Covariance and contravariance | Fabulous adventures in coding

Posts about Covariance and contravariance written by ericlippert

Ask HN: What do people use to prevent crawlers? | Hacker News -
Ask HN: HNers who got their “Show HNs” on homepage, how is your site doing now? | Hacker News -
Ask HN: If you were a coder who successfully changed careers, what do you do now? | Hacker News -

Ask HN: What books had the greatest effect on how you structure your code? | Hacker News - t
GitHub - brannondorsey/wifi-cracking: Crack WPA/WPA2 Wi-Fi Routers with Airodump-ng and Aircrack-ng/Hashcat ? -
Bulma: a modern CSS framework based on Flexbox -

These are my links for July 20th through July 24th:

Ask HN: Best-architected open-source business applications worth studying? | Hacker News -
Monospaced Programming Fonts with Ligatures | Hacker News -
The language of choice - Propositional logic was discovered by Stoics around 300 B.C., only to be abandoned in later antiquity and rebuilt in the 19th century by George Boole’s successors. One of them, Charles Peirce, saw its significance for what we now call logic circuits, yet that discovery too was forgotten until the 1930s. In the ’50s John McCarthy invented conditional expressions, casting the logic into the form we’ll study here; then in 1986 Randal Bryant repeated one of McCarthy’s constructions with a crucial tweak that made his report “for many years the most cited paper in all of computer science, because it revolutionized the data structures used to represent Boolean functions” (Knuth).1 Let’s explore and code up some of this heritage of millennia, and bring it to bear on a suitable challenge: playing tic-tac-toe.
Then we’ll tackle a task that’s a little more practical: verifying a carry-lookahead adder circuit. Supposedly logic gets used all the time for all kinds of serious work, but for such you’ll have to consult the serious authors; what I can say myself, from working out the code to follow, is that the subject offers a fun playground plus the most primitive form of the pun between meaning and mechanism.

You’re encouraged to read with this article’s code cloned and ready

Absurdle, an adversarial version of Wordle January 15, 2022
it changes the word based on the possibility space; see also: HATETRIS from the same creator #
The Extraordinary Details of Tiny Creatures Captured with a Laser-Scanning Microscope by Igor Siwanowicz October 13, 2016
Acilius diving beetle male front tarsus (foot) 100x If you’ve ever wondered how a diving beetle swims through the water or manages to rest just on the surface, the answer is in part because its foot is infinitely more complicated than your own. As seen above, this microscopic image of a male Acilius sulcatus (diving […]
61 Glimpses of the Future July 13, 2016
Jan Chipchase is the founder of Studio D Radiodurans, which is sort of a modern day A-Team, except with more field research and fewer guns. For example, Chipchase is the sort of person who, for vacation, does not sip pina coladas in Bali but heads for "Kyrgyzstan, Tajikistan's GBAO region and China's western provinces". At […]
Building a race simulator October 4, 2014
One of the most fascinating aspects of modern Formula 1 is the use of computer simulations to predict car performances and race strategies. By the early 1990s, teams like Benetton had begun to develop simple race simulators to estimate optimal strategies. Today, teams develop highly sophisticated models based on massive amounts of telemetry data. Constructing mathematical […]
Photo August 20, 2014
Breathtaking Aerial Landscapes of Iceland by Sarah Martinet August 17, 2014
While on a recent trip to Iceland, photographer Sarah Martinet had the opportunity to shoot these amazing landscapes from a plane with open windows. You can see much more of her work (as well as more from this trip) on 500px and Facebook.

Chris's Digital Detritus

Videotext for the twenty first century.

Covariance and contravariance | Fabulous adventures in coding