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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.
This is indeed a great quote (one of many gems from Sir Tony) but I think the context that follows it is also an essential insight:
> The first method is far more difficult. It demands the same skill, devotion, insight, and even inspiration as the discovery of the simple physical laws which underlie the complex phenomena of nature. It also requires a willingness to accept objectives which are limited by physical, logical, and technological constraints, and to accept a compromise when conflicting objectives cannot be met. No committee will ever do this until it is too late.
(All from his Turing Award lecture, "The Emperor's Old Clothes": https://www.labouseur.com/projects/codeReckon/papers/The-Emp...)
"At first I hoped that such a technically unsound project would collapse but I soon realized it was doomed to success. Almost anything in software can be implemented, sold, and even used given enough determination. There is nothing a mere scientist can say that will stand against the flood of a hundred million dollars. But there is one quality that cannot be purchased in this way-- and that is reliability. The price of reliability is the pursuit of the utmost simplicity. It is a price which the very rich find most hard to pay."
This explain quite a lot actually!
Very poignant, thank you. I can see my absolute core principle - KISS reflected in this. I still struggle to find a single use in my career where it wouldn't be the best approach, especially long term.
From the linked lecture, which I printed out to read as part of a new less is more screen time management regime (where I print out longer form writing for reading) I found this very interesting tidbit in the context of Tony having made a delivery miscalculation and his team failing to deliver on one of their products; which is where I think a lot people are today with LLMs:
"Each of my managers explained carefully his own theory of what had gone wrong and all the theories were different. 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. "
"No committee will ever do this until it is too late."
The software I like best was not written by "teams"
I prefer small programs written by individuals that generally violate memes like "software is never finished" and "all software has bugs"
(End user perspective, not a developer)
One of my biggest accomplishments was shipping a suite of 5 apps from four divisions where three of them resented each other’s existence and seemed bound and determined to build rules in the system that made sure the other two couldn’t function. Which made no goddamn sense because it was a pipeline and you can’t get anything out one end if it gets jammed in the middle.
I was brought in to finish building the interchange format. The previous guy was not up to snuff. The architect I worked for was (with love) a sarcastic bastard who eventually abdicated about 2 rings of the circus to me. He basically took some of the high level meetings and tapped in when one of us thought I might strangle someone.
Their initial impression was that I was a prize to be fought over like a child in a divorce. But the guy who gives you your data has you by the balls, if he is smart enough to realize it, so it went my way nine times out of ten. It was a lot of work threading that needle, (I’ve never changed the semantics of a library so hard without changing the syntax), but it worked out for everyone. By the time we were done the way things worked vs the way they each wanted it to work was on the order of twenty lines of code on their end, which I essentially spoonfed them so they didn’t have a lot of standing to complain. And our three teams always delivered within 15% of estimates, which was about half of anyone else’s error bar so we lowly accreted responsibilities.
I ended up as principal on that project (during a hiring/promotional freeze on that title. I felt bad for leaving within a year because someone pulled strings for that, but I stayed until I was sure the house wouldn’t burn down after I left, and I didn’t have to do that). I must have said, “compromise means nobody gets their way.” About twenty times in or between meetings.
These are the projects that give us confidence.
Also, this software is free. Generally the authors were not paid to write it
It's the committee vs the dictator issue - a small driven individual (or group) can achieve a lot, but they can also turn into tyrants.
A committee forms when there's widespread disagreement on goals or priorities - representing stakeholders who can't agree. The cost is slower decisions and compromise solutions. The benefit is avoiding tyranny of a single vision that ignores real needs.
We are poorer for him having waited to drop that sentence at his Turing Award acceptance speech. I use it all the time.
Tony might be my favorite computer scientist.
There was an article posted here a few weeks ago titled "Nobody Gets Promoted for Simplicity."
I've been thinking about it a lot, and now, in turn, the memory of Mr. Hoare.
It seems that with vibe coding our industry has finally, permanently embraced the latter approach. RIP Tony.
> permanently
don't bet on it
Can’t argue with the quote. However my current boss has been pushing this to the extreme without much respect for real-world complexities (or perhaps I’m too obtuse to think of a simple solution for all our problems), which regrettably gives me a bit of pause when hearing this quote.
Reminds me of another good one: Make everything as simple as possible, but not simpler. (-- probably not Einstein)
aged very well
Reminds me of this Pascal quote: "I would have written a shorter letter, but I did not have the time."
https://www.npr.org/sections/13.7/2014/02/03/270680304/this-...
"Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away."
Antoine de Saint-Exupéry
"The greatest ideas are the simplest."
- William Golding
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Reminds me of this quote... “A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work.”
https://en.wikipedia.org/wiki/John_Gall_(author)#Gall's_law
The book is well worth reading.
Seconded.
Someone once described Systemantics as the book that systwm designers read under the covers at night with a torch.
or should do!
Reading it now on Kindle Scribe without the help of AI ;-).
When I am done, I might simply replace SOUL.md with it and move on.
https://openlibrary.org/books/OL4904457M/Systemantics
(Systemantics is available for borrowing, Systems Bible is not yet, a copy has been sent for digitizing)
One of the policies of The Rhinoceros Party in Canada was to increase the complexity of the taxation system so much that nobody could find the loopholes to exploit.
Had to look them up (WP), wasn't disappointed. We have the Monster Raving Loony Party in the UK.
One of the Rhino's Party policies stands out - are you sure Trump wasn't born a Cannuck and was stolen at birth by racoons and smuggled down south?
"Annexing the United States, which would take its place as the third territory in Canada's backyard (after the Yukon and the Northwest Territories—Nunavut did not yet exist), in order to eliminate foreign control of Canada's natural resources"
I like them
Good thing we now have technology that allows us to crank out complex software at rates never-before seen.
Complex software full of very obvious deficiencies that nobody bothered to look for.
It can also be used to simplify existing code bases.
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.
What is the equivalent of correspondence today?
I guess back then each letter had a cost, in (delivery) time and money, so you better make it count.
My guess is that these correspondences were often interesting to read because they had to be worthwile to send because of the associated cost.
Time of delivery would be the biggest factor. Today we can send multiple quick messages to anyone, at that time people had to batch big discussions in a long articulated text, since it would take days to it arrive.
I guess the closest to that nowadays would be blog articles, RFC discussions or long-form email threads.
John Backus had some correspondence with Dijkstra that's worth a read: https://medium.com/@acidflask/this-guys-arrogance-takes-your...
