Hi, and welcome to Mathstodon, a Mastodon instance largely focused on maths and related topics.
It's still pretty quiet here, but growing slowly, and we look forward to seeing what you choose to share. The more you say about what you're doing, the more likely you are to get people replying, following, and generally interacting.
So, tell us about yourself, using the hashtag #Introduction
Cheers!
If you're an academic, you're probably unhappy with Chegg. I know I am. Not so much for promoting intellectual property theft, but because they profit from miseducating students by luring them into copying rather than getting the benefit of their own work, and because they greatly boost my workload by forcing me to make up new problems instead of reusing them. But did you know that your university's retirement fund investors may well be financial supporters of Chegg? See https://www.chronicle.com/article/work-in-public-education-and-hate-chegg-you-might-be-an-investor
I just released #Tusky 18.0, but do you know what is even more exciting?
The feature drop coming to Tusky nightly today!
Unified push 👀
ugly parser hack
From an old Donald Knuth paper, discovered a scheme for implementing operator precedence that was used in the first Fortran compiler:
Just do a search-and-replace of + with )))+(((, of * with ))*((, etc., then put ((())) around the whole thing. More parens = lower precedence operator. Since this is purely textual preprocessing, the compiler doesn't need to know about operator precedence after that. Surprisingly, it actually works!
While taking shots of this Ichneumonid Wasp (family Ichneumonidae), I noticed something on its back leg. Zooming in, I saw it had a hitch-hiker: a Chernetid Pseudoscorpion (family Chernetidae). Taken at Sungei Buloh Wetland Reserve, Singapore, on 1 May 2022.
On iNaturalist:
- https://www.inaturalist.org/observations/114162572
- https://www.inaturalist.org/observations/114162573
#iNaturalist #Nature #Singapore #Photography #Insects #Wasps #Hymenoptera #Arachnids #Arachnida #Pseudoscorpions #Pseudoscorpiones
Terry Tao tries to make mathematical sense of notations like ± or O(...) that specify something partially rather than exactly: https://terrytao.wordpress.com/2022/05/10/partially-specified-mathematical-objects-ambient-parameters-and-asymptotic-notation/
It's a long post, but I think much less technical than most of Tao's posts.
Dear #Scipy, #Python, and #GraphTheory experts, I want to find a sparse distance matrix of a subgraph, using #CSR matrices. I appreciate any ideas, here are the details: https://stackoverflow.com/questions/72184296/run-a-multiple-source-dijkstra-to-the-k-closest-sinks-via-a-scipy-csr-matrix?stw=2.
Hey coding peeps! 👋 What project practice makes you smile when you join a community:
* concise commit messages?
* tons of inline code documentation?
* well maintained changelogs?
* code of conduct?
…
And what makes you go nuts?
Here's something I made a couple of weeks ago, before The Stressful Week: Farmyard Befunge.
Digital marbling: https://amandaghassaei.com/projects/digital_marbling/
A recent physics-based simulation project for paper marbling, by Amanda Ghassaei, who was also responsible for an origami simulator (https://origamisimulator.org/) that I linked with a different url a few years ago.
A Martian Eclipse: Phobos Crosses the Sun: apod.nasa.gov/apod/ap220509.… youtube.com/watch?v=aKK7vS… https://twitter.com/apod/status/1523520663369121793
I think these two grids are all you need to memorise. Suppose you're multiplying by \(10a+b\), [^0]. Rotate the grid so that \( b\) is in the top left. If \( b \lt 5\), write down the \(a\) times table in front, but bump it up by one every time you cross a vertical line. If \(b\gt5\), write down the \(a+1\) times table, but drop it by one each time you cross a vertical line.
[^0] Sigh, because mathematicians: \(a\) and \(b\) integers, \(0\le a\lt10\) and \(1\le b\le 9\), \(b\ne 5\). Honestly.
For example, for the 47 times table, write down the grid with 7 in the top right:
| 7 4 1
| 8 5 2
| 9 6 3
Then prepend the five times table, knocked down by one for each line you've crossed:
\( \begin{pmatrix} 47 & 94 & 141 \\ 188 & 235 & 282 \\ 329 & 376 & 423 \end{pmatrix} \)
Boom!
Quant, Scientific consultant, Applied Mathematician, Dad, Husband. Avid programmer, blogger, book writer. Fanatic of soccer, sci-fi, Shotokan karate, chess, climbing...