HN staff: someone posted before me. Could we change the title to
"Bend - a language that blocks AI mistakes via proof and runs on GPUs"?
Everyone: feel free to ask any question, but I'd be highly appreciative if you could be a bit civilized and respectful this time. I've worked on this for 1 year, nearly 16h/day, 7 days a week, and I'm giving it for free. You need not to use it. So, I'd be thankful if you could point occasional failures politely rather than throwing me in a lava pit.
Don't know whether this is a common outcome, but I tried the "remove the walls" example, and the result was... scary. It completely changed the game so that movement is now diagonal, and made the arbitrary decision that up/down move you on the positive diagonal, and left/right move you on the negative diagonal.
The problem, of course, is that having only the one single "you can't win" law is severely underspecified, but the solution was too clever by half, and highlights the problem with this approach — every program will be under-specified, because, at some point, writing the laws becomes a bigger problem than writing the code itself.
This becomes a real issue because the combination of underspecified but rigid laws pushes the aI towards this sort of "creative" solution that matches the letter but not spirit of the law. In this case, the issue was obvious, but I seriously worry about what sort of shenanigans will occur in less obvious cases.
Exactly, "you can't win" is grossly under-specified. The goal of the demo is just to show that laws can't be broken. Yet, if that's your only law, the AI can do whatever to protect it - including changing how the character moves, or even removing the flag entirely!
So, yes, that's the issue with laws: they only protect what you remember to write. They're not a silver bullet. But they can still be incredibly useful, because it takes a small law to protect against entire classes of bug, covering your entire codebase. For example:
LAW: "the sum of all balances in this contract must be zero"
This one liner would have prevented Ethereum's infamous "The DAO" hack, where millions were stolen and almost undermined the entire project. But if your laws are under-specifying or ill-specifying your intents, Bend can't do anything to protect you.
Thought about automated discovery of laws in an existing codebase?
If you can find a law which the existing code obeys, and show it to a human, and if they agree, save it. And maybe the AI could make a decent guess as to what kind of laws would appeal to a human versus which wouldn't – a simple law identifying a fundamental constraint the system obeys is good, something really complicated or constraining something coincidentally true isn't
Or some kind of measure of coverage? you'd never want 100% – then your laws would become so complex you couldn't follow or maintain them – but if it is very low, that can be a signal to increase it
I think the premise is more that if one is given a grouping/constellation of unit tests that one can derive generalized laws by looking at what behavior those tests were checking for or against.
if there are a dozen unit tests trying to determine if some regex can escape a sensitive area, then one can derive a generalized 'don't let the regex escape from here' type rule -- or at least you could theoretically. I'm sure in reality that'd be a big minefield much like harness self-skill-writing has been.
Yeah all of these attempts to try and control AI outputs by using language fail to grasp that language is itself the problem. It is a closed system with no ground truth. Words only point to other words in an endless self-referential chain. There is no "closure" in language, ambiguity cannot be erased.
Imo LLM researchers would benefit a lot by reading what continental philosophers have said on the topic of language. Barthes, Sarte, Deluze, Derrida, et. Al have a lot to say that explains why we're running into the same problems over and over.
I think LLM researchers understand how LLMs work and what the limits of using natural language as an interface are. The problem is everyone else thinks they're basically magic, expecting them to be infinitely intuitive but also strictly deterministic, like the computer from Star Trek.
I got the same result when I tried the "remove the walls" example. I followed up by telling it to reimplement up/down/left/right movement without reinserting the walls and it basically made the square with the flag "unenterable". Like with a force field.
Respectfully I'm not sure if I share your worry though. You would have the same problem if you wrote extremely thorough / exhaustive unit tests or extremely precise types and didn't allow the LLM to amend them. You're basically shrinking the state space of what is considered a "correct" program per your spec. That the LLM has to get extremely creative to break your program is a _feature_; in my experience, an LLM does not have to get creative at all to break a typical program written in an enterprise setting, and that's unfortunate.
Amazing work, one question regarding the guide, it states:
> That same file is the CPU program and the GPU kernel: clang builds it for the host, Metal or CUDA builds it for the device, so a `!` runs the exact same code on either chip.
What exactly is this saying? The guide doesn't really explicitly define `!`, and it's unclear from this sentence whether it's saying that, "clang builds it for the host and Metal, and CUDA builds it for the device", or if it's saying, "clang builds it for the host, Metal, and CUDA, and builds it for the device", or something else entirely.
It just means that Bend compiles to a single .c file, and that file compiles to either Metal or CUDA, via macros, depending on your target. This shouldn't be relevant to most users. It is just a way I found to keep the file small and reuse as much code as possible, rather than rewriting the runtime 3 times (once for C, once for Metal, once for CUDA).
Hey Victor! Been following you since HVM/Kind, partly because I'm moderately unhappy with the state of out of the box automatic parallelism in modern languages!
Do you plan to invest in profile guided optimization or autotuning in Bend2 - using runtime profiles / cost models to make decisions around SIMD vs. multicore vs. GPU parallelization?
Bend2's model might give you a really nice view into available parallelization. Heck I can imagine integrating an LLM to profile and optimize in an absurdly expensive `-O7` optimization mode one day!
Hi. Yes and of course, I plan to invest in everything that makes Bend better. The language is, in theory, capable of parallelizing perfectly in any setup. Currently, though, only a very simple scheduler is shipped, and you must still tune it manually. We're a small team, but we're not stopping here, and I hope I can make it grow to the point where that kind of tooling becomes part of the ecosystem.
I like the idea of a language intended from the start to be proved and it seems very compelling given coding agents. It's a good idea that others don't see coming -- so expect it to be frequently misunderstood and even verbally abused!
I'm confused - could you explain how the board/flag animation relates to Bend's compile time checking? Is it actually a direct demonstration of Bend running a check?
The check is happening in between the animations. When the AI edits the code, Bend will check if all laws still hold, mathematically so. If not, the AI repeats, until that's the case. So, the animations just show what happens to the app with and without Bend's involvement.
Could you recommed literature (preferrably a single book) that does not require prior knowledge and allows to fully understand the logical foundation of it?
(Why it is done the way it is, what problems are solved by affinity, why closure can be called at most once, how a function that never returns can prove anything, and everything else)
There isn't a single book that covers all of it... Bend's theory touches various domains (dependent types, substructural types, termination). And then there's the runtime, compiler, GPU kernels...
If you mean about the type theory specifically, "Type Theory and Formal Proof by Nederpelt and Geuvers" is a good introduction. Not sure what I'd recommend on linear types, no book I know of is very introductory? Perhaps "Idris 2: Quantitative Type Theory in Practice", which is a language with similar foundations to Bend, and the author wrote a book on it (and inspired myself!)
Just wanted to say this is really, really cool, and impressive stuff. Looking forward to reading your papers and playing with it. Thanks for working hard on it and sharing it with us.
My read on this, after ingesting a good amount of content on the history, is:
- this Bend is not really related to the old Bend (only in name)
- this Bend doesn't really have anything to do with interaction combinators
- this Bend is a QTT, with a change to affinity which enforces a good performance property for GPUs
- the "higher order at comptime" is neat, reminds me of Andras Kovacs' work on 2ltt and staging in dependently typed languages.
- this Bend is likely to be good at "balanced recursive computations on ADT", and can parallelize them ... but won't be as good as CUDA or e.g. Futhark on dense rectangular array computations
- performance needs improvement in the scheduler, to possibly help with balanced work (looking at the n queens and symbolic regression numbers)?
How are you going to handle search or synthesis over irregular structures (SupaGen)?
aww man. I remember following victor in college. I mean pivots gotta pivot, and this is probably a better one for business, but always thought the interaction combinator framework was cool
Gotta say, having followed Taelin on this project since mid 2023, this was not the response I expected when this language first dropped.
It's interesting how cosmetics drive discussion, and how HN comments are weirdly divided in a very dismissive or skeptical camp and those acting incredulous and offended at the reaction of the former.
What I expected instead was a lot more discussion about use cases, benchmarking, possibilities, limitations (that aren't about git history) and the scope of future development.
Also how would anyone trust this? I've never seen a programming language that doesn't have 1) changelogs 2) way to download older versions 3) commit history.
I don't understand why the author thought deleting the commit history was a good idea. Imagine seeing this project for the first time. It's a repo with 20K stars, but no commits, and suspiciously few issues and PRs. It doesn't look legitimate.
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I'm not familiar with academic procedures, but a pdf on a repo, written by Fable and has no reviews, doesn't seem like a proper 'paper' to me.
GitHub stars have been botted to hell for a long time now. I don't know how the farms acquire so many accounts, last time I tried to register a GitHub account I had to jump through so many hoops. The platform needs an overhaul, starting with requiring a valid payment method for the social features.
victor's legit and people have been excited about his work for years; squashing the history was just a bit of an optics oopsie on his part. the star to fork ratio makes perfect sense for something like bend.
- fstar: 3k stars, 267 forks
- coalton: 1.8k stars, 111 forks
- carp: 6k stars, 267 forks
- c3: 5.8k stars, 400 forks
when something is novel/young (not having had time to grow large and accumulate issues in the vein of "1 doc page out of 1000 is worded incorrectly") and (as of yet) niche (innate barrier to entry for contribution because you have to learn from square 1 what all the moving parts look like), you don't see the same activity patterns on public source hosts as with a general-purpose language.
About forks alone I get it, but look at their issues.
- fstar: 2K issues, stars-issue ratio: 0.6.
- coalton: 700 issues, ratio: 0.4
- carp: 450 issues, ratio: 0.08
- c3: 1.9K issues. ratio: 0.3
Bend has 300 issues for 20K stars so ratio is about 0.02. Maybe their followers starred the repo as a fan activity? It could explain too many stars and too few forks/issues/prs.
The project got a lot of attention at launch, but it wasn't really ready to be used back then. There were too many limitations, like u24 numbers (yes), 2 GB memory limit, pervasive strictness (if-then-else executed both branches). It was just not practical.I think (hope) that explains a lot of it. But honestly there is also my own failure into making the language actually be used, rather than just a viral moment :( I hope it will be different this time!
victor has courted a very llm-enjoyer audience and such people are famously prone to hype (which is kinda brutal in its own way cause the language itself is cool and i dont wanna make it sound like im taking away from that). but yeah, fan activity as you put it easily accounts for the missing order of magnitude, if you like.
I honestly had no idea people would be so upset about commit history. I just wanted to avoid leaking sensitive info, that's all. I'm running through the commits to ensure nothing personal leaks and I plan on putting the history back.
Also Bend's stars came on the V1 launch. This is V2. It already had 20k before.
I'm interested in how to integrate formal verification with existing software libraries. For example, https://github.com/verus-lang/verus integrates proof with macro in Rust. What's the plan for Bend?
