skysight-inc/HackerNews huggingface dataset:
I find that at a high Bachelor's or low Master's level in physics I always have to re-explain determinants. People learn the idea and they take away "it's really complicated and has something to do with whether the matrix is invertible."

An eigenvector of a matrix M is a vector v such that M v = k v -- in this direction, the matrix only scales the vector and does not rotate it to some other direction. Some matrices do not have a complete set of eigenvectors -- a rotation matrix is a good example! -- but then there is a generalized notion of eigenvectors which you can fall back on.[1] You can prove that you always have a complete set of eigenvectors for any square matrix, in the generalized sense.

The trace is the sum of the eigenvalues; the determinant is the product of the eigenvalues. This drives in part the parallelepiped interpretation that the article is giving; in fact if you have a full set of eigenvectors then any volume can be made up out of little boxes made of the eigenvectors, and so any hyper-volume must transform under the linear map by multiplying by the determinant. This in turn tells you why det(A B) = det(A) det(B) -- B must scale volumes by some amount, then A must scale volumes by some amount, and to compose those two scalings you must take their product.

A matrix is not invertible if it projects away some axis, so that information is lost. This means that one of the eigenvalues is 0. Take the product of the eigenvalues -- if it's 0, the matrix is not invertible! Done, simple.

It tells you that the determinant of a triangular matrix is the product of the diagonal elements (since those are the eigenvalues), and it also tells you that a determinant of a block-diagonal matrix is given by the product of the determinants of the blocks. This is important because the whole "why does the determinant flip sign when you interchange two columns?" question is now answered. To flip two columns, you multiply by a matrix which looks like:

1 0 0 0 0
0 1 0 0 0
0 0 0 1 0
0 0 1 0 0
0 0 0 0 1

In other words, it's block diagonal with two blocks being identity matrices and one block being [0 1; 1 0]. That block has eigenvectors [1 1] with eigenvalue +1 and [1 -1] with eigenvalue -1, so it has determinant -1. The determinant of the two identity blocks are also 1, so the whole matrix determinant is therefore -1, and det(A B) = det(A) det(B) = - det(A), where B is the block-diagonal column-swapping matrix.

With a bit of effort you can figure out the antisymmetric form for actually computing the determinant without diagonalizing the matrix; but this comment is long enough as it is. The only thing which is much simpler about the antisymmetric symbolic form for the determinant is that you immediately see that the determinant is symmetric under transpose, which tells you something a bit surprising: that a square matrix has the same left-eigenvalues as right-eigenvalues (since an eigenvalue is det(A - λ I) = 0 and all of 0, det, and I are transpose-symmetric.

[1] https://en.wikipedia.org/wiki/Generalized_eigenvector
The slide right seems broken.
Code Duplication is a Rampant Disease
While this is an interesting method (packaged in a broad, bait-ish claim), I'd like to see where the described benefits are actually worth the increased complexity and difficulty: for situations with a few 10-100.000 inserts/day, you will not run into locking issues and beyond that, the wasted disk space will become noticeable to prohibitive, especially on cloud-hosted systems. History and undo might be useful in some situations (not likely with password changes as in the example though), debugging is probably better achieved with rotated logs, not extra data in your database (which you might want to backup regularly...).
No one should be compelled to help prosecute themselves.
Often when we switch from GMT to BST (one hour ahead) I have to Google the time in the UK (because of Apple's trouble in the past with daylight savings, I can't trust my phone).

It would be reasonable to expect someone to go to the BBC homepage and see what the current time is after the daylight savings switch, and wrong to find the time was incorrect due to their PC not being configured correctly.
I don't think the clock has to be accurate to the ms. The latency between client and server will almost always be < 1 second. They can probably get away with time being accurate to ~1minute
Interesting. Your post makes Go seem pretty approachable. What do you use for testing?
adria richards would love a pycon in india I'm sure
When I used to go cross-country backpacking last year, I often went out of reception range for cell signals. Most of the time I was hiking in the wilderness, away from most civilization. Sometimes on day trips, sometimes on weekend trips.

