<rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>Hacker News: tmoertel</title><link>https://news.ycombinator.com/user?id=tmoertel</link><description>Hacker News RSS</description><docs>https://hnrss.org/</docs><generator>hnrss v2.1.1</generator><lastBuildDate>Wed, 23 Sep 2026 08:25:39 +0000</lastBuildDate><atom:link href="https://hnrss.org/user?id=tmoertel" rel="self" type="application/rss+xml"></atom:link><item><title><![CDATA[New comment by tmoertel in "The trouble with 'ntile()'"]]></title><description><![CDATA[
<p>Tl;dr: The trouble with ntile seems to be that, when the author of the post imagined what it did based solely on its name and she imagined wrong, she ran with her imaginary version way too long before checking the documentation, which was very clear about its behavior:<p>> Unlike other ranking functions, ntile() ignores ties: it will create evenly sized buckets even if the same value of x ends up in different buckets.</p>
]]></description><pubDate>Wed, 23 Sep 2026 00:12:12 +0000</pubDate><link>https://news.ycombinator.com/item?id=49809981</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49809981</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49809981</guid></item><item><title><![CDATA[New comment by tmoertel in "Divide by depth for instant 3D"]]></title><description><![CDATA[
<p>You don't need to use homogeneous coordinates to represent a series of linear transformations as a single matrix. That's just basic linear algebra: any series of linear transformations is itself a linear transformation, and any linear transformation can be represented as an equivalent transformation matrix.<p>But you <i>do</i> need homogenous coordinates if you want to include translations (fixed distance shifts, such as moving the camera) in the set of operations you can represent as linear transformations and thereby gain all the benefits of linear algebra, including the benefit of being able to include them in a series of operations that you can represent with a single transformation matrix.</p>
]]></description><pubDate>Tue, 22 Sep 2026 13:39:42 +0000</pubDate><link>https://news.ycombinator.com/item?id=49801140</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49801140</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49801140</guid></item><item><title><![CDATA[New comment by tmoertel in "Divide by depth for instant 3D"]]></title><description><![CDATA[
<p>No, the 2d x-y plane in your example cannot pass through the 3d space’s origin because that would imply that you fixed the z coordinate at zero. The plane must be fixed at some nonzero z because you need to be able move x and y values by some scaled version of z to make translation happen. If z is zero, that scheme does not work.<p>Consider a transformation f where we wish to move x-y coordinates s units to the right. In 2d, we could express it as:<p>f(x, y) = (x + s, y)<p>But that transformation is affine not linear. There is no way to generate the value s as a linear combination of the inputs x and y. So, our workaround is to embed the x-y plane into 3d space at z=1. Then we can move (x,y,1) points in that plane s units to the right using this transformation:<p>f(x, y, z) = (x + s*z, y, z)<p>This new transformation is linear: it maps (0,0,0) to itself. But it maps our embedded 2d plane's origin (0,0,1) to (s,0,1), shifting it right by s units, as we want.<p>The matrix form of that transformation is:<p><pre><code>    [[1 0 s]
     [0 1 0]
     [0 0 1]]
</code></pre>
The same scheme would work if we had embedded the plane at any fixed z=r for nonzero r. We would only have to rescale the s in the matrix to s/r. Again, however, if r=0, this scheme will not work, as 1/r has gone to infinity.</p>
]]></description><pubDate>Tue, 22 Sep 2026 03:30:18 +0000</pubDate><link>https://news.ycombinator.com/item?id=49796503</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49796503</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49796503</guid></item><item><title><![CDATA[New comment by tmoertel in "Divide by depth for instant 3D"]]></title><description><![CDATA[
<p>The explanation of "What's that extra 1 for?" in the column representation of 3-d coordinates (<i>x y z</i> 1) could benefit from mentioning that <i>translation</i>—moving things—is not a linear transformation (the origin is not mapped to itself) but an affine transformation. Therefore, you cannot represent translation in 3-d space with a 3x3 matrix. What you can do, though, is embed that 3-d space within a 4-d space fixed at some coordinate on its 4th dimension, typically <i>w</i>=1. Then, a translation in the original 3-d space <i>can</i> be represented as a linear transformation in the 4-d space and thus can also be represented by a 4x4 matrix multiplication. So the extra 1 is actually what allows all common 3-d operations, including translation, to be done via linear algebra and thereby harness the brutal power of matrix multiplication on modern computing devices.</p>
]]></description><pubDate>Tue, 22 Sep 2026 01:09:29 +0000</pubDate><link>https://news.ycombinator.com/item?id=49795612</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49795612</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49795612</guid></item><item><title><![CDATA[New comment by tmoertel in "Asking authors about their own papers"]]></title><description><![CDATA[
