Safe Dynamic Memory Management in Ada and SPARK by Maroua Maalej, Tucker Taft, Yannick Moy:

Handling memory in a correct and efficient way is a step toward safer, less complex, and higher performing software-intensive systems. However, languages used for critical software development such as Ada, which supports formal verification with its SPARK subset, face challenges regarding any use of pointers due to potential pointer aliasing. In this work, we introduce an extension to the Ada language, and to its SPARK subset, to provide pointer types (“access types” in Ada) that provide provably safe, automatic storage management without any asynchronous garbage collection, and without explicit deallocation by the user. Because the mechanism for these safe pointers relies on strict control of aliasing, it can be used in the SPARK subset for formal verification, including both information flow analysis and proof of safety and correctness properties. In this paper, we present this proposal (which has been submitted for inclusion in the next version of Ada), and explain how we are able to incorporate these pointers into formal analyses

For the systems programmers among you, you might be interested in some new developments in Ada where they propose to add ownership types to Ada's pointer/access types, to improve the flexibility of the programs that can be written and whose safety can be automatically verified. The automated satisfiability of these safety properties is a key goal of the SPARK Ada subset.

An enjoyable 25-minute introductory talk: YOW! Lambda Jam 2019 - Ken Scambler - Applied Category Theory (slides)

What do programming, quantum physics, chemistry, neuroscience, systems biology, natural language parsing, causality, network theory, game theory, dynamical systems and database theory have in common?

As functional programmers, we know how useful category theory can be for our work - or perhaps how abstruse and distant it can seem. What is less well known is that applying category theory to the real world is an exciting field of study that has really taken off in just the last few years. It turns out that we share something big with other fields and industries - we want to make big things out of little things without everything going to hell! The key is compositionality, the central idea of category theory.

Previously: Seven Sketches in Compositionality: An Invitation to Applied Category Theory.

(via Brian McKenna)

In 2017, a team from Northeastern University released Turnstile, a framework for implementing propositionally typed languages in Racket; cf. naasking's story Type Systems as Macros. The system was really nice because it allowed type systems to be expressed in a manner similar to the way theoretical PL researchers would in a paper, and because it hooked into Racket's clean compiler backend.

Now Stephen Chang, one of that team, together with new coauthors Michael Ballantyne, Usamilo Turner and William Bowman, have released a rewrite that they call Turnstile+, together with a POPL article, Dependent Type Systems as Macros. From that article's introduction:

Turnstile+ represents a major research leap over its predecessor. Specifically, we solve the major challenges necessary to implement dependent types and their accompanying DSLs and extensions (which Turnstile could not support), while retaining the original abilities of Turnstile. For example, one considerable obstacle was the separation between the macro expansion phase and a program’s runtime phase. Since dependently typed languages may evaluate expressions while type checking, checking dependent types with macros requires new macrology design patterns and abstractions for interleaving expansion, type checking, and evaluation. The following summarizes our key innovations.

• Turnstile+ demands a radically different API for implementing a language’s types. It must be straightforward yet expressive enough to represent a range of constructs from base types, to binding forms like Π-types, to datatype definition forms for indexed inductive type families.
• Turnstile+ includes an API for defining type-level computation, which we dub normalization by macro expansion. A programmer writes a reduction rule using syntax resembling familiar on-paper notation, and Turnstile+ generates a macro definition that performs the reduction during macro expansion. This allows easily implementing modular type-level evaluation.
• Turnstile+’s new type API adds a generic type operation interface, enabling modular implementation of features such as error messages, pattern matching, and resugaring. This is particularly important for implementing tools like tactic systems that inspect intermediate type-checking steps and construct partial terms.
• Turnstile+’s core type checking infrastructure requires an overhaul, specifically with first-class type environments, in order to accommodate features like dependent binding structures of the shape[x:τ]...,i.e., telescopes [de Bruijn 1991; McBride 2000].
• Relatedly, Turnstile+’s inference-rule syntax is extended so that operations over telescopes, or premises with references to telescopes, operate as folds instead of as maps

The code is available at https://github.com/stchang/macrotypes.

