Hacker News Reader

That's impressive. Together with (neo)vim as $GIT_EDITOR I can see that being really nice to use.

Now you could decide to systematize the "grammar" of your shortcuts somehow, and, well... it's definitely an idea people have had before. ;)

https://magit.vc/screenshots/popup-diff.png

Not an Emacs fanboy, by any means: I use Spacemacs. Magit is objectively excellent, though.

mrkgnaoon Build Your Own Text Editor

I know. The "I guess" was because I hadn't actually counted the lines to see if there were more comments.

mrkgnaoon Jeff Bezos Is Selling $1B a Year in Amazon Stock to Finance Race to Space

Preface: I'm Indian, and I genuinely want ISRO to be the space agency: if not today, then certainly in fifty years.

> Trust me, every 'poor country' must have good science projects going. If not space projects, then at least some hard engineering ones.

Exactly my point. There was a ton of nonsense around the time of Chandrayaan about whether or not it was right to spend money on such things "when people were starving": in case it wasn't clear, I think that's bullshit. And I'm worried about it coming back, and actually doing some serious damage this time.

> Indians works on these projects if they don't name the project in their language what other language should they call it in?

As some of the other replies to your comment also point out: my problem is not the Hindi. If we launched a space telescope, I fear it'd end up named "Mahakashdoorbeen" or something. Why not something less boring than "Mars Vehicle" (which is what Mangalyaan translates to)? Remember, a 19- or 20-year-old is still young enough to be attracted to shiny things, so moralizing about how this is "useless nonconstructive criticism" doesn't help. The name doesn't increase the maximum pressure the rocket can survive, but it gets you people who can.

> Im not sure if NASA has such practices. In fact me be the exact opposite. In short ISRO makes failure cheap.

That's very interesting: it's reminiscent of Erlang, in a way. Launch a ton of cheap missions, expect some to fail, work on reducing the failure rate while not crying because a couple went up in smoke. I could see this turning into something big if they took it farther in public.

> ISRO is a government run firm, which hires Indian nationals who come out of local colleges. The kind of types no software company likes to hire, in fact you will be surprised most go for jobs there because they wouldn't have got jobs elsewhere.

Why does it need to stay that way? It seems you know more than me about how ISRO works, so this just makes me sadder.

It seems from the downvotes that people think I'm one of the rabid "India is a toilet" types that surface on /r/worldnews whenever there's some good news about India. I'm not: it's just I think that more Indian leadership (for lack of a better word, again) in space (and STEM more generally) is something to legitimately care and feel proud about.

mrkgnaoon Jeff Bezos Is Selling $1B a Year in Amazon Stock to Finance Race to Space

You do realise I'm Indian too? And that my point was that a lack of young people in the space agency, of all things, is a very bad thing? ISRO is doing good work, yes, and undercutting the ESA/NASA on price, but they're not doing unheard-of things. And others are. Jugaad can paper over a bug in course correction software or what-have-you, perhaps, but it can't create the propensity to make (metaphorical) moonshots that young people, who are not usually very risk-averse, are more likely to want. Right now, as the sibling commenter puts it, they're just hitting low-hanging fruit, and it's cheap because they have economies of scale and the comparative advantage of being able to get away with paying people less (which is not at all something bad, but it means they can do a lot more).

Anecdata: I have a friend who's wanted to work in this area for as long as I've known him (which is at least 7 or 8 years now), and he's far happier to try and find work outside India -- knowing how hard it is to find aerospace engineering work in, say, the US, with all the "weapons technology" trouble that makes gaining citizenship a requirement -- or, failing that, work at some Indian startup rather than ISRO. To be very honest, that's sad, and it's definitely not an exception. I don't see why that has to be the case: I've accepted with some resignation that math and theoretical physics/CS never will be, but space can definitely be -- for lack of a better word -- sexy. Our Lord and Savior[0] Elon Musk isn't the only one who can (or should) do it.

[0]: /s

mrkgnaoon Fun at the Unix Terminal

asciiquarium and pipes, too.

mrkgnaoon Jeff Bezos Is Selling $1B a Year in Amazon Stock to Finance Race to Space

They'd certainly be served better with fewer (at least not ~90%) old "management"-looking people on their webcasts, which could've looked like they were made in the last five years (and less misleading people with talk of "hundreds of satellites" that in reality, IIRC, weigh just about the conventional PSLV cargo capacity[0]).

