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One of my favorite quotes: “There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies.”

I think about this a lot because it’s true of any complex system or argument, not just software.

Rest in peace, he hasn't seen the industry change.

"A consequence of this principle is that every occurrence of every subscript of every subscripted variable was on every occasion checked at run time against both the upper and the lower declared bounds of the array. Many years later we asked our customers whether they wished us to provide an option to switch off these checks in the interests of efficiency on production runs. Unanimously, they urged us not to they already knew how frequently subscript errors occur on production runs where failure to detect them could be disastrous. I note with fear and horror that even in 1980 language designers and users have not learned this lesson. In any respectable branch of engineering, failure to observe such elementary precautions would have long been against the law."

-- C.A.R Hoare's "The 1980 ACM Turing Award Lecture"

As Dijkstra was preparing for his end of life, organizing his documents and correspondence became an important task. Cancer had snuck up on him and there was not much time.

One senior professor, who was helping out with this, asked Dijkstra what is to be done with his correspondences. The professor, quite renowned himself, relates a story where Dijsktra tells him from his hospital bed, to keep the ones with "Tony" and throw the rest.

The professor adds with a dry wit, that his own correspondence with Dijsktra were in the pile too.

Fun story - at Oxford they like to name buildings after important people. Dr Hoare was nominated to have a house named after him. This presented the university with a dilemma of having a literal `Hoare house` (pronounced whore).

I can't remember what Oxford did to resolve this, but I think they settled on `C.A.R. Hoare Residence`.

He was the professor in the Programming Research Group (known universally as the PRG) at Oxford when I was doing my DPhil and interviewed me for the DPhil. I spent quite a bit of time with him and, of course, spent a lot of time doing stuff with CSP including my entire DPhil.

Sad to think that the TonyHoare process has reached STOP.

RIP.

The confusion is possibly almost appropriate, given so much of his work was on creating systems which avoid confusion through using proper synchronized communication channels. The null pointer stuff is famous, but it's occam and the Communicating Sequential Processes work that were brilliant. Maybe it's also brilliantly wrong, as I think Actor model people could argue, but it is brilliant.

My favourite quote of his is “There are two ways of constructing a piece of software: One is to make it so simple that there are obviously no errors, and the other is to make it so complicated that there are no obvious errors.”

While we hope it's not true, if it is a very deserved RIP.

Incredibly sad news. His contributions to the foundations of computing will remain relevant for generations to come.

I lucked in to meeting him once, in Cambridge. A gentle intellectual giant.

I repeatedly borrow this quote from his 1980 Turing Award speech, 'The Emperor's Old Clothes'... "At last, there breezed into my office the most senior manager of all, a general manager of our parent company, Andrew St. Johnston. I was surprised that he had even heard of me. "You know what went wrong?" he shouted--he always shouted-- "You let your programmers do things which you yourself do not understand." I stared in astonishment. He was obviously out of touch with present day realities. How could one person ever understand the whole of a modern software product like the Elliott 503 Mark II software system? I realized later that he was absolutely right; he had diagnosed the true cause of the problem and he had planted the seed of its later solution."

My interpretation is that whether shifting from delegation to programmers, or to compilers, or to LLMs, the invariant is that we will always have to understand the consequences of our choices, or suffer the consequences.

Tony's An Axiomatic Basis for Computer Programming[1] is the first academic paper that I read that I was able to understand when I was an undergrad. I think it unlocked something in me because before that I never believed that I would be able to read and understand scientific papers.

That was 35ish years ago. I just pulled up the paper now and I can't read the notation anymore... This might be something that I try applying an AI to. Get it to walk me through a paper paragraph-by-paragraph until I get back up to speed.

[1]:https://dl.acm.org/doi/10.1145/363235.363259

I remember attending a tech event at MSR Cambridge, and a speaker made some disparaging comment about older developers not being able to keep up in this modern world of programming.

An older gentleman stood up and politely mentioned they knew a thing or two.

That was Tony Hoare.

From his Oxford bio: "To assist in efficient look-up of words in a dictionary, he discovered the well-known sorting algorithm Quicksort."

I always liked this presentation. I think it's equally fine to say "invented" something, but I think this fits into his ethos (from what I understand of him.) There are natural phenomena, and it just takes noticing.

I've had the good fortune to attend two of his lectures in person. Each time, he effortlessly derived provably correct code from the conditions of the problem and made it seem all too easy. 10 minutes after leaving the lecture, my thought was "Wait, how did he do it again?".

RIP Sir Tony.