Incredible letters, thanks for sharing. I wish some of this correspondence was published in physical books. What a joy it would be to read.
There's that immortal Alan Kay line "arrogance in computer science is measured in nano Dijkstras".
That's a famous quote and age might have mellowed him. But he was not like that at all in person with his students. He did insist that one be precise with ones words.
The origin of the quote may have more to do with cultural differences between the Dutch and Americans.
That's a great point which never occurred to me about Dijkstra, even though I knew where he came from. My father in law used to like this joke: "He was Dutch and behaved as such."
I feel there is a tension between computer science is math and computer science is plumbing.
Why not the both?
Some seem to think that math is somehow above plumbing, but modern society couldn't exist without both, and I'd argue that modern plumbing is more critical to our health and well being than modern math.
plumbing is one of those inventions that's so old we forget its importance
The plumber knows how many inches per foot the pipe has to drop in order for the poop to flow away and not get stuck in the pipe. It's easy enough to either not drop it enough and everything gets stuck or for it to drop too much and the water flows away but the poop stays in place. And they're the ones that actually make it happen and their clients really do care about that in the end. Without knowing this the plumber is nothing. They don't necessarily need to know they why and especially don't need to calculate it out!
Some mathematician can probably calculate that properly. Some mathematician probably first did calculate that out to prove it. I'm not entirely certain that a mathematician was the reason that we know what drop we need. A lot of things in "real life" were "empirically discovered" and used and done for centuries before a mathematician proved it.
Exceptions prove the rule, like when we calculate(d) things out for space travel before ever attempting it ;)
I’d want to see an example of Dijkstra’s “arrogance” that wasn’t justified.
The “truths that might hurt” essay is a great example. Yeah, the truth hurts for many people. People don’t like being called out on their folly, particularly if it’s something they don’t personally control. That Durant make it “arrogant” to point it out.
Also, Alan Kaye is overrated. Object orientation is one of those painful truths.
Object orientation is a great tool and I wouldn't be without it. But like all tools it has to be applied in the right way in the appropriate situation and is not universally useful.
I'm less concerned about "justified" and more about "useful". If you behave offensively to everyone around you, then you have become your own worst enemy in the war of ideas.
Ignaz Semmelweis was right. He also died in an asylum, having utterly failed to convince doctors to wash their hands between patients.
Alan Kay himself said this quote is taken out-of-context and so people need to stop repeating it - https://news.ycombinator.com/item?id=11799963
The quote makes much more sense as an in-joke between two like-minded people, because Alan Kay isn't exactly humble himself nor does he avoid provocative statements.
And speaking as a Dutch man, given the kind of humor we have I'm pretty certain Dijkstra appreciated a good roast like that too.
The actual context is in this video where Kay makes the comment - https://news.ycombinator.com/item?id=47328782
Have seen that presentation, but that still does not give the full context. At least, I don't think it is obvious from the video alone whether this remark was a friendly jab between friends, or whether it was a stereotypical vicious academic back-and-forth between to big names in a field.
I think this is the sequence that led to the quote.
1) People are miffed with Dijkstra due to his abrasive style.
2) John Backus has a back-and-forth with Dijkstra where he calls him arrogant.
3) The community knows of the above.
4) Dijkstra writes paper comparing Computer Science approaches in Europe vs. USA in his usual sharp style.
5) American Scientists perceive the above as dissing them and take umbrage.
6) Alan Kay writes a paper rebutting Dijkstra's paper pointing out that most of the Software is written on the American side.
7) Alan Kay then disses Dijkstra with this quote half-in-annoyance/half-tongue-in-cheek.
> and so people need to stop repeating it
That would seem to be your sentiment, not his, based on the link you shared. Rather than being censorious he shared a nice story on the matter.
No, it is not my sentiment nor am i being censorious.
It can be inferred from Kay's own words. He probably was just poking fun in a tongue-in-cheek manner often seen amongst larger-than-life figures.
John Backus called Edsger Dijkstra arrogant since the latter was highly critical of the former's research in functional programming (not the substance but the hyping). Kay was probably riffing off of that.
The problem is that a lot of noobs/kids/oldies-who-should-know-better often dismiss(!) Dijkstra's work because of this silly quote. Thus in this case, a "nice story" is actually an obstacle to people reading Dijkstra.
> Kay was probably riffing off of that.
You don't need to hypothesize about all this, to put things in their proper context you could listen to the speech where he famously said it.
Yeah, i knew of the video. That somewhat proves the point i make here - https://news.ycombinator.com/item?id=47331352
People only focus on that phrase since it makes a nice "talking point" and ignore all the other interesting things from Kay's talk. For example; i never knew that most of Euler's proofs were wrong w.r.t. rigorous approach as defined today!
> It can be inferred from Kay's own words. He probably was just poking fun in a tongue-in-cheek manner often seen amongst larger-than-life figures.
...is that not obvious from the original quote? Maybe it's a cultural difference (I'm from Ireland), but that's how I've always interpreted and it's never occurred to me that people took it seriously or as anything other than tongue in cheek.
The problem is with folks who don't know/have never read (seriously that is) Dijkstra.
For example, every time somebody posts something about Dijkstra on HN/etc. somebody will trot out this silly quote and then others pile on (since it requires no effort) and derail any interesting conversation.
It is human nature to have an opinion on everything and mediocrity often takes great pleasure in tearing down the greats (i mean the true ones) in order to soothe their own egos (since they know they don't measure up) i.e. "see? the great one is as flawed/mundane as us and i am showing him up".
And Dijkstra was Dutch who are famously known to be blunt which is often perceived as arrogance by others :-)
Weirdly, that ten-year-old Alan Kay comment is shown as "1 day ago" by HN.
Oof - not sure what happened there but it was probably a fat-fingered thing from me merging today's threads. Fixed now. Thanks for the heads-up!
That's a wild ride of passive aggressive academia in a field I know something about. A rare treat. Thanks for sharing!
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`.
There's the Tony Hoare Room [1] in the Robert Hooke Building. We held our Reinforcement Learning reading group there.
[1] https://www.cs.ox.ac.uk/people/jennifer.watson/tonyhoare.htm...
>our Reinforcement Learning reading group there //
Anyone else, like me, imagining ML models embodied as Androids attending what amounts to a book club? (I can't quite shake the image of them being little CodeBullets with CRT monitors for heads either.)
