There Is(Ǝ) – Such That (∋) | Hacker News Reader

There Is(Ǝ) – Such That (∋)

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105 pointsevakhoury33 comments

I don’t think I have ever seen ∋ used to mean “such that” so I was very confused until I got to the explanation (as it were; why CONTAINS AS MEMBER is being used to mean “such that” is never explained).

as a math major i had the same confusion; for such that i use "s.t.". but apparently peano used ∋ to mean such that:

https://math.stackexchange.com/questions/15455/backwards-eps...

It also doesn't make much sense

> There exists a raven such that the vector of hours.

The vector of hours what?

The correct statement seems to be: raven = vector of hour hand

But maybe that sounded too simple?

Interesting, my experience in classes using set theory was the opposite, where ∋ only meant “such that” and ∈ only meant “is a member of”.

Learning programming syntax at the same time made it frustrating to learn that math symbols were less strictly defined and less universal, that it was best to write proofs/derivations/etc in plain English in many cases instead of the neat symbols

Same. I recalled pipe being used for "such that". But [per wikipedia](https://en.wikipedia.org/wiki/Glossary_of_mathematical_symbo...), that's specifically "set-builder notation", and the _last one_ of the twelve instances of the string "such that" on the page (though I don't know if they're ordered by usage, "alphabetically", or what).

Yeah in my experience (and on my bookshelf), I see “:”, “|”, “s.t.” And the words “such that” or “with” (this often works in context for lots of properties) and I have literally never seen that inverse membership sign before.

Not a huge fan of quantifier symbols in published notation. For example I use backwards E all over the place in my notes, but in everything I typeset I say “there exists”. Mathematics is supposed to be written in complete sentences anyway so you are going to have some words, so this doesn’t seem a particularly useful two words to turn into a symbol.

This isn't quite what's going on. A better reading might be "which is a";

"Ǝx s.t. x∈ℕ" (there exists an x such that x is in the naturals) is just being shortened to "Ǝx∋ℕ" (there exists an x in the naturals), or there exists an x which is in the naturals.

It's not really that different from the normal usage.

If that’s it, why is it using ∋ rather than ∈? I would expect “Ǝx∈ℕ”.

Oh, doh! I'd missed that.

Yeah, that's...an unusual choice.

> Ǝx∋ℕ

"There is an x such that the set of natural numbers is a member of x"?

Yeah, my bad. My eyes autocorrected it.

I love this: a DSL that makes clocks out of birds and math. Really, this is a glorious little project.

The thing I bounced off isn't the high-concept art, or the abstract math. It’s the combination of the two without enough bridge between them. You have to infer too much about how the poetic layer, the mathematical notation, and the actual machinery relate.

You can do mind-expansion by induction in a math journal. This is not that venue. And this project is too good to waste by letting people walk away confused.

I’d love a very plain “one clock, end to end” walkthrough: primitives, composition, graph, rendered result.

For me at least, the post is kinda confusing and feels a bit overwrought (“there exists a raven such that the vector of hours”?), and was hard to understand at first. Sadly, in the wonderful year of 2026, I can’t help myself wondering if it was all written by an LLM, prompted by “be mysterious” or similar — though I still wouldn’t bet on it.

The project is cool! It’s a simple visual graph layout system for making your own clock.

the structure and cadence feels very organic to me - it might not be generated.

This just reads way to creative. At least no spidey sense triggered for me.

Pangram says human-written. It does have some stylistic quirks often associated with LLMs, but those aren't a reliable indicator.

Whichever field of study these backwards E symbols are from, I've never taken a course in it.

So for me it's "Backwards E a raven Italics Backwards E the vector of hours" and I closed the tab there.

After reading this comment the symbols are now clear but by that point I'd already lost interest and moved on with my life.

Maybe this is only for people who already know set theory or whatever the backwards E comes from, and that's fine, I guess, but it was pretty annoying not to have any explanation whatsoever at the top.

I only learned that this is something to do with clocks from the comments.

I keep hearing about the "Recurse center". I tried to understand from their website what exactly is it, but only thing I got was "a sabbatical where you work on random stuff and talk with people doing the same" which still doesn't really click. But clearly it leads to cool stuff like this.

Which part of it doesn't click? Attending the Recurse center means you commit to spending a few weeks on spare time programming projects and you get to work on these projects around other people who do the same.

Do the concepts of meetups or hackathons make sense for you? Take that concept and stretch it out to a few weeks.

I attended a decade ago and it was great, lots of people working and exploring a lot of cool stuff! I think what I would quibble with is that yes it is “random” what people work on, but there’s certainly themes and some people have pretty clear directions about what they are up to and want to learn. If you want to focus on That One Open Source Project for a couple months, that’s cool and encouraged.

I think you've got it. You go in each day and work on things and talk with people working on things. There are multiple opportunities to share weekly, one or two are pretty regular and the rest are self-organized. Maybe you learn about something new and dive in, maybe you come up with a project and share it with others.

I think the beating heart is that everyone is there with some passion to learn and build and you're encouraged to do so collaboratively. It's surprising, I feel, how rare it is to have a community of folks who are all learning together and not afraid to dive in and figure things out. Recurse Center is a chance to spend 6 or 12 weeks building and then living in a place like that.

For a moment I thought this was a nature-inspired introduction to Quantum Computation and Quantum Information[1]

[1]: https://en.wikipedia.org/wiki/Quantum_Computation_and_Quantu...

Although the notation choice is tediously abstract (imo) the set of available scalars (and vector components) here is actually a relabeling of Q[e^i], the smallest field containing the rationals and e^i.

It was a fun three minute proof, if any of you are like me in enjoying this kind of thing.

Reads a bit like the "Little Alchemy 2" game!

https://www.crazygames.com/game/little-alchemy-2

I’m a little lost though this seems like it could be fun, on safari mobile whatever I build keeps losing some of the connections as I tap on other things so it’s hard to get far with it.

For a moment I thought this was another case of AI psychosis, like the post from week ago about the "content-addressed lattice heap" but this is actually pretty neat.

The kind of exploration that would require a massive one-month of full-time investment before LLMs. Now doable in days.

(I don't know on which side of this author was)

I've seen such explorations done over a couple of days during weekend hackathons or gamejams.

Have we gotten so addicted to our daily token fix that we can't even fathom focusing for 48h?

Not me, but I would produce a much larger output with 48h focus on my token fix.

I didn't get it at all

I don't either, maybe my mathematical maturity is not high enough to be able to work at the level of abstraction that can see a connection between ravens and "vector of hours".

I also played around with the canvas and couldn't draw anything, I tried taking the dot product of a "raven" and a "crow", piping it to a "sun", and didn't see anything. I would have expected something since a raven and crow are similarish so should have a non-zero dot product. But for that matter a dot product of a raven and a raven piped to a sun doesn't show anything either so I'm just completely lost.

i had flash backs to failed discrete mathematics being unable to read symbols correctly

thanks

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