Short one this time because I have a lot going on this week. In computation complexity, NP is the class of all decision problems (yes/no) where a potential proof (or "witness") for "yes" can be verified in polynomial time. For example, "does this set of numbers have a subset that sums to zero" is in NP. If the answer is "yes", you can prove it by presenting a set of numbers. We would then verify the witness by 1) checking that all the numbers are present in the set (~linear time) and 2) adding up all the numbers (also linear). NP-complete is the class of "hardest possible" NP problems. Subset sum is NP-complete. NP-hard is the set all problems at least as hard as NP-complete. Notably, NP-hard is not a subset of NP, as it contains problems that are harder than NP-complete. A natural question to ask is "like what?" And the canonical example of "NP-harder" is the halting problem (HALT): does program P halt on input C? As the argument goes, it's undecidable, so obviously not in NP. I think this is a bad example for two reasons: All NP requires is that witnesses for "yes" can be verified in polynomial time. It does not require anything for the "no" case! And even though HP is undecidable, there is a decidable way to verify a "yes": let the witness be "it halts in N steps", then run the program for that many steps and see if it halted by then. To prove HALT is not in NP, you have to show that this verification process grows faster than polynomially. It does (as busy beaver is uncomputable), but this all makes the example needlessly confusing.1 "What's bigger than a dog? THE MOON" Really (2) bothers me a lot more than (1) because it's just so inelegant. It suggests that NP-complete is the upper bound of "solvable" problems, and after that you're in full-on undecidability. I'd rather show intuitive problems that are harder than NP but not that much harder. But in looking for a "slightly harder" problem, I ran into an, ah, problem. It seems like the next-hardest class would be EXPTIME, except we don't know for sure that NP != EXPTIME. We know for sure that NP != NEXPTIME, but NEXPTIME doesn't have any intuitive, easily explainable problems. Most "definitely harder than NP" problems require a nontrivial background in theoretical computer science or mathematics to understand. There is one problem, though, that I find easily explainable. Place a token at the bottom left corner of a grid that extends infinitely up and right, call that point (0, 0). You're given list of valid displacement moves for the token, like (+1, +0), (-20, +13), (-5, -6), etc, and a target point like (700, 1). You may make any sequence of moves in any order, as long as no move ever puts the token off the grid. Does any sequence of moves bring you to the target? This is PSPACE-complete, I think, which still isn't proven to be harder than NP-complete (though it's widely believed). But what if you increase the number of dimensions of the grid? Past a certain number of dimensions the problem jumps to being EXPSPACE-complete, and then TOWER-complete (grows tetrationally), and then it keeps going. Some point might recognize this as looking a lot like the Ackermann function, and in fact this problem is ACKERMANN-complete on the number of available dimensions. A friend wrote a Quanta article about the whole mess, you should read it. This problem is ludicrously bigger than NP ("Chicago" instead of "The Moon"), but at least it's clearly decidable, easily explainable, and definitely not in NP. It's less confusing if you're taught the alternate (and original!) definition of NP, "the class of problems solvable in polynomial time by a nondeterministic Turing machine". Then HALT can't be in NP because otherwise runtime would be bounded by an exponential function. ↩

Carson Gross has a post about vendoring which brought back memories of how I used to build websites in ye olden days, back in the dark times before npm. “Vendoring” is where you copy dependency source files directly into your project (usually in a folder called /vendor) and then link to them — all of this being a manual process. For example: Find jquery.js or reset.css somewhere on the web (usually from the project’s respective website, in my case I always pulled jQuery from the big download button on jQuery.com and my CSS reset from Eric Meyer’s website). Copy that file into /vendor, e.g. /vendor/jquery@1.2.3.js Pull it in where you need it, e.g. <script src="/vendor/jquery@1.2.3.js"> And don’t get me started on copying your transitive dependencies (the dependencies of your dependencies). That gets complicated when you’re vendoring by hand! Now-a-days package managers and bundlers automate all of this away: npm i what you want, import x from 'pkg', and you’re on your way! It’s so easy (easy to get all that complexity). But, as the HTMX article points out, a strength can also be a weakness. It’s not all net gain (emphasis mine): Because dealing with large numbers of dependencies is difficult, vendoring encourages a culture of independence. You get more of what you make easy, and if you make dependencies easy, you get more of them. I like that — you get more of what you make easy. Therefore: be mindful of what you make easy! As Carson points out, dependency management tools foster a culture of dependence — imagine that! I know I keep lamenting Deno’s move away from HTTP imports by default, but I think this