The CB reference is appreciated, he isn't talked about enough here
I had countless lectures and classes there
Our Graphics Lab at University used to be in an old house opposite a fish and chip shop. The people at the fish and chip shop were suspicious of our lab as all they saw was young men (mostly) entering and leaving at all hours of the night. We really missed an opportunity to name it "Hoare House" after one of our favourite computer scientists.
Cowards.
I was awarded the CAR Hoare prize from university, which is marginally better than the hoare prize I suppose
Shame the university takes itself so seriously. The illustrative example of overloading would have been pertinent to his subject of expertise.
I mean, I like puns but they're a flash in the pan. Jokes get old after a while and you don't want to embed them in something fairly permanent like a building name.
This particular word for the oldest profession goes back to Old English. I am fairly sure it would outlive the building.
If the problem is when the joke lives on amusing undergrads long after you've tired of it, that just makes it worse.
Wait until they hear about what Magpie Lane in Oxford used to be called.
A historical bawdy pun is one of the most Oxfordian things I can think of. If we can incorporate a man in drag, we're in real business.
"Surely you've all heard of the Hoare house on campus?" seems like a pretty timeless way to a) keep people from dozing off during that bit of lecture b) cause a whole bunch of people to remember who this guy was and what he did.
"Hoare House" would trigger millions of idiots, from rude little children to pontifying alpha ideologues. In perpetuity.
The University was correct in saying "nope" to the endless distractions, misery, and overhead of having to deal with that.
Imagine being a world-famous computer scientist and dying and one of the top threads in a discussion of your life is juvenile crap about how your name sounds like "whore".
Chill out, I doubt he would've minded and humorous anecdotes are great ways to grieve
Imagine being an adult human but not being able to extract a tiny chuckle from such a silly thing.
Well, I do have a rather special last name which makes me susceptible.
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GP is well known, you really needn't guess if you're that fascinated.
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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.
I think I and most people had hoped that he would DIV instead.
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.
> I realized later that he was absolutely right
It would have been fun if he’d directly said “You’re absolutely right!”
"Around Easter 1961, a course on ALGOL 60 was offered in Brighton, England, with Peter Naur, Edsger W. Dijkstra, and Peter Landin as tutors. I attended this course with my colleague in the language project, Jill Pym, our divisional Technical Manager, Roger Cook, and our Sales Manager, Paul King. It was there that I first learned about recursive procedures and saw how to program the sorting method which I had earlier found such difficulty in explaining. It was there that I wrote the procedure, immodestly named Quicksort, on which my career as a computer scientist is founded. Due credit must be paid to the genius of the designers of ALGOL 60 who included recursion in their language and enabled me to describe my invention so elegantly to the world. I have regarded it as the highest goal of programming language design to enable good ideas to be elegantly expressed." - C.A.R Hoare, The Emperor's Old Clothes, Comm. ACM 24(2), 75-83 (February 1981).
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.
Followup on the above with these two classics;
Retrospective: An Axiomatic Basis For Computer Programming. This was written 30 years after An Axiomatic Basis for Computer Programming to take stock on what was proven right and what was proven wrong - https://cacm.acm.org/opinion/retrospective-an-axiomatic-basi...
How Did Software Get So Reliable Without Proof? More detailed paper on the above theme (pdf) - https://6826.csail.mit.edu/2020/papers/noproof.pdf
Thanks for the recommendation. I downloaded both social.pdf and noproof.pdf on my Kindle Scribe to read them carefully and revisited the discussions on EWD638 and EWD692.
It is very interesting to see how Sir Tony diverged from EDW: one is right in theoretical sense but cynical about human fallacies and how the society is heading towards more wasteful complexity, one is to live with it and stay optimistic.
There is a proverb in Chinese Taoism:
小隱隱於野，大隱隱於市
A small recluse hides in the wild, while a great recluse hides in the city
Nice comparison of Hoare vs. Dijkstra.
Hoare was more focused and diplomatic while Dijkstra was more of a free-ranging philosopher.
I still remember the first time i came across Hoare Logic/Triple and Dijkstra's GCL/Weakest precondition, understanding nothing and feeling like a complete dolt.
As a young'un i thought knowing the syntax of a language and learning some idioms/patterns was all you needed for programming. Reading Hoare/Dijkstra showed me where mathematical theory met programming practice.
I can recommend NotebookLM [1] for reading through scientific papers. You can then ask it questions and even get a podcast generated.
Please don't, can't we just have one thread without this shit
One of the greats. Invented quicksort and concurrent sequential processes. I always looked up to him because he also seemed very humble.
He also invented many other things, like enumeration types, optional types, constructors. He popularized the "unions" introduced by McCarthy, which were later implemented in ALGOL 68, from where a crippled form of them was added to the C language.
Several keywords used in many programming languages come from Hoare, who either coined them himself, or he took them from another source, but all later programming language designers took them from Hoare. For example "case", but here only the keyword comes from Hoare, because a better form of the "case" statement had been proposed first by McCarthy many years earlier, under the name "select".
Another example is "class" which Simula 67, then all object-oriented languages took from Hoare, However, in this case the keyword has not been used first by Hoare, because he took "class", together with "record", from COBOL.
Another keyword popularized by Hoare is "new" (which Hoare took from Wirth, but everybody else took from Hoare), later used by many languages, including C++. At Hoare, the counterpart of "new" was "destroy", hence the name "destructor", used first in C++.
The paper "Record Handling", published by C.A.R. Hoare in 1965-11 was a major influence on many programming languages. It determined significant changes in the IBM PL/I programming language, including the introduction of pointers . It also was the source of many features of the SIMULA 67 and ALGOL 68 languages, from where they spread in many later programming languages.
The programming language "Occam" has been designed mainly as an implementation of the ideas described by Hoare in the "Communicating Sequential Processes" paper published in 1978-08. OpenMP also inherits many of those concepts, and some of them are also in CUDA.
And, of course, the Go programming language.
I would not say he invented Go, although Go is probably the only relevant implementation of CSP nowadays.
I was adding Go to the list at the very end of the comment:
>OpenMP also inherits many of those concepts, and some of them are also in CUDA.
And regretful inventor of the null reference!
His “billion dollar mistake”:
https://www.infoq.com/presentations/Null-References-The-Bill...
The mistake was not null references per se. The mistake was having all references be implicitly nullable.
He states around minute 25 the solution to the problem is to explicitly represent null in the type system, so nullable pointers are explicitly declared as such. But it can be complex to ensure that non-nullable references are always initialized to a non-null value, which is why he chose the easy solution to just let every reference be nullable.