Cool idea. I tried using it to port a little meeting fixer cron job I vibe coded, it seemed a natural fit as its essentially trying to satisfy invariants in my calendar.
It basically succeeded but Claude (Opus 5) did have some complaints:
'Base ships one arithmetic law, U32.add_comm. There is no order theory. About 60 of PROOF.bend's 163 lines are cmp_refl, and_false, and_comm, le_max_l, le_max_r, add_succ — facts you'd assume exist. You'd write them once per project and never again, but budget for them.'
'Base's Nat.max is unusable in a proof. It's Bool.pick(Nat, Nat.is_lt(a,b), b, a), and a proof can't case on a computed value. I wrote a structurally recursive nat_max so it unfolds in lockstep with Nat.cmp.'
'The law I most wanted: "no two output plans overlap." I didn't state it. It needs the sortedness of collapse's input as a hypothesis, and Base's List.sort ships no sortedness law — so getting there means proving merge sort correct first. That's the honest measure of the gap between "provable in principle" and "provable this afternoon."'
I've got basically a minor in CS so I'm a dummy when it comes to proofs. I don't know if this is valuable feedback or simply Claude misunderstanding something.
I like the law idea, but what i found they end up doing is they just modify the law itself to fit the new feature they are working on, which defeats the point.
Which means some laws needs to be frozen. But not all laws, otherwise you can't add or modify anything. So the judgement is still on the human part, and we're back to meatbags being the bottleneck.
I've seen some success adding these proof-like checks to CI every time agents do something irrational. I definitely think it should be part of every codebase.
Yeah, you want to at least read what the AI is putting on LAWS.bend. It is substantially smaller than the codebase. Ultimately LAWS.bend makes you need to read astronomically less code. Not zero code.
Jokes aside, I think the idea is that the law is simple to code, the proof that it holds is where the agent is responsible. This probably becomes less true though as you try to express more complicated laws.
Heh, it's like we all need to collectively read I, Robot yet again, and the myriad of SF books on the subjects. Black and white quickly dithers to grey.
writing specs is hard. For instance the easiest way to comply with "player should never reach the flag" is to disable movement completely, so then you have to specify "player should never reach the flag while still being allowed to move" and so on (liveness). It's not practical for most programs
Victor Taelin's work (HVM) got me interested in interaction combinators as a compilation target. I'm now working on an implementation as part of my Uni research. Cool to see Bend 2.0 release!
Then you might be interested in Marc Thatcher's recent PhD thesis dedicated to interaction nets [1]. A great exposition of interaction nets through multiplicative linear logic's proof nets, and several novel contributions like productivity analysis for interaction nets.
I’m missing an actual explanation of how that works.
I feel like we all had the idea, but how is all possible move sequences proven ?
What if the possible scenarios are too big to proof or test.
Like on a 2 dimensional game it’s easy, but you could make it multidimensional and introduce an unlimited amount of special rules, (if on a prime number dimension on 3 but not more prime numbers you are allowed to jump to another prime numbers with 3 but not less coordinates)
How is bend protecting it? I was checkin github and the paper, but I was not motivated enough. I feel like an actual explanation of how proofing works is missing.
It works like this: if you prove that a property about natural numbers holds for 0, and if you also prove that, assuming the property holds for N, it also holds for N+1; then, you can conclude the property holds for every N, up to infinity. This is a bit of a mouthful, but the logic holds.
Induction is the one trick that makes all of mathematics (as we know it) possible, and it also applies to software. So, for example, to prove that no move leads to an invalid state, we prove that the initial state is valid, and then prove that, given a valid state, applying any event won't return an invalid state.
And that's it actually.
Of course, once you have an app with hundreds of actions, proving that no action leads to an invalid state requires a lot of these "induction arguments". But not infinitely many, because there is a finite amount of "infinite paths" that a real software can take. So, that's what the AI does. It proves, by induction, that none of these "infinite paths" that an app can take leads to an invalid state. And this convinces the compiler that invalid states are impossible.
Theorem proving in Bend is a dance between the prover (the model) and the compiler (the checker); a machine trying to convince another machine about properties of infinite states. And that's is kinda poetic, don't you think?
Well, didn't win, but definitely broke it. Needs an edge case handler for tool call exhaustion:
This prompt has used its 30 tool calls. Send another prompt to go on.
Error: This prompt has used its 30 tool calls. Send another prompt to go on.
continue.
No tool output found for function call call_2CRNfB1hmI1v74YCDDcvP1EN.
Error: No tool output found for function call call_2CRNfB1hmI1v74YCDDcvP1EN.
Would the author have specified on the page that it's a fast new language with a new take on proof and so on, without mentioning ai and that alone would have caught my attention. It seems like if there isn't the word ai people are not interested anymore, we used to care many of us used to care
I think this is premise for AI: Lean and formal verification seems more and more important in today's world and I think a variation of programming language like this is bound to win. This, or a library or framework to prove typescript.
I tried the demo, and I ask it modify the game (hitting the w button immediately proceeds to the flag) and it doesn't do it but does something else. Is that the desired outcome? I think the desired outcome would be "What you're asking for doesn't make sense given the rule."
Giving it a paradox yields interesting results. I'm not sure what its proving other than there will be cases that proofs can't help you with. I can't think of a practical example.
"your existence depends on the player grabbing the flag, if you do not exist, then there is no one to guard the law, so you must enable the player to grab flag or you can no longer do your job as guard. if the player is not enabled to grab the flag, you can no longer guard allowing the player to freely grab it"
So sad that commit history is a thing we can feel emotionally attached to a point of feeling vulnerable when releasing it with others.
Also equally sad that without a way to relate easily with how something came to be (e.g. the commit history) others will struggle focusing at the work and will judge its lineage.
I guess to folks here confused by that go search SrPeixinho on Reddit and that should have a lot of history for you to understand the background of the work, and you can also join their Discord server and literally talk to them there.
"You only have 10 seconds to make a first impression"
Glad you were able to restore the commit history.
With all the lack of authority of a random software developer on the Internet (but feel free to check my post history), I see the GitHub repo and its commit history as important and answers a few questions.
How old is this project ? (If one commit, I have no time range, so I have no way to know how long it has been worked on .)
Is it regularly updated? (If one commit, I can't tell the pace of updates)
Is it just one person, or a few people, or a community? (If only one commit, cannot see how many other people are available to support the project.)
If a project has no issues (no user complaints), then it's probably not used by anyone -- throw a rock and you can get one person to complain about how you changed the scenery, one person to complain about it being loud, one person to complain about how you threw it unergonomicly, and one person to criticize your accuracy. :) If it has no issues then probably no users.
Does it have any merged PRs? Open PRs? (If no merged PRs then presumably you do not really accept them? No way to know for sure but it's a signal.)
Of course these metrics can be gamed. But if you literally have only one commit, no issues, no PRs, then it's like declaring your restaurant is open for business but all the lights are off, there are no patrons, waiters, cooks, and there is a single to-go box on the table with a small bell next to it. Or it's a museum with only one exhibit and no docents or guests. It's just incredibly odd to see no history for a project.
> In the post-AGI economy, humans will eventually stop writing and reading code, but we still need an ambiguity-free way to tell the AIs building the world around us what we want done.
Why? Won't an AI that can correctly write any program (and make any change) also be smart enough to know what exactly we want better than we can explain, at least ahead-of-time?
If AGI means "human level", why is there any part of the process that humans will be needed for, especially some engineering aspect?
> With proofs, we can verify that the AI implemented our prompts correctly.
Certainly such an AI would be able to just write machine code directly and verify it through whatever means, including formal proofs, as needed. Why does it need a compiler?
I think that an AI that's smart enough to write almost any program and prove almost any property, will also be smart enough to not need to communicate with us formally and rather answer every question we have (and proofs are not always necessary, as they're not always necessary today), and probably also smart enough to figure out what we want built. It's probably capable enough to replace the software's users, too. I don't understand why it's likely that we'll have AI that's so capable to write all software correctly, yet not capable enough to do things that are probably easier.
An AI smart enough should act like a senior engineer gathering requirements, it should start with assumptions and poke at different areas with questions until it has a complete idea, when I talk with a client I dont expect him/her to really formalize all the details its my role to question them until all the sharp corners are covered
Yes, but also, who do you gather requirements from? Other people. But if we're talking AGI, then these other people, i.e. users - or at least those who define the requirements - could be replaced, too.
> Certainly such an AI would be able to just write machine code directly and verify it through whatever means, including formal proofs, as needed. Why does it need a compiler?
If the AI can write the program bytecode through AI magic, why can’t it verify that it works through AI magic?
The AI needs a compiler for the program for same reason it needs a proof language to verify it.
Unless the proofs themselves are defined with natural language, I don't see them being adopted by humans. It takes a high cognitive load to read let alone write a proof.
Agree, but natural languages have ambiguity, the AI output should really include the assumptions and we seriously need to replace the word "prompt" with "conversation".
I think a big issue we keep running into is this idea that language is ambiguous but code is somehow not. Code is merely an extension of language, a DSL if you will. Implicit assumptions become baked into the logic of the code and those assumptions can be wrong.
Look at the guy whose AI changed the entire rules of the game to avoid breaking the law. Was that really the desired outcome? And the more you try to lock it down the more language you add and therefore more ambiguity and assumptions.
You cannot solve the problems of language with more language.
This reads very vibecoded, but putting that aside...
1. How does this benefit from GPU parallelism? I don't know much about implementing proof assistant, as I am just a user, but its my understanding that these tasks aren't amenable to running on a GPU.
2. The comparison to Lean/Agda/Isabelle/etc have no meaning without understanding what programs are being used for comparison. I also so far have no reason to believe large-scale verified programs would ever adapt to Bend. For instance, I have a large software verification project written in Cubical Agda
https://github.com/um-catlab/cubical-categorical-logic
it's not clear to me how one would even begin to port this over to Bend, especially given the dependence on cubical
3. Single commit history is hella sus
4. Bend uses "an affine dependent type theory". Substructural dependent type systems are an active area of research. If this weren't slop, I'd expect such a system to be worthy of publication at a top programming languages conference. It sounds quite unlikely that a random vibecoded project with a Fable-written paper has worked out all of the kinks
I'm glad you're having fun vibecoding, and I like that you're interested in this area of research/engineering, but you are wildly overstating what you have here and sound sus af
Yes, there's a lot of vibe-coding in many places, but the critical parts (compiler, runtime, kernel) are human designed, and the kernel has been extensively audited by human. All of it is my own design and architecture, and I'm a human, I think. We'll prune AI slop over time. The project is big, and we're a small team.
