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Ask HN: Concepts that clicked only years after you first encountered them?

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Re: Ask HN: Concepts that clicked only years after you first encountered them?

#21

Post by luispauloml »

btrettel wrote: post #13

It took a couple years in college for me to understand entropy. Entropy in classical thermodynamics is presented in a mysterious way that leads to confusion. Entropy in statistical thermodynamics, however, is logical. Once one understands basic statistical thermodynamics, entropy isn't mysterious. The book in my statistical thermodynamics class was An Introduction to Thermal Physics by Daniel Schroeder, which is an e…

I had to study entropy twice in college for different courses that were 2 years apart from each other, and I still remember this one quote I read somewhere:

  The first time you study entropy, you won't understand it. The second time you study it, you'll think you understood it until you realize you didn't. By the third time you study it, you just don't care anymore and just use it.
10 years after graduating, and I haven't encontered entropy again after the second time, so you can guess where I'm at in this quote. But thank you, for now I know how to attack it if I ever need it again.

Re: Ask HN: Concepts that clicked only years after you first encountered them?

#22

Post by _xnmw »

mumblemumble wrote: post #15

The monitor model in second language acquisition. Or, more accurately, the more contemporary synthesis that it's developed into in the decades since it was first proposed. The model itself is easy enough to grasp. But concretely understanding what it implies about how I should be studying took much, much longer.

Very intriguing! Any links you can share on this theory? A quick Google search gave me an overview, but I don’t see how this is particularly useful for second language acquisition.

Re: Ask HN: Concepts that clicked only years after you first encountered them?

#23

Post by monero-xmr »

bsuvc wrote: post #2

Unit testing and using dependency injection to write test-able code. I'm not sure if it was years, but it wasn't immediate. I just didn't understand why dependency injection was good at first, and not just someone's weird personal code style choice. I thought it was just people being "Enterprisey" which I'd encountered many times over the years. Once I committed to unit testing, I realized how necessary it is. Unfort…

Another solution is to eliminate classes and only use structs or similar plain objects. Makes mocking and testing functions much easier. At this point I see no reason for OOP whatsoever and consider it a big mistake.

Re: Ask HN: Concepts that clicked only years after you first encountered them?

#24

Post by ericlewis »

number6 wrote: post #18
bsuvc wrote: post #2

Unit testing and using dependency injection to write test-able code. I'm not sure if it was years, but it wasn't immediate. I just didn't understand why dependency injection was good at first, and not just someone's weird personal code style choice. I thought it was just people being "Enterprisey" which I'd encountered many times over the years. Once I committed to unit testing, I realized how necessary it is. Unfort…

Can you explain the concept? I feel I didn't grok it fully

Not sure about poster above, but I found a large amount of value in writing tests when developing API backends. I knew the shapes and potential data. Was easier to write tests to confirm endpoints looked right than manually hit the api endpoints.

Re: Ask HN: Concepts that clicked only years after you first encountered them?

#26

Post by bsuvc »

closeparen wrote: post #20
bsuvc wrote: post #2

Unit testing and using dependency injection to write test-able code. I'm not sure if it was years, but it wasn't immediate. I just didn't understand why dependency injection was good at first, and not just someone's weird personal code style choice. I thought it was just people being "Enterprisey" which I'd encountered many times over the years. Once I committed to unit testing, I realized how necessary it is. Unfort…

Seven years into my career I'm increasingly convinced that the emperor has no clothes with respect to unit tests that are just transcripts of the code under test with "mock.EXPECT()" prepended to everything - 95% by volume of the unit test code I've ever read, written, or maintained.

Yeah, the mere presence of unit tests is not enough. It has to actually assert something useful.

When I code review, I try to make sure I call out "fake tests".

Re: Ask HN: Concepts that clicked only years after you first encountered them?

#27

Post by rramadass »

The use of Predicate Calculus in coming up with the Proof along with the Program.

Predicate Calculus is used to show that the path followed by a Process through a Cartesian Product space (created from all the memory variables in a Program) is the one you had in mind w.r.t. its Specifications. Suddenly you start to understand basic Set Theory, Types, Relations (Functions) and Logic.

Re: Ask HN: Concepts that clicked only years after you first encountered them?

#29

Post by sjaak »

tails4e wrote: post #11

The fourier transform. Encountered it first in my undergrad engineering degree, it was presented as dry mathematics, with no real explanation, just threw complex exponentials at us, and pages of derivations. Years later I actually use it in my job, and through that and other material can see its beauty, and how its actually not that complicated. Some great resources like this helped a lot: [0] https://betterexplained…

This is what made it click for me, can recommend it:

3Blue1Brown -- But what is the Fourier Transform? A visual introduction.

https://www.youtube.com/watch?v=spUNpyF58BY

Re: Ask HN: Concepts that clicked only years after you first encountered them?

#30

Post by rzzzt »

robg wrote: post #8

The autonomic nervous system and the adrenal cortex. Homeostasis is taught as a textbook fact, the body reverting to a baseline over time. What’s not taught is how much the impacts of daily life events drive a continuous stress response. Fight or flight is not just a reaction to deadly threats. It’s active every moment of every day to ensure survival. The adrenal cortex is always active, to traffic, your boss and col…

"Understanding Stresses and Strains" from 1968 presents a good depiction of the mechanism with familiar-looking cartoon characters: https://archive.org/details/understandingstressesandstrains

The caveman pressing the alarm button is something I think of a lot.

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