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The appeal of "vibe coding" — where programmers lean back and prompt their way through an entire project with AI — appears partly to be based on the fact that so many development environments are deeply unpleasant to work with. So it's no wonder that all these programmers stuck working with cumbersome languages and frameworks can't wait to give up on the coding part of software development. If I found writing code a chore, I'd be looking for retirement too. But I don't. I mean, I used to! When I started programming, it was purely because I wanted programs. Learning to code was a necessary but inconvenient step toward bringing systems to life. That all changed when I learned Ruby and built Rails. Ruby's entire premise is "programmer happiness": that writing code should be a joy. And historically, the language was willing to trade run-time performance, memory usage, and other machine sympathies against the pursuit of said programmer happiness. These days, it seems like you can eat...
a month ago

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More from David Heinemeier Hansson

Gender and Sexuality Alliances in primary school at CIS?!

The Copenhagen International School is a wonderful private school located in the North Harbor of the city. It's home to over 900 students from around the world. This is where ambassadors, international executives, and other expats send their kids to get a great education in English while stationed in Denmark. As a result, it's perhaps the most diverse, inclusive school in all of Copenhagen. Lovely. What's less lovely is the fact that CIS seems to have caught some of the same gender-ideology obsession that has ravaged many schools in America. We thought Copenhagen would offer a respite from the woke nonsense that's been plaguing California — where some schools in our social circle ended up with a quarter or more of the student body identifying as trans or gender nonconformative — but it seems ideological contagions travel as fast as airplanes these days. It started last week, when the primary school, which includes kindergarten, declared its intention to spend every morning meeting for the entire week focused on gender dysphoria, transgenderism, they/them pronoun protocols, and coloring pride flags. That just sounded a bit odd and a bit much at first, but after reviewing the associated material, it actually looked downright devious. Just look at this example: Draw yourself in the mirror, then adorn it with trans colors? And the guiding example is a boy who sees himself as a girl? As you can imagine, many parents at the school were mortified by the idea of their children participating in this kind of overt indoctrination activities, and some of them let the school know. That's when the revisions started rolling out.  First, the program was revised to no longer apply to kindergarten and first grade, just second through fifth. Then the "draw yourself in the mirror and use trans colors to decorate it" activity was pulled from the program. Then the schedule was reduced from all week to just a single session this Monday while the rest of the material is being "reconsidered". And that's where it stands today. But that's not all. After talking to a number of other parents, I learned that CIS has other highly objectionable programs in this sphere. Like "Gender and Sexuality Alliances" where primary school students in G3-5, meaning kids as young as eight, are invited to join in lunch and recess meetings to talk more about gender, sexuality, and how to become a good ally to the 2SLGBTQIA+ community. According to one parent I spoke to (who's considering pulling their kids out over this), CIS hasn't wanted to disclose all specifics about the staff conducting these lunch and recess meetings with the children. Because while it's billed as "student led" on their website, the sessions are actually facilitated by CIS staff on campus.  I've asked the same question of the school administration, including what qualifications these individuals might have, and have not received an answer either. But ultimately, it shouldn't even matter, because this shouldn't even be happening! There's simply no responsible explanation for having kids as young as eight, or even as old as 11, in lunch and recess meetings with CIS staff to discuss gender and sexuality on school campus. It's preposterous, if not outright creepy. The school's mission is no cover either. The commitment to an inclusive school does not offer a license to indulge in this kind of overt indoctrination or inappropriate lunch meetings where minors discuss gender and sexuality with school staff. And it has to stop. CIS, like any other school, should not be a subsidiary of any specific interest organization. We don't want our kids to get their information about climate change from either Extinction Rebellion or fossil-fuel lobbyists. We expect our school to stay politically neutral on the international conflicts, like the one in Gaza. In higher grades where these topics are appropriate, they should be discussed in a context that also includes things like the Cass Review and the recent UK Supreme Court ruling. It's the same reason Copenhagen Pride Week saw a massive loss of sponsorship after trying to cajole major companies into a position on Gaza last year. Novo, Maersk, Google, and many others rejected this organization (and they're not returning this year either) for their partisan politics. It's bizarre that those same companies now have the children of their employees programmed by this organization's agenda at school.  CIS needs to return to its high-level mission of focusing on giving kids an excellent education, teaching them objectively about the world, and upholding general standards for kindness and caring. Not coloring partisan flags during school programs, not facilitating inappropriate meeting forums about gender and sexuality between staff and children.