One of the greats. Invented quicksort and concurrent sequential processes. I always looked up to him because he also seemed very humble.

Tony advised me to make money with the software model checker I have been writing. In contrast to the typical practice to make these tools open source and free for use. Would have loved to learn more from him. He was a great teacher but also a great and sharp listener. Still remember the detour we made on the way to a bar in London, talking too much and deep about refinement relations. RiP.

Damn.

Tony Hoare was on my bucket list of people I wanted to meet before I or they die. My grad school advisor always talked of him extremely highly, and while I cannot seem to confirm it, I believe Hoare might have been his PhD advisor.

It's hard to overstate how important Hoare was. CSP and Hoare Logic and UTP are all basically entire fields in their own right. It makes me sad he's gone.

Sir Tony Hoare visited Institute for System Programming in Moscow and gave a lecture quarter of the century ago. It was unforgettable experience to see the living legend of your field. He was a senior person then already and today I am going to celebrate his long and wonderful life.

He came to give a lecture at UT Austin, where I did my undergrad. I had a chance to ask him a question: "what's the story behind inventing QuickSort?". He said something simple, like "first I thought of MergeSort, and then I thought of QuickSort" - as if it were just natural thought. He came across as a kind and humble person. Glad to have met one of the greats of the field!

Sad that his (and many others') dream of widespread formal verification of software never came true. He made really fundamental contributions to computer science but will probably be mostly known for quicksort and the quote about his "billion dollar mistake", not his decades-long program to make formal methods more tractable.

Makes me think of an anecdote where Dijkstra said that he feared he would only be remembered for his shortest path algorithm.

Random anecdote and Mr. Hoare (yep not a Dr.) has always been one of my computing heroes.

Mr. Hoare did a talk back during my undergrad and for some reason despite totally checked out of school I attended, and it is one of my formative experiences. AFAICR it was about proving program correctness.

After it finished during the Q&A segment, one student asked him about his opinions about the famous Brooks essay No Silver Bullet and Mr. Hoare's answer was... total confusion. Apparently he had not heard of the concept at all! It could be a lost in translation thing but I don't think so since I remember understanding the phrase "silver bullet" which did not make any sense to me. And now Mr. Hoare and Dr. Brooks are two of my all time computing heroes.

I first came across Tony Hoare about 24 years ago while learning C from The C Programming Language by Kernighan and Richie. I knew him only as C. A. R. Hoare for a long time. When I got on the Internet, it took me a while to realise that when people said Tony Hoare, it was the same person I knew as C. A. R. Hoare. Quoting the relevant text from the book:

> Another good example of recursion is quicksort, a sorting algorithm developed by C.A.R. Hoare in 1962. Given an array, one element is chosen and the others partitioned in two subsets - those less than the partition element and those greater than or equal to it. The same process is then applied recursively to the two subsets. When a subset has fewer than two elements, it doesn't need any sorting; this stops the recursion.

> Our version of quicksort is not the fastest possible, but it's one of the simplest. We use the middle element of each subarray for partitioning. [...]

It was one of the first few 'serious' algorithms I learnt to implement on my own. More generally, the book had a profound impact on my life. It made me fall in love with computer programming and ultimately choose it as my career. Thanks to K&R, Tony Hoare and the many other giants on whose shoulders I stand.

"Communicating Sequential Processes" by Tony Hoare: https://www.cs.cmu.edu/~crary/819-f09/Hoare78.pdf

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.

From the article:

> 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!

RIP.

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'.

I wrote both my master thesis and PhD on Hoare's Communicating Sequential Processes. I really enjoyed it's simplicity, expandability, and was always amazed that it inspired and influenced language constructs in Go, Erlang, occam and the likes.

https://news.ycombinator.com/item?id=47316880

249 points by nextos 16 hours ago | 61 comments

With respect I say that the one can only feel gobsmacked about how much complexity has grown.

In the 60s inventing one single algorithm with 10 lines of code was a thing.

If you did that today nobody would bat an eye.

Today people write game engines, compilers, languages, whole OS and nobody bats an eye cause there are thousands of those.

Quick sort isn't even a thing for leet code interviews anymore because it's not hard enough.

I saw a casual lecture given by Tony Hoare as a teenager. The atmosphere was warm and welcoming, even if I didn't fully understand all of the content. I remember he was very kind and answered my simple questions politely.