I think even having references that aren't necessarily null is only part of it. Image that your language supports two forms of references, one nullable, one not. Let's just borrow C++ here:
&ref_that_cannot_be_null
*ref_that_can_be_null
ref_that_can_be_null->thing()
It's an error that can be caught by the type system (any number of other languages demonstrate that), and null pointer derefs are one of those bugs that just plague the languages that have it.
TypeScript actually supports nulls through type unions, exactly as Hoare suggests. It will not let you derefence a possibly-null value without a check.
C# also supports null-safety, although less elegantly and as opt-in. If enabled, it won’t let you deference a possibly-null reference.
> If enabled, it won’t let you deference a possibly-null reference.
It will moan, it doesn't stop you from doing it, our C# software is littered with intentional "Eh, take my word for it this isn't null" and even more annoying, "Eh, it's null but I swear it doesn't matter" code that the compiler moans about but will compile.
The C# ecosystem pre-dates nullable reference types and so does much of our codebase, and the result is that you can't reap all the benefits without disproportionate effort. Entity Framework, the .NET ORM is an example.
You can certainly set unsafe null dereferencs to be a compiler error in C#. It is just not the default for reasons of backwards compatibility.
Add WarningsAsErrors for prject and you are done.
The null reference was invented by Hoare as a means to implement optional types, which works regardless of their binary representation.
Optional types were a very valuable invention and the fact that null values have been handled incorrectly in many programming languages or environments is not Hoare's fault.
Having "Optional types" only makes sense if your type system is powerful enough.
There are two ways this might happen, both will solve the Billion Dollar Problem but I think one is the clear winner. The first way is explicit optionality, often retro-fitted to languages for example in C# the difference between the types Goose and Goose? are that (in a suitable C# project enabling this rule) the first one is always a Goose and the second might be null instead.
The second way is if you have Sum types you can just add "or it's null" to the type.
I think sum types are better because they pass my "three purposes" rule where I can think of not one (Option<T> replaces optionality) or two (Result<T,E> for error handling) but at least three (ControlFlow<B, C> reifies control flow) distinct problems I don't need separate solutions for any more if I have this feature.
If your type system is too weak you suffer the Billion Dollar problem with Hoare's idea and perhaps if this "feature" had never been invented we'd have all migrated to languages with a better type system decades ago.
I agree that for the correct use of both Optional types and Sum types (a.k.a. Union types) a type system that is powerful enough is essential. Moreover, a convenient syntax is also important.
In my opinion, besides being passed as arguments of functions whose parameters are declared as having the corresponding Optional or Sum type, there is only one other permissible use of values of such types.
Variables of an Optional type shall be allowed in the Boolean expression of an "if" or equivalent conditional statement/expression, while variables of a Sum type shall be allowed in an expression that tests which is the current type in a select/case/switch or whatever is the name used for a conditional statement or expression with multiple branches.
Then in the statements or expressions that are guarded by testing the Optional- or Sum-type variable, that variable shall be used as having the corresponding non-optional type or the type among those possible for a Sum type that has been determined by the test.
This syntax ensures that such variables will not be misused, while also avoiding the excessive and unhelpful verbosity that exists in some languages.
I disagree. Only true is true and only false is false, Some(1234) isn't true and None isn't false, for the same reason the string "A" isn't the ASCII byte 'A' and the 8-bit unsigned integer 10 isn't the 64-bit floating point number 10.0
When you muddle these things it makes life very slightly easier, very briefly and then you introduce impossible to find bugs and ruin your life. People tend to imagine that OK, maybe C went too far with coercions, but I can handle smaller things, that'll be fine, and in my experience they're wrong.
I like the fact that in Rust I'm expected to write if opt.is_none() rather than just treat it as if it was a boolean when it isn't. The resulting machine code isn't different, so we're talking about communicating our intent to human programmers, such as our future selves or our colleagues and I'm certain opt.is_none() communicates that intent better than coercing it to a boolean.
I don't like the other idea you propose, but it's less of a footgun and so I don't mind that e.g. C# programmers often write this way. I wouldn't choose it myself in many cases, but I don't write "No, fix this" in reviews of such code.
I'm pretty sure that this is not true. I talked to Bud Lawson (the inventor of the pointer) and he claimed that they had implemented special behaviour for null pointers earlier. When I talked to Tony later about it, he said he had never heard of Bud Lawson. So probably both invented them independently, but Bud came first.
If we start playing the "who was first" game, then for the Soviet machine Kiev (Kyiv), an "address language" with a "prime operation" was created in 1957-59.
The prime operation and address mapping.
The prime operation defines a certain single‑argument function. Its symbol (a prime mark) is written above and to the left of the argument: 'a = b where a is the argument and b is the result of the operation. This is read as: "prime a equals b" (or "b is the contents of a"). The argument a is called an address, and the function value b is called the contents of the address. The prime function ' defines a mapping from the set of addresses A to the set of contents B, which we will call an address mapping.
Page 36, chapter III https://torba.infoua.net/files/kateryna-yushchenko/Vychislit...
Pointers and indirect addressing were used in assembly languages and machine languages much earlier than that, perhaps even in some relay-based computers.
In any case, by 1954 already most or all electronic computers used this.
The only priority questions can refer to which are the first high-level programming languages that have used pointers.
In my opinion the first language having pointers with implicit dereferencing was CPL, published in 1963-08, and the first language having pointers with explicit dereferencing was Euler, published completely in 1966-01, but this feature had already been published in 1965-11. The first mainstream programming language, with a large installed base, which had pointers, was the revised IBM PL/I, starting with its version from 1966-07.
Thanks for the link to the book describing the "Kiev" computer. It seems an interesting computer for the year 1957, but it does not have anything to do with the use of pointers in high-level programming languages.
At the page indicated by you there is a description of what appears to be a symbolic assembler. The use of a symbolic assembly language was a great progress at that early date, because many of the first computer programs had been written directly in machine language, or just with a minimal translation, e.g. by using mnemonics instead of numeric opcodes.
However this does not have anything to do with HLL pointers and means to indicate indirect addressing in an assembly language have existed earlier, because they were strictly necessary for any computed that provided indirect addressing in hardware.
In the very first computers, the instructions were also used as pointers, so a program would modify the address field of an instruction, which was equivalent to assigning a new value to a pointer, before re-executing the instruction.