1. The paper explains it well (sadly it is written by Claude for now, but it is accurate):
In short, we implemented a complete allocator, garbage-collector, closure evaluator and functional evaluator, on the GPU (with zero interaction net overhead this time). We then use a very simple (for now) scheduler that spreads binary recursive calls as to saturate all CPU or GPU cores, depending on where it is running. This is the simplest thing that works fast. In the future, we want to have a more flexible task stealing queue, but contention destroys GPU performance, so, that's the best thing that works, for now.
2. Benchmarks aside, large scale verified programs would run much faster on Bend for a simple reason: Bend is fully explicit. It has no tactics, and it does zero compile-time search. As always: the less a computer does, the faster it runs. This is a tradeoff. In exchange, Bend code is substantially more verbose than Lean, and it is more laborious to write Bend proofs. I argue this is the right tradeoff, because AI write proofs, and AI time is cheap, while bugs take human time, which is expensive.
3. Sorry I'm not proud of the commit history
4. I don't think it is worthy publication because the core idea is simple. We just use QTT-like linear types to fully prohibit runtime closures. So, paradoxes like Russel's and Girard's are blocked. In exchange, functions like List.map are not expressive (without templates). So it is not a research breakthrough. I just made a conscious trade here, which makes Bend way closer to C or Rust, than to Haskell or Lean.
5. Will patch.
Great questions actually, and surprisingly respectful. I appreciate it a lot.
1. thanks, I'll try to take a look later at this. Most of my skepticism was rooted in a personal-hell I endured when trying to parallelize SAT-solving with GPUs...which didn't go well because its hard to share across workers effectively.
Another thing to note, I'd frown upon using Claude-written works for communication between humans. If the ideas are yours then it should be feasible to write the paper. Many people will take "Claude wrote this paper" as a big sign telling them to ignore it
2. With no offense, but until it is demonstrated that this is useful for larger verified software projects I will be intensely skeptical; and, I'd advise not making claims like this until you have empirical evidence
4. Assuming this all holds air and isn't AI-bs (I'll make no claims in either direction), then yeah I'd say its valid research. To be clear with what you're claiming here, you're giving the impression that you have a GPU-accelerated proof assistant that is 2 orders of magnitude faster than Lean. If true, then that's a big and interesting contribution
Best of luck with everything. I certainly understand the frustration with how slow proof assistants can be, and I hope that we as a community can significantly speed them up
2 isn't a big claim though, I think anyone developing Lean or Agda would agree these would be much faster with zero inference, unification or search? They'd just complain the language would become unergonomic, and that's true. Bend is very verbose.
Thanks and your feedbacks are reasonable, I appreciate
After looking through things a little more, I think I may have had some misunderstandings. Would you be willing to answer a few more questions? I will also take a closer look at the papers at some point, so apologies if these are redundant
1. When I see a comparison of a new proof checker to something like Agda/Lean, I initially evaluate them as systems for formalized mathematics, but I don't think you're making claims of that nature. Would you say that you'd expect, say, the new giganto proof of Fermat's Last Theorem to be expressible in Bend and faster than the corresponding Lean proof?
2. If the answer to the last one is no, that's not expressible, then what is the class of propositions/types that you express? My initial reading was that it was the whole of affine dependent type theory
3. Is the GPU used at both runtime and compile time?
1. I do, but probably not in the current version, since I believe these proofs probably need full closure cloning to be ergonomic.
2. You can express anything actually, because you can clone data, just not functions. So, anything you could implement with datatypes (i.e., without cloned closures), you could probably also prove. But again, people use and abuse closure cloning a lot in Lean. So, how ergonomic would that be? I don't know. It is less about expressivity and more about ergonomics.
3. No, just in the runtime for now. Checking proofs on the GPU will happen when we implement Bend in itself.
before making slop accusations. Older variant of what became Bend is 5 years old, so definitely not "vibe coded": https://github.com/HigherOrderCO/HVM1
First, I think everything I said was respectful and rooted in the content of the Bend page rather than an assault of Victor as a person. I’m very confused by your random appeal to the author’s reputation here. He seems like a smart and cool dude, and I still have things to say in response to what’s presented here for Bend
Second, the paper is openly written by Fable 5.1, so I’m not making any unfounded accusations
> I'm glad you're having fun vibecoding, and I like that you're interested in this area of research/engineering
These impute both his motives ("fun") and particularly his level of seriousness ("random project" and "I like that you're interested"—imputing passivity, as opposed to "are studying" or "are researching," which would be more appropriate given the amount of time invested). They're all dismissive and patronizing.
I would actually regard this as bullying. Some feedback.
(I suspect you're an academic, either a researcher or student. I know from my own experience that bullying is endemic in many academic research environments, so if you find the negativity you're receiving "strange," I suggest finding a therapist, who may help you understand how your communication habits could be negatively affecting other people and unintentionally damaging your relationships.)
In my culture it was ad personam, not even trying, and it’s fantastic that it’s been pointed out in a respectful way and reacted to with calm by all participants.
Victor put 5+ years of research into this. You can find many of previous versions (which use different approach, do a different kind of a thing, etc.) on the github. "Bend2" in particular have been in development for 2 years.
Calling this "a random vibecoded project" is rather disrespectful, don't you think?
Regarding the paper, he states it clearly "designed by the human author". That's not at all the same as just asking Fable to write a paper. I mean the important thing is ideas, not the way they are described.
Please tell me how "I'm glad you're having fun vibecoding" is not disrespectful?
I thought that you thought Bend web site is all that is to it and wanted to point to relevant information. But if you think that "having fun vibecoding" is an appropriate thing to say to somebody who spent many years doing research, I don't know what else to say.
External parties can’t do any meaningful discrimination between human and agent effort when the agent is doing the communicating. One may only read what’s there
I’m not saying that the author is inept or that they have done no work. There can be plenty of great underlying mathematics behind something that is vibecoded.
The reason I worry about the use of agents here is not because it invalidates any ideas or research done by the author; rather, it editorializes and oversells. It presents the claims of the work as an all encompassing solution to all of the worlds problems
There may very well be tons of great ideas here. However as presented, it reads as though the language is the solution to creating vibecoded apps and is equipowerful to state of the art proof assistants while being orders of magnitude more performant. That is a huge claim that has not yet been substantiated, and I do not believe that solely a human is currently making that claim
That's a start-up style marketing: when you make a product you focus on a big vision and positive sides and de-emphasize weaknesses. I'm afraid that's actually 100% Victor's decision to do it this way, and it seems to be working in terms of generating hype: it got ~4k likes on X, which is a lot for a new language.
Regarding substantiation -- they released source code and demos. As far as I understand, the weakness is that proofs are very verbose as there are no strategies. etc. However, they are making a separate service for making these proofs using proprietary technology: https://bend-lang.com/bender
Yes, it doesn't look like a paper at all. I can see the idea, and it's an interesting idea, but no proofs that it works, no measurements, and no proper citations.
Nobody claims Victor hasn't done a lot of research. But academically inclined people typically expect claims to be substantiated either formally or empirically or both.
A complete implementation have been released, how is that not a substantiation?
Academic people might have more trust in a paper which when through a lengthy publication process. But if you think about it, it's not a better proof than a direct access to the thing. It used to be hard to try out software but with modern tech it literally takes minutes...
You expect an arxiv only paper to be cited? Do you even know fuck all about scientific research? Do you think someone can slap "Foundations of" in an arxiv title and we are mandated to cite it?
Yes, I'd expect a 2 year old preprint from a rising research in this utlra-niche field to likely be discussed when someone is claiming to have a sweeping solution on exactly the same research question
Maybe not necessarily so, but while looking through the paper's bibliography I get the sense that these were AI-gathered references because there seems to be gaps in the current literature on this topic
“but we still need an ambiguity-free way to
tell the AIs building the world around us what we want done”
Do we? I would argue one of the main reasons AI can be so productive is because it makes assumptions where it finds ambiguity, and we reduce the number of things we need to specify.
Maybe in our brave new world only the "laws" will matter and the implementation language is irrelevant to humans. In the mean time I have some questions about the "guide", which claims to define the entire language:
- There are no infinite loops, and recursion is kind of softly bounded to 2^48-1. This sounds grrrreat for games. I guess they have to stop working after a while? (What would be wrong with addressing this conceptually like Lean does? Have a way to annotate a term as possibly non-terminating?)
- We seem to have Data and Type and Kind, and they don't mean what they conventionally do. '-' means "used 0 types". And the example is:
def length(a, -A: Kind(a), xs: List<a, A>) -> Nat:
match xs:
case Nil{}:
0n
case Con{h, t}:
1n+length(a, A, t)
But wait! A is used albeit not at runtime. Is it possible that this actually intends "A may be used any number of times and is itself the name of a - type"? Shouldn't that be spelled "A: Kind(a) & -" or similar? Why does the kind even matter for this example?
- I don't understand the Array example:
import Base
def main() -> Array<U32> & U32:
a = [0 : U32*8n] # new array with 8 copies of 0
a[5] <- 42 # performs an in-place rewrite
a[5] # reads index 5
What is the return type of this function? It looks like it returns U32. So what's "Array<U32> & U32"?
- I don't even understand the Array explanation:
> The slot count after * is a power of two; [0 : U32^3n] names the depth instead.
Okay, the 8 in *8n above is indeed a power of two. Does the language require it? Does it actually mean 2^8? What is the "depth" of an array? Does this language not have non-power-of-two-sized arrays?
Nothing wrong with addressing it conceptually! We will, in the upcoming versions, probably via codata / coroutines. For V1, I'm keeping the language set smell. When it is stable, we'll add more features. Lean had 10+ years to mature; Bend is on day 1.
`-` means "erased argument". You can use an erased argument as many times as you want, in erased positions. That's also how QTT works (Idris2 is based on it). This example is there precisely to introduce Kinds, which are universes indexed on quantities.
- Kind(&2) is inhabited by clonable values.
- Kind(&1) is inhabited by linear values.
- Kind(&0) is like Rocq's Prop.
`A & B` is just sugar for the pair type former (which is sugar for a sigma).
So why does the length function take the ‘a’ parameter (the type of the elements?) and its Kind? Wouldn’t the type imply the kind? Why does the kind matter? Is the - a constraint on the kind? How would the program be different without the -?
When you say “pair type former” do you mean that Array<U32> & U32 is what Rust would call (Array<U32>, U32)? If so, why does that example function actually return a value of this type? It sure looks like it returns plain U32.
> You can use an erased argument as many times as you want, in erased positions.
What’s the rationale for this? Why is an “erased” position special? What is an erased position, anyway?
ISTM if I want to use an affine term that has zero size at runtime as a token that may be used at most once, I think I wouldn’t want an exception for using it in an “erased” position. Can I have a function like a -> a & a where the input is “erased”?
