Posted by speckx 7 hours ago
It had intrigued me due to its promise of designing lock-free concurrent systems, that can (I think) also be proven to be deadlock-free.
You do this by building a simple concurrent block that is proven to work correctly, and then build bigger ones using the smaller, proven blocks, to create more complex systems.
The way it is designed is processes don't share data and don't have locks. They use synchronized IPC for passing and modifying data. It seemed to be a foundational piece for designing reliable systems that incorporate concurrency in them.
249 points by nextos 16 hours ago | 61 comments
His presentation on his billion dollar mistake is something I still regularly share as a fervent believer that using null is an anti-pattern in _most_ cases. https://www.infoq.com/presentations/Null-References-The-Bill...
That said, his contributions greatly outweigh this 'mistake'.
Without things like null pointers, goto, globals, unsafe modes in modern safe(r) languages you can get yourself into a corner by over designing everything, often leading to complex unmaintainable code.
With judicious use of these anti-patterns you get mostly good/clean design with one or two well documented exceptions.
You just don't need it but it isn't there as some sort of "escape hatch" it's more out of stubbornness. Languages which don't have it are fine, arguably easier to understand by embracing structure more. I happen to like Rust's "break 'label value" but there are plenty of ways to solve even the trickier parts of this problem (and of course most languages aren't expression based and wouldn't need a value there).
The OpenJDK HashMap returns null from get(), put() and remove(), among others. Is this just because it hasn't been reviewed enough yet?
Code reviews 'somehow' strip out poorly thought out new uses of escape hatches.
For your example, it would be an use of get, put or remove without checking the result.
SIR_TONY_HOARE = μX • (think → create → give → X)
-- process ran from 1934 to 2026 -- terminated with SKIP -- no deadlock detected -- all assertions satisfied -- trace: ⟨ quicksort, hoare_logic, csp, monitors, -- dining_philosophers, knighthood, turing_award, -- billion_dollar_apology, structured_programming, -- unifying_theories, ... ⟩ -- trace length: ∞ The channel is closed. The process has terminated. The algebra endures.
> On the topic of films, I wanted to follow up with Tony a quote that I have seen online attributed to him about Hollywood portrayal of geniuses, often especially in relation to Good Will Hunting. A typical example is: "Hollywood's idea of genius is Good Will Hunting: someone who can solve any problem instantly. In reality, geniuses struggle with a single problem for years". Tony agreed with the idea that cinema often misrepresents how ability in abstract fields such as mathematics is learned over countless hours of thought, rather than - as the movies like to make out - imparted, unexplained, to people of 'genius'. However, he was unsure where exactly he had said this or how/why it had gotten onto the internet, and he agreed that online quotes on the subject, attributed to him, may well be erroneous.
Somewhat off-topic, but it's cool hearing this from someone who's contributed so much to the fields of programming and mathematics. It makes me hopeful that my own strugglings with math will pay out over time!
he read the algol 60 report (Naur, McCarthy, Perlis, …)
and that described "recursion"
=> aaah!
Virtual HLF 2020 – Scientific Dialogue: Sir C. Antony R. Hoare/Leslie Lamport