Later, to avoid the re-writing of instructions, both index registers and indirect addressing were introduced. Indirect addressing typically reserved one bit of an address to mark indirection. So when the CPU loaded a word from the memory, if the indirect addressing bit was set, it would interpret the remainder of the word as a new address, from which a new word would be loaded. This would be repeated if the new word also had the indirection bit set.
The assembly languages just had to use some symbol to indicate that the indirection bit must be set, which appears to have been "prime" for "Kiev".
Pity you didn't look a little further, where there was more syntax and semantics... The concept of a high-level language is, of course, relative, but if, for example, someone considers Forth to be an HLL, then imho, the language/formalism from the book about the Kiev machine was definitely one, and it was described in more detail by its chief architect, Katherine Yushchenko, in a book from 1963: https://it-history.lib.ru/TEXTS/Adresnoe-programmirovanie_EY...
If you are still interested, you can look at page 35, where there are several examples, including finding the GCD.
> the first language having pointers with explicit dereferencing was Euler, published completely in 1966-01
I could only find a manual for PDP-10 Euler with references. Do you have a source for an Euler with pointers?
"Reference" was the original term used in the languages derived from ALGOL for what is now called "pointer".
The distinction that exists in C++ between "reference" and "pointer" is something very recent. In the past the 2 terms were synonymous.
The term "pointer" was introduced by IBM PL/I in July 1966, where it replaced "reference".
PL/I has introduced many terms that have replaced previously used terms. For example:
reference => pointer
record => structure
process => task
and a few others that I do not remember right now.
"Pointer" and "structure" have become dominant after they have been taken by the C language from PL/I and then C has become extremely popular. Previously "reference" and "record" were more frequently used.
But the "references" in Euler seem to be close to references nowadays. There is no access to the address, no pointer arithmetic etc. such as in PL/I.
Euler had both an address-of operator, which was prefix "@" and an indirect addressing a.k.a. pointer dereferencing operator, which was a postfix middle dot.
So it had everything that C has, except pointer arithmetic.
Only a subset of the programming languages that have pointers also allow pointer arithmetic, because many believe that whenever address arithmetic is needed only indices shall be used, not pointers, because with indices it is much easier for the compiler to determine the range of addresses that may be accessed.
Nice, and that was implemented and qualifies as high-level language?
You should provide a citation for where Bud Lawson has published his invention.
The use of pointers in assembly language does not count as an invention, as it was used since the earliest automatic computers. The use of implicit reference variables, which cannot be manipulated by the programmer, like in FORTRAN IV (1962) does not count as pointers.
The method for forcing another level of evaluation of a variable by using a "$" prefix, which was introduced in SNOBOL in January 1964, and which has been inherited by the UNIX shell and its derivatives does not count as a pointer.
The term "pointer" was introduced in a revision of the IBM PL/I language, which was published in July 1966. In all earlier publications that I have ever seen the term used was "reference", not "pointer".
There are 2 high-level programming languages that were the first to introduce explicit references (i.e. pointers). One language was Euler, published in January 1966 by Niklaus Wirth and Helmut Weber. However Hoare knew about this language before the publication, so he mentioned it in his paper from November 1965, where he discussed the use of references (i.e. pointers).
The other language was the language CPL, which had references already in August 1963. The difference between how CPL used references and how Euler used references is that in Euler pointer dereferencing was explicit, like later in Pascal or in C. On the other hand, in CPL (the ancestor of BCPL), dereferencing a pointer was implicit, so you had to use a special kind of assignment to assign a new value to a pointer, instead of assigning to the variable pointed by the pointer.
Looking now in Wikipedia, I see a claim that Bud Lawson has invented pointers in 1964, but there is no information about where he has published this and about which is the high-level programming language where the pointers of Bud Lawson had been used.
If the pointers of Bud Lawson were of the kind with explicit dereferencing, they would precede by a year the Euler language.
On the other hand, if his pointers were with implicit dereferencing, then they came a year after the British programming language CPL.
Therefore, in the best case for Bud Lawson, he could have invented an explicit dereferencing operator, like the "*" of C, though this would not have been a great invention, because dereferencing operators were already used in assembly languages, they were missing only in high-level languages.
However, the use of references a.k.a. pointers in a high-level programming language has already been published in August 1963, in the article "The main features of CPL", by Barron, Buxton, Hartley, Nixon and Strachey.
Until I see any evidence for this, I consider that any claim about Bud Lawson inventing pointers is wrong. He might have invented pointers in his head, but if he did not publish this and it was not used in a real high-level programming language, whatever he invented is irrelevant.
I see on the Internet a claim that he might have been connected with the pointers of IBM PL/I.
This claim appears to be contradicted by the evidence. If Bud Lawson had invented pointers in 1964, then the preliminary version of PL/I would have had them.
In reality, the December 1964 version of PL/I did not have pointers. Moreover, the first PL/I version used in production, from the middle of 1965 also did not have pointers.
The first PL/I version that has added pointers was introduced only in July 1966, long enough after the widely-known publications of Hoare and of Wirth about pointers. That PL/I version also added other features proposed by Hoare, so there is no doubt that the changes in the language were prompted by the prior publications.
So I think that the claim that Bud Lawson has invented pointers is certainly wrong. He might have invented something related to pointers, but not in 1964.
PL/I had one original element, the fact that pointer dereferencing was indicated by replacing "." with "->". This has later been incorporated in the language C, to compensate its mistake of making "*" a prefix operator.
The "->" operator is the only invention of PL/I related to pointers, so that is a thing that has been invented by an IBM employee, but I am not aware of any information about who that may be. In any case, this was not invented in 1964, but in 1966.
He (Lawson) can only point to his paper from 1967 and the fact that in 1964 he was asked to join PL/I team due to his earlier published works on linked lists.
https://dl.acm.org/doi/epdf/10.1145/363332.363344
PS He didn't mention it in his recollections [1], but 1978 paper The Early History and Characteristics of PL/I [2] claims that a paper was produced in October 1965.
[1] https://archive.computerhistory.org/resources/access/text/20... [2] https://dl.acm.org/doi/pdf/10.1145/960118.808389
Thanks for the link to his paper.
Like I have said, PL/I did not have pointers in the beginning, i.e. since 1964 until July 1966.
So I think that this claim about Lawson having invented pointers comes from a misunderstanding. It is likely that Lawson has been the lead developer for adding pointers to PL/I.
Someone has heard this and because the first version of PL/I was developed during 1964, a false conclusion was inferred, i.e. that Lawson had invented pointers in 1964, before Euler.
That conclusion was wrong, because pointers have been added to PL/I much later, not during the initial development.