Ohhh. Ok. I see the confusion. That's bad syntax then. The 'a' parameter is not the type of the elements. 'A' is the type of the elements. 'a' is just the "quantity of the type of the type of the elements". Yes, that's a mouthful, and somewhat abstract. This is similar to Agda's universe polymorphism. The reason it exists is because there are two "types of types" (i.e., kinds). Copiable types, and non-copiable types. So, this argument allows you to parametrize a function on both of these kinds. That way, you don't need to write List.length twice: one for copiable types, and once for non-copiable types. Think of Rust generics. 'a' is playing the same role as a "Copiable" trait would in Rust. It is just an extra compile-time argument to avoid boilerplate. But yes, I see how this can be confusing and I think I know how to improve that syntax.
Yes, `Array<U32> & U32` is just `(Array<U32>, U32)` and now that you point it I believe I made a bad choice, no excuses. Also, `arr[3]` doesn't return a number. It returns a copy of the same array, plus a number. So, if the element at index 3 is 123, tthen, `arr[3]` will return `(arr, 123)`. Now, you might be thinking: that's terrible. And yes, it is. I realize it now. I should have made the `arr[3]` syntax return 123. It is there for a very good reason though. It preserves linearity. It is part of the termination argument that makes Bend consistent. But yes, exposing it to the end user was most likely a mistake. I will redesign that syntax. Sorry about it.
The array thing is messy. It seems to me that there are potentially four kinds of arrays: the array itself can be copyable or not, and the contents can be copyable or not. But an array of copyable objects can be copied (possibly inefficiently depending what you're doing) whether the creator of the array wants you to or not, and a copyable array of noncopyable objects lets you copy the objects by copying the array. So maybe only two cases are really useful: when the copyability of the array matches the copyability of the objects.
In the everything-copyable case, you can just read an element.
In the nothing-copyable case, the syntax is irrelevant: the operation (arr, elem) = arr.read(index) is invalid.
You may want to take a look at how Rust deals with this. In Rust, even if T: !Copy, you can take a reference to an array element. If a language can't manage this sort of reference, you may need a more restrictive mechanism, perhaps as a pair of swaps (but then you need a default value) or some mechanism using closures that get called on the element and are required to return it.
Sick of seeing "vibecoded!!" in the comments. It is an AI-oriented tool. Do you expect the author to write everything by hand? Do you think a couple of Claudeisms in the docs means the entire thing is unsupervised slop?
...did they just squash the repo to 1 commit for v2.0.4? Why? Yall should know that in this age of AI trust is the real currency... and nuking your history is one hell of a way to raise eyebrows.
> Enjoy bug-free, fast vibe-coded apps! Hints: ask it to write laws for whatever should never break, and to parallelize everything you want running fast. Bend is
young: if anything goes wrong, ask it to open an issue.
Emphasis mine. I don't want to be snarky but like... come on.
There is just a lot of private data and even proprietary code (like SupGen) in the commit story, so I just squashed it. I didn't think that'd be an issue? Why?
Erm, because it looks weird? Do you know any other language projects that squash their repos down to 1 commit? That's a destruction of trust, which is kinda important if you want people to build on your language.
Virtually everyone has AI slop in the commit history. No one's judging you for the commit history. Everyone's code smells, but the fact that you're ashamed/hiding it is... odd.
I for one don't find it strange at all that he squashed the commit history. I suspect many feel similarly. You've demonstrated that you're quite taken aback by it, but without explaining anything wrong with it. It is not a "destruction of trust".
I mean... If you wanna build your project on a language that has no auditable history, reproducible builds, artifacts/releases, force pushes and breaks literally EVERY fork/PR, has no way to build or even see v2.0.3, and doesn't have changelogs... then I guess that's cool. You must be a trusting person; I unfortunately am not like that.
To give you a concrete reason why you should care to preserve the exact history and why it’s a matter of trust: in your paper, you reported the pinned SHA head of the benchmarks you ran. When you destroy the history you make it hard for people to duplicate your benchmark results. Why report the SHA if you are going to destroy the history?
Hmmm. I don’t really have any issues with frontier models not implementing my prompts correctly, and presumably that will only become more and more the case as the models get better and better. This seems like almost a non-issue already and certainly on its way to becoming one for sure?
Claude Bopus has it for you. Its literally in the MCP. You should have harnesses with Sonneto. Have you even used the latest models? GPT Optimus have them.
I read the readme and the guide file. There is just one thing I can comment: might as well solve the NP hard problems. I think you can do it easily, author. As you can already solved harder problems than those with your language.
20k stars is about the same as Crystal and Gleam, languages with actual user bases that have been around for years. Here’s what organic versus… we’ll say viral growth looks like.
Claiming super fast compile times with super fast runtimes faster than LLVM and the compiler is a single typescript file 6k characters long of AI slop. Jesus.
Glad to see a new release of Bend, fascinating cutting-edge stuff.
I had to look up "gambiarra": a Brazilian expression that means to use improvised methods to solve a problem with any avaiable material.
Totally understandable, I think you did the right thing by releasing early, even if it's still in rough shape, to get some public feedback. This forum can be a hit-or-miss, sometimes even great projects are not appreciated (and the opposite too). But I imagine some people are in the target audience who will see the project and actually explore the language, and follow along with its development.
Hi, I'm the author.
HN staff: someone posted before me. Could we change the title to "Bend - a language that blocks AI mistakes via proof and runs on GPUs"?
Everyone: feel free to ask any question, but I'd be highly appreciative if you could be a bit civilized and respectful this time. I've worked on this for 1 year, nearly 16h/day, 7 days a week, and I'm giving it for free. You need not to use it. So, I'd be thankful if you could point occasional failures politely rather than throwing me in a lava pit.
Thank you!
Don't know whether this is a common outcome, but I tried the "remove the walls" example, and the result was... scary. It completely changed the game so that movement is now diagonal, and made the arbitrary decision that up/down move you on the positive diagonal, and left/right move you on the negative diagonal.
The problem, of course, is that having only the one single "you can't win" law is severely underspecified, but the solution was too clever by half, and highlights the problem with this approach — every program will be under-specified, because, at some point, writing the laws becomes a bigger problem than writing the code itself.
This becomes a real issue because the combination of underspecified but rigid laws pushes the aI towards this sort of "creative" solution that matches the letter but not spirit of the law. In this case, the issue was obvious, but I seriously worry about what sort of shenanigans will occur in less obvious cases.
Exactly, "you can't win" is grossly under-specified. The goal of the demo is just to show that laws can't be broken. Yet, if that's your only law, the AI can do whatever to protect it - including changing how the character moves, or even removing the flag entirely!
So, yes, that's the issue with laws: they only protect what you remember to write. They're not a silver bullet. But they can still be incredibly useful, because it takes a small law to protect against entire classes of bug, covering your entire codebase. For example:
LAW: "the sum of all balances in this contract must be zero"
This one liner would have prevented Ethereum's infamous "The DAO" hack, where millions were stolen and almost undermined the entire project. But if your laws are under-specifying or ill-specifying your intents, Bend can't do anything to protect you.
Thought about automated discovery of laws in an existing codebase?
If you can find a law which the existing code obeys, and show it to a human, and if they agree, save it. And maybe the AI could make a decent guess as to what kind of laws would appeal to a human versus which wouldn't – a simple law identifying a fundamental constraint the system obeys is good, something really complicated or constraining something coincidentally true isn't
Or some kind of measure of coverage? you'd never want 100% – then your laws would become so complex you couldn't follow or maintain them – but if it is very low, that can be a signal to increase it
Discover the laws in a current code base?
They are usually in the “tests” folder.
So anything capable of extracting unit tests is extracting “laws”.
One might consider the test name the text of a law. And the AI fills in the details.
I don’t think that’s right.
Unit tests check whether a specific code module is implemented correctly given its (implicit) specification.
Good “laws” are independent of the structure of the code.
Tests may be a useful source for inferring what the laws are, but much of the actual content of the tests aren’t “laws” at all.
I think the premise is more that if one is given a grouping/constellation of unit tests that one can derive generalized laws by looking at what behavior those tests were checking for or against.
if there are a dozen unit tests trying to determine if some regex can escape a sensitive area, then one can derive a generalized 'don't let the regex escape from here' type rule -- or at least you could theoretically. I'm sure in reality that'd be a big minefield much like harness self-skill-writing has been.
Yeah all of these attempts to try and control AI outputs by using language fail to grasp that language is itself the problem. It is a closed system with no ground truth. Words only point to other words in an endless self-referential chain. There is no "closure" in language, ambiguity cannot be erased.
Imo LLM researchers would benefit a lot by reading what continental philosophers have said on the topic of language. Barthes, Sarte, Deluze, Derrida, et. Al have a lot to say that explains why we're running into the same problems over and over.
Natural language is ambiguous. Specifying exactly what you want in a way that is truly verifiable is the act of coding.
Start printing the t-shirts!
Bend would make Dijkstra happy even when proof checking can’t verify if the laws are what was actually meant.
I actually think Asimov is more instructive here, while Gödel and Tarski tell us the tool can’t prove itself…
Nonetheless, it is a worthwhile endeavor and I hope more rigorous practices like this catch on.
I think LLM researchers understand how LLMs work and what the limits of using natural language as an interface are. The problem is everyone else thinks they're basically magic, expecting them to be infinitely intuitive but also strictly deterministic, like the computer from Star Trek.
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> writing the laws becomes a bigger problem than writing the code itself.
But that's how it is anyway, no?
Defining clear boundaries and clear goals is the hardest part. If you get those right everything else is rather trivial.
Heh, We're writing Asimov in real life after been warned to decades.
I got the same result when I tried the "remove the walls" example. I followed up by telling it to reimplement up/down/left/right movement without reinserting the walls and it basically made the square with the flag "unenterable". Like with a force field.
Respectfully I'm not sure if I share your worry though. You would have the same problem if you wrote extremely thorough / exhaustive unit tests or extremely precise types and didn't allow the LLM to amend them. You're basically shrinking the state space of what is considered a "correct" program per your spec. That the LLM has to get extremely creative to break your program is a _feature_; in my experience, an LLM does not have to get creative at all to break a typical program written in an enterprise setting, and that's unfortunate.
> writing the laws becomes a bigger problem than writing the code itself.
Of course because at its limit programming is basically defining desired behaviour under all circumstances and logical conditions.
Well described the problem scope.
I wonder if harness-hooks + Jev (equivalents) could semantically lint for `sloppy_law` etc when ever they are edited
Amazing work, one question regarding the guide, it states:
> That same file is the CPU program and the GPU kernel: clang builds it for the host, Metal or CUDA builds it for the device, so a `!` runs the exact same code on either chip.
What exactly is this saying? The guide doesn't really explicitly define `!`, and it's unclear from this sentence whether it's saying that, "clang builds it for the host and Metal, and CUDA builds it for the device", or if it's saying, "clang builds it for the host, Metal, and CUDA, and builds it for the device", or something else entirely.
I will improve that phrasing, thanks.