1. Viroloog Marion Koopmans: 'Als het misgaat, hebben we echt een megaprobleem'  AD.nl
2. Ook Nederlandse viroloog verwacht tweede coronagolf | Buitenland | Nieuws  Het Laatste Nieuws
3. Viroloog: “Nieuwe coronagolf verwacht, alles staat of valt met hoe we ons gedragen”  Oog TV
4. BLIJF BANG! Viroloog Marion Koopmans waarschuwt: 'Die tweede coronavirus-golf komt er'  De Dagelijkse Standaard
5. Viroloog: 'Er komt een tweede coronagolf die mogelijk nog krachtiger is dan de eerste'  ThePostOnline
6. Hele verhaal bekijken via Google Nieuws

1. Remco Evenepoel: "Vandaag had een heel belangrijke dag moeten zijn"  sporza.be
2. Remco Evenepoel verkiest Giro boven Luik-Bastenaken-Luik | Wielrennen | Sport  Het Laatste Nieuws
3. Contador over 20 minuten-test Evenepoel: “Als die klopt, kan hij nu al de Giro winnen”  WielerFlits.be
4. Patrick Lefevere bevestigt dat Remco Evenepoel de Giro gaat rijden  Wielerkrant.be
5. Remco Evenepoel rijdt Giro in het najaar: "Intriest dat hij Luik niet kan rijden"  sporza.be
6. Hele verhaal bekijken via Google Nieuws

1. TV-bazen over de impact van corona - DEEL 2. Davy Parmentier van VTM: “Hoe het straks verder moet, weet vandaag nog niemand”  Het Laatste Nieuws
2. 'Een vrijscène met 1,5 meter afstand, hoe doe je dat?'  De Tijd
3. TV-bazen over de impact van corona - DEEL 1. Olivier Goris van VRT: “Ik hou er rekening mee dat we de komende zes maanden geen seconde fictie draaien”  Het Laatste Nieuws
4. Zomer vol herhalingen, en herhalingen van herhalingen: coronacrisis is opdoffer voor alle tv-zenders, en vooral voor VRT  Het Laatste Nieuws
5. Hele verhaal bekijken via Google Nieuws

1. 'Temptation'-verleidster Eline verrast: “Vriendinnen met Elke, géén contact meer met Arda”  Het Laatste Nieuws
2. 'Kk hadt naaien', een slappe worst en een ongeziene belediging: dit viel onze 'Temptation'-watcher op  Het Nieuwsblad
3. Eline uit Temptation Island doet pikante uitspraken: 'Elke moet mij dankbaar zijn'  Nieuws365
4. Een erg straffe Elke, harde levenslessen en vreemde kronkels: dit was aflevering 12 van 'Temptation Island'  Het Laatste Nieuws
5. Zach over zijn gedrag in 'Temptation Island': “Ik wou een psychologisch spelletje spelen met Romee”  Het Nieuwsblad
6. Hele verhaal bekijken via Google Nieuws

1. Muzikanten brengen ultiem eerbetoon aan alle 'heroes' vanop het dak van het Jessa Ziekenhuis  Het Laatste Nieuws
2. Flip Kowlier en Isolde Lasoen filmen cover van Heroes op dak van Jessa  Het Belang van Limburg
3. Hele verhaal bekijken via Google Nieuws

Motorrijder uit Zottegem overleden na zwaar ongeval in Zwalm, bestuurster auto zwaargewond  Het NieuwsbladHele verhaal bekijken via Google Nieuws

1. Minister van Toerisme Demir wil toeristen in Vlaanderen spreiden  De Standaard
2. Minister van Toerisme Demir wil met druktebarometer toeristen in Vlaanderen spreiden  Het Laatste Nieuws
3. Minister Zuhal Demir licht toerismeplan voor de zomer toe: “Ik wil dat de mensen Vlaanderen herontdekken”  Het Nieuwsblad
4. Ziekenhuizen kust ongerust over komst toeristen  Focus en WTV
5. Minister van Toerisme Demir werkt aan plan om toeristen in Vlaanderen te spreiden  De Morgen
6. Hele verhaal bekijken via Google Nieuws

Man die fietspad bezaait met prikkeldraad, spijkers en glas praat zichzelf aan de galg tegen visser die stiekem filmt  Het Laatste Nieuws

Sunday is Mothers Day Streaming Love

Besides being one of the stars of “The Booksellers,” Henry Wessells is also the proprietor of the micro-publisher, Temporary Culture. His latest booklet, “She Saved Us From World War Three,” brings together an interview, essay and two letters highlighting the friendship between Gardner Dozois, the longtime editor of Asimov’s Science Fiction Magazine, and Alice Sheldon, the former Washington intelligence agent whose intense, sometimes feminist sci-fi — no one ever forgets “The Women Men Don’t See” — was written using the pseudonym James Tiptree Jr. In one letter Sheldon explains that she has pretty much stopped writing because “the stories were getting to hurt too much.”