It was stunningly effective at allowing me to do deep thinking. To make it less abstract, for me this meant gaining a new perspective in my life (usually in the form of realizing I'm not the center of the world) and new insights into problems. What is surprising was that this was not stressful at all. On the contrary I always came back to the city fully recharged.

Did I think about other stuff such as having sex or buying a new computer? Of course. But it's like meditation: you have to notice when your mind wanders and bring it back.
>Drag and drop sometimes stops working and you lose the ability to move those tabs around (change their order).

I haven't had that happen for months, so I'm hoping that it was a long standing bug that just got fixed.
Yes. Also, these low-level primitives already exist in Go, as support for pointers, or references. The missing bit is requiring references to be explicitly annotated as nullable or non-nullable.
Using http://feedly.com
Good UI both in the mobile app and Web app.
I work in the smart grid industry, and have watched and studied several years of the Stanford Energy Seminars [1]. I totally agree that Solar/Wind are the future - but we know how to supply our electrical needs with Coal (and Natural gas in part of the United States) and Nuclear power today. It's going to take 20+ years to transition to a Wind/Solar future, so the real question is not whether we should transition to wind/solar (we should) - but what do we invest our resources in while we transition to that future? Do we build (A) More coal plants or (B) More nuclear plants. (Throw in the curveball (C) start fracking more and exporting natural gas - which comes with it's own environmental costs)

I've just spent the last two weeks in the UK working on various Low Carbon smart grid projects, and the challenges of Distributed Generation (mostly wind right now in the UK) are significant - the large one being building the Transmission/Distribution network to handle this somewhat erratic source of power.

So - the future is clear, but the journey is still in question. I vote nuclear power - The impact to future generations of carefully buried waste will be much, much less than the impact of global warming.

[1] http://energyseminar.stanford.edu/event-archive
It seems easy enough to reduce leakage or fuzz the signal.

I don't have the background to try to pull the limits up out of the white paper, but I think the current implementation is more or less looking for movement in 1 dimension (towards and away from the receiver). So plenty of time to decide whether radio waves are revealing anything that sight and sound are not.
"There is no way we could switch to solar/wind without moving to the 1800's."

That is false in that the system currently cannot do it because we've promised 100% uptime and all the users have designed around perhaps 99% uptime. Lower uptime on the coasts, much higher in civilized areas (Dang near 100% by the great lakes, for example, where interestingly AC power has been much more reliable than UPS/generator transfer switches)

That is, obviously, a stable and profitable system design.

Multi-generationally, we could move to a system that can insta-shed perhaps 99% of load. Suddenly its not so hard.

I've done stuff with CAD/CAM machines. They don't like power interruptions because ignoring the problem is simpler than dealing with them. There's no technological reason why a next gen system can't have a functionality like "Hey, your power is shutting off in 5 seconds, so go into controlled shutdown mode and prepare to instantly come out of power saving mode momentarily". This isn't someone from the outside speculating but someone from the inside describing.

I would imagine a reasonably intelligent HVAC system talking to a smart enough grid could coordinate such that during worst case intervals they're off.

My phone has 8 or so hours at night to do its 30 minute or so top off charge, so why does it draw full power when the grid is stressed? Yeah that's just a couple watts, but 400 million 10 watt phones and tablets adds up to quite a draw. Laptop draw is even more impressive.

Why isn't every installed UPS legally or contractually required to be a smart grid controllable grid tie inverter on demand?

I sympathize that its harder to design an aluminum refinery to insta drop. Too bad, do it anyway. That limited hydro power is going to be needed by the hospital patients, traffic lights, SOME telecom gear, etc. Interestingly the improved insulation and control and dumping gear has the opportunity to lower overall energy use and possibly increase safety if done right.