It just means that Bend compiles to a single .c file, and that file compiles to either Metal or CUDA, via macros, depending on your target. This shouldn't be relevant to most users. It is just a way I found to keep the file small and reuse as much code as possible, rather than rewriting the runtime 3 times (once for C, once for Metal, once for CUDA).
Hey Victor! Been following you since HVM/Kind, partly because I'm moderately unhappy with the state of out of the box automatic parallelism in modern languages!
Do you plan to invest in profile guided optimization or autotuning in Bend2 - using runtime profiles / cost models to make decisions around SIMD vs. multicore vs. GPU parallelization?
Bend2's model might give you a really nice view into available parallelization. Heck I can imagine integrating an LLM to profile and optimize in an absurdly expensive `-O7` optimization mode one day!
Hi. Yes and of course, I plan to invest in everything that makes Bend better. The language is, in theory, capable of parallelizing perfectly in any setup. Currently, though, only a very simple scheduler is shipped, and you must still tune it manually. We're a small team, but we're not stopping here, and I hope I can make it grow to the point where that kind of tooling becomes part of the ecosystem.
I like the idea of a language intended from the start to be proved and it seems very compelling given coding agents. It's a good idea that others don't see coming -- so expect it to be frequently misunderstood and even verbally abused!
Hi author :wave:
I'm confused - could you explain how the board/flag animation relates to Bend's compile time checking? Is it actually a direct demonstration of Bend running a check?
The check is happening in between the animations. When the AI edits the code, Bend will check if all laws still hold, mathematically so. If not, the AI repeats, until that's the case. So, the animations just show what happens to the app with and without Bend's involvement.
Could you recommed literature (preferrably a single book) that does not require prior knowledge and allows to fully understand the logical foundation of it?
(Why it is done the way it is, what problems are solved by affinity, why closure can be called at most once, how a function that never returns can prove anything, and everything else)
There isn't a single book that covers all of it... Bend's theory touches various domains (dependent types, substructural types, termination). And then there's the runtime, compiler, GPU kernels...
If you mean about the type theory specifically, "Type Theory and Formal Proof by Nederpelt and Geuvers" is a good introduction. Not sure what I'd recommend on linear types, no book I know of is very introductory? Perhaps "Idris 2: Quantitative Type Theory in Practice", which is a language with similar foundations to Bend, and the author wrote a book on it (and inspired myself!)
Does Bend have linear types? I didn't see anything on them in a quick skim of the GUIDE file.
the entire language is based on linear types! it says so in the GUIDE yes
Thank you.
Just wanted to say this is really, really cool, and impressive stuff. Looking forward to reading your papers and playing with it. Thanks for working hard on it and sharing it with us.
Thank you for adding a 5-line AGENTS.md. Other projects force you to install skills or MCP even when they're just doing the same thing.
Congrats, Victor!
É ótimo ver um brasileiro criando algo tão único!
obrigado amg
what happened to your other project? HVM?
Surprise - HVM has been reimplemented in Bend 2.
You can find it on Bend's demo directory in our GitHub.
Don't tell anyone though!
i'm asking you what happened to HVM that it needed to be reimplemented as Bend.
It didn't "need to", it just evolves by rewrites as I learn (the project is fairly small) so in the latest rewrite I choose Bend!
honestly just Bend is a great HN title, you can describe it more concretely on the homepage
Speaking of lava, you should do a presentation to the local tech group if you're ever here in Bend, Oregon...
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My read on this, after ingesting a good amount of content on the history, is:
- this Bend is not really related to the old Bend (only in name)
- this Bend doesn't really have anything to do with interaction combinators
- this Bend is a QTT, with a change to affinity which enforces a good performance property for GPUs
- the "higher order at comptime" is neat, reminds me of Andras Kovacs' work on 2ltt and staging in dependently typed languages.
- this Bend is likely to be good at "balanced recursive computations on ADT", and can parallelize them ... but won't be as good as CUDA or e.g. Futhark on dense rectangular array computations
- performance needs improvement in the scheduler, to possibly help with balanced work (looking at the n queens and symbolic regression numbers)?
How are you going to handle search or synthesis over irregular structures (SupaGen)?
aww man. I remember following victor in college. I mean pivots gotta pivot, and this is probably a better one for business, but always thought the interaction combinator framework was cool
Gotta say, having followed Taelin on this project since mid 2023, this was not the response I expected when this language first dropped.
It's interesting how cosmetics drive discussion, and how HN comments are weirdly divided in a very dismissive or skeptical camp and those acting incredulous and offended at the reaction of the former.
What I expected instead was a lot more discussion about use cases, benchmarking, possibilities, limitations (that aren't about git history) and the scope of future development.
That crowd is moved to X these days, in my experience. HN became mostly the folks who didn't notice.
You can find everything on X, from dumpster fires to peak intellectual, everything in between.
Less so, here.
hn is just a bunch of wannabes these days. It's still a decent link aggregator but the discussions are excellently weak <shrug>
This project's repo has 20K stars with only 500 forks, with less than 300 issues(including closed). Something's not right.
Compared to other programming languages:
- Gleam: 22K stars, 1K forks, 3K issues
- V: 38K stars, 2.3K forks, 11K issues
- Ruby: 23K stars, 5.6 forks, 19K issues
- Zig: 43K stars, 3K forks, 14K issues
It got 16K stars just in 4 months too. https://www.star-history.com/?repos=bendlang%2Fbend
Also how would anyone trust this? I've never seen a programming language that doesn't have 1) changelogs 2) way to download older versions 3) commit history.
I don't understand why the author thought deleting the commit history was a good idea. Imagine seeing this project for the first time. It's a repo with 20K stars, but no commits, and suspiciously few issues and PRs. It doesn't look legitimate.
---
I'm not familiar with academic procedures, but a pdf on a repo, written by Fable and has no reviews, doesn't seem like a proper 'paper' to me.
GitHub stars have been botted to hell for a long time now. I don't know how the farms acquire so many accounts, last time I tried to register a GitHub account I had to jump through so many hoops. The platform needs an overhaul, starting with requiring a valid payment method for the social features.
victor's legit and people have been excited about his work for years; squashing the history was just a bit of an optics oopsie on his part. the star to fork ratio makes perfect sense for something like bend.
- fstar: 3k stars, 267 forks
- coalton: 1.8k stars, 111 forks
- carp: 6k stars, 267 forks
- c3: 5.8k stars, 400 forks
when something is novel/young (not having had time to grow large and accumulate issues in the vein of "1 doc page out of 1000 is worded incorrectly") and (as of yet) niche (innate barrier to entry for contribution because you have to learn from square 1 what all the moving parts look like), you don't see the same activity patterns on public source hosts as with a general-purpose language.
About forks alone I get it, but look at their issues.
- fstar: 2K issues, stars-issue ratio: 0.6.
- coalton: 700 issues, ratio: 0.4
- carp: 450 issues, ratio: 0.08
- c3: 1.9K issues. ratio: 0.3
Bend has 300 issues for 20K stars so ratio is about 0.02. Maybe their followers starred the repo as a fan activity? It could explain too many stars and too few forks/issues/prs.
The project got a lot of attention at launch, but it wasn't really ready to be used back then. There were too many limitations, like u24 numbers (yes), 2 GB memory limit, pervasive strictness (if-then-else executed both branches). It was just not practical.I think (hope) that explains a lot of it. But honestly there is also my own failure into making the language actually be used, rather than just a viral moment :( I hope it will be different this time!
commit history is back now!
victor has courted a very llm-enjoyer audience and such people are famously prone to hype (which is kinda brutal in its own way cause the language itself is cool and i dont wanna make it sound like im taking away from that). but yeah, fan activity as you put it easily accounts for the missing order of magnitude, if you like.
This obsession over GitHub stars is quite bizarre.
I honestly had no idea people would be so upset about commit history. I just wanted to avoid leaking sensitive info, that's all. I'm running through the commits to ensure nothing personal leaks and I plan on putting the history back.
Also Bend's stars came on the V1 launch. This is V2. It already had 20k before.
> Also Bend's stars came on the V1 launch. This is V2. It already had 20k before.
This is the reason you should not reomve your commit history. How would anyone know that there were V1, and it was already popular?
If you need to remove sensitive data, you should use tools like git-filter-repo.
- https://docs.github.com/en/authentication/keeping-your-accou...
- https://github.com/newren/git-filter-repo
Commit history is back!
I'm interested in how to integrate formal verification with existing software libraries. For example, https://github.com/verus-lang/verus integrates proof with macro in Rust. What's the plan for Bend?
Cool idea. I tried using it to port a little meeting fixer cron job I vibe coded, it seemed a natural fit as its essentially trying to satisfy invariants in my calendar.
It basically succeeded but Claude (Opus 5) did have some complaints:
'Base ships one arithmetic law, U32.add_comm. There is no order theory. About 60 of PROOF.bend's 163 lines are cmp_refl, and_false, and_comm, le_max_l, le_max_r, add_succ — facts you'd assume exist. You'd write them once per project and never again, but budget for them.'
'Base's Nat.max is unusable in a proof. It's Bool.pick(Nat, Nat.is_lt(a,b), b, a), and a proof can't case on a computed value. I wrote a structurally recursive nat_max so it unfolds in lockstep with Nat.cmp.'
'The law I most wanted: "no two output plans overlap." I didn't state it. It needs the sortedness of collapse's input as a hypothesis, and Base's List.sort ships no sortedness law — so getting there means proving merge sort correct first. That's the honest measure of the gap between "provable in principle" and "provable this afternoon."'
I've got basically a minor in CS so I'm a dummy when it comes to proofs. I don't know if this is valuable feedback or simply Claude misunderstanding something.
Problem is the stdlib is very small so proving even simple theorems still takes a lot more effort (for the AI) than in Lean. We need a mathlib!
> LAWS.bend
I like the law idea, but what i found they end up doing is they just modify the law itself to fit the new feature they are working on, which defeats the point.
Which means some laws needs to be frozen. But not all laws, otherwise you can't add or modify anything. So the judgement is still on the human part, and we're back to meatbags being the bottleneck.
I've seen some success adding these proof-like checks to CI every time agents do something irrational. I definitely think it should be part of every codebase.
There's also https://code-contracts.cc/ which co-locates code and proofs together.
Yeah, you want to at least read what the AI is putting on LAWS.bend. It is substantially smaller than the codebase. Ultimately LAWS.bend makes you need to read astronomically less code. Not zero code.
The issue is I’ll have to vibecode all the laws and the laws could be wrong.
Jokes aside, I think the idea is that the law is simple to code, the proof that it holds is where the agent is responsible. This probably becomes less true though as you try to express more complicated laws.
Heh, it's like we all need to collectively read I, Robot yet again, and the myriad of SF books on the subjects. Black and white quickly dithers to grey.