<p>But the public is still made a victim by being deceived about the authorship and hence the value and reliability of the work.</p>
]]></description><pubDate>Sun, 20 Sep 2026 14:53:02 +0000</pubDate><link>https://news.ycombinator.com/item?id=49776471</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49776471</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49776471</guid></item><item><title><![CDATA[New comment by tmoertel in "'Mad honey' that can stop your heart is being sold online"]]></title><description><![CDATA[
<p>Another is <i>Kalmia latifolia</i>, the mountain laurel, the state flower of Pennsylvania. According to records at the Carnegie Museum of Natural History [1], "Benjamin Smith Barton (an American botanist in the late 1700s) wrote that in the autumn and winter of the year 1790, many people died in Pennsylvania from the effects of wild honey, collected from <i>Kalmia</i> plants."<p>[1] <a href="https://carnegiemnh.org/collected-day-1959/" rel="nofollow">https://carnegiemnh.org/collected-day-1959/</a></p>
]]></description><pubDate>Tue, 01 Sep 2026 03:08:47 +0000</pubDate><link>https://news.ycombinator.com/item?id=49517547</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49517547</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49517547</guid></item><item><title><![CDATA[New comment by tmoertel in "Things I want in a modern relational query language"]]></title><description><![CDATA[
<p>The problem with alternative query languages is that the people who have the most knowledge about creating queries and of the relational domains underlying their businesses are all experts in SQL. Introducing something else, then, means your most natural user base must migrate away from something they understand how to use well, and that's a hard sell.<p>So, until the ultimate query language is developed, I'll take SQL with pipes. It's an easy sell and good enough to eliminate 90% of my gripes about SQL.</p>
]]></description><pubDate>Sun, 23 Aug 2026 15:35:00 +0000</pubDate><link>https://news.ycombinator.com/item?id=49409676</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49409676</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49409676</guid></item><item><title><![CDATA[New comment by tmoertel in "To become a better writer, read as much as you can"]]></title><description><![CDATA[
<p>> Please please suggest me some books where language and style of speaking sentences takes the crown rather than the story being the selling point.<p>I will give you approximately twenty delightful novels where the prose and the stories are both excellent: Patrick O’Brian’s Aubrey–Maturin series.<p>I avoided these books for the longest time because I didn't believe I was the kind of person who would read “books about tall ships.” But so many people recommend these particular books because of the masterly writing that I tried the first, <i>Master and Commander</i>. Immediately, I was taken by O’Brian’s writing: vivid, lively, and engaging, while also utterly precise.<p>Give that first novel a try. It’s not easy, but it is oh so rewarding.<p>Edited to add some examples from the first novel:<p>“I have never yet known a man admit that he was either rich or asleep: perhaps the poor man and the wakeful man have some great moral advantage.”<p>“Where there was no equality there was no companionship: when a man was obliged to say ‘Yes, sir,’ his agreement was of no worth even if it happened to be true.”<p>“He held up two fingers, in case a landman might not fully comprehend so great a number.”<p>“But you know as well as I, patriotism is a word; and one that generally comes to mean <i>either my country, right or wrong</i>, which is infamous, or <i>my country is always right</i>, which is imbecile.”</p>
]]></description><pubDate>Sun, 23 Aug 2026 14:56:24 +0000</pubDate><link>https://news.ycombinator.com/item?id=49409340</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49409340</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49409340</guid></item><item><title><![CDATA[New comment by tmoertel in "Scrap (2006)"]]></title><description><![CDATA[
<p>> I also think that we should have mercy for people who’ve made mistakes.<p>Yes. When people make mistakes, they sometimes fall into holes that are hard to climb out of. It is in society’s interest to place ladders in these holes so that these unfortunate people can climb out and become productive members of society.<p>Instead, we have self-interested parties who have figured out how to extract rents from keeping people trapped in holes. Some of these parties are preventing ladders from being built. Others are destroying existing ladders. Others still are even inventing deeper, stickier holes—crypto scams, ubiquitous gambling, addictive gas-station drugs, dopamine-hit apps—to trap even greater numbers of their fellow human beings.<p>When a society allows the suffering of others to become a profitable business model, good things rarely follow.</p>