The reason I'm not very gung-ho right now is because there is, just maybe, a future in which ISRO isn't just "one of the space agencies that have made it into orbit", but as important to the future of space as NASA was a decade or two earlier, and getting there involves not just doing good work, but being ambitious at the scale of SpaceX and such. ISRO is being funded well right now, but if they can't "make it" in the next decade, with NASA in a slightly precarious position and private companies with no history of going into space doing all manner of remarkable things, they are going to miss this shot, and that can be dangerous in a political climate where the "can such a poor country really afford to go into space" types might drown out more reasonable people and shutter things for good. I'm enthusiastic about ISRO being able to compete on price -- and it looks like they can go much further, considering that their labor costs are far less than they are for a private American space company, who I doubt can afford not to pay typical SF-style salaries to their engineers and designers.

Good promotional material attracts talent: I seem to remember someone from SpaceX saying "our webcasts are actually recruitment propaganda", and, well, they work! Maybe the first step towards making young engineers want to work at ISRO is to not, e.g. name the Mars mission, of all things, "Mars Vehicle" in Hindi?

[0]: Around 1.5 tons, and, no, I'm not discounting the challenges of actually releasing that many microsatellites.

https://en.wikipedia.org/wiki/PSLV-C28

mrkgnaoon Build Your Own Text Editor

https://github.com/jameysharp/corrode/blob/master/src/Langua...

Corrode is absolutely incredible. This file is literate Haskell, which means there's more documentation than code (I guess), and it transforms C into Rust.

mrkgnaoon Dolphins' elaborate octopus-hunting strategy

Delicatessen is also plural in German if you use it to mean "delicacy", instead of an adjective ("chai tea"-style).

mrkgnaoon Scala interview questions

They're still better than the x = x + (y+=(++x)) things I've encountered in school assignments. I've always wondered why knowledge of what ought to be akin to undefined behavior is a good thing, excepting "idioms" like

  do {...} while ((line = file.read()) != 0)

which one no longer understands after a week away from the language robs you of a short-term mental model of the language's quirks and evaluation strategies and what-have-you.

mrkgnaoon Scala interview questions

  lazy val x = {
    println("computing x")
    3
  }

unsafePerformIO, unsafePerformIO everywhere...

mrkgnaoon “Let’s have some fun I’m offering two grants of $5,000 for whatever you want”

Is the Idris book on your list?

mrkgnaoon Category Theory for Programmers (2014)

https://arxiv.org/list/math.CT/recent

mrkgnaoon Ask HN: How to handle a cease and desist?

The most honest answer you're going to get is the one you already suspect you will: get a lawyer, and don't underestimate how easy it is for $EVIL_CORP to bury most people or orgs with legal costs alone however unjustifiable (or not) the cause for their ire might be.

mrkgnaoon Category Theory for Programmers (2014)

It might be interesting to see what mathematicians-in-the-wild think about higher category theory, which is viewed in a somewhat similar way by people who don't work in certain fields.[0]

http://mathoverflow.net/questions/169187/what-non-categorica...

I suspect the reasons are broadly analogous. To paraphrase a quote of Atiyah's, the usefulness of theory is that once a field is complex enough, a little bit of it can serve to provide "organizing principles" (quoting Qiaochu Yuan from the MO post above) that help both learners (who can exploit similarities in different fields so that unfamilar things feel less alien) and experts (for whom many things are made easier, or even possible, by working at higher levels of abstraction[1]).

Knowledge just keeps piling up, and abstraction is one way of increasing the "density" of information one takes in so that one doesn't have to spend one's whole life trying to learn enough to work -- or, in the researcher's case, getting to the frontiers of current knowledge.

[0]: Roughly, my understanding of it is that it's what happens when you don't require properties like associativity, but say that (ab)c should be "deformable" into a(bc) in some way. Complications arise, interesting stuff happens. The usual.

[1]: Akin to the birds of Freeman Dyson's "birds and frogs".

http://www.math.columbia.edu/~woit/wordpress/?p=1506

mrkgnaoon Why are The Economist’s writers anonymous?

"I'll write under a pseudonym and you'll see what I can do to him!"

I mean, the Federalist Papers "fifty-one!" sequence would probably have made a better refernce, but they're not too explicit about the pseudonyms there.

mrkgnaoon Adobe Sensei

Previous discussion:

https://news.ycombinator.com/item?id=13446478 https://news.ycombinator.com/item?id=13440651

mrkgnaoon Adobe Sensei

Is it the hackerly affinity for Zen Buddhism (e.g. koans, among other similar things), perhaps? Or Steve Jobs' fascination with it, or the countercultural openness to "exotic"/Eastern spirituality that many of the people driving tech today grew up around?