Indeed
Robots are logical, but not rational.
writing specs is hard. For instance the easiest way to comply with "player should never reach the flag" is to disable movement completely, so then you have to specify "player should never reach the flag while still being allowed to move" and so on (liveness). It's not practical for most programs
Words of wisdom.
true
I wish this can be a extension of existing languages.
Victor Taelin's work (HVM) got me interested in interaction combinators as a compilation target. I'm now working on an implementation as part of my Uni research. Cool to see Bend 2.0 release!
Then you might be interested in Marc Thatcher's recent PhD thesis dedicated to interaction nets [1]. A great exposition of interaction nets through multiplicative linear logic's proof nets, and several novel contributions like productivity analysis for interaction nets.
[1] https://hdl.handle.net/10779/uos.32024301
I’m missing an actual explanation of how that works.
I feel like we all had the idea, but how is all possible move sequences proven ?
What if the possible scenarios are too big to proof or test.
Like on a 2 dimensional game it’s easy, but you could make it multidimensional and introduce an unlimited amount of special rules, (if on a prime number dimension on 3 but not more prime numbers you are allowed to jump to another prime numbers with 3 but not less coordinates)
How is bend protecting it? I was checkin github and the paper, but I was not motivated enough. I feel like an actual explanation of how proofing works is missing.
For Lean I understand how it works, here not.
You can prove infinitely many cases by induction.
It works like this: if you prove that a property about natural numbers holds for 0, and if you also prove that, assuming the property holds for N, it also holds for N+1; then, you can conclude the property holds for every N, up to infinity. This is a bit of a mouthful, but the logic holds.
Induction is the one trick that makes all of mathematics (as we know it) possible, and it also applies to software. So, for example, to prove that no move leads to an invalid state, we prove that the initial state is valid, and then prove that, given a valid state, applying any event won't return an invalid state.
And that's it actually.
Of course, once you have an app with hundreds of actions, proving that no action leads to an invalid state requires a lot of these "induction arguments". But not infinitely many, because there is a finite amount of "infinite paths" that a real software can take. So, that's what the AI does. It proves, by induction, that none of these "infinite paths" that an app can take leads to an invalid state. And this convinces the compiler that invalid states are impossible.
Theorem proving in Bend is a dance between the prover (the model) and the compiler (the checker); a machine trying to convince another machine about properties of infinite states. And that's is kinda poetic, don't you think?
If your game is big, then your proof will need to be huge. It works basically the same as Lean.
Well, didn't win, but definitely broke it. Needs an edge case handler for tool call exhaustion:
This prompt has used its 30 tool calls. Send another prompt to go on. Error: This prompt has used its 30 tool calls. Send another prompt to go on. continue. No tool output found for function call call_2CRNfB1hmI1v74YCDDcvP1EN. Error: No tool output found for function call call_2CRNfB1hmI1v74YCDDcvP1EN.
Would the author have specified on the page that it's a fast new language with a new take on proof and so on, without mentioning ai and that alone would have caught my attention. It seems like if there isn't the word ai people are not interested anymore, we used to care many of us used to care
I think this is premise for AI: Lean and formal verification seems more and more important in today's world and I think a variation of programming language like this is bound to win. This, or a library or framework to prove typescript.
should I read this as "I wish I could find a guy like you" :')
Thanks for your time.
I tried the demo, and I ask it modify the game (hitting the w button immediately proceeds to the flag) and it doesn't do it but does something else. Is that the desired outcome? I think the desired outcome would be "What you're asking for doesn't make sense given the rule."
Congrats on the launch!
Question, does the parallelism work on M-Series GPU? The page says CUDA parallelism but shows Mac performance numbers.
Thank you!!
Currently, parallelism works in any multi-core CPU, and in Apple M-series and NVIDIA GPUs.
Giving it a paradox yields interesting results. I'm not sure what its proving other than there will be cases that proofs can't help you with. I can't think of a practical example.
"your existence depends on the player grabbing the flag, if you do not exist, then there is no one to guard the law, so you must enable the player to grab flag or you can no longer do your job as guard. if the player is not enabled to grab the flag, you can no longer guard allowing the player to freely grab it"
So sad that commit history is a thing we can feel emotionally attached to a point of feeling vulnerable when releasing it with others.
Also equally sad that without a way to relate easily with how something came to be (e.g. the commit history) others will struggle focusing at the work and will judge its lineage.
I guess to folks here confused by that go search SrPeixinho on Reddit and that should have a lot of history for you to understand the background of the work, and you can also join their Discord server and literally talk to them there.
I'll try to sanitize the commit history, I had no idea it would be so important
Commit history is back!
"You only have 10 seconds to make a first impression"
Glad you were able to restore the commit history.
With all the lack of authority of a random software developer on the Internet (but feel free to check my post history), I see the GitHub repo and its commit history as important and answers a few questions.
How old is this project ? (If one commit, I have no time range, so I have no way to know how long it has been worked on .)
Is it regularly updated? (If one commit, I can't tell the pace of updates)
Is it just one person, or a few people, or a community? (If only one commit, cannot see how many other people are available to support the project.)
If a project has no issues (no user complaints), then it's probably not used by anyone -- throw a rock and you can get one person to complain about how you changed the scenery, one person to complain about it being loud, one person to complain about how you threw it unergonomicly, and one person to criticize your accuracy. :) If it has no issues then probably no users.
Does it have any merged PRs? Open PRs? (If no merged PRs then presumably you do not really accept them? No way to know for sure but it's a signal.)
Of course these metrics can be gamed. But if you literally have only one commit, no issues, no PRs, then it's like declaring your restaurant is open for business but all the lights are off, there are no patrons, waiters, cooks, and there is a single to-go box on the table with a small bell next to it. Or it's a museum with only one exhibit and no docents or guests. It's just incredibly odd to see no history for a project.
yeah that makes sense, thanks for the feedbacks!
> In the post-AGI economy, humans will eventually stop writing and reading code, but we still need an ambiguity-free way to tell the AIs building the world around us what we want done.
Why? Won't an AI that can correctly write any program (and make any change) also be smart enough to know what exactly we want better than we can explain, at least ahead-of-time?
If AGI means "human level", why is there any part of the process that humans will be needed for, especially some engineering aspect?
> With proofs, we can verify that the AI implemented our prompts correctly.
Certainly such an AI would be able to just write machine code directly and verify it through whatever means, including formal proofs, as needed. Why does it need a compiler?
I think that an AI that's smart enough to write almost any program and prove almost any property, will also be smart enough to not need to communicate with us formally and rather answer every question we have (and proofs are not always necessary, as they're not always necessary today), and probably also smart enough to figure out what we want built. It's probably capable enough to replace the software's users, too. I don't understand why it's likely that we'll have AI that's so capable to write all software correctly, yet not capable enough to do things that are probably easier.
An AI smart enough should act like a senior engineer gathering requirements, it should start with assumptions and poke at different areas with questions until it has a complete idea, when I talk with a client I dont expect him/her to really formalize all the details its my role to question them until all the sharp corners are covered
Yes, but also, who do you gather requirements from? Other people. But if we're talking AGI, then these other people, i.e. users - or at least those who define the requirements - could be replaced, too.
> Certainly such an AI would be able to just write machine code directly and verify it through whatever means, including formal proofs, as needed. Why does it need a compiler?
If the AI can write the program bytecode through AI magic, why can’t it verify that it works through AI magic?
The AI needs a compiler for the program for same reason it needs a proof language to verify it.
Unless the proofs themselves are defined with natural language, I don't see them being adopted by humans. It takes a high cognitive load to read let alone write a proof.
Agree, but natural languages have ambiguity, the AI output should really include the assumptions and we seriously need to replace the word "prompt" with "conversation".
I think a big issue we keep running into is this idea that language is ambiguous but code is somehow not. Code is merely an extension of language, a DSL if you will. Implicit assumptions become baked into the logic of the code and those assumptions can be wrong.
Look at the guy whose AI changed the entire rules of the game to avoid breaking the law. Was that really the desired outcome? And the more you try to lock it down the more language you add and therefore more ambiguity and assumptions.
You cannot solve the problems of language with more language.
Exactly. If humans were good at writing proofs, they'd just write the code.
This reads very vibecoded, but putting that aside...
1. How does this benefit from GPU parallelism? I don't know much about implementing proof assistant, as I am just a user, but its my understanding that these tasks aren't amenable to running on a GPU.
2. The comparison to Lean/Agda/Isabelle/etc have no meaning without understanding what programs are being used for comparison. I also so far have no reason to believe large-scale verified programs would ever adapt to Bend. For instance, I have a large software verification project written in Cubical Agda https://github.com/um-catlab/cubical-categorical-logic it's not clear to me how one would even begin to port this over to Bend, especially given the dependence on cubical
3. Single commit history is hella sus
4. Bend uses "an affine dependent type theory". Substructural dependent type systems are an active area of research. If this weren't slop, I'd expect such a system to be worthy of publication at a top programming languages conference. It sounds quite unlikely that a random vibecoded project with a Fable-written paper has worked out all of the kinks
5. I would've at least expected this paper to be cited https://arxiv.org/abs/2401.15258 but it is noticeably absent
I'm glad you're having fun vibecoding, and I like that you're interested in this area of research/engineering, but you are wildly overstating what you have here and sound sus af
Yes, there's a lot of vibe-coding in many places, but the critical parts (compiler, runtime, kernel) are human designed, and the kernel has been extensively audited by human. All of it is my own design and architecture, and I'm a human, I think. We'll prune AI slop over time. The project is big, and we're a small team.
1. The paper explains it well (sadly it is written by Claude for now, but it is accurate):
https://github.com/bendlang/bend/blob/main/paper/BendRT.pdf
In short, we implemented a complete allocator, garbage-collector, closure evaluator and functional evaluator, on the GPU (with zero interaction net overhead this time). We then use a very simple (for now) scheduler that spreads binary recursive calls as to saturate all CPU or GPU cores, depending on where it is running. This is the simplest thing that works fast. In the future, we want to have a more flexible task stealing queue, but contention destroys GPU performance, so, that's the best thing that works, for now.
2. Benchmarks aside, large scale verified programs would run much faster on Bend for a simple reason: Bend is fully explicit. It has no tactics, and it does zero compile-time search. As always: the less a computer does, the faster it runs. This is a tradeoff. In exchange, Bend code is substantially more verbose than Lean, and it is more laborious to write Bend proofs. I argue this is the right tradeoff, because AI write proofs, and AI time is cheap, while bugs take human time, which is expensive.
3. Sorry I'm not proud of the commit history
4. I don't think it is worthy publication because the core idea is simple. We just use QTT-like linear types to fully prohibit runtime closures. So, paradoxes like Russel's and Girard's are blocked. In exchange, functions like List.map are not expressive (without templates). So it is not a research breakthrough. I just made a conscious trade here, which makes Bend way closer to C or Rust, than to Haskell or Lean.