(edited to add that only EEs are going to understand what this means, but a law that any plug in device with an effective negative resistance must implement full remotely controllable high speed low latency smart grid tech would go a heck of a long way toward grid stability in a renewables situation)
Umm, no. Taxpayers are still subsidizing $7,500 per Tesla sold.
I understand the frustration with GH limitations (no burn charts and hardly any reporting). For us, the minimalism ended up working in harmony with our process, but I can see situations where it wouldn't.

The UI and milestones, though, I think are good. JIRA is to me the king of clunky. I've used it in 3 projects over the years and evaluated it last year, and I've been pretty disappointed with it.

To borrow from another comment here, it has a bit of a Bugzilla feel, like it just grew and grew, and you have tons of fields and features, but they're poorly designed and put together. A bit of a mess, to put it bluntly. FogBugz has a similar feel to me.

I encourage you to check out JetBrains' YouTrack. I never used it in a project, but a couple days evaluating gave me a good impression. Good luck with your search.
Pa11y, your automated accessibility testing pal
The perception of being exotic can also be an advantage, though. Would you rather buy olive oil from a brand named Granny Smith or Emilia-Romagna? As another example, Häagen-Dazs was named to "sound Danish" to American consumers, despite not actually meaning anything in Danish. I think the name has worked rather well for them.

Exotic product names in the U.S., however, must somehow be Anglicized to make them easy for American consumers to pronounce and remember. Flickr and Tumblr are okay, despite the missing vowel, because everyone knows how to read them. Mazda was smart enough to bastardize their founder's name (Matsuda) before trying to sell cars in America. But good luck if your company is named Xaro Xhoan Daxos!
You don't know what reading comprehension means. Hint: Remembering a small username not even visible when replying to a comment deeper down in a thread has nothing to do with it.
To do nothing at all is the most difficult thing in the world, the most difficult and the most intellectual
–Oscar Wilde 1891.

“Without a considerable amount of leisure a man is cut off from many of the best things…What will happen when the point has been reached where everybody could be comfortable without working long hours?”

-Bertrand Russell

“We keep a large percentage of the working population idle, because we can dispense with their labour by making the others overwork. When all these methods prove inadequate, we have a war: we cause a number of people to manufacture high explosives, and a number of others to explode them, as if we were children who had just discovered fireworks. By a combination of all these devices we manage, though with difficulty, to keep alive the notion that a great deal of severe manual work must be the lot of the average man.”

-Bertrand Russell

“There will be happiness and joy of life, instead of frayed nerves, weariness, and dyspepsia. The work exacted will be enough to make leisure delightful, but not enough to produce exhaustion…At least 1 per cent will probably devote the time not spent in professional work to pursuits of some public importance…men and women, having the opportunity of a happy life, will become more kindly and less persecuting and less inclined to view others with suspicion. The taste for war will die out, partly for this reason, and partly because it will involve long and severe work for all…Modern methods of production have given us the possibility of ease and security for all; we have chosen, instead, to have overwork for some and starvation for the others.”

-Bertrand Russell proposing a 4 hour work day
Ruby Implementors panel at dotRB in Paris on October 18th
Having sailed a 420 competitively, I can confirm that standing out on the trapeze wire whilst on the plane is indeed "a very cool feeling". :-)

For real hydroplaning dinghies you could try a Int. Moth: http://www.youtube.com/watch?v=gK60RZDtnT8
Breather may end up a success. As far as I can tell, it's riffing on AirBnB -- instead of monetizing unused residential space, they're monetizing unused commercial space. OK. That's actually a very good idea.

But "changing the landscape of cities forever"? I don't know about that. Perhaps there's a Segway partnership they haven't mentioned yet.
The critical component, by far, is the battery. If you find ways to build a better battery, electric cars are a practical reality. Academia is perfect for battery research.
And then you end up with the old Netscape Communicator suite, until someone wants a "fast" minimal browser, maybe by moving some of the features out of the main browser into extensions....