puts a finger on why I’m sad: it perpetuates the status quo, whereas a stance on aligning imports with how the browser works would not perpetuate this dependence on dependency resolution tooling. There’s no package manager or dependency resolution algorithm for the browser. I was thinking about all of this the other day when I then came across this thread of thoughts from Dave Rupert on Mastodon. Dave says: I prefer to use and make simpler, less complex solutions that intentionally do less. But everyone just wants the thing they have now but faster and crammed with more features (which are juxtaposed) He continues with this lesson from his startup Luro: One of my biggest takeaways from Luro is that it’s hard-to-impossible to sell a process change. People will bolt stuff onto their existing workflow (ecosystem) all day long, but it takes a religious conversion to change process. Which really helped me put words to my feelings regarding HTTP imports in Deno: i'm less sad about the technical nature of the feature, and more about what it represented as a potential “religious revival” in the area of dependency management in JS. package.json & dep management has become such an ecosystem unto itself that it seems only a Great Reawakening™️ will change it. I don’t have a punchy point to end this article. It’s just me working through my feelings. Email · Mastodon · Bluesky

I’ve been writing some internal dashboards recently, and one hard part is displaying timestamps. Our server does everything in UTC, but the team is split across four different timezones, so the server timestamps aren’t always easy to read. For most people, it’s harder to understand a UTC timestamp than a timestamp in your local timezone. Did that event happen just now, an hour ago, or much further back? Was that at the beginning of your working day? Or at the end? Then I remembered that I tried to solve this five years ago at a previous job. I wrote a JavaScript snippet that converts UTC timestamps into human-friendly text. It displays times in your local time zone, and adds a short suffix if the time happened recently. For example: today @ 12:00 BST (1 hour ago) In my old project, I was using writing timestamps in a <div> and I had to opt into the human-readable text for every date on the page. It worked, but it was a bit fiddly. Doing it again, I thought of a more elegant solution. HTML has a <time> element for expressing datetimes, which is a more meaningful wrapper than a <div>. When I render the dashboard on the server, I don’t know the user’s timezone, so I include the UTC timestamp in the page like so: <time datetime="2025-04-15 19:45:00Z"> Tue, 15 Apr 2025 at 19:45 UTC </time> I put a machine-readable date and time string with a timezone offset string in the datetime attribute, and then a more human-readable string in the text of the element. Then I add this JavaScript snippet to the page: window.addEventListener("DOMContentLoaded", function() { document.querySelectorAll("time").forEach(function(timeElem) { // Set the `title` attribute to the original text, so a user // can hover over a timestamp to see the UTC time. timeElem.setAttribute("title", timeElem.innerText); // Replace the display text with a human-friendly date string // which is localised to the user's timezone. timeElem.innerText = getHumanFriendlyDateString( timeElem.getAttribute("datetime") ); }) }); This updates any <time> element on the page to use a human friendly date string, which is localised to the user’s timezone. For example, I’m in the UK so that becomes: <time datetime="2025-04-15 19:45:00Z" title="Tue, 15 Apr 2025 at 19:45 UTC"> Tue, 15 Apr 2025 at 20:45 BST </time> In my experience, these timestamps are easier and more intuitive for people to read. I always include a timezone string (e.g. BST, EST, PDT) so it’s obvious that I’m showing a localised timestamp. If you really need the UTC timestamp, it’s in the title attribute, so you can see it by hovering over it. (Sorry, mouseless users, but I don’t think any of my team are browsing our dashboards from their phone or tablet.) If the JavaScript doesn’t load, you see the plain old UTC timestamp. It’s not ideal, but the page still loads and you can see all the information – this behaviour is an enhancement, not an essential. To me, this is the unfulfilled promise of the <time> element. In my fantasy world, web page authors would write the time in a machine-readable format, and browsers would show it in a way that makes sense for the reader. They’d take into account their language, locale, and time zone. I understand why that hasn’t happened – it’s much easier said than done. You need so much context to know what’s the “right” thing to do when dealing with datetimes, and guessing without that context is at the heart of many datetime bugs. These sort of human-friendly, localised timestamps are very handy sometimes, and a complete mess at other times. In my staff-only dashboards, I have that context. I know what these timestamps mean, who’s going to be reading them, and I think they’re a helpful addition that makes the data easier to read. [If the formatting of this post looks odd in your feed reader, visit the original article]

We might be seeing the end of remote coding interviews as we know them, and a return of in-person interviews, trial days and longer trial periods. Could hiring be returning to pre-pandemic norms?