The paper written by Lawson about using pointers was sent for publication in August 1966, i.e. one month after the official introduction of a new PL/I version with pointers.
Due to the timing of the implementation of a PL/I extension with pointers, a short time after a public debate about how programming languages such as ALGOL must be improved, with most proposals integrated and analyzed in the papers published by Hoare, Wirth and a few others, I believe that it is rather certain that the impulse to add pointers to PL/I was not internal to IBM, but it was caused directly or indirectly by watching this debate.
The paper written by Radin, linked by you, confirms that IBM has added pointers to PL/I after an important customer, General Motors, has requested this, presumably in Q4 1965.
Because Lawson was the one who reported the end result of this work of extending PL/I with pointers, I assume that he was the lead developer of this project, which must have happened mostly during the first half of 1966.
As I have said, the only original element of the PL/I pointers was the "->" indirect addressing operator. Unlike in C, no other operator was needed, because PL/I followed the recommendation of Hoare, which was to use pointers only as structure members, where they are useful for implementing linked data structures, and not also as independent variables.
Therefore it seems likely that Harald Lawson was the one who invented the "->" operator.
However, he clearly had not invented pointers, as those (under the alternative name of "references") had been used earlier in the languages CPL and Euler and the implementation of pointers in PL/I done by Lawson followed closely the recommendations made by Hoare in his "Record Handling" paper.
Talking about Quicksort, John Bentley’s deep dive in Quicksort is quite illuminating. https://m.youtube.com/watch?v=QvgYAQzg1z8
oh man, google tech talks. what a throwback.
there was a time, 10-15 years ago, when they were super cool. at some point they """diluted""" the technicality content and the nature of guests and they vanished into irrelevance.
much like google doodle
Yes, but don't forget his formal work also (Hoare logic).
To me, this is his most important contribution; Everybody else built on top of this.
Hoare Logic - https://en.wikipedia.org/wiki/Hoare_logic
Rediscovering it through the Dafny programming language. Brings back memories of a 1994 University course.
I think it is even more relevant today.
Hoare Logic + Dijkstra's weakest precondition + Meyer's Design-by-Contract is what should be used to get LLMs to generate proof with code in a correctness-by-construction approach to implementation.
References:
Correctness-by-Construction (CbC) - https://www.tu-braunschweig.de/en/isf/research/cbc
A Course on Correctness by Construction - https://wp.software.imdea.org/cbc/
You might find this paper interesting (uses examples in Dafny) - https://news.ycombinator.com/item?id=47334375
They were never concurrent, they were communicating. https://en.wikipedia.org/wiki/Communicating_sequential_proce...
That is indeed the correct title, but the processes were concurrent.
However, they were not just concurrent, but also communicating.
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.
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.
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.
CSP and Hoare logic were brilliant. He was a huge proponent of formal methods.
He famously gave up on making formal methods mainstream, but I believe there will be a comeback quite soon.
On generated code, verification is the bottleneck. He was right, just too early.
(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)
And here we are throwing all that brilliance away with Async abominations. Software can be so simple and elegant.
Actor model would also be brilliantly wrong: it doesn't compose smaller correct systems into larger correct systems.
(Software) Transactional Memory and other ideas inspired by databases have a much better shot at this.
Is this why software transactional memory is so prevalent today and the actor model is barely used?
Locks are even more prevalent today. And so was leaded gasoline.
(To be less snarky, locks are one way you can implement both actor model and Transactional Memory. But just like JMP instructions in your CPU, it's probably better to provide programmers with a higher level of abstraction.)
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.
You can always check his entry on the Mathematics Genealogy Project: https://mathgenealogy.org/id.php?id=45760
I actually knew about that, but it says "advisor unknown".
Regardless, he certainly knew Tony Hoare, and spoke extremely highly of him.
You've probably tried this already, but just in case: If you can find a copy of his PhD thesis it's likely (or at least would be likely without the information that you've had trouble tracking down his advisor) to have some mention of his advisor's name in it.
When I met him unfortunately I didn't realize how important he was (1987). The place where I worked used formal methods to verify the design of an FPU, in collaboration with the PRG. iirc the project was a success. I never heard of formal methods being successfully used again until TLA+ a few years ago.
Inmos’ Occam-based verification of their FPU in collaboration with researchers at Bristol and Oxford iirc? Citation: http://people.cs.bris.ac.uk/~dave/formalmethods.pdf
David May was my PhD supervisor and always spoke very highly of Sir Tony Hoare.
Edit: I’m also lucky enough to have worked with Geoff Barrett, the guy that completed that formal verification (and went on to do numerous other interesting things). Some people may be interested to learn that this work was the very first formal verification of an FPU - and the famous Intel FPU bug could have been avoided had Intel been using the verification methods that the Inmos and University teams pioneered.
I actually had two PhD advisors [1]; Jim Woodcock and Simon Foster.
Both of them are legitimately wonderful and intelligent humans that I can only use positive adjectives to describe, but the one I was referring to in this was Jim Woodcock [2]. He had many, many nice things to say about Tony Hoare.
[1] Just so I'm not misleading people, I didn't finish my PhD. No fault at all of the advisor or the school.
I remember Jim Woodcock as really inspirational - he was working with my PhD supervisor in 1987. We were working on a variant of Z for specifying what, today, we would call CRDTs. I was also lucky enough to meet Tony Hoare the same year and discuss those concepts.
Jim is an amazing guy. One of the rare people who are absolutely brilliant in their respective field, and are equally good at teaching the subject. He's also just a really kind, nice person who is delightful to chat with, though that's true of pretty much anyone in York [1].
I also think his book "Software Engineering Mathematics" [2] is an extremely approachable book for any engineer who wants to learn a bit more theory.
As I said, my dropped PhD is not a failure in any capacity from my advisors or the school, mostly just life juggling stuff.
[1] I don't know why exactly, but of all the places I've been, York has the highest percentage of "genuinely nice" people. It's one of my favorite spots in the UK as a result.
[2] https://a.co/d/02M25LcY, not a referral link.
Inmos? Transputers were inspired by Hoare’s CSP.
“Inspired by” is an understatement of the century lol. David May and Sir Tony worked very closely together to enable the architecture to be as pure a runtime for CSP as you could get - at least in early versions of the architecture and accompanying Occam language. It expanded and deviated a bit later on iirc.
Source: David loved to tell some of these stories to us as students at Bristol.