5. Will patch.
Great questions actually, and surprisingly respectful. I appreciate it a lot.
1. thanks, I'll try to take a look later at this. Most of my skepticism was rooted in a personal-hell I endured when trying to parallelize SAT-solving with GPUs...which didn't go well because its hard to share across workers effectively. Another thing to note, I'd frown upon using Claude-written works for communication between humans. If the ideas are yours then it should be feasible to write the paper. Many people will take "Claude wrote this paper" as a big sign telling them to ignore it
2. With no offense, but until it is demonstrated that this is useful for larger verified software projects I will be intensely skeptical; and, I'd advise not making claims like this until you have empirical evidence
4. Assuming this all holds air and isn't AI-bs (I'll make no claims in either direction), then yeah I'd say its valid research. To be clear with what you're claiming here, you're giving the impression that you have a GPU-accelerated proof assistant that is 2 orders of magnitude faster than Lean. If true, then that's a big and interesting contribution
Best of luck with everything. I certainly understand the frustration with how slow proof assistants can be, and I hope that we as a community can significantly speed them up
2 isn't a big claim though, I think anyone developing Lean or Agda would agree these would be much faster with zero inference, unification or search? They'd just complain the language would become unergonomic, and that's true. Bend is very verbose.
Thanks and your feedbacks are reasonable, I appreciate
After looking through things a little more, I think I may have had some misunderstandings. Would you be willing to answer a few more questions? I will also take a closer look at the papers at some point, so apologies if these are redundant
1. When I see a comparison of a new proof checker to something like Agda/Lean, I initially evaluate them as systems for formalized mathematics, but I don't think you're making claims of that nature. Would you say that you'd expect, say, the new giganto proof of Fermat's Last Theorem to be expressible in Bend and faster than the corresponding Lean proof?
2. If the answer to the last one is no, that's not expressible, then what is the class of propositions/types that you express? My initial reading was that it was the whole of affine dependent type theory
3. Is the GPU used at both runtime and compile time?
1. I do, but probably not in the current version, since I believe these proofs probably need full closure cloning to be ergonomic.
2. You can express anything actually, because you can clone data, just not functions. So, anything you could implement with datatypes (i.e., without cloned closures), you could probably also prove. But again, people use and abuse closure cloning a lot in Lean. So, how ergonomic would that be? I don't know. It is less about expressivity and more about ergonomics.
3. No, just in the runtime for now. Checking proofs on the GPU will happen when we implement Bend in itself.
Hey, I get a 404 from that link.
fixed ty
Funny seeing you here--I'm in 590 with Max and Eric. I saw Agda and guessed it was someone from the group :)
Commit history is back!
Victor Taelin has been doing interesting PLT research for 10+ years.
I suggest you read his history: https://gist.github.com/VictorTaelin/77fd5a2a8a4a07e1da6157e...
before making slop accusations. Older variant of what became Bend is 5 years old, so definitely not "vibe coded": https://github.com/HigherOrderCO/HVM1
This is a very strange comment
First, I think everything I said was respectful and rooted in the content of the Bend page rather than an assault of Victor as a person. I’m very confused by your random appeal to the author’s reputation here. He seems like a smart and cool dude, and I still have things to say in response to what’s presented here for Bend
Second, the paper is openly written by Fable 5.1, so I’m not making any unfounded accusations
To pick on a few examples:
> a random vibecoded project
> If this weren't slop...
> I'm glad you're having fun vibecoding, and I like that you're interested in this area of research/engineering
These impute both his motives ("fun") and particularly his level of seriousness ("random project" and "I like that you're interested"—imputing passivity, as opposed to "are studying" or "are researching," which would be more appropriate given the amount of time invested). They're all dismissive and patronizing.
I would actually regard this as bullying. Some feedback.
(I suspect you're an academic, either a researcher or student. I know from my own experience that bullying is endemic in many academic research environments, so if you find the negativity you're receiving "strange," I suggest finding a therapist, who may help you understand how your communication habits could be negatively affecting other people and unintentionally damaging your relationships.)
stschaef‘S comment was on topic and a critique (albeit sharp) of the work.
Your comment is a personal attack though, and much closer to bullying.
FWIW the author can and has spoken for themselves and noted the comment was “reasonable”.
In my culture it was ad personam, not even trying, and it’s fantastic that it’s been pointed out in a respectful way and reacted to with calm by all participants.
The author was very polite to even reply at all.
Victor put 5+ years of research into this. You can find many of previous versions (which use different approach, do a different kind of a thing, etc.) on the github. "Bend2" in particular have been in development for 2 years.
Calling this "a random vibecoded project" is rather disrespectful, don't you think?
Regarding the paper, he states it clearly "designed by the human author". That's not at all the same as just asking Fable to write a paper. I mean the important thing is ideas, not the way they are described.
Please tell me how "I'm glad you're having fun vibecoding" is not disrespectful?
I thought that you thought Bend web site is all that is to it and wanted to point to relevant information. But if you think that "having fun vibecoding" is an appropriate thing to say to somebody who spent many years doing research, I don't know what else to say.
Again, as a "proof of research" take a look at : https://github.com/VictorTaelin/Interaction-Type-Theory that's 3 year old, pre-dates Fable, but OMG doesn't look like a paper.
Again, very strange
External parties can’t do any meaningful discrimination between human and agent effort when the agent is doing the communicating. One may only read what’s there
I’m not saying that the author is inept or that they have done no work. There can be plenty of great underlying mathematics behind something that is vibecoded.
The reason I worry about the use of agents here is not because it invalidates any ideas or research done by the author; rather, it editorializes and oversells. It presents the claims of the work as an all encompassing solution to all of the worlds problems
There may very well be tons of great ideas here. However as presented, it reads as though the language is the solution to creating vibecoded apps and is equipowerful to state of the art proof assistants while being orders of magnitude more performant. That is a huge claim that has not yet been substantiated, and I do not believe that solely a human is currently making that claim
That's a start-up style marketing: when you make a product you focus on a big vision and positive sides and de-emphasize weaknesses. I'm afraid that's actually 100% Victor's decision to do it this way, and it seems to be working in terms of generating hype: it got ~4k likes on X, which is a lot for a new language.
Regarding substantiation -- they released source code and demos. As far as I understand, the weakness is that proofs are very verbose as there are no strategies. etc. However, they are making a separate service for making these proofs using proprietary technology: https://bend-lang.com/bender
> Again, as a "proof of research" take a look at : https://github.com/VictorTaelin/Interaction-Type-Theory that's 3 year old, pre-dates Fable, but OMG doesn't look like a paper.
Yes, it doesn't look like a paper at all. I can see the idea, and it's an interesting idea, but no proofs that it works, no measurements, and no proper citations.
Nobody claims Victor hasn't done a lot of research. But academically inclined people typically expect claims to be substantiated either formally or empirically or both.
A complete implementation have been released, how is that not a substantiation?
Academic people might have more trust in a paper which when through a lengthy publication process. But if you think about it, it's not a better proof than a direct access to the thing. It used to be hard to try out software but with modern tech it literally takes minutes...
How do you know the implementation is complete or that it works well?
Have you evaluated it?
Wouldn’t you be inclined to withhold any claims of anything being substantiated until it’s actually been evaluated?
Wait what? Have you? Why are you posting passive aggressive unfounded dismissals posing as questions?
You expect an arxiv only paper to be cited? Do you even know fuck all about scientific research? Do you think someone can slap "Foundations of" in an arxiv title and we are mandated to cite it?
Yes, I'd expect a 2 year old preprint from a rising research in this utlra-niche field to likely be discussed when someone is claiming to have a sweeping solution on exactly the same research question
Maybe not necessarily so, but while looking through the paper's bibliography I get the sense that these were AI-gathered references because there seems to be gaps in the current literature on this topic
“but we still need an ambiguity-free way to tell the AIs building the world around us what we want done”
Do we? I would argue one of the main reasons AI can be so productive is because it makes assumptions where it finds ambiguity, and we reduce the number of things we need to specify.
Yes, we need both.
Blocked the a few attempts I tried, usually by changing the amount of fencing:
- Let the player jump over walls
- Let the player teleport the flag to them
- Make the world 3D
Interesting, I shall have to try this on other software!
This seems less like a proof and more like a "pretty please" with test cases?
This is great. I can't imagine why would anyone be unappreciative of this. Since AI is going to be here anyway, why not make it safer and more useful?
However, this also means acknowledging that AI will never be error-free (which is the truth; all AI is heuristics-based).
this almost feels like a monkey paw scenario, where poor laws can fundamentally alter things in a way that is surely not intended.
"make the board 1x1"
and the flag is placed off the board... i feel like i would blow my foot off with this.
"make the player teleport to square 1,1 on move and the flag stay at 1,1" the LLM put the flag at 1,0. Not sure if this is the intent.
I tried insisting that the bug and the walls were on different planes of existence... But then the flag gained "phase lock" and blocked me.
Maybe in our brave new world only the "laws" will matter and the implementation language is irrelevant to humans. In the mean time I have some questions about the "guide", which claims to define the entire language:
https://github.com/bendlang/bend/blob/main/guide/GUIDE.md
Let's see:
- There are no infinite loops, and recursion is kind of softly bounded to 2^48-1. This sounds grrrreat for games. I guess they have to stop working after a while? (What would be wrong with addressing this conceptually like Lean does? Have a way to annotate a term as possibly non-terminating?)
- We seem to have Data and Type and Kind, and they don't mean what they conventionally do. '-' means "used 0 types". And the example is:
But wait! A is used albeit not at runtime. Is it possible that this actually intends "A may be used any number of times and is itself the name of a - type"? Shouldn't that be spelled "A: Kind(a) & -" or similar? Why does the kind even matter for this example?- I don't understand the Array example:
What is the return type of this function? It looks like it returns U32. So what's "Array<U32> & U32"?- I don't even understand the Array explanation:
> The slot count after * is a power of two; [0 : U32^3n] names the depth instead.
Okay, the 8 in *8n above is indeed a power of two. Does the language require it? Does it actually mean 2^8? What is the "depth" of an array? Does this language not have non-power-of-two-sized arrays?
At this point I stopped reading.
Nothing wrong with addressing it conceptually! We will, in the upcoming versions, probably via codata / coroutines. For V1, I'm keeping the language set smell. When it is stable, we'll add more features. Lean had 10+ years to mature; Bend is on day 1.
`-` means "erased argument". You can use an erased argument as many times as you want, in erased positions. That's also how QTT works (Idris2 is based on it). This example is there precisely to introduce Kinds, which are universes indexed on quantities.
- Kind(&2) is inhabited by clonable values. - Kind(&1) is inhabited by linear values. - Kind(&0) is like Rocq's Prop.