Tony Hoare on how he came up with Quicksort:

he read the algol 60 report (Naur, McCarthy, Perlis, …)

and that described "recursion"

=> aaah!

https://www.youtube.com/watch?v=pJgKYn0lcno

unless its greatly exagerated - he was quite mind sharp in his 80s

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.

“I never had a doctorate, so I had to make do with Quicksort.” —Sir Tony Hoare (unpublished interview for Algorithms to Live By)

RIP: https://youtu.be/tAl6wzDTrJA

I watched this video a few months ago.

Virtual HLF 2020 – Scientific Dialogue: Sir C. Antony R. Hoare/Leslie Lamport

https://www.youtube.com/watch?v=wQbFkAkThGk

This is devastating news.

When I started university he gave a talk to all the new CompScis which as you can imagine was incredibly inspirational for an aspiring Software Engineer.

Grateful to have had that experience.

RIP

Never made it as a wise man I couldn't cut it as a poor man stealing Tired of livin' like a blind man I'm sick of sight without a sense of feeling And this is how you remind me

This is how you remind me of what I really am This is how you remind me of what I really am

It's not like you to say sorry I was waitin' on a different story This time I'm mistaken For handing you a heart worth breakin' And I've been wrong, I've been down Been to the bottom of every bottle These five words in my head Scream, "Are we havin' fun yet?"

Yet, yet, yet, no, no Yet, yet, yet, no, no

It's not like you didn't know that I said, "I love you," and I swear I still do And it must have been so bad 'Cause livin' with me must have damn near killed you

And this is how you remind me of what I really am This is how you remind me of what I really am

It's not like you to say sorry I was waitin' on a different story This time I'm mistaken For handing you a heart worth breakin' And I've been wrong, I've been down Been to the bottom of every bottle These five words in my head Scream, "Are we havin' fun yet?"

Yet, yet, yet, no, no Yet, yet, yet, no, no Yet, yet, yet, no, no Yet, yet, yet, no, no

Never made it as a wise man I couldn't cut it as a poor man stealin' And this is how you remind me This is how you remind me

This is how you remind me of what I really am This is how you remind me of what I really am

It's not like you to say sorry I was waitin' on a different story This time I'm mistaken For handing you a heart worth breakin' And I've been wrong, I've been down Been to the bottom of every bottle These five words in my head Scream, "Are we havin' fun yet?"

Yet, yet, are we havin' fun yet? Yet, yet, are we havin' fun yet? Yeah, yeah (These five words in my head scream) Are we havin' fun yet? Yeah, yeah (These five words in my head) No, no

Absolutely the GOAT of concurrency. May his ring never die.

One of Billy Crystal's later standup bits was talking about how his parents have hit an age where their favorite game with their friends is called, "Guess Who Died". I've been thinking about that bit an awful lot the last couple of years.

1) ACM published this book in 2021; Theories of Programming: The Life and Works of Tony Hoare - https://dl.acm.org/doi/book/10.1145/3477355

See the "preface" for details of the book - https://dl.acm.org/doi/10.1145/3477355.3477356

Review of the above book - https://www.researchgate.net/publication/365933441_Review_on...

Somebody needs to contact ACM and have them make the above book freely available now; there can be no better epitaph.

2) Tony Hoare's lecture in honour of Edsger Dijkstra (2010); What can we learn from Edsger W. Dijkstra? - https://www.cs.utexas.edu/~EWD/DijkstraMemorialLectures/Tony...

Somebody needs to now write a similar one for Hoare.

Truly one of the absolute greats in the history of Computer Science.

He was a professor at my old alma mater, Queen's University of Belfast. I remember hearing a story about him going to Harvard to give a lecture and, as he was presented, one of their professors referred to himself as the "Hoare of Harvard"

always knew him as C.A.R. Hoare, takes me way back to freshman college years

RIP good sir

Assert early, assert often!

"The null reference was my billion dollar mistake responsible for innumerable errors, vulnerabilities and system crashes" (paraphrasing). I don't know. This design choice exposed the developer to system realities, and modern language approaches are based on decades of attempts to improve on it, and they are not necessarily better. Safer yes, but more weighty.

Can anyone suggest a better approach for a situation like this in the future? What's better than exposing addressing the problem with a light solution?

One of the greatest figure of computing in history and an example of humility as a human.

Thank you for your work on ALGOL, you were multiple decade ahead of your time.

Rest in peace.

RIP Sir Tony Hoare

Turing Award Legend.

RIP Legend

Rest in peace.

Rest in peace

How many jobs were had or not due to the candidates ability to implement his algorithms?

Needs a black bar!

this is black bar grade great. give us black bar