appears perfectly natural โ€“ it can be read and understood by any speaker of English โ€“ it is in fact a formal language.

ACE and its related tools have been used in the fields of software specifications, theorem proving, text summaries, ontologies, rules, querying, medical documentation and planning.

Here are some simple examples:

  1. Every woman is a human.
  2. A woman is a human.
  3. A man tries-on a new tie. If the tie pleases his wife then the man buys it.

ACE construction rules require that each noun be introduced by a determiner (a, every, no, some, at least 5, ...). Regarding the list of examples above, ACE interpretation rules decide that (1) is interpreted as universally quantified, while (2) is interpreted as existentially quantified. Sentences like "Women are human" do not follow ACE syntax and are consequently not valid.

Interpretation rules resolve the anaphoric references in (3): the tie and it of the second sentence refer to a new tie of the first sentence, while his and the man of the second sentence refer to a man of the first sentence. Thus an ACE text is a coherent entity of anaphorically linked sentences.

The Attempto Parsing Engine (APE) translates ACE texts unambiguously into discourse representation structures (DRS) that use a variant of the language of first-order logic. A DRS can be further translated into other formal languages, for instance AceRules with various semantics, OWL, and SWRL. Translating an ACE text into (a fragment of) first-order logic allows users to reason about the text, for instance to verify, to validate, and to query it.

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๐Ÿ”— Boids

๐Ÿ”— Computer science

Boids is an artificial life program, developed by Craig Reynolds in 1986, which simulates the flocking behaviour of birds. His paper on this topic was published in 1987 in the proceedings of the ACM SIGGRAPH conference. The name "boid" corresponds to a shortened version of "bird-oid object", which refers to a bird-like object. Incidentally, "boid" is also a New York Metropolitan dialect pronunciation for "bird".

As with most artificial life simulations, Boids is an example of emergent behavior; that is, the complexity of Boids arises from the interaction of individual agents (the boids, in this case) adhering to a set of simple rules. The rules applied in the simplest Boids world are as follows:

  • separation: steer to avoid crowding local flockmates
  • alignment: steer towards the average heading of local flockmates
  • cohesion: steer to move towards the average position (center of mass) of local flockmates

More complex rules can be added, such as obstacle avoidance and goal seeking.

The basic model has been extended in several different ways since Reynolds proposed it. For instance, Delgado-Mata etย al. extended the basic model to incorporate the effects of fear. Olfaction was used to transmit emotion between animals, through pheromones modelled as particles in a free expansion gas. Hartman and Benes introduced a complementary force to the alignment that they call the change of leadership. This steer defines the chance of the boid to become a leader and try to escape.

The movement of Boids can be characterized as either chaotic (splitting groups and wild behaviour) or orderly. Unexpected behaviours, such as splitting flocks and reuniting after avoiding obstacles, can be considered emergent.

The boids framework is often used in computer graphics, providing realistic-looking representations of flocks of birds and other creatures, such as schools of fish or herds of animals. It was for instance used in the 1998 video game Half-Life for the flying bird-like creatures seen at the end of the game on Xen, named "boid" in the game files.

The Boids model can be used for direct control and stabilization of teams of simple Unmanned Ground Vehicles (UGV) or Micro Aerial Vehicles (MAV) in swarm robotics. For stabilization of heterogeneous UAV-UGV teams, the model was adapted for using onboard relative localization by Saska etย al.

At the time of proposal, Reynolds' approach represented a giant step forward compared to the traditional techniques used in computer animation for motion pictures. The first animation created with the model was Stanley and Stella in: Breaking the Ice (1987), followed by a feature film debut in Tim Burton's film Batman Returns (1992) with computer generated bat swarms and armies of penguins marching through the streets of Gotham City.

The boids model has been used for other interesting applications. It has been applied to automatically program Internet multi-channel radio stations. It has also been used for visualizing information and for optimization tasks.

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  • "Boids" | 2020-03-28 | 391 Upvotes 80 Comments

๐Ÿ”— TLA+

๐Ÿ”— Computer science

TLA+ is a formal specification language developed by Leslie Lamport. It is used to design, model, document, and verify programs, especially concurrent systems and distributed systems. TLA+ has been described as exhaustively-testable pseudocode, and its use likened to drawing blueprints for software systems; TLA is an acronym for Temporal Logic of Actions.

For design and documentation, TLA+ fulfills the same purpose as informal technical specifications. However, TLA+ specifications are written in a formal language of logic and mathematics, and the precision of specifications written in this language is intended to uncover design flaws before system implementation is underway.

Since TLA+ specifications are written in a formal language, they are amenable to finite model checking. The model checker finds all possible system behaviours up to some number of execution steps, and examines them for violations of desired invariance properties such as safety and liveness. TLA+ specifications use basic set theory to define safety (bad things won't happen) and temporal logic to define liveness (good things eventually happen).

TLA+ is also used to write machine-checked proofs of correctness both for algorithms and mathematical theorems. The proofs are written in a declarative, hierarchical style independent of any single theorem prover backend. Both formal and informal structured mathematical proofs can be written in TLA+; the language is similar to LaTeX, and tools exist to translate TLA+ specifications to LaTeX documents.

TLA+ was introduced in 1999, following several decades of research into a verification method for concurrent systems. A toolchain has since developed, including an IDE and distributed model checker. The pseudocode-like language PlusCal was created in 2009; it transpiles to TLA+ and is useful for specifying sequential algorithms. TLA+2 was announced in 2014, expanding language support for proof constructs. The current TLA+ reference is The TLA+ Hyperbook by Leslie Lamport.

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  • "TLA+" | 2021-03-08 | 230 Upvotes 69 Comments
  • "TLA+" | 2015-05-25 | 105 Upvotes 21 Comments

๐Ÿ”— Kateryna Yushchenko

๐Ÿ”— Biography ๐Ÿ”— Soviet Union ๐Ÿ”— Computing ๐Ÿ”— Computer science ๐Ÿ”— Women scientists ๐Ÿ”— Biography/science and academia ๐Ÿ”— Ukraine

Kateryna Lohvynivna Yushchenko (Ukrainian: ะšะฐั‚ะตั€ะธะฝะฐ ะ›ะพะณะฒะธะฝั–ะฒะฝะฐ ะฎั‰ะตะฝะบะพ, Russian: ะ•ะบะฐั‚ะตั€ะธะฝะฐ ะ›ะพะณะฒะธะฝะพะฒะฝะฐ ะฎั‰ะตะฝะบะพ, December 8, 1919, Chyhyryn - died August 15, 2001) was a Ukrainian computer and information research scientist, corresponding member of USSR Academy of Sciences (1976), and member of The International Academy of Computer Science. She developed one of the world's first high-level languages with indirect address in programming, called the Address programming language. Over the period of her academic career, Yushchenko supervised 45 Ph.D students. Further professional achievements include Yushchenko being awarded two USSR State Prizes, The USSR Council of Ministers Prize, The Academician Glushkov Prize, and The Order of Princess Olga. Yushchenko was the first woman in the USSR to become a Doctor of Physical and Mathematical Sciences in programming.

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