It's the circle of life!
Around minute 25 there appears to be a very awkward waiting-for-the-Steve-Jobs-applause moment after Elon explains the updated navigation system. A few more announcements are made without applause and then finally, just before the 31 minute mark, applause is finally handed out when the launch date of the Model X is announced. I hope Elon didn't feel disappointed with himself or the audience. Applause is cheap. The questions that followed demonstrated audience buy-in more than any amount of applause could ever achieve.
>Chrome clearly does perform significantly better than Firefox. While the Firefox supporters like to trumpet how Firefox is "comparable to Chrome" in the arewefastyet.com micro-benchmarks, this just isn't observed under real usage patterns.

Not under my usage patterns. I rarely have fewer than 30 or so tabs open, and Chrome is simply useless for this.
Let me delete this one. Thanks for pointing that out.
Even worse, he never explained why it was weird, as per the title, nor even why its not really weird after all.

A better title and overall theme would be something like "A really good short summary of why determinants are useful and their applications".
Wacko in the Morning 06/05 by Wacko Bob
How Clash of Clans earns $500,000 a day with in-app purchases
I was just thinking the exact opposite. I am really not convinced that the site can be maintained indefinitely for a $15 one-off payment per user. And when it inevitably closes down I will feel cheated out of the "lifetime" of service I paid my $15 for, whereas I would have been happy to pay $60 a year for it. ($5/month would also ring alarm bells for me, even though the total price would be the same.)
Making customer service human
Because we're subsidizing inefficient actors already, that makes it okay to subsidize other actors? Why subsidize any of the inefficiency at all? Tesla is certainly not curbing carbon emissions. More efficient combustible engines however are doing that, despite the lack of subsidies.
This sounds a lot like the mobile phone sonar that Batman used in the Dark Knight which seemed utterly ridiculous to me and many others at the time:

http://sfblunders.wordpress.com/2008/08/07/dark-knight-sonar...
There is a glut of white heterosexual male role models in science and technology, and that shapes cultural perceptions regarding what a programmer should be like, and causes discrimination against people who do not fit this mold[1].

This might be a clumsy solution (promoting people as successful programmer/role models based on considerations other than achievement), but the risk is low (lower the value of PyCon France slightly) and the reward is potentially very large (increase Python's stake in an underutilized labour pool), if the experiment is successful.

[1] http://www.pnas.org/content/109/41/16474.full.pdf+html
I get an "undefined is not an object" TypeError in Safari on OSX.
I had the idea for Facebook at the same time Zuckerberg did it. Why aren't I a billionaire?
Go has a built-in testing framework, but I've yet to play around with it.
George Monbiot on atmospheric carbon dioxide concentrations reaching 400ppm
The New Samsung Victory Over Apple - What It Means To Cupertino
The author does know that the US has never promised to pay back debts in US dollars in anything other than US dollars, right? There never was any promise to pay back with "real" money (as if such a thing exists!)

At any rate the US is in no danger of going bankrupt. They do run a certain risk of having their purchasing power decreasing, but of course their exports will automatically become cheaper for other countries to buy, which will turn around the balance of trade.

The real risk is being run by those that are holding large balances of US dollars - they risk taking a bath if (or when) the US dollar is dramatically devalued. But then, they knew that going in, so I have limited sympathy.
The point is that this could be solved by a solution that is completely external to their current infrastructure, meaning they don't even have to mess with any integration or legacy code. Agile in this case seems perfectly suitable because they can easily have a fallback when the server doesn't respond to a "time"-request, that falls back to the current state (i.e. use client-side time). So we've got the perfect storm of no integration with current systems, tiny overhead on requests (it's basically an ECHO server), unimportant feature and easy fallback.

In fact I have an enterprise plan to sell them that does exactly this if they would like to externalise this problem.
I don't see the problem here. You get a 204, you don't expect content. If your consumer hits a URL, ignores status codes, and expects content, You're Doing It Wrong.