It’s also worth highlighting that the mathematical purity of the designs were also partly the problem with them. As a field, we’re still developing the maths of Effects and Effectful Algebras that are needed to make these systems both mathematically ‘pure’ (or at least sound to within some boundary) and ALSO capable of interfacing to the real world.
Transputer and Occam were, in this sense, too early. A rebuild now combining more recent developments from Effect Algebras would be very interesting technically. (Commercially there are all sorts of barriers).
Further Reading for the curious:
On specifically the relationship between Occam and Transputer architecture: http://people.cs.bris.ac.uk/~dave/transputer1984.pdf
Wider reading: http://people.cs.bris.ac.uk/~dave
Yes.
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.
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!
Happy to meet you. I was there and I remember that question being asked. I think it was 2010.
If I remember correctly he had two immediate ideas, his first was bubble sort, the second turned out to be quicksort.
He was already very frail by then. Yet clarity of mind was undiminished. What came across in that talk, in addition to his technical material, was his humor and warmth.
That's right - it was bubble sort first. Absolutely - frail, yet sharp. I'm happy to hear several of us didn't forget this encounter with him.
I remember this vividly! I believe he said that he thought of _Bubble Sort_ first, but that it was too slow, so he came up with QuickSort next
Good to hear from you after a while, Gaurav (I think?!).
He discusses this and his sixpence wager here: https://youtu.be/pJgKYn0lcno
(Source: TFA)
Haha I was there too. I remember he made thinking clearly seem so simple. What a humble man.
If I remember correctly, his talk was about how the world of science-the pure pursuit of truth-and the world of engineering-the practical application of solutions under constraints-had to learn from each other.
I'm glad you remember it as well! I didn't think to see if there was a recording or something of this talk, until now. It looks like the text of the talk was published here: https://www.cs.utexas.edu/~EWD/DijkstraMemorialLectures/Tony...
And the talk wasn't a random talk, but a memorial talk for Dijkstra: "The 2010 Edsger W. Dijkstra Memorial Lecture". I forgot this aspect as well!
I was introduced to him pretty late in the game, in this interview where he and Joe Armstrong and Carl Hewitt talked concurrency! It was interesting hearing them discuss their different thoughts and approaches
How sad that we all missed when Carl Hewitt submitted that video to HN: https://news.ycombinator.com/item?id=19202209.
I had no idea that a discussion between the three of them even existed.
Also sad that now all three are gone.
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.
A near neighbour described being interviewed by Tony Hoare for his first job after graduating (he got the job!). Sounds like the interview process in those days was a chat over lunch rather than coding exercises. https://news.ycombinator.com/item?id=43592201
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.
Almost all of the earliest cited works on concurrency management in software were authored by C A R 'Tony' Hoare.
I genuinely forget he authored quicksort on the regular.
Actually, thanks to AI, this may change soon! we may be in a place where widespread formal verification is finally possible.
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.
"Sir", not "Mr." if you're going to be pedantic about titles ;)
Edit: Oh and he has multiple honorary doctorates (at least 6!), so would be just as much "Dr." too!
Lol you are totally right! ;-)
I am normally a casual guy but for a giant being a bit more formal (pun intended) seems appropriate. Or maybe I am a nerd through and through :-)
It is not usual to call people with an honorary doctorate "Doctor" except in the context of the awarding institution. Most likely the awarding institutions will have actually specified that the recipient should not give anybody the false impression and I can't imagine Tony is the type to do otherwise.
His title at Oxford was 'Professor', and he was addressed as 'Tony'.
He made incoming DPhil (PhD) students a cup of tea individually in his office at the Computing Laboratory. It was a small group, but still I appreciated this personal touch.
I never met Tony, but I liked his work. I'm not much of a one for tea, but I don't think either of my PhD supervisors ever bought me a drink - I didn't finish (got cancer, I'm fine now†, some cancers are very curable, but frankly I was struggling anyway so it was a good excuse to quit) and I'm sure it's traditional to buy something a bit harder than a cup of tea if you pass, but I didn't get that far.
Anyway my point here was just a PSA that honorary degrees "don't count". If somebody only has an honorary doctorate but insists on being called "Doctor" they're an asshole. In fact, even outside University I know a lot of MDs and PhDs and in most contexts if they insist on the title "Doctor" they're an asshole even though they're entitled.
† Well not fine, I'm old but I think that's an inevitable side effect of surviving so the alternative was worse.
There's having An honorary degree... and then there's having 6 of them plus numerous other awards, and all the achievements to back them up :)
Regardless, I've met people with only honorary doctorates, and it's a mixed bag when it comes to preferred titles. Often, though, the ones that really care, soon acquire a 'superior' title anyway, so it ends up becoming a moot point.
You’re right. And ‘Professor’ comes and goes with the job, independent of degrees held.
Sometimes I feel completely separated to mainstream culture.
That the death of Sir Tony Hoare has been completely ignored by mainstream news is one of them.
Not a peep anywhere for a man that put a big dent in reality.
Mainstream news have not been presenting much actual relevant content beyond reporting on wars.
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 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.
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.
TIL his first publication was in Russian, published in the USSR where he spent a year as an exchange student. I wonder if Igor Mel’čuk [0] remembers him.
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"
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'.
You misunderstand the “billion dollar mistake”. The mistake is not the use of nulls per se, the mistake is type-systems which does not make them explicit.
Anti patterns are great, they act as escape hatches or pressure release valves. Every piece of mechanical equipment has some analogue for good reason.
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.
The "goto" in languages like C or C++ is de-fanged and not at all similar to the sequence break jump in "Go To Statement Considered Harmful". That doesn't make it a good idea, but in practice today the only place you'll see the unstructured feature complained of is machine code/ assembly language.
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).
That relies on a programmer doing the right thing and knowing when to use the escape valve. From the codebases I've seen, I don't trust humans in doing the right thing and being judicious with this. But it's a good point, knowing when to deviate from a pattern is a strong plus.
> I don't trust humans in doing the right thing and being judicious with this.
Language-level safety only protect against trivial mistakes like dereferencing a null-pointer. No language can protect against logical errors. If you have untrusted people comitting unvetted code, you will have much worse problems.
That's why code reviews exist, it's good process to make code reviews mandatory.
It's too much of a stretch to call null an escape hatch, or to pretend that code reviews will somehow strip it out.
The OpenJDK HashMap returns null from get(), put() and remove(), among others. Is this just because it hasn't been reviewed enough yet?
> pretend that code reviews will somehow strip it out.
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.