a week ago 8 votes
Denmark gets more serious about digital sovereignty

The recent disconnection of the ICC's chief prosecutor, at the behest of the American administration, could not have come at a worse time for Microsoft. Just a month prior, the folks from Redmond tried to assure Europe that all was well. That any speculation Europeans could get cut off from critical digital infrastructure was just fear, doubt, and uncertainty. Then everything Europeans worried could happen happened in Hague. Oops! Microsoft's assurances met reality and reality won. That reality is that all American administrations have the power to disconnect any individual, company, or foreign government from digital infrastructure provided by American Big Tech. So in that sense, it's pointless to blame Microsoft for the sanctioning power vested in the Oval Office. But we certainly can blame them for gaslighting Europe about the risk. What's more important than apportioning blame, though, is getting out of the bind that Europe is in. The continent is hopelessly dependent on American Big Tech for even the most basic of digital infrastructure. If this American administration, or the next, decides to use its sanctioning power again, Europe is in a real pickle. And with the actions taken against the ICC in Haag, Europe would be negligent to ignore the threat. Denmark even more so. It's no secret that tensions between Denmark and the US are at a historic high. Trump keeps repeating a desire to take over Greenland by fuzzy means possible. The American intelligence services have been directed to increase their spying on Denmark and Greenland. Naturally, the Danes are spooked. They should be! Regardless of what happens with Greenland, trade negotiations, or geopolitical disagreements, though, it would suit Europe well to become digitally sovereign. That doesn't mean cutting off all American tech, but it does mean rejecting any services that can be turned off from Washington. So in terms of Microsoft, it means no more Microsoft 365, no more Teams, no more Azure. And that's exactly what the two biggest counties in Denmark have announced plans to do. Copenhagen and Aarhus just declared that they're going to get rid of Microsoft products for all their workers. The Copenhagen county is the largest employer in Denmark with over 40,000 employees. So this is a big deal! The chairman of the Copenhagen committee who pushed this forward made this comment to Danish media:  If, theoretically, the relationship to the US gets worse, we could fear that Microsoft would be forced to shut everything down. That possibility exists. And if we suddenly can't access our emails or communicate via our systems, we'll be challenged. That's an understatement. Denmark is one of the most highly digitalized countries in the world. It's also one of the most Microsoft dependent. In fact, Microsoft is by far and away the single biggest dependency, so it makes perfect sense to start the quest for digital sovereignty there. But Denmark is also full of unambitious, defeatist bureaucrats who can't imagine a world without Microsoft. Just today, the IT director for The Capital Region declared it to utopian to think Denmark could ever achieve digital sovereignty or meaningfully replace Microsoft. Not even a decade would make a dent, says the director, while recognizing that if we'd done something 15 years ago, we wouldn't be in this pickle. A remarkable illustration of cognitive dissonance! Sadly, this is not an uncommon conclusion from people who work inside the belly of bureaucracies for too long. Whatever has always done too often seems like the only thing that ever could be done. But, as Mandela said, it always seems impossible until it's done. So let's get it done. Digital sovereignty isn't easy, but neither was securing a sovereign energy supply. Nor will it be to rebuild a credible defensive military. Europe needs all of it, yesterday. The bureaucrats who aren't interested in making it happen should find employment elsewhere.