Why all the secrecy?

If you follow the news in Toronto or if you’re interested in technology, you’ve probably heard of Sidewalk Toronto by now. It’s a joint project of Sidewalk Labs, a sister company of Google, and Waterfront Toronto. This is the tech giant’s first foray into urban development and infrastructure, with Toronto hosting the pilot project. In […]

The post Civic Tech: We tried to get a copy of the Sidewalk Toronto agreement appeared first on Torontoist.

Unable to stage its big fundraiser because of the pandemic, Figure Skating in Harlem is going from the ice to the internet

Analysis: Tennis pros' US return amid pandemic no true model

На третий месяц конституционной истерики индеец Зоркий Глаз догадался, что над ним просто издеваются.

На самом деле это удивительное ощущение, когда ты смотришь живое кино о бесстыдстве эпохи. Только это не эпоха какого-нибудь Нерона, а наши дни в отдельно взятой стране.

Единственная цель изменений в Конституции — это как-то объяснить, почему Владимир Путин больше 20 лет не может выпустить из жадного кулака власть, данную ему однажды на 4 года. Это беда не Путина, к слову, а народа: на всем постсоветском пространстве, кроме самых цивилизованных республик (Украины, Грузии, немножко Армении) установилась та же ситуация: побултыхавшись немного без Генерального секретаря партии республики, помыкавшись со своей новой прогрессивной Конституцией самостоятельного государства, феодальное общество быстро заскучало и выдвинуло нового царька на веки вечные. И каждый из этих царьков по-своему объяснил своему народу, почему закон о смене власти конкретно к нему не относится. Ну там в Белоруссии он типа лучший хозяйственник и без него все развалится, в Туркмении — великий сын неба или кто он там, в Казахстане — отец народа великой степи, и так далее. Этот процесс кристаллизации местных царьков на обломках СССР идёт уже 30 лет, и мы привыкли. В России до последнего года пытались делать вид, что мы Европа и у нас все цивилизованно, без царьков, просто законы такие, что позволили чуть задержаться. Но в 2020 решили, что зачем цирк, расшаркивания и исходные схемы, если можно все обнулить без цирковых номеров и джигитовки. Тоже смешно, но речь не об этом. Затем были выделены деньги на рекламу — надо как-то объяснить народу, почему важно прийти и проголосовать за изменения в Конституции, которые касаются не его (народа), а одного лишь Путина. И понеслось... Это жалкое зрелище, когда задача поставлена, а как ее решить — креатива нет:

Какие нахуй семейные ценности будут в исправленной Конституции, каких не было в старой? Или вот совсем кризис мысли — котики. В любой непонятной ситуации рисуй котиков. Котиков все любят, проголосуют за котика, заодно и за поправки в Конституцию. Вид у котика на снимке совершенно охуевший, и его можно понять:

Какие нахуй отношения с животными регламентирует Конституция РФ?! Это же смех и портрет эпохи. А вот совсем уже прекрасно — волонтеры. Вообще волонтерское движение возникает по определению там, где не справляется власть. Поэтому в Конституции оно не прописано ни в какой. Ни в новой, ни в старой, ни в американской. Но мне всё-таки кажется, что художник тонко троллил, нарисовав добровольцев, закапывающих новую Конституцию нахуй:

The 1996 Ig Nobel Prize for biology was awarded to Anders Barheim and Hogne Sandvik of the University of Bergen, Norway, for their tasty and tasteful report, “Effect of Ale, Garlic, and Soured Cream on the Appetite of Leeches.” Recently, Bradley Allff, writing in Atlas Obscura, looked at the role medical leeches sometimes play in medicine in the USA. […]

Crazy-seeming research, every now and then, leads to something really, really wonder-filled. In this case, the discovery of something long-predicted (by Einstein) but seemingly impossible to perceive: gravity waves. (HT Maggie Lettvin)

[h/t Stephan Hurtubise]  

Dear Idea Seeker or Ally of the Idea Seekers, I have great news!  Greedy Cloud has been chased away and Spec and Tra discovered some new spring time house and garden items that he was hiding from everyone. Check them out in my house and garden, or go see Spec, Tra and Skeeter’s houses. Here […]

From the submitter:

The Antennae snapped off of our radio at work. We fixed it at first by putting a metal scraper on top, but when we needed to use it, the music was gone. I put the fork in the hole. Now it works almost as good as before!