Leslie Lamport hosted a chat with him a few years back: https://www.youtube.com/watch?v=wQbFkAkThGk. They spoke about general CS stuff and some aspects of concurrency.
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 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.
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!
Here is my favorite visualization of quicksort, by a group of Hungarian dancers:
Thank you for this!
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.
"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.
BTW Rob Pike designed the Go language channels inspired by this work: https://go.dev/tour/concurrency/2
Tony Hoare on how he came up with Quicksort:
he read the algol 60 report (Naur, McCarthy, Perlis, …)
and that described "recursion"
=> aaah!
I had the privilege to attend his "Billion Dollar Mistake" talk in person at QCon London 2009. Little did I know that this talk would go down in software development history! What an honor to have witnessed this live!
https://www.infoq.com/presentations/Null-References-The-Bill...
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 never had a doctorate, so I had to make do with Quicksort.” —Sir Tony Hoare (unpublished interview for Algorithms to Live By)
Rest in peace to a real one, we've lost one of the brightest minds of our century
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I watched this video a few months ago.
Virtual HLF 2020 – Scientific Dialogue: Sir C. Antony R. Hoare/Leslie Lamport
One of the most important papers of all time.
Just one word: Quicksort.
One-of-a-kind genius.
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
Just two days ago I was curious about the PhD advisor of my PhD advisor and so on, and discovered that I am actually an academic great-grandson of Hoare (shame on me, I should have realised that earlier), and joked, "Wow, they are all still alive!". Then I saw the news yesterday on HN.
"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?
"The problem isn't the concept of 'null', but rather that everything can be null, which makes it impossible to distinguish between the cases where null is an appropriate and expected value, from the cases where null is a defect."
https://blog.ploeh.dk/2015/04/13/less-is-more-language-featu...
Which system reality? Plenty of architectures don't have a concept of a null pointer at the hardware level. Other architectures provide multiple address spaces, or segmented memory addressing. Even when a null pointer exists at the hardware level, it doesn't have to be the zero address.
Null pointers are a software abstraction, and nowadays we have better abstractions.
Some kind of an optional/variant type, enforced by the type system.
Or if even that feels too verbose, just a 'nullable' modifier on the variable or field definition, with the default being not nullable.
(Although Optional/Maybe types are definitely my preference based on the languages I've used)
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.
A collection of Tony Hoare's memorable quotes - https://en.wikiquote.org/wiki/C._A._R._Hoare
Hoare's papers were some of my favorite. Rest in peace
Assert early, assert often!
Absolutely the GOAT of concurrency. May his ring never die.
Incredibly sad news. His contributions to the foundations of computing will remain relevant for generations to come.
His paper on communicating processes was a great read when I was new to computer science research.
Hoare logic: https://en.wikipedia.org/wiki/Hoare_logic
> The central feature of Hoare logic is the Hoare triple. A triple describes how the execution of a piece of code changes the state of the computation. A Hoare triple is of the form {P}C{Q} where P and Q. are assertions and C is a command.
> P is named the precondition and Q the postcondition: when the precondition is met, executing the command establishes the postcondition. Assertions are formulae in predicate logic.
> Hoare logic provides axioms and inference rules for all the constructs of a simple imperative programming language.
[...]
> Partial and total correctness
> Using standard Hoare logic, only partial correctness can be proven. Total correctness additionally requires termination, which can be proven separately or with an extended version of the While rule
I was lucky enough to see Sir Tony Hoare speak at EuroPython in 2009. This was his last slide:
One Day
- Software will be the most reliable component of every product which contains it.
- Software engineering will be the most dependable of all engineering professions.
-Because of the successful interplay of research:
- into the science of programming;
- and the engineering of software.
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"
wow, but lived a full life
RIP
Rest in peace, Sir Tony Hoare
I didn't know him, but every time I've read one of his papers I've learned something and changed my viewpoint. I'm never worried that my effort will be betrayed reading Hoare (Especially rare in a field that moves so fast like applied CS)
always knew him as C.A.R. Hoare, takes me way back to freshman college years
RIP good sir
RIP
RIP Sir Tony Hoare
Turing Award Legend.
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.
ACEEE IN PRST
RIP
Rest in peace
Rest in peace.
I am greatly saddened by the passing of Tony Hoare. His work has affected me deeply; in personal, academic, and professional life. Without visionaries like him, I would not find the love in computer science as I do now. It would be a great honor to have accomplished a fraction of what he did. My condolences to his close friends and family.
RIP Legend
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.
How many jobs were had or not due to the candidates ability to implement his algorithms?
As a junior dev, I loved to ask interview candidates to implement merge sort or quick sort on whiteboards.
As a non-junior dev I realize how stupid that was.
I think the first enlightenment is that software engineers should be able to abstract away these algorithms to reliable libraries.
The second enlightenment is that if you don't understand what the libraries are doing, you will probably ship things that assemble the libraries in unreasonably slow/expensive ways, lacking the intuition for how "hard" the overall operation should be.
Needs a black bar!
Seconded.
Finally. The black bar is there.
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The part about 'genius' being slow and about wrestling with difficult problems resonates.
The idea of 'genius' or in fact 'intelligence' being about speed isn't just a Hollywood thing though; it's also been a Silicon Valley thing as well; it's why most big tech interviews are time-constrained.
Over the years, I've also heard many tech CEOs say stuff alongside "There's only one type of intelligence" or "All intelligent people are intelligent in the same way."
These kinds of statements raised my eyebrows but now with LLMs being able to solve most puzzle problems rapidly but struggling with complex problems it's completely obvious that it's not the case.
What it says is frightening. The CEOs of big companies have been giving positions to people who have the same thinking style as them. Quick puzzle-solving tech tests are literal discrimination against the neurodivergent and also against geniuses. They've been embracing wordcels and rejecting shape rotators.
I think a guy like Tony Hoare would struggle to find a job these days.
You could argue that the issue extends beyond Hollywood and Silicon Valley... The whole education system is centered around puzzle-solving speed. It's hilarious that AI is now solving all these tests within minutes with better scores than humans. Crazy to think that LLMs could graduate from university based on current assessment policies! It's very revealing of what kind of education system we have.
this is black bar grade great. give us black bar
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https://news.ycombinator.com/item?id=47316880
249 points by nextos 16 hours ago | 61 comments
Thanks! We'll merge those comments hither.
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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
I uploaded lecture to Claude and asked to create skill using principles described. I guess we shall see if AI can actually follow them. :)
Crafted by Rajat
Source Code