To me, it looks like the HTTP equivalent of a C function that returns NULL.
I was surprized that he created a LLC to run his wedding. Is this normal for high budget weddings ? What might be advantages of doing so? Just curious.
I understand your point but no fine should be levied? This kind of behaviour should be discouraged and a fine is entirely appropriate to discourage it.
DataBin, a paste for tables
Hm, I was going to say it is slightly messed up in Opera -- the boxes don't move like they should -- but I guess it's not going to matter in the very near future. :(
Why Epic Fails might not always be failures...
No, if you study the automotive industry, you'll see that those car manufacturers have been trying to get around those dealers by building their own dealerships (which are quickly shut) or selling their cars online (which again are prevented). They're not lobbying for dealerships in countries where you can sell cars directly to the consumer. Take Brazil or Germany for instance.
What is the next feature you'd like to see on sharefest.me?
looking at fairness in retrospect. Musk justified the loan. He built the damn thing, an (possibly) eco friendly, not dependent on fossil fuel car that people love.

back in my country we have our own electric car company, which have been able to do the thing, but they havent been able to get people support.

Musk was able to do that.
Maybe I'm missing something, but how is "largest" defined here? Looks like only $1,200 has been pledged so far.
ShowHN: WideArea Google Chrome Plugin
The thing is, when a car hits water, it is usually in a violent way where I would imagine people would be momentarily stunned. By that time, the water pressure outside would be too high for them to open the door. Breaking the window is a bit hard to do as well for most people in that situation. Breakout window tools are great, but most people leave their tools in the trunk. This is where the controlled breathing is vital. I have not been in this situation, but I have been in drowning situations where I have helped someone in the ocean. I took quick, deep breaths and it helped me while I was underneath the water searching. When I was a kid, I took swimming lessons, and the first thing the trainer talked about was controlled breathing. Before we even started swimming around, he would make us stay still while taking deep breaths. Try it anywhere and you will see how your body reacts to it afterwards.
People are always complaining about existing features being lost.

"I am not using firefox again until they reinstate the back button!"

I see this kind of stuff on reddit and slashdot all the time. Is it some sort of FUD campaign against Firefox?

Click view > Enter Fullscreen

You can also use F11, unless you set OSX to high-jack that button. You can also use the fullscreen button in the top right corner on lion versions of OSX.
A lot of bad blood in windows Ads. See the rivalry in the commercials
Yet another megamenu for Twitter Bootstrap (yamm)
Turk media almost didn't report the news. How would you call that?
I am not sure whether it was in France or England before the industrial revolution when a nobility could get away with running over a peasant with a carriage only with a fine. It did not end well.

The only way the rich can live with the others in stable society if there are a lot of things money can't buy.
What The Hell Did Penguin Do?
So any startup that competes in the pharmaceutical sector or biotechnology industry should be given hundreds of millions of dollars in taxpayer-funded loans?
http://calv.info/node-and-express-tips/ Here's a link with some information.
Why would consent be required? I don't recall any consent being granted for the wedding.

If you didn't consent, should I only be responsible for paying for your medical bills and missed work?

Should billionaires be allowed to walk down the street kicking children as long as they throw a few bucks on their prone, sobbing bodies afterwards - like a cartoonish Dickensian nightmare?
The trees did not consent. Or the park authorities.
You should at least follow some process like the snowflake method [0] to maintain consistency.

[0] http://www.advancedfictionwriting.com/articles/snowflake-met...
What about nuclear waste though? You end up with some tons of radioactive material which you have to store in high-security underground facilities with the hope that in some time in the future humanity will find a way to dispose it in a safer way.
Top 31 SEO Experiment​s You Want To Know About
You had the idea at the right time, but did you have the idea at the right place?

Zuckerberg had it at Harvard. There was prestige and an aura of exclusivity associated with Facebook in the early days, which was integral to its viral growth.

Don't get me wrong, I think Zuckerburg is a pretty competent player, but he clearly had a lot of things going for him and working in his favour.