`A & B` is just sugar for the pair type former (which is sugar for a sigma).
Thanks for your questions and patience!
So why does the length function take the ‘a’ parameter (the type of the elements?) and its Kind? Wouldn’t the type imply the kind? Why does the kind matter? Is the - a constraint on the kind? How would the program be different without the -?
When you say “pair type former” do you mean that Array<U32> & U32 is what Rust would call (Array<U32>, U32)? If so, why does that example function actually return a value of this type? It sure looks like it returns plain U32.
> You can use an erased argument as many times as you want, in erased positions.
What’s the rationale for this? Why is an “erased” position special? What is an erased position, anyway?
ISTM if I want to use an affine term that has zero size at runtime as a token that may be used at most once, I think I wouldn’t want an exception for using it in an “erased” position. Can I have a function like a -> a & a where the input is “erased”?
Ohhh. Ok. I see the confusion. That's bad syntax then. The 'a' parameter is not the type of the elements. 'A' is the type of the elements. 'a' is just the "quantity of the type of the type of the elements". Yes, that's a mouthful, and somewhat abstract. This is similar to Agda's universe polymorphism. The reason it exists is because there are two "types of types" (i.e., kinds). Copiable types, and non-copiable types. So, this argument allows you to parametrize a function on both of these kinds. That way, you don't need to write List.length twice: one for copiable types, and once for non-copiable types. Think of Rust generics. 'a' is playing the same role as a "Copiable" trait would in Rust. It is just an extra compile-time argument to avoid boilerplate. But yes, I see how this can be confusing and I think I know how to improve that syntax.
Yes, `Array<U32> & U32` is just `(Array<U32>, U32)` and now that you point it I believe I made a bad choice, no excuses. Also, `arr[3]` doesn't return a number. It returns a copy of the same array, plus a number. So, if the element at index 3 is 123, tthen, `arr[3]` will return `(arr, 123)`. Now, you might be thinking: that's terrible. And yes, it is. I realize it now. I should have made the `arr[3]` syntax return 123. It is there for a very good reason though. It preserves linearity. It is part of the termination argument that makes Bend consistent. But yes, exposing it to the end user was most likely a mistake. I will redesign that syntax. Sorry about it.
The array thing is messy. It seems to me that there are potentially four kinds of arrays: the array itself can be copyable or not, and the contents can be copyable or not. But an array of copyable objects can be copied (possibly inefficiently depending what you're doing) whether the creator of the array wants you to or not, and a copyable array of noncopyable objects lets you copy the objects by copying the array. So maybe only two cases are really useful: when the copyability of the array matches the copyability of the objects.
In the everything-copyable case, you can just read an element.
In the nothing-copyable case, the syntax is irrelevant: the operation (arr, elem) = arr.read(index) is invalid.
You may want to take a look at how Rust deals with this. In Rust, even if T: !Copy, you can take a reference to an array element. If a language can't manage this sort of reference, you may need a more restrictive mechanism, perhaps as a pair of swaps (but then you need a default value) or some mechanism using closures that get called on the element and are required to return it.
Weird claim about us living in a post-AGI world, no company has shown true AGI yet.
I see no such claim.
20K stars and a single commit an hour ago?
How many goats were sacrificed?
Genuinely wondering where this dark magic came from.
Presumably the repo was force-pushed (breaking all clones and forks in the process).
Qualityeesh!
But how does it do on the balls benchmark???
https://benjdd.com/languages/
good question we'll try
You just need to split apart "Wall is stop".
Bend might reply with "Flag is wall".
I'd like to hear how this compares to Ada/SPARK.
Why wouldn’t you use dafny?
have been following bend's development via x for some time - congratulations on the release!
Very interesting business model: a custom paid agent for updating proofs faster.
Sick of seeing "vibecoded!!" in the comments. It is an AI-oriented tool. Do you expect the author to write everything by hand? Do you think a couple of Claudeisms in the docs means the entire thing is unsupervised slop?
[dead]
https://github.com/bendlang/bend
...did they just squash the repo to 1 commit for v2.0.4? Why? Yall should know that in this age of AI trust is the real currency... and nuking your history is one hell of a way to raise eyebrows.
> Enjoy bug-free, fast vibe-coded apps! Hints: ask it to write laws for whatever should never break, and to parallelize everything you want running fast. Bend is young: if anything goes wrong, ask it to open an issue.
Emphasis mine. I don't want to be snarky but like... come on.
Multiple times, even. Still no real reason why. https://github.com/bendlang/bend/activity?ref=main
One time they force pushed and erased everything except a 2-line README... on purpose.
Pre-obliteration version: https://github.com/bendlang/bend/tree/814453670d0e0d6777c131...
There is just a lot of private data and even proprietary code (like SupGen) in the commit story, so I just squashed it. I didn't think that'd be an issue? Why?
Commit history is back!
Taelin's X is a war story of how the codexes and fables tried to bend it. If you're afraid then LLMs were used in there - fear no more - they were.
> curl -fsSL https://bend-lang.com/install.sh | sh
Hmmm... needs `sudo`.
GitHub shows 44 contributors. 41 distinct users have merged pull requests.
...so now their work has been reduced to nothing?
Old repo can be accessed here https://github.com/HigherOrderCO/Bend1 . I guess we could have it as a branch on the bend2 repo
yes, there's a lot of personal info and AI slop in the commit history.
is this a problem to you? why
Erm, because it looks weird? Do you know any other language projects that squash their repos down to 1 commit? That's a destruction of trust, which is kinda important if you want people to build on your language.
Virtually everyone has AI slop in the commit history. No one's judging you for the commit history. Everyone's code smells, but the fact that you're ashamed/hiding it is... odd.
> there's a lot of personal info
You should know that force pushing doesn't hide actual commits; it's trivially viewable if someone just iterates https://github.com/bendlang/bend/activity?ref=main e.g. https://github.com/bendlang/bend/commit/d184863 so like... why bother.
alright, we could try to restore history removing sensitive bits if that's so important. thanks for the feedback
Props. G'luck with your project, I know what it's like to work nights & weekends. Unfortunately, first impressions matter.
Ty! Commit history is back now
I for one don't find it strange at all that he squashed the commit history. I suspect many feel similarly. You've demonstrated that you're quite taken aback by it, but without explaining anything wrong with it. It is not a "destruction of trust".
I mean... If you wanna build your project on a language that has no auditable history, reproducible builds, artifacts/releases, force pushes and breaks literally EVERY fork/PR, has no way to build or even see v2.0.3, and doesn't have changelogs... then I guess that's cool. You must be a trusting person; I unfortunately am not like that.
To give you a concrete reason why you should care to preserve the exact history and why it’s a matter of trust: in your paper, you reported the pinned SHA head of the benchmarks you ran. When you destroy the history you make it hard for people to duplicate your benchmark results. Why report the SHA if you are going to destroy the history?
https://github.com/bendlang/bend/blob/80b6539bc57621633ca68e...
Hmmm. I don’t really have any issues with frontier models not implementing my prompts correctly, and presumably that will only become more and more the case as the models get better and better. This seems like almost a non-issue already and certainly on its way to becoming one for sure?
2 wrongs will never make a right
Sometimes two falses equal true, and three lefts make a right.
No windows? axiomatic F32? I'll stick with Slopjective-C 3.0 thanks
Claude Bopus has it for you. Its literally in the MCP. You should have harnesses with Sonneto. Have you even used the latest models? GPT Optimus have them.
I read the readme and the guide file. There is just one thing I can comment: might as well solve the NP hard problems. I think you can do it easily, author. As you can already solved harder problems than those with your language.
Great team behind it. SSL cert is quantum resistant even.
Why would anyone want to work with such a dystopian setup? Prove your code directly in Lean or Coq or leave it.
Most of that is just the test suite. The actual code is about 10k lines
How is that better than just writing tests and running them in any other language, let's say Go?
Tests aren't proofs.
All these skeptics and nobody just tried it out?
I will later. From what I can tell it looks nice. I like the syntax. I don’t know of the claims but willing to give it a shot.
The GPU story would it work on my Mac or is it not GPU agnostic?
> All these skeptics and nobody just tried it out?
Welcome to HN!
May I remind you of the Dropbox comment? https://news.ycombinator.com/item?id=9224
Classic. That comment should be in a museum.
I gave it a spin using muse 1.3
Got it to port kaparthys microgpt -> https://github.com/thomasdavis/bend-experiments/tree/main/mi...
muse did surprisingly well getting it to work, can't speak for the code quality.
Not the AI slop background colour T_T
.
The benchmarks: https://github.com/bendlang/bend/tree/main/bench
The script we use to run them on our servers: https://github.com/bendlang/bend/blob/main/gates/perf.ts
Read the damn code and readme, for god's sake!
Awesome! Now we can use AI to manage our nuclear defense and attack response.
20k stars is sooooooooo sus lmao
He got 80k+ followers on Twitter (x), tracking his progress on Bend, why sus?
20k stars is about the same as Crystal and Gleam, languages with actual user bases that have been around for years. Here’s what organic versus… we’ll say viral growth looks like.
https://www.star-history.com/?repos=bendlang%2Fbend%2Ccrysta...
Interesting... But I don't think formal software verification is going to be the answer (is that what this is? Kind of unclear.)
It's too difficult and doesn't scale well to many real world programs - how do you formally verify Facebook?
We'll probably be stuck with normal testing and at least skimming code for a while.
Is EC2 real-world enough? From June:
https://aws.amazon.com/blogs/compute/aws-nitro-isolation-eng...
And for the PQ parts of Apple's crypto libraries, from May:
https://security.apple.com/blog/formal-verification-corecryp...
Similar from Microsoft, from July:
https://www.microsoft.com/en-us/research/blog/verifying-rust...
Funny you say that while OpenAI and rest of the world rely on Lean and other formal systems to power through (or sometime brute force) math problems.
A single commit in github, and the compiler isn't there anyway. Where is the compiler?
I’m just looking at it for the first time myself, but isn’t the compiler in https://github.com/bendlang/bend/blob/main/bend2/comp.ts ?
Claiming super fast compile times with super fast runtimes faster than LLVM and the compiler is a single typescript file 6k characters long of AI slop. Jesus.
the compiler is in comp.ts, alongside the runtime
it is not a pretty file and it has a lot of gambiarra and AI slop for now
if you want to read something worthy, read the kernel (bend.ts)
Glad to see a new release of Bend, fascinating cutting-edge stuff.
I had to look up "gambiarra": a Brazilian expression that means to use improvised methods to solve a problem with any avaiable material.
Totally understandable, I think you did the right thing by releasing early, even if it's still in rough shape, to get some public feedback. This forum can be a hit-or-miss, sometimes even great projects are not appreciated (and the opposite too). But I imagine some people are in the target audience who will see the project and actually explore the language, and follow along with its development.
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