]]></description><pubDate>Sun, 23 Aug 2026 03:25:05 +0000</pubDate><link>https://news.ycombinator.com/item?id=49405851</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49405851</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49405851</guid></item><item><title><![CDATA[New comment by tmoertel in "Scrap (2006)"]]></title><description><![CDATA[
<p>I'm not who you asked, but I moved to Pittsburgh for a job, figuring I would earn money for a few years then move to real city. That was over thirty years ago. Turns out, I love the place.<p>Pittsburgh has most of the benefits of a larger city without most of the problems. Its infrastructure is in many ways over-provisioned, being built for past industry and a larger population (but the maintenance burden is catching up). Its unusually hilly and berivered geography has allowed its neighborhoods to escape homogenization and retain their individual ethnic characters. And the setting, with rivers, bridges, trails, forests, is beautiful. Plus the airport recently got overhauled to meet the region’s actual needs, making it way more convenient.<p>Oh, if you're in to sports, Pittsburgh has some great teams and a great fan base.<p>Yeah, I like the ’Burgh.</p>
]]></description><pubDate>Sat, 22 Aug 2026 23:08:18 +0000</pubDate><link>https://news.ycombinator.com/item?id=49404744</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49404744</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49404744</guid></item><item><title><![CDATA[New comment by tmoertel in "Scrap (2006)"]]></title><description><![CDATA[
<p>Yeah, most people probably underestimate the effect that several things have on where they end up in life: education, self discipline, hard work, making good decisions, persistence, and, especially, chance. If you screw up majorly on any the factors under your control, you dramatically reduce your chances of “the good life.” But, even if you do all of them right, you are still at the mercy of chance. Get born in the wrong year or at the wrong place or into the wrong family or with the wrong genetics and that's all it takes to set you up for a hard life.<p>The tragedy is that we could have a society that gives people more opportunities to escape the downward pull of chance gone wrong early in life. Maybe someday we'll get there.</p>
]]></description><pubDate>Sat, 22 Aug 2026 21:53:18 +0000</pubDate><link>https://news.ycombinator.com/item?id=49404229</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49404229</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49404229</guid></item><item><title><![CDATA[New comment by tmoertel in "People of ACM – Russ Cox"]]></title><description><![CDATA[
<p>It's available online for free: <a href="https://abseil.io/resources/swe-book" rel="nofollow">https://abseil.io/resources/swe-book</a><p>And, yep, it's worth a read.</p>
]]></description><pubDate>Fri, 21 Aug 2026 21:59:27 +0000</pubDate><link>https://news.ycombinator.com/item?id=49394239</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49394239</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49394239</guid></item><item><title><![CDATA[New comment by tmoertel in "Blog about things you don't understand yet"]]></title><description><![CDATA[
<p>> Please, no. Don't blog about things you don't understand yet.<p>Do you really mean this? Or do you mean "When you blog, be honest. Don't pretend to understand things you don't."?<p>Blogging about things you are learning about, especially if you invite feedback, is a great way to learn and to build a shared understanding within a larger community.<p>But I agree 100% on the fake-it-till-you-make-it posts on blogs and LinkedIn. That stuff is a blight on the web.<p>ADDED a concrete example: Consider this post: <a href="https://blog.moertel.com/posts/2026-07-23-on-the-nature-and-purpose-of-code.html" rel="nofollow">https://blog.moertel.com/posts/2026-07-23-on-the-nature-and-...</a>. Do you think that posts like this are useful? Or net harmful?</p>
]]></description><pubDate>Fri, 14 Aug 2026 04:29:05 +0000</pubDate><link>https://news.ycombinator.com/item?id=49294765</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49294765</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49294765</guid></item><item><title><![CDATA[New comment by tmoertel in "Blog about things you don't understand yet"]]></title><description><![CDATA[
<p>You raise an interesting point. I agree that discussing a subject with a knowledgeable mentor, AI or otherwise, is a great way to learn. But I think back-and-forth discussions are limited as a means of testing your mastery of a subject. Especially with complex and nuanced subjects, being able to organize them in your mind is an essential part of mastery. You will not know if you have mastered them unless you can generate a clear and coherent description of them entirely on your own. With a mentor prompting you, step by step, you are relying in part on the mentor’s understanding of the subject to guide your thinking.<p>It is like the difference between multiple-choice and essay exams. In the former, the questions you are asked reveal much about the structure of the subject to be explored and of the relative importance of its facets and the many nuances within. In the latter, you are on your own: you must conceive of a coherent map, render its form onto a blank sheet, and populate it with what is important, with everything being sensibly connected.</p>
