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Ask HN: Teach me something new

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271–280 of 782 posts

Re: Ask HN: Teach me something new

#271

In a lot of terminals, Alt+. (or Option+. on Mac) will paste in the last argument of the previous command. $ mkdir hi $ cd You can hit . several times to cycle through earlier final args.

zsh has "take" to mkdir and cd to it. Something like take() { mkdir -p "$1" && cd "$1" }

Re: Ask HN: Teach me something new

#272
post #238

Earlier quoted context omitted.

What's the most pointless compiler optimization you're aware of? (Obviously a subjective question in practice, so chances are you might need to add a bit of qualification)

Infinite loops are considered undefined behaviour in C++.

Infinite loops are undefined (actually, undecidable) behaviour in any Turing machine.

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

Re: Ask HN: Teach me something new

#273

I've described this on HN before; forgive me if you've already seen it. I have chronic migraine. It sounds worse than it is; I rarely suffer attacks anymore, and when I do, they're usually mostly harmless, as in the case I'll describe below. Contrary to popular belief, migraine is not a headache. It's something a little more like an epileptic seizure. Intense headaches are one common symptom, but there are a lot of o…

There is a condition which manifests itself as complete blindness, but if you ask a person to try to guess what's in front of them they usually "guess" correctly:

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

Re: Ask HN: Teach me something new

#274
post #2

Quantitative easing (sometimes mistaking called "money printing") isn't directly inflationary. Because when central banks buy bonds, they do not pay with normal money. Instead, they pay with a special type of money that can never enter the real economy (as to not create inflation). This special type of money are called "bank reserves". And bank reserves can only be used to 1) settle interbank transfers and 2) buy mor…

Throwing Japan as an example you want to generalize defeats your purpose.

As has been famously said, there are only three types of economies: Japan, Argentina, and the rest of the world.

So, next time, pick an example from the rest of the world.

Is there many where QE did not lead to inflation?

Re: Ask HN: Teach me something new

#275
post #232

Ordering a typical printed circuit board with components placed on it is so cheap nowadays that this is a viable option for electeonic hobbyists nowadays (e.g. just ordered 50 pieces of audio output amplifiers at 3,49 € per piece (customs and shipping included), where 1.60 € would be the parts cost of the two chips on it. Only thing you need for this is: 1. An idea and some knowledge about electronics 2. An EDA softw…

Story time:

Back when I was in school, our introductory electronics class had us make a PCB for a PICmicro programmer on our first day. We got a handout of the schematics. We had to transfer its negative to a copper coated plate using some chemical, used UV light to fixate it, then dissolved the rest of the copper in acid. Finally we got to drill the holes for through-hole soldering points.

Next class we soldered all components. And by the end of two classes, everyone had their own functioning (or not ...) programmer, which we used the rest of the year on a variety of electronics projects. Great fun.

Re: Ask HN: Teach me something new

#276

An electric guitarist usually has a pedalboard that they use to make different guitar tones. Let's approach this like an electrical engineer might. Time is a straight arrow: call it t. The guitarist plays, and their guitar pickup records a signal. At any time t, measure the value of this signal's waveform: call it x. That signal can go into a pedal that maps each value to create an output signal. Call it f(x, t). The…

> Another cool thing about LTI systems is that when you chain multiple of them together, the order does not matter. Reverb, delay, EQ, and wah are all LTI. Delay and reverb may be LTI in your definition, but they very much do matter what order they are in, every time. Delay before reverb is going to give a more staccato sound, whereas the reverb before delay is probably just going to wash the whole thing out if you’r…

I suspect you are right when it comes to analog circuits, but they are definitely LTI in a typical digital implementation. I checked this by adding reverb+delay and delay+reverb to two copies of a track in REAPER. I inverted the phase of one, played them together, and they cancelled out.

Re: Ask HN: Teach me something new

#277
post #120

By far the most important martial arts skill is the ability to function effectively after receiving a powerful blow to the face, solar plexus, etc. The only way to develop this skill is by practicing it; very few people do, for obvious reasons. If your martial arts training does not include this, it may have many benefits, but is severely lacking as training for actual fighting.

My teacher used to say the most important martial arts skill for real life is predicting a fight and turning around and running away.

Check out Krav Maga. It's a self defense "martial art" with the only goal of quickly incapacitating an enemy to be able to flee. Very practical.

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

Re: Ask HN: Teach me something new

#278
post #31

There are no aliens[1] or alien technologies at Area 51. 1. Other than a gag mannequin or few.

Edward Snowden, who had access to basically all the US governments secrets for NSA and CIA with the highest above top-secret clearance, went specifically looking for stuff related to this and says that he came up with nothing. Out of anyone who could know things about this, I find his situation and argument to be most convincing.

Re: Ask HN: Teach me something new

#279
post #154

Earlier quoted context omitted.

Isn't that what conferences and journals are for? Reviewing and selecting the most important papers? When something is really solved (a solution exists without negative side-effects; and this fact has been verified several times), they should indeed look for new problems.

In theory, not in practice. Revolutionary papers ignored by all are the rule, not the exception. I have seen hundreds. See e.g. This 410% reduction of ALL cause mortality. No side effects and in addition significant amelioration of quality of life (sleep, etc) It was twenty years ago and will keep being ignored for the rest of eternity. https://pubmed.ncbi.nlm.nih.gov/12577695/ The human condition is miserable becaus…

I’d like a 410% reduction in all cause mortality as much as the next Joe, but the Pubmed similar articles list isn’t very encouraging. Nearly all the 90 articles listed spanning 40 years are from Russia, many from the same small group of researchers. I observe: 1) there HAS been a sustained effort and publication among a substantial group of investigators, and yet 2) these dramatic results have failed to attract further attention.

I (non-scientist, applying Occam’s razor and the principle of “if it seems too good to be true, it surely is”) conclude there is probably a fundamental flaw, like, perhaps, after a few years of “improvement” people suddenly shrivel up into a husk.

https://pubmed.ncbi.nlm.nih.gov/?linkname=pubmed_pubmed&from...

Re: Ask HN: Teach me something new

#280
Humans might just be the stupidest animals on the planet when it comes to seasonal migration, we get tied down by our monetary system, taxes, government policies, borders, etc., while polluting our planet with patchwork solutions like air conditioning for the summer or burning fossil fuels to heat our surroundings in the winter.

We can't simply just "move" to a different location like other animals.

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