There's this association of Eastern countries with "wisdom", too. I'm reminded of Feynman's anecdote from Surely You're Joking where he visits Japan with a colleague and it transpires that a woman (a hotel staff member, iirc) happens to see him naked as he emerges from the bathroom, and surprisingly little "drama" ensues. He remarks that if it were the USA, there would have been a lot of "little shrieks", and his colleague exclaims, "God, are we uncivilized!"

mrkgnaoon 88% of all integers have a factor under 100

School has forced me to take a break (thankfully coming to an end now) from learning math for the past few months, so throwing walls of text at the gracious HN crowd simultaneously makes for good practice and expository-itch-scratching. You're welcome.

mrkgnaoon 88% of all integers have a factor under 100

Apologies. I was remembering more than I was thinking: you are right in that the relation doesn't hold at the level of elements[0]. The correct statement is

  (2) = (1+i)^2

where (2) and (1+i) represent the ideals generated by 2 and 1+i respectively. Officially, an ideal of a ring R is a subset I of R which is closed under addition and under and multiplication by elements of R:

  i, j ∈ I implies  i + j ∈ I
  i    ∈ I implies     ri ∈ I for all r ∈ R

For our purposes, a simpler case -- that of principal ideals -- suffices, and that's what I'll discuss in the rest of this comment.

The ideal generated by an element a of a ring R, usually denoted (a) or aR, is essentially the subset of all multiples of a in R. For instance, over the integers, we have ideals like

  (2) = {...,  -4, -2, 0, 2, 4,  ...} 
  (3) = {...,  -6, -3, 0, 3, 6,  ...}
  (4) = {...,  -8, -4, 0, 4, 8,  ...}
  (6) = {..., -12, -6, 0, 6, 12, ...}

One can also define the ideal generated by the elements a,b,c,... of R:

  (a,b,c,...) = {aa' + bb' + cc' + ... : a',b',c' ∈ R}

i.e. the "linear combinations" of a, b, c, and so on.

Here are a few things you might like to verify (i.e. just nod along) about some ideals of Z, to get familiar with the notation:

  (1) = Z (i.e. all the integers)
  (2) = (-2)
  (6) = (2) ∩ (3) 
  15Z =  3Z ∩ 5Z

where ∩ is the intersection of the two sets, or the set of common elements. ("Fact": The intersection of two ideals is also an ideal.)

In general, if you have an ideal of the form (a), then we always have

  (a) = (ua) for all units u

Write G (for Gauss?) for Z[i]. In G, the previous statement means that (2) = (2i). To check this, note that we have

      x ∈ (2) 
  iff x =  2y            for some y
  iff x = (2i)(-yi)
  iff x ∈ (2i)

so all elements of (2) are in (2i), and vice versa.

Now one defines the product of ideals: given ideals I and J in some ring R,

  IJ = ideal generated by the elements {ij : i ∈ I, j ∈ J}

In our case, if I = (a) and J = (b), IJ is just (ab). Question: what's the relation between (ab) and (a) ∩ (b)?

For instance, you can verify that

  (2)(3) = (6)

and, to bring us back to our original point,

  (1+i)(1-i) = (2i) = (2) = (1+i)^2

where all the products are ideal products.

There is a very incomplete treatment at [1] (with a bit of the LaTeX broken) that is meant to provide background for a sequence of posts on algebraic geometry -- it's been suspended for a while, but I'm going to look over a couple of drafts this week!

[1]: https://mrkgnao.github.io/prime-ideals/

[0]: As always in math: if you can't prove it, just add a few adjectives or simply change the language. Facts arrived at by alternative definitions, if you will. :)

mrkgnaoon 88% of all integers have a factor under 100

Wouldn't the function sort of "eat itself" if it grew too fast? I can't make this precise, but if it grew fast enough, then most numbers would have many factors accounted for among the smaller numbers already (in a sort of "greedy" manner).

mrkgnaoon 88% of all integers have a factor under 100

The concept of factorization, properly defined, usually excludes "units", that is, numbers with an inverse. So 1 is a unit, since we can solve

  1x = 1

by letting x = 1. -1 is a unit too, since (-1)x = 1 is also solvable.

Factorization is then defined "upto units and reordering", so, for instance,

  6 = 2 * 3 = (-2) * (-3) = 3 * 2 = (-3) * (-2)

are all considered the same factorization.

Why might this be useful? Sometimes, number systems ("rings") we care about might have more units, and in order for there to be a sensible theory of factorization[1], we have to take these things into account. Not all rings are as nice as Z[2].

