"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?
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"
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.
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.
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.
(btw the "confusion" here was confusion about whether he had actually died. this comment was originally posted to https://news.ycombinator.com/item?id=47316880, which was the thread we merged hither)
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.
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.
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.
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.
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 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.
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`.
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?".
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.
Hoare's undergraduate degree from Oxford was in Literae Humaniores, nicknamed Greats - ancient Rome, ancient Greece, Latin, Ancient Greek, and philosophy. In the US, this course of study is usually called "Classics".
According to Wikipedia, "It is an archetypal humanities course."
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.
97 comments
[ 2.7 ms ] story [ 106 ms ] threadCan 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?
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.
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.
RIP good sir
Makes me think of an anecdote where Dijkstra said that he feared he would only be remembered for his shortest path algorithm.
That work contributes to static analysers' data flow analysis algorithms and is very widespread, even if it's in a limited capacity.
C#, gcc, clang, and even dmd, with my fast DFA engine, utilise it.
We can't all be using Astrée, far too expensive ;)
> 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.
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 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.
249 points by nextos 16 hours ago | 61 comments
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 can't remember what Oxford did to resolve this, but I think they settled on `C.A.R. Hoare Residence`.
RIP Sir Tony.
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.
Hoare's undergraduate degree from Oxford was in Literae Humaniores, nicknamed Greats - ancient Rome, ancient Greece, Latin, Ancient Greek, and philosophy. In the US, this course of study is usually called "Classics". According to Wikipedia, "It is an archetypal humanities course."
Sad to think that the TonyHoare process has reached STOP.
RIP.