HackerNews Summary (2023-06-06 08AM)

Source: boyter/cs: command line codespelunker or code search

Summary
Codespelunker (cs) is a command-line search tool to search over text or code files in the current directory, using boolean queries or regular expressions. It has a TUI and HTTP server interface, and ranks results on the fly.

Fact

🔎 Brute force calculation is done on the fly. There is no indexing involved.

🚀 Cs is reasonably fast and can search a checkout of the linux source code in ~2.5 seconds on a Macbook Air M1.

💻 It works on both text and code documents, with full support for .ignore and .gitignore files.

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Source: Counterexamples in Type Systems

at exhibit surprising behavior in statically-typed languages. Summary
This book is a collection of programs that exhibit impossible behavior in statically-typed languages. Each program comes with an explanation of what went wrong and references to the languages or systems in which the problem occurred.

Fact

💥 Some statically-typed programs can exhibit impossible behavior, such as memory corruption or unexpected crashes.

🧐 Type systems do local checks of a program’s source code to establish some global property about the program’s behavior.

🤔 Passing type checks does not necessarily guarantee a program’s behavior and some type systems can be unsound.

🕵️‍♀️ Statically-typed languages that claim to have sound type systems include Java, Haskell, and Rust.

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Source: Quanta Magazine

Summary
The difficulty of measuring circuit complexity made it unpopular among scientists. However, computer scientists have now realized its value in understanding the AdS/CFT duality. The translation from a black hole to a hot plasma is hard, making it expected that measurable physics quantities on one side are “unfeelable” on the other. However, the rate at which circuit complexity grows with time remains a challenge to understand.

Fact
💻 Circuit complexity is a valuable physical quantity to understand the AdS/CFT duality.
🔍 The difficulty of measuring circuit complexity is a result of the challenge of the black hole-to-plasma translation.
📈 The rate at which circuit complexity grows with time remains a challenge to understand.

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Source: Hierapolis sawmill

Summary
The water-powered Hierapolis sawmill in Asia Minor, dating back to 3rd century AD, had a crank and connecting rod mechanism recognised as the earliest machine of its kind. This corresponds with the machine combined with the crank slider mechanism.

Fact

🧰 Hierapolis sawmill in Asia Minor is the earliest machine to combine a crank with a connecting rod to form a crank slider mechanism.

📜 Literary evidence of water-powered sawmills similar to Hierapolis is found in Ausonius’ late 4th century AD poem Mosella and indicated by Christian saint Gregory of Nyssa from Anatolia.

🔙 First time all essential components of steam engine were assembled by one technological culture; millennia before steam engines were invented, all elements – such as Hero’s aeolipile, gearing, cylinder, piston, non-return valves and water mills – had already been recognised by the Romans.

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Source: ‘Guilt Tipping’: Pressure to tip everywhere has gotten out of control

Summary
Tablet-style tipping at counter-service spots such as coffee shops and fast food restaurants has become the norm, with touchscreens suggesting to add anywhere from 18% to 30%, or even higher, to your order. While some feel that there is no added service to justify tipping, others feel guilty and feel obligated to do so, but most agree that excessive tipping is not reasonable.

Fact

💰 Some wonder if businesses are doing this to pad their bottom line.

💻 The popular electronic payment process system Square lets business owners dole out the electronic tips in a variety of ways.

🧾 Unlike the old days when you might directly hand a 10-spot to your server, nobody seems to have a handle on where the counter-service tips go exactly.

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