What is this music crap you kids are listening to?

Submitter Denene's mechanic took this photo.

I recently received an email from Infolinks a contextual affiliate advertiser. It seems they want to expand their service and get more blogs and websites using their service. Now I have no problem with this and have found their services pretty good overall. However how they want to expand is by getting you to spam comments for them.

This is a Star Wars tribute video to the original movies using the song map of the problematique by Muse.

I get scam emails all the time, all claiming that I have untold riches waiting for me. All I need to do is fill out a simple form with either my credit card or social security information or simply send them a cheque to “release my money” It’s hard to imagine that anyone would buy into these scams, but they wouldn’t keep doing them if there wasn’t some poor sucker out there buying into it.

It doesn’t matter what website you’re looking at, every site online has something that naturally catches your attention. It could be a picture, a graphic, a video, there will be something that naturally stands out and gets your attention. If you’re looking at turning your website into a source of revenue you want your ads or products displayed in such a way that they grab your visitor’s attention. There are two ways you can go about doing this, the wrong way which is to force your ads on people which will drive them away from your site. Or using heat maps to attract your visitors to them without forcing them..........

Knowing how to start a fire without matches is an important skill you need to know. Personally I recommend you never venture into the woods be it a camping or hiking trip without a means to start a fire, such as a magnesium fire starter, or wind and waterproof matches. That being said, in a disaster or emergency situation you might not have access to those emergency supplies you have stored in your bug out bag or emergency survival kit.......................

The game Dead Island, a game set on a fictional tropical island where you get to kill zombies hasn’t had very much luck with its recent release. Those who’ve purchased the game on Steam downloaded an incorrect build of the game full of bugs and glitches. On top of that most couldn’t connect online to play multiplayer.............

NIH clinical trial testing antiviral remdesivir plus anti-inflammatory drug baricitinib for COVID-19 begins  National Institutes of HealthView Full coverage on Google News

1. In pictures: Last supermoon of 2020 rises on a world grappling to overcome pandemic  DAWN.com
2. May's flower moon lights up the sky around the globe  ABC News
3. Hurry up: Last chance to see a supermoon this year  Euronews
4. Last supermoon of the year, Photos News & Top Stories  The Straits Times
5. Stunning supermoon lights up New Zealand's skies overnight  New Zealand Herald
6. View Full coverage on Google News

1. Players to air concerns to Premier League executives over restart  The Guardian
2. Every Premier League Goal 2002/03: Baros and Murphy make their mark  Liverpool FC
3. Project Restart Q&A: What next for Premier League after government announcement?  Sky Sports
4. Premier League must be very careful or the empire will come crashing down  The Guardian
5. Premier League considering new broadcast access - including inside changing rooms  Daily Star
6. View Full coverage on Google News

1. In the midst of the coronavirus pandemic, China forces out foreign reporters  ABC News
2. China relations: ‘National security cowboys’ put nation’s interests at unnecessary risk  The Australian
3. Chinese buyers abandon Australian property, replaced by US investors: FIRB report  Domain News
4. Four Things to Know About China's Foreign-Investor Programs  Caixin Global
5. China to scrap foreign investment quotas in financial markets to lure more capital  The Star Online
6. View Full coverage on Google News

1. Barbaro family makes emotional plea as manhunt continues following death of Melbourne mum  9News
2. Ellie Price’s murder investigation ramps up as police from three states unite in manhunt for Ricardo Barbaro  7NEWS.com.au
3. 'Please come forward': Fugitive's step mum pleads for Ricardo Barbaro to make contact  The Age
4. Ricardo Barbaro’s stepmother pleads ‘please come forward’ as police continue manhunt  NEWS.com.au
5. Fugitive suspected of murdering Ellie Price, 26, in Melbourne had just got out of jail  Daily Mail
6. View Full coverage on Google News

"Mad Mike" Hughes, a self-styled explorer and daredevil bent on proving that the earth is flat was killed over the weekend when his homemade rocket crashed in the California desert over the weekend.

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What's your grandma cooking for Thanksgiving? These lucky people are dancing, parodying and rapping about all the delicious potential for tasty holiday foods.

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From the darkness emerges a boot. An old leather, steel-toed, work boot. It shouldn’t be there resting on the seafloor nearly two kilometers deep. I’m…