Hacker News: cka

New comment by cka in "Tin Can, a 'landline' for kids"

cka — Mon, 23 Mar 2026 14:40:10 +0000

Same! They have a thing called presentation city that is a slide deck that is a sort of ad hoc social media platform.

New comment by cka in "There is no comfortable reading position"

cka — Mon, 19 Jan 2026 20:45:13 +0000

My kid usually sits perched on the floor and holds the book open with his foot. It looks so uncomfortable but he seems fine with it.

New comment by cka in "New knot theory discovery overturns long-held mathematical assumption"

cka — Wed, 03 Sep 2025 23:57:07 +0000

Wow, this problem has been around for a long time. Exciting to see this finally figured out.

New comment by cka in "A Typology of Canadianisms"

cka — Wed, 09 Jul 2025 23:45:49 +0000

Colored pencils

New comment by cka in "From Finite Integral Domains to Finite Fields"

cka — Thu, 29 May 2025 16:15:42 +0000

Yeah, and constructability is usually handled by proving that a length is constructable if it lives in an iterated quadratic extension of the rationals. Pi does not lie in such an extension, so is not a constructable length (and neither is its square root).

New comment by cka in "The Efficiency of Vim"

cka — Thu, 27 Feb 2025 04:22:01 +0000

Or 'caw' if you want to change the whole word, even if cursor is in the middle somewhere. I read it as "change a word".

New comment by cka in "I tasted Honda’s spicy rodent-repelling tape and I will do it again (2021)"

cka — Wed, 12 Feb 2025 00:30:05 +0000

It's entertaining when reading is entertaining. This was a great "read while eating lunch at work" read because it was entertaining.

I didn't really care too much about rodent-repelling tape before reading and don't care much now. It was the entertaining writing that brought value for me.

New comment by cka in "CDC data are disappearing"

cka — Sat, 01 Feb 2025 23:10:28 +0000

Definitely troubling. Not a replacement, but you might be interested in EHR derived communicable disease data available here:

https://www.epicresearch.org/data-tracker/communicable-disea...

New comment by cka in "MomBoard: E-ink display for a parent with amnesia"

cka — Thu, 14 Nov 2024 17:19:04 +0000

My kid just figured it out, so generation parity can break

New comment by cka in "Introducing Copilot+ PCs"

cka — Tue, 21 May 2024 02:41:03 +0000

I think you meant Azure Windows Surface Copilot for Workgroups 360.Net. Everything at Microsoft is Azure now.

New comment by cka in "Trapped in the Ivory Basement (2021)"

cka — Sun, 10 Mar 2024 17:31:04 +0000

I'm a math PhD, was a tenured professor and then transitioned to industry. We've got two humanities PhDs that work as QA testers on our team. They're both fantastic, especially in thinking about either big picture questions or nuanced takes that others missed out on.

New comment by cka in "Shave and a Haircut"

cka — Fri, 01 Mar 2024 02:54:06 +0000

There's a common workflow I use at work that involves taking the default 10 times before inputting what I need to use. I do double shave and a haircut quickly instead of counting return presses.

New comment by cka in "How to lose your work using Undo Copy in Windows"

cka — Sat, 13 May 2023 12:18:16 +0000

A similar annoyance is the fact that excel's undo applies to all open excel files. Make a change in a.xls, make a change in b.xls. if you ctrl-z twice with b.xls focused, it'll undo both of the above changes!

This has bitten me more than once. Does anyone actually want this behavior?

New comment by cka in "Coltrane: A music theory library with a command-line interface"

cka — Sat, 11 Mar 2023 18:27:50 +0000

In your third paragraph, I think you're talking about modes: https://en.m.wikipedia.org/wiki/Mode_(music)

New comment by cka in "Japan's PM to ask all schools to temporarily close"

cka — Thu, 27 Feb 2020 14:39:14 +0000

I can't speak for the op, but in Minnesota (in the northern part of the US), there are days in the winter when the temperature gets as low as -30F (~ -35C) with very high winds. This can make for very dangerous travel. Occasionally there are snow storms that make the roads impassable for part of the day.

On these sorts of days, the schools are sometimes closed to keep people off the roads.

New comment by cka in "Homology"

cka — Fri, 15 Nov 2019 23:34:26 +0000

A curve is a 1-dimensional space. Even though you draw a picture of it in a 2 (or maybe higher?) dimensional space, you should think of the set of points in the curve as being the only points that we care about.

In a closed curve, you can never fall out of the space by moving around in it. In a curve with endpoints, you can fall out of the space by walking across one of the endpoints, so the endpoints are considered to be boundary components.

New comment by cka in "Ask HN: How is your mental health?"

cka — Tue, 05 Nov 2019 22:03:25 +0000

Bad. I've suffered from depression for ages. I'm an academic teaching at a small college in a small rural town. I wish I could regularly see a therapist, but there's no one within an hour of where I live. Definitely feel trapped.

New comment by cka in "The exponential function is a miracle"

cka — Fri, 13 Sep 2019 13:25:58 +0000

Further evidence that e^{ix} = cos(x) + i sin(x) is natural is that it fits in nicely with power series representations. If you define cos(x), sin(x), and e^x by their power series centered at 0 then it's straightforward to see that substituting ix into the power series for e^x yields the sum of the power series for cos(x) and i*sin(x) (as long as you accept that theorems about absolute convergence and rearranging terms extend to the complex numbers).