Notices by Omar Antolín (oantolin@mathstodon.xyz)

@tusharhero As @simontatham implicitly points out, the existence of a nohup program does not disprove the existence of a shell with a nohup built-in that performs the same function.

New post on M-x apropos Emacs! Exploring large amounts of data with completion.

https://www.matem.unam.mx/~omar/apropos-emacs.html#exploring-data-with-completion

Please consider this a last minute entry for the #Emacs Carnival, @sacha.

@clive Wow, this is big news! To save people a click: the proof in question is not that there are uncountable many real numbers (which is what I thought you.meant by "Cantor's infinity proof"), but the proof that there are countably many algebraic numbers, and it was stolen from Dedekind. This explains why Dedekind seems so hostile to Cantor in other writings of his.

@clive A more detailed story appeared in Quanta: https://www.quantamagazine.org/the-man-who-stole-infinity-20260225/ (There I learned that it wasn't just the proof of the countability of algebraic numbers: for the proof that the real numbers are uncountable, Cantor found a proof first, but Dedekind suggested a simplification and that simplified version is what Cantor published!)

And Demian Goos's paper about this is linked from his personal website: https://demian-goos.de/

You've probably heard of the Birthday Paradox, that among 23 people the probability that two share a birthday is more than 50%.

This is easy to prove by calculating the complementary that no two of the 23 share a birthday. There are 365 options for the first birthday, then only 364 for the second, 363 for the third, etc. So the probability that all 23 people have different birthdays is (365×364×...×343)/365²³ ≈ 0.4927.

That calculation assumes the uniform probability distribution on birthdays, that is, that every day is equally likely to be a birthday. That's not a very realistic assumption for the actual distribution of people's birthdays, so it's worth thinking about what happens for other distributions. My instinct was that any non-uniform distribution has some higher probability clump, where birthdays would tend to bunch up with even fewer people; so that any non-uniform distribution is even "more paradoxical" than the uniform one.

This turned out to be easy to prove.

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#math #probability

There is much truth to this post about about #math textbooks.

You know how people advise you not to use mathematical formulas in section titles in LaTeX? Listen to them!

When someone says: "There's this great dynamically-typed programming language with a useful and expressive type system, powerful macros and multiple-dispatch that solves the 'two language problem' (meaning that you can quickly and comfortably write a prototype in the language but then also write the fast production version in the same language), that has roots in academia but with uptake in industry, a great interactive coding experience in the REPL (including the ability to show you the assembly code for any function!) and [an] excellent compiler[s]" you don't know if they're talking about #CommonLisp or #JuliaLang until they choose either the plural or singular for the word "compiler"! 😛

@fanf Here in