Ask HN: Teach me something new • Hacker News Board

Re: Ask HN: Teach me something new

#231

Post by _zywo » Sat, Apr 30, 2022, 8:26 AM UTC

vishnugupta wrote: post #204

> command line trick 1. "cat foo.json | python -m json.tool" pretty print on console. 2. "cal" pretty prints current month on console. "cal 2022" pretty print current year. > interesting to you 1. Bank of England one of the earliest banks to issue paper money was establish to finance war expenditure. 2. Federal reserve is holding (and hence funding) ~$2.7T worth of mortgage backed securities[1]. It started out as a s…

For JSON pretty printing I generally use jq (`cat foo.json | jq`). It highlights and indents the output, and it's easy to add a filter.

Re: Ask HN: Teach me something new

#232

Post by atoav » Sat, Apr 30, 2022, 8:27 AM UTC

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 software where you design the schematic and the PCB (Horizon EDA, KiCAD, Eagle, ...). This software will give you the Gerber files needed to manufacture the PCBs and the BOM (Bill of Materials) and a Pick-and-Place file which is basically just a CSV telling the manufacturer which part goes where and in which orientation.

3. Using the BOM you find corresponding parts the manufacturer has and put create a CSV that matches their format requirements

4. You order (e.g. I ordered at jcbpcb)

The electronics knowledge is the hardest part.

Re: Ask HN: Teach me something new

#233

Post by tigershark » Sat, Apr 30, 2022, 8:27 AM UTC

sudo means “I sweat” in Italian.

Re: Ask HN: Teach me something new

#234

Post by nathias » Sat, Apr 30, 2022, 8:29 AM UTC

mikelevins wrote: post #28

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…

Yes, there are many levels of perception (there is also blindsight), this can be studied by looking at what happens in neurological disorders like yours and more severe ones. Read the book The Man Who Mistook His Wife by Oliver Sacks if you find this kind of stuff interesting.

Re: Ask HN: Teach me something new

#235

Post by ggambetta » Sat, Apr 30, 2022, 8:29 AM UTC

bluejay2 wrote: post #3

The Spanish language uses the same word to signify "wife" and "handcuffs" (la esposa/las esposas).

Can confirm. "Las esposas" also means "the wives", so it really is the same word.

Re: Ask HN: Teach me something new

#236

Post by mdp2021 » Sat, Apr 30, 2022, 8:30 AM UTC

laserlight wrote: post #230

mdp2021 wrote: post #199

Earlier quoted context omitted.

Colours are, in the outside world, fuzzy ranges of electromagnetic frequencies: they do «exist outside of your brain». (Similarly, "brain" and "mind" are not the same.) Otherwise, the intended general idea is that found e.g. at the beginning of Arthur Schopenhauer's Welt als Wille und Vorstellung : > "The world is my representation": this holds true for every living, cognitive being, although only a human being can b…

Some electromagnetic frequencies are colors, but not all colors are electromagnetic frequencies. That’s why parent stated that color is a brain phenomenon.

> not all colors are electromagnetic frequencies

What do you mean? (Outside the detail that "hues" are electromagnetic frequencies, while colours are compositions - there I just simplified.) Which colour is not such?

Re: Ask HN: Teach me something new

#237

Post by r6203 » Sat, Apr 30, 2022, 8:31 AM UTC

mikelevins wrote: post #48

krasotkin wrote: post #43

Earlier quoted context omitted.

I have experienced this several times and almost never have a headache. I definitely can't read what's beyond/obscured by the scotoma. The first time it happened was during a test in high school and the splotch grew until I was forced to read the questions in my peripheral. I have an anecdote that corroborates your observation that cognitive experiences are more complicated then assumed: I was once very, very sleep d…

One of the other weird things I referred to is best described as discovering that I could be awake and asleep at the same time. I think it might be another case of our naive ideas about cognitive processes being a little oversimplified. It sounds like nonsense, of course, but that's because we naively assume that sleep and wakefulness are opposites--that they are mutually exclusive. What if we're wrong about that? Wh…

I could be wrong but the experience you're describing sounds like lucid dreaming.

Re: Ask HN: Teach me something new

#238

Post by _zywo » Sat, Apr 30, 2022, 8:31 AM UTC

exikyut wrote: post #185

mhh__ wrote: post #164

Earlier quoted context omitted.

If it's proven then we can add a new pointless compiler optimization (some of them are already allowed to assume some things never terminate, even)

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++.

Re: Ask HN: Teach me something new

#239

Post by nstart » Sat, Apr 30, 2022, 8:33 AM UTC

aspaviento wrote: post #209

Harmonicas are amazing instruments. At first people assume them to be like toys (you can buy really cheap ones everywhere) and initially the concept seems really easy: 10 holes, drawing air produces some notes and blowing air produces other notes. But the more you get into it, the more amazing it gets. Soon you discover that you can bend notes by positioning your tongue in a specific way and your repertoire increases…

Fabulous addition. For anyone looking to see what a master harmonica player looks like, highly recommend looking up blues traveller / John Popper.

In particular, there’s a live performance of no woman no cry that has John Popper alongside Ziggy Marley. Mind blowing. Watch it. You won’t regret it.

https://youtu.be/9zk0HFG5mDw

Re: Ask HN: Teach me something new

#240

Post by omnibrain » Sat, Apr 30, 2022, 8:33 AM UTC

mncharity wrote: post #6

Consider arm sized, hand sized, fingernail sized, and pinched-fingers "tiny" sized. About 1000, 100, 10, 1 mm. Tray of cookies, hand-sized cookie, chocolate chip, and tiny crumb - yum. Now zoom 1000x, taking tiny sized to arm sized, and they become 1000, 100, 10, 1 um. Call this microview, with microscopic microorganisms measured in micrometers. A grain of salt is sized like a cardboard box, a head hair like a hand-s…

There is a book from the 80ies/early 90ies "POWERS OF TEN: About the Relative Size of Things in the Universe" by Philip & Phylis Morrison. That is exactly that.