a week ago 6 votes
Omarchy: Bottling that inspiration before it spoils

Over the years, I've learned not to question inspiration. To simply let it drive when it shows up with a full tank. Quite often, I don't exactly know where we're going or even why we're going, but it's repeatedly taken me to just the right place at just the right time, so now I just hop in and say: Let's go! Case in point: Arch + Hyprland. It's been over a year since I created Omakub to smooth out my own exit path from macOS to Linux, and in the process, helped thousands of others enjoy a beautiful, preconfigured, and relatively familiar desktop experience with Ubuntu. And I continue to think this is an excellent choice for Linux, especially for first-time Mac and Windows defectors. But this weekend, I just happened to be home alone, and the hype around Arch + Hyprland got the better of me. While Ubuntu is all about being a friendly place for newcomers to Linux, Arch + Hyprland is the exact opposite: It's Linux on hard mode!  At least that's the reputation, and there's certainly something to that. The Arch ISO literally just dumps you into a terminal with scarcely any direction. Just getting on the Wi-Fi requires learning the arcane command-line options for the iwctl terminal configurator. But besides iwctl, it's actually not that bad anymore. We now have a cheat code for installing Arch in the form of archinstall. It's a terminal interface for getting all the bits like picking a disk and creating the first user done in the correct order, without having to set aside an entire evening just to get the OS installed. So it didn't take long to get Arch up and running. That doesn't get you much further, though! By default, Arch is about as minimal as it gets. There's no default graphical interface. There are no niceties. Not even wget or curl by default! It really is just a bare-bones installation of Linux. But on the other hand, Arch is blessed with the AUR — a Wikipedia-style, community-maintained package management system that seems to have literally every piece of software ever released on Linux, and always in the latest version. A quarter of Omakub is trying to work around the fact that helpful tools like Alacritty or LazyGit or whatever rarely have official packages for Ubuntu, so you're left doing a lot of manual scripting to get everything a developer would want from a modern Linux setup. Not so with the AUR! So that's Arch. But Hyprland is even more hilarious. It's a tiling window manager with something as rare in the Linux world as a keen focus on aesthetics! It looks like it was written by visual artists rather than neckbeards. And it's at the core of the modern r/unixporn Linux ricing subculture. That's not the funny part, though. The funny part is how ridiculously atomized the entire thing is. Hyprland comes with absolutely nothing out of the box. No login screen, no menu bar, no notification system, no file manager, no visual settings application. Just a text-based configuration file, a wiki, and an outline on a map for how to design your own adventure. This means that if you're interested in running Hyprland, and you intend to set it all up from scratch, you're probably signing up for at least a good 10+ hours — just to install and configure everything! Now, there are some precompiled setup scripts out there already, but most of them still require you to do a ton of manual legwork before you reach that beautiful summit of a complete system. So while the downside of Arch + Hyprland is that literally every last detail requires you to make a choice and a config file to move on, it's also its upside: you can change EVERYTHING! And the core window tiling magic of Hyprland is one of the most intoxicating ways of using a computer that I've ever experienced. It looks amazing; it feels amazing (if you prefer using a keyboard instead of a mouse!). I've poured hours and hours into this quest over the weekend, and yet I'm still not even done with my first Arch + Hyprland build! My login screen looks like shit. I haven't decided on a final menu bar configuration. But what is working — the basic tiling flow and look — is so nice that the inspiration keeps driving the project forward. Which, of course, I've already decided to codify. I'm not going through all this work to set up a beautiful, preconfigured, fully-functional, out-of-the-box Arch + Hyprland combo and then not share it with anyone who's curious (and might not have 10–20 hours for this kind of side quest available in their schedule). So of course I registered a domain and found a way to draw some ASCII art: Omarchy is on the way!

a week ago 9 votes
HEY is finally for sale on the iPhone!

Our battle with Apple over their gangster attempt to extort 30% of our HEY revenues was one of the defining moments of my career. It was the kind of test that calls you to account for what you believe and asks what you're willing to risk to see it through. Well, we risked everything, but also secured a four-year truce, and now near-total victory is at hand: HEY is finally for sale on the iPhone in the US! Credit for this amazing turn of events goes to Epic Games founders Tim Sweeney and Mark Rein, who did what no small developer like us could ever dream of doing: they spent over $100 million to sue Apple in court. And while the first round yielded very little progress, Apple's (possibly criminal) contempt of court is what ultimately delivered the resolution. Thanks to their fight for Fortnite, app developers everywhere are now allowed to link out of apps to their own web-based payment system in the US store (but, sadly, nowhere else yet). This is all we ever wanted from Apple: to have a way to distribute our iPhone apps and keep the customer relationship by billing directly. The 30% toll gets all the attention, and it is ludicrously egregious, but to us, it's just as much about retaining that direct customer relationship, so we can help folks with refunds, so they don't tie their billing for a multi-platform email system to a single manufacturer. Apple always claims to put the needs of the users first, and that whatever hardship developers have to carry is justified by their customer-focused obsession. But in this case, it's clear that the obsession was with collecting the easiest billions Apple has ever made, by taking an obscene cut of all software and subscription sales on the platform. This obsession with squeezing every last dollar from developers has produced countless customer-hostile experiences on the iPhone. Like how you couldn't buy a book in the Kindle app before this (now you can!). Or sign up for a Netflix subscription (now you can!). Before, users would hunt in vain for an explanation inside these apps, and thanks to Apple's gag orders, developers were not even allowed to explain the confusing situation. It's been the same deal with HEY. While we successfully fought off Apple's attempt to extort us into using their in-app payment system (IAP), we've been stuck with an awkward user experience ever since. One that prevented new customers from signing up for a real email address in the application, and instead sent them down this bizarre burner-account setup. All so the app would "do something", in order to please an argument that App Store chief Phil Schiller made up on the fly in an interview. That's what we can now get rid of. No more weird burner accounts. Now you can sign up directly for a real email address in HEY, and if you like what we have to offer (and I think you will!), you'll be able to pay the $99/year for a subscription via a web-based flow that it's now kosher to link to from the app itself. What a journey, and what a needless torching of the developer relationship from Apple's side. We've always been happy to pay Apple for hosting our application on the App Store, as all developers have always needed to do via the $99/year developer fee. But being forced to hand over 30% of the business, as well as the direct customer relationship, was always an unacceptable overreach. Now that's been arrested by Judge Yvonne Gonzalez Rogers from the United States District Court of Northern California, who has delivered app developers the only real relief that we've seen in this whole sordid monopoly affair that's been boiling since 2020. It's a beautiful thing. It also offers Apple an opportunity to bury the hatchet with developers. They can choose to accept the court's decision in full and worldwide. Allow developers everywhere the right to link to their own billing flow, so they can retain their own customer relationship, and so business models that can't carry a 30% toll can flourish. Besides, Apple's own offering will likely still have plenty of pull. I'm sure many small developers would continue to consider IAP to avoid having to worry about international taxes or even direct customer service. Nobody is taking that away from Apple or those developers. All Judge Rogers is demanding is that Apple compete fairly with alternative arrangements. In case Apple doesn't accept the court's decision — and there's sadly some evidence to that — I hope the European antitrust regulators watch the simple yet powerful mechanism that Judge Rogers has imposed on Apple. While I'd love side loading as much as the next sovereign techie who wants to own the hardware I buy, I think we can get the lion's share of independence by simply being allowed to link out of the apps, just like has been so ordered by this District Court. I do hope, though, that Apple does accept the court's decision. Both because it would be a stain on their reputation to get convicted of criminal contempt of court, but also because I really want Apple to return to being a shining city on the hill. To show that you can win in the market merely by making better products. Something Apple never used to be afraid of doing. That they don't need these gangster extortion techniques to make the numbers that Cook has promised Wall Street. Despite moving on to Linux and Android, I have a real soft spot for Apple's taste, aesthetics, and engineering prowess. They've lost their way and moral compass over the last half decade or so, but that's only one leadership pivot away from being found again. That won't win back all the trust and good faith that was squandered right away, but they'll at least be on the long road to recovery. Who knows, maybe developers would even be inclined to assist Apple next time they need help launching a new device in need of third-party software to succeed.

3 weeks ago 11 votes
Have you tried the exact opposite?

Have you thought about doing the opposite of whatever you're doing or considering? It's a really helpful way to test your assumptions and your values. What does the opposite look like, how would it work? It's so easy to get stuck in a groove of what works, what you believe to be right. But helpful assumptions have a half-life, just like facts. And it's ever so easy to miss the shift when circumstances change, if you're not regularly stress-testing your core beliefs. That doesn't mean you're just a flag in the wind, blowing whichever way. But it does mean having enough intellectual humility and creative flexibility to consider that what you believe to be true about your business, about your team, about your technology might not be so. We did this a while back with full-time managers. We'd been working for nearly two decades without any, but exactly because it'd been so long, we were drawn to try the opposite, just to see what we might have missed. So we did. Hired a few full-time managers to help us test that assumption for a few years. In the end, we decided that our managers-of-one culture worked better, but it wasn't a given at the outset. To try the opposite, you really have to believe that you might have been wrong. Because you're wrong about something. I guarantee it. We all are.

3 weeks ago 13 votes

More in programming

What is the competitive advantage of authors in the age of LLMs?

Over the past 19 months, I’ve written Crafting Engineering Strategy, a book on creating engineering strategy. I’ve also been working increasingly with large language models at work. Unsurprisingly, the intersection of those two ideas is a topic that I’ve been thinking about a lot. What, I’ve wondered, is the role of the author, particularly the long-form author, in a world where an increasingly large percentage of writing is intermediated by large language models? One framing I’ve heard somewhat frequently is the view that LLMs are first and foremost a great pillaging of authors’ work. It’s true. They are that. At some point there was a script to let you check which books had been loaded into Meta’s LLaMa, and every book I’d written at that point was included, none of them with my consent. However, I long ago made my peace with plagiarism online, and this strikes me as not particularly different, albeit conducted by larger players. The folks using this writing are going to keep using it beyond the constraints I’d prefer it to be used in, and I’m disinterested in investing my scarce mental energy chasing through digital or legal mazes. Instead, I’ve been thinking about how this transition might go right for authors. My favorite idea that I’ve come up with is the idea of written content as “datapacks” for thinking. Buy someone’s book / “datapack”, then upload it into your LLM, and you can immediately operate almost as if you knew the book’s content. Let’s start with an example. Imagine you want help onboarding as an executive, and you’ve bought a copy of The Engineering Executive’s Primer, you could create a project in Anthropic’s Claude, and upload the LLM-optimized book into your project. Here is what your Claude project might look like. Once you have it set up, you can ask it to help you create your onboarding plan. This guidance makes sense, largely pulled from Your first 90 days as CTO. As always, you can iterate on your initial prompt–including more details you want to include into the plan–along with follow ups to improve the formatting and so on. One interesting thing here, is that I don’t currently have a datapack for The Engineering Executive’s Primer! To solve that, I built one from all my blog posts marked with the “executive” tag. I did that using this script that packages Hugo blog posts, that I generated using this prompt with Claude 3.7 Sonnet. The output of that script gets passed into repomix via: repomix --include "`./scripts/tags.py content executive | paste -d, -s -`" The mess with paste is to turn the multiline output from tags.py into a comma-separated list that repomix knows how to use. This is a really neat pattern, and starts to get at where I see the long-term advantage of writers in the current environment: if you’re a writer and have access to your raw content, you can create a problem-specific datapack to discuss the problem. You can also give that datapack to someone else, or use it to answer their questions. For example, someone asked me a very detailed followup question about a recent blog post. It was a very long question, and I was on a weekend trip. I already had a Claude project setup with the contents of Crafting Engineering Strategy, so I just passed the question verbatim into that project, and sent the answer back to the person who asked it. (I did have to ask Claude to revise the answer once to focus more on what I thought the most important part of the answer was.) This, for what it’s worth, wasn’t a perfect answer, but it’s pretty good. If the question asker had the right datapack, they could have gotten it themselves, without needing me to decide to answer it. However, this post is less worried about the reader than it is about the author. What is our competitive advantage as authors in a future where people are not reading our work? Well, maybe they’re still buying our work in the form of datapacks and such, but it certainly seems likely that book sales, like blog traffic, will be impacted negatively. In trade, it’s now possible for machines to understand our thinking that we’ve recorded down into words over time. There’s a running joke in my executive learning circle that I’ve written a blog post on every topic that comes up, and that’s kind of true. That means that I am on the cusp of the opportunity to uniquely scale myself by connecting “intelligence on demand for a few cents” with the written details of my thinking built over the past two decades of being a writer who operates. The tools that exist today are not quite there yet, although a combination of selling datapacks like the one for Crafting Engineering Strategy and tools like Claude’s projects are a good start. There are many ways the exact details might come together, but I’m optimistic that writing will become more powerful rather than less in this new world, even if the particular formats change. (For what it’s worth, I don’t think human readers are going away either.) If you’re interested in the fully fleshed out version of this idea, starting here you can read the full AI Companion to Crafting Engineering Strategy. The datapack will be available via O’Reilly in the next few months. If you’re an existing O’Reilly author who’s skepical of this idea, don’t worry: I worked with them to sign a custom contract, this usage–as best I understood it, although I am not a lawyer and am not providing legal advice–is outside of the scope of the default contract I signed with my prior book, and presumably most others’ contracts as well.

yesterday 3 votes
TypeScript Conditional Types for Type Safety (Without Assertions)

Using conditional types to achieve type safety without having to use 'as'

yesterday 2 votes
Solving LinkedIn Queens with SMT

No newsletter next week I’ll be speaking at Systems Distributed. My talk isn't close to done yet, which is why this newsletter is both late and short. Solving LinkedIn Queens in SMT The article Modern SAT solvers: fast, neat and underused claims that SAT solvers1 are "criminally underused by the industry". A while back on the newsletter I asked "why": how come they're so powerful and yet nobody uses them? Many experts responded saying the reason is that encoding SAT kinda sucked and they rather prefer using tools that compile to SAT. I was reminded of this when I read Ryan Berger's post on solving “LinkedIn Queens” as a SAT problem. A quick overview of Queens. You’re presented with an NxN grid divided into N regions, and have to place N queens so that there is exactly one queen in each row, column, and region. While queens can be on the same diagonal, they cannot be adjacently diagonal. (Important note: Linkedin “Queens” is a variation on the puzzle game Star Battle, which is the same except the number of stars you place in each row/column/region varies per puzzle, and is usually two. This is also why 'queens' don’t capture like chess queens.) Ryan solved this by writing Queens as a SAT problem, expressing properties like "there is exactly one queen in row 3" as a large number of boolean clauses. Go read his post, it's pretty cool. What leapt out to me was that he used CVC5, an SMT solver.2 SMT solvers are "higher-level" than SAT, capable of handling more data types than just boolean variables. It's a lot easier to solve the problem at the SMT level than at the SAT level. To show this, I whipped up a short demo of solving the same problem in Z3 (via the Python API). Full code here, which you can compare to Ryan's SAT solution here. I didn't do a whole lot of cleanup on it (again, time crunch!), but short explanation below. The code from z3 import * # type: ignore from itertools import combinations, chain, product solver = Solver() size = 9 # N Initial setup and modules. size is the number of rows/columns/regions in the board, which I'll call N below. # queens[n] = col of queen on row n # by construction, not on same row queens = IntVector('q', size) SAT represents the queen positions via N² booleans: q_00 means that a Queen is on row 0 and column 0, !q_05 means a queen isn't on row 0 col 5, etc. In SMT we can instead encode it as N integers: q_0 = 5 means that the queen on row 0 is positioned at column 5. This immediately enforces one class of constraints for us: we don't need any constraints saying "exactly one queen per row", because that's embedded in the definition of queens! (Incidentally, using 0-based indexing for the board was a mistake on my part, it makes correctly encoding the regions later really painful.) To actually make the variables [q_0, q_1, …], we use the Z3 affordance IntVector(str, n) for making n variables at once. solver.add([And(0 <= i, i < size) for i in queens]) # not on same column solver.add(Distinct(queens)) First we constrain all the integers to [0, N), then use the incredibly handy Distinct constraint to force all the integers to have different values. This guarantees at most one queen per column, which by the pigeonhole principle means there is exactly one queen per column. # not diagonally adjacent for i in range(size-1): q1, q2 = queens[i], queens[i+1] solver.add(Abs(q1 - q2) != 1) One of the rules is that queens can't be adjacent. We already know that they can't be horizontally or vertically adjacent via other constraints, which leaves the diagonals. We only need to add constraints that, for each queen, there is no queen in the lower-left or lower-right corner, aka q_3 != q_2 ± 1. We don't need to check the top corners because if q_1 is in the upper-left corner of q_2, then q_2 is in the lower-right corner of q_1! That covers everything except the "one queen per region" constraint. But the regions are the tricky part, which we should expect because we vary the difficulty of queens games by varying the regions. regions = { "purple": [(0, 0), (0, 1), (0, 2), (0, 3), (0, 4), (0, 5), (0, 6), (0, 7), (0, 8), (1, 0), (2, 0), (3, 0), (4, 0), (5, 0), (6, 0), (7, 0), (8, 0), (1, 1), (8, 1)], "red": [(1, 2), (2, 2), (2, 1), (3, 1), (4, 1), (5, 1), (6, 1), (6, 2), (7, 1), (7, 2), (8, 2), (8, 3),], # you get the picture } # Some checking code left out, see below The region has to be manually coded in, which is a huge pain. (In the link, some validation code follows. Since it breaks up explaining the model I put it in the next section.) for r in regions.values(): solver.add(Or( *[queens[row] == col for (row, col) in r] )) Finally we have the region constraint. The easiest way I found to say "there is exactly one queen in each region" is to say "there is a queen in region 1 and a queen in region 2 and a queen in region 3" etc." Then to say "there is a queen in region purple" I wrote "q_0 = 0 OR q_0 = 1 OR … OR q_1 = 0 etc." Why iterate over every position in the region instead of doing something like (0, q[0]) in r? I tried that but it's not an expression that Z3 supports. if solver.check() == sat: m = solver.model() print([(l, m[l]) for l in queens]) Finally, we solve and print the positions. Running this gives me: [(q__0, 0), (q__1, 5), (q__2, 8), (q__3, 2), (q__4, 7), (q__5, 4), (q__6, 1), (q__7, 3), (q__8, 6)] Which is the correct solution to the queens puzzle. I didn't benchmark the solution times, but I imagine it's considerably slower than a raw SAT solver. Glucose is really, really fast. But even so, solving the problem with SMT was a lot easier than solving it with SAT. That satisfies me as an explanation for why people prefer it to SAT. Sanity checks One bit I glossed over earlier was the sanity checking code. I knew for sure that I was going to make a mistake encoding the region, and the solver wasn't going to provide useful information abut what I did wrong. In cases like these, I like adding small tests and checks to catch mistakes early, because the solver certainly isn't going to catch them! all_squares = set(product(range(size), repeat=2)) def test_i_set_up_problem_right(): assert all_squares == set(chain.from_iterable(regions.values())) for r1, r2 in combinations(regions.values(), 2): assert not set(r1) & set(r2), set(r1) & set(r2) The first check was a quick test that I didn't leave any squares out, or accidentally put the same square in both regions. Converting the values into sets makes both checks a lot easier. Honestly I don't know why I didn't just use sets from the start, sets are great. def render_regions(): colormap = ["purple", "red", "brown", "white", "green", "yellow", "orange", "blue", "pink"] board = [[0 for _ in range(size)] for _ in range(size)] for (row, col) in all_squares: for color, region in regions.items(): if (row, col) in region: board[row][col] = colormap.index(color)+1 for row in board: print("".join(map(str, row))) render_regions() The second check is something that prints out the regions. It produces something like this: 111111111 112333999 122439999 124437799 124666779 124467799 122467899 122555889 112258899 I can compare this to the picture of the board to make sure I got it right. I guess a more advanced solution would be to print emoji squares like 🟥 instead. Neither check is quality code but it's throwaway and it gets the job done so eh. "Boolean SATisfiability Solver", aka a solver that can find assignments that make complex boolean expressions true. I write a bit more about them here. ↩ "Satisfiability Modulo Theories" ↩

3 days ago 6 votes
Why Go iterators are ugly, clever and elegant

Go 1.23 adds iterators. An iterator is a way to provide values that can be used in for x := range iter loops. People are happy the iterators were added to the language. Not everyone is happy about HOW they were implemented. This person opined that they demonstrate “typical Go fashion of quite ugly syntax”. The ugly Are Go iterators ugly? Here’s the boilerplate of an iterator: func IterNumbers(n int) func(func(int) bool) { return func(yield func(int) bool) { // ... the code } } Ok, that is kind of ugly. I can’t imagine typing it from memory. The competition We do not live in a vacuum. How do other languages implement iterators? C++ I recently implemented DirIter class with an iterator in C++, for SumatraPDF. I did it to so that I can write code like for (DirEntry* e : DirIter("c:\")) { ... } to read list of files in directory c:\. Implementing it was no fun. I had to implement a class with the following methods: begin() end() DirEntry* operator*() operator==() operator!=() operator++() operator++(int) Oh my, that’s a lot of methods to implement. A bigger problem is that the logic is complicated. This is an example of pull iterator where the caller “pulls” next value out of the iterator. The caller needs at least two operations from an iterator: give me next value do you have more values? In C++ it’s more complicated than that because “Overcomplication” is C++’s middle name. A function that reads a list of entries in a directory is relatively simple. The difficulty of implementing pull iterator comes from the need to track the current state of iteration to be able to provide “give me next value” function. A simple directory traversal turned into complicated tracking of what I have read so far, did the process finish and reading the next directory entry. C C# also has pull iterators but they removed incidental complexity present in C++. It reduced the interface to just 2 essential methods: T Next() which returns next element bool HasMore() which tells if there are more values to read Here’s an iterator that returns integers from 1 to n: class NumberIterator { private int _current; private int _end; public NumberIterator(int n) { _current = 0; _end = n; } public bool HasMore() { return _current < _end; } public int Next() { if (!HasMore()) { throw new InvalidOperationException("No more elements."); } return ++_current; } } Much better but still doesn’t solve the big problem: the logic is split across many calls to Next()so the code needs to track the state. C# push iterator with yield Later C# improved this by adding a way to implement push iterator. An iterator is just a function that “pushes” values to the caller using a yield statement. Push iterator is much simpler: static IEnumerable<int> GetNumbers(int n) { for (int i = 1; i <= n; i++) { yield return i; } } Clever and elegant Here’s a Go version: func GetNumbers(n int) func(func(int) bool) { return func(yield func(int) bool) { for i := i; i <= n; i++ { if !yield(i) { return } } } } The clever and elegant part is that Go designers figured out how to implement push iterators in a way very similar to C#’s yield without adding new keyword. The hard part, the logic of the iterator, is equally simple as with yield. The yield statement in C# is kind of magic. What actually happens is that the compiler rewrites the code inside-out and turns linear logic into a state machine. Go designers figured out how to implement it using just a function. It is true that there remains essential complexity: iterator is a function that returns a function that takes a function as an argument. That is a mind bend, but it can be analyzed. Instead of yield statement pushing values to the loop driver, we have a function. This function is synthesized by the compiler and provided to the iterator function. The argument to that function is the value we’re pushing to the loop. It returns a bool to indicate early exit. This is needed to implement early break out of for loop. An iterator function returns an iterator object. In Go case, the iterator object is a new function. This creates a closure. If function is an iterator object then local variables of the function are state of the iterator. I don’t know why Go designers chose this design over yield. I assume the implementation is simpler so maybe that was the reason. Or maybe they didn’t want to add new keyword and potentially break existing code.

3 days ago 4 votes
The Continuum From Static to Dynamic

Dan Abramov in “Static as a Server”: Static is a server that runs ahead of time. “Static” and “dynamic” don’t have to be binaries that describe an entire application architecture. As Dan describes in his post, “static” or “dynamic” it’s all just computers doing stuff. Computer A requests something (an HTML document, a PDF, some JSON, who knows) from computer B. That request happens via a URL and the response can be computed “ahead of time” or “at request time”. In this paradigm: “Static” is server responding ahead of time to an anticipated requests with identical responses. “Dynamic” is a server responding at request time to anticipated requests with varying responses. But these definitions aren’t binaries, but rather represent two ends of a spectrum. Ultimately, however you define “static” or “dynamic”, what you’re dealing with is a response generated by a server — i.e. a computer — so the question is really a matter of when you want to respond and with what. Answering the question of when previously had a really big impact on what kind of architecture you inherited. But I think we’re realizing we need more nimble architectures that can flex and grow in response to changing when a request/response cycle happens and what you respond with. Perhaps a poor analogy, but imagine you’re preparing holiday cards for your friends and family: “Static” is the same card sent to everyone “Dynamic” is a hand-written card to each individual But between these two are infinite possibilities, such as: A hand-written card that’s photocopied and sent to everyone A printed template with the same hand-written note to everyone A printed template with a different hand-written note for just some people etc. Are those examples “static” or “dynamic”? [Cue endless debate]. The beauty is that in proving the space between binaries — between what “static” means and what “dynamic” means — I think we develop a firmer grasp of what we mean by those words as well as what we’re trying to accomplish with our code. I love tools that help you think of the request/response cycle across your entire application as an endlessly-changing set of computations that happen either “ahead of time”, “just in time”, or somewhere in-between. Email · Mastodon · Bluesky

4 days ago 4 votes