Nearly a quarter of seventeen-year-old boys in America have an ADHD diagnosis. That's crazy. But worse than the diagnosis is that the majority of them end up on amphetamines, like Adderall or Ritalin. These drugs allow especially teenage boys (diagnosed at 2-3x the rate of girls) to do what their mind would otherwise resist: Study subjects they find boring for long stretches of time. Hurray? Except, it doesn't even work. Because taking Adderall or Ritalin doesn't actually help you learn more, it merely makes trying tolerable. The kids might feel like the drugs are helping, but the test scores say they're not. It's Dunning-Kruger — the phenomenon where low-competence individuals overestimate their abilities — in a pill. Furthermore, even this perceived improvement is short-term. The sudden "miraculous" ability to sit still and focus on boring school work wanes in less than a year on the drugs. In three years, pill poppers are doing no better than those who didn't take amphetamines at all. These are all facts presented in a blockbuster story in New York Time Magazine entitled Have We Been Thinking About A.D.H.D. All Wrong?, which unpacks all the latest research on ADHD. It's depressing reading. Not least because the definition of ADHD is so subjective and  situational. The NYTM piece is full of anecdotes from kids with an ADHD diagnosis whose symptoms disappeared when they stopped pursuing a school path out of step with their temperament. And just look at these ADHD markers from the DSM-5: Inattention Difficulty staying focused on tasks or play. Frequently losing things needed for tasks (e.g., toys, school supplies). Easily distracted by unrelated stimuli. Forgetting daily activities or instructions. Trouble organizing tasks or completing schoolwork. Avoiding or disliking tasks requiring sustained mental effort. Hyperactivity Fidgeting, squirming, or inability to stay seated. Running or climbing in inappropriate situations. Excessive talking or inability to play quietly. Acting as if “driven by a motor,” always on the go. Impulsivity Blurting out answers before questions are completed. Trouble waiting for their turn. Interrupting others’ conversations or games. The majority of these so-called symptoms are what I'd classify as "normal boyhood". I certainly could have checked off a bunch of them, and you only need six over six months for an official ADHD diagnosis. No wonder a quarter of those seventeen year-old boys in America qualify! Borrowing from Erich Fromm’s The Sane Society, I think we're looking at a pathology of normalcy, where healthy boys are defined as those who can sit still, focus on studies, and suppress kinetic energy. Boys with low intensity and low energy. What a screwy ideal to chase for all. This is all downstream from an obsession with getting as many kids through as much safety-obsessed schooling as possible. While the world still needs electricians, carpenters, welders, soldiers, and a million other occupations that exist outside the narrow educational ideal of today. Now I'm sure there is a small number of really difficult cases where even the short-term break from severe symptoms that amphetamines can provide is welcome. The NYTM piece quotes the doctor that did one of the most consequential studies on ADHD as thinking that's around 3% — a world apart from the quarter of seventeen-year-olds discussed above. But as ever, there is no free lunch in medicine. Long-term use of amphetamines acts as a growth inhibitor, resulting in kids up to an inch shorter than they otherwise would have been. On top of the awful downs that often follow amphetamine highs. And the loss of interest, humor, and spirit that frequently comes with the treatment too. This is all eerily similar to what happened in America when a bad study from the 1990s convinced a generation of doctors that opioids actually weren't addictive. By the time they realized the damage, they'd set in motion an overdose and addiction cascade that's presently killing over a 100,000 Americans a year. The book Empire of Pain chronicles that tragedy well.  Or how about the surge in puberty-blocker prescriptions, which has now been arrested in the UK, following the Cass Review, as well as Finland, Norway, Sweden, France, and elsewhere. Doctors are supposed to first do no harm, but they're as liable to be swept up in bad paradigms, social contagions, and ideological echo chambers as the rest of us. And this insane over-diagnosis of ADHD fits that liability to a T.