For instance, allow me to go off on a tangent: consider the set of all numbers of the form

  a + ib (a, b integers)

called the Gaussian integers (written Z[i]). One can show that the units here are 1, -1, and also two new ones: i and -i. Studying factorization in this ring -- what numbers can we factorize further now? -- is very interesting. It turns out that not all of our usual prime numbers "remain prime":

   2 = 1  + 1 = 1 -  i^2   = (1 + i)^2
   3 = 3 
   5 = 1  + 4 = 1 - (2i)^2 = (1 + 2i)(1 - 2i)
   7 = 7
  11 = 11
  13 = 4  + 9 = 4 - (3i)^2 = (2 + 3i)(2 - 3i)
  ...

The key to this puzzle is to notice that the primes that "split"[3] all leave a remainder of 1 modulo 4. It is a beautiful fact that the converse also holds: if

  p = 1 (mod 4)

then it must factor in Z[i], and, further, it always factors as

  p = (a + ib)(a - ib) = a^2 + b^2

(And, of course, if we have p = a^2 + b^2, it can be factored just like we did above.) In other words,

  Theorem[4] (Fermat, sometimes called the "Christmas theorem"). 
  The primes that can be written as a sum of two squares are exactly those congruent to 1 mod 4.

Neither the question (which primes can be written as a sum of two squares) nor the answer (those congruent to 1 mod 4) involve any of the machinery we used in getting from one to the other. :)

PS. Yes, I may or may not have ignored the case of 2 above. Tons of theorems in number theory are stated for "odd primes". 2 is, after all, the oddest prime.

[1]: e.g. it turns out that "p is prime", defined as

  p | ab implies p | a or p | b

and "p is irreducible" (i.e. not factorizable in any sensible way), defined as

  p = ab implies either a or b is a unit

are not equivalent! One direction always holds, but the other doesn't come for free.

https://en.wikipedia.org/wiki/Prime_element

[2]: Each step up the ladder of class inclusions adds some nice property that makes life easier, but diminishes the power of the theorems one proves. (Euclidean domains are almost perfect in that sense!) Behold, a bestiary most vile:

https://en.wikipedia.org/wiki/Euclidean_domain

[3]: Notice that 2 factorizes as a power, not as a product of distinct factors. This is technically "ramification", not "splitting" (that term is reserved for the distinct-factors case). The following Wikipedia page treats the entire content of this post far better, and has links to the "real" algebraic number theory pages ;)

https://en.wikipedia.org/wiki/Splitting_of_prime_ideals_in_G...

The numbers that don't factorize at all are said to remain "inert". (And there's something related called an "inertia group" that disappointingly has little to do with mechanics.)

[4]: https://en.wikipedia.org/wiki/Fermat%27s_theorem_on_sums_of_...

mrkgnaoon Idris 1.0

I wrote this a while back. You might find it of some use.

https://news.ycombinator.com/item?id=13907573

mrkgnaoon Idris 1.0

I remember seeing an Edwin Brady talk (it featured a now-possibly-famous Brexit joke) in which the compiler almost inferred ... I think it was either zip or a fold.

mrkgnaoon Iosevka – A Typeface for Code, from Code

Yes, it does.

mrkgnaoon Noiszy – A Chrome plugin that creates meaningless web tracking data

> webcomics

https://www.reddit.com/r/KenM/

mrkgnaoon SES-10 Mission

Might have been an early mobile phone camera.

mrkgnaoon SES-10 Mission

He's definitely matured a ton as a speaker. I mean, he isn't smooooth now, but there are far fewer pauses, to the point where it's just another striking feature about him instead of making his words hard to follow.

Also, the kid being held aloft at 34:20 was a very cute touch. https://youtu.be/8FQhtMrUQlE?t=34m20s

mrkgnaoon SES-10 Mission

As is, on the other end of the spectrum, "lithobraking" :)

mrkgnaoon Ted Chiang's Soulful Science Fiction

> "Exhalation" is my favourite Ted Chiang story.

I haven't audibly exhaled (I am honestly not trying to pun here) at a story this way in quite a while. Thank you.

mrkgnaoon Ted Chiang's Soulful Science Fiction

> In “Understand,” he pointed out, the protagonist learns to reprogram his own mind. He knits together the vocabularies of science and art, memory and prediction, literature and math, physics and emotion. “He’s searching for the perfect language, a cognitive language in which he can think,” Chiang said. “A language that will let him think the kinds of thoughts he wants.”

I wonder how many of us have, at some point, harbored the (if poorly formed and not at all thought-through) beginnings of such an idea.