]]></description><pubDate>Fri, 14 Aug 2026 03:54:17 +0000</pubDate><link>https://news.ycombinator.com/item?id=49294575</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49294575</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49294575</guid></item><item><title><![CDATA[New comment by tmoertel in "Blog about things you don't understand yet"]]></title><description><![CDATA[
<p>One of the best ways to clarify your thoughts about a subject is to write about it, and one of the best ways to prove to yourself that you understand it is to be able to write about it <i>clearly</i>. Indeed, my primary motivation to write is to order my thoughts and better understand the universe I live in.<p>It is surprisingly difficult work, but so is lifting weights. That is precisely why I insist on doing it myself. If I let an AI write for me, it would be the same as letting a robot lift weights for me. Yeah, it would be easier, but I would not get stronger, nor would I gain the confidence and self discipline that comes from doing hard things.</p>
]]></description><pubDate>Fri, 14 Aug 2026 01:55:42 +0000</pubDate><link>https://news.ycombinator.com/item?id=49293934</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49293934</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49293934</guid></item><item><title><![CDATA[The Improbable, Inevitable Return of the Suit]]></title><description><![CDATA[
<p>Article URL: <a href="https://www.bloomberg.com/news/articles/2026-08-13/the-suit-makes-a-fashion-comeback">https://www.bloomberg.com/news/articles/2026-08-13/the-suit-makes-a-fashion-comeback</a></p>
<p>Comments URL: <a href="https://news.ycombinator.com/item?id=49287481">https://news.ycombinator.com/item?id=49287481</a></p>
<p>Points: 3</p>
<p># Comments: 0</p>
]]></description><pubDate>Thu, 13 Aug 2026 15:28:18 +0000</pubDate><link>https://www.bloomberg.com/news/articles/2026-08-13/the-suit-makes-a-fashion-comeback</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49287481</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49287481</guid></item><item><title><![CDATA[When the Denominator Disappears: FDA's Next Evolution Should Be Causal Inference]]></title><description><![CDATA[
<p>Article URL: <a href="https://www.realclearhealth.com/articles/2026/08/05/when_the_denominator_disappears_1198625.html">https://www.realclearhealth.com/articles/2026/08/05/when_the_denominator_disappears_1198625.html</a></p>
<p>Comments URL: <a href="https://news.ycombinator.com/item?id=49280863">https://news.ycombinator.com/item?id=49280863</a></p>
<p>Points: 2</p>
<p># Comments: 0</p>
]]></description><pubDate>Thu, 13 Aug 2026 01:38:03 +0000</pubDate><link>https://www.realclearhealth.com/articles/2026/08/05/when_the_denominator_disappears_1198625.html</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49280863</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49280863</guid></item><item><title><![CDATA[New comment by tmoertel in "Discovery Loop"]]></title><description><![CDATA[
<p>They do not call attention to this aspect of their new company, but it is implicit in their business model:<p><a href="https://xcancel.com/JeffDean/status/2085034604172603724" rel="nofollow">https://xcancel.com/JeffDean/status/2085034604172603724</a><p>In short, they are in the business of using AI to automate the discovery of useful knowledge, not to sell general-purpose AI capabilities that could be directly used in troubling ways.</p>
]]></description><pubDate>Wed, 05 Aug 2026 20:36:46 +0000</pubDate><link>https://news.ycombinator.com/item?id=49188667</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49188667</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49188667</guid></item><item><title><![CDATA[New comment by tmoertel in "Discovery Loop"]]></title><description><![CDATA[
<p>Do you believe that securing cyberspace is problematic solely because it has military implications? I mean, <i>everything</i> has military implications. That fact doesn't imply, however, that those things are bad for society.</p>
]]></description><pubDate>Wed, 05 Aug 2026 18:17:51 +0000</pubDate><link>https://news.ycombinator.com/item?id=49186738</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49186738</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49186738</guid></item><item><title><![CDATA[New comment by tmoertel in "Discovery Loop"]]></title><description><![CDATA[
<p>Note that Jeff and crew have cleverly structured their company to avoid problematic uses of AI (e.g., weapons or tracking humans). I suspect that many top researchers will want to work there for this reason, and to work with other top researchers who have a history of delivering results.</p>
]]></description><pubDate>Wed, 05 Aug 2026 18:04:25 +0000</pubDate><link>https://news.ycombinator.com/item?id=49186537</link><dc:creator>tmoertel</dc:creator><comments>https://news.ycombinator.com/item?id=49186537</comments><guid isPermaLink="false">https://news.ycombinator.com/item?id=49186537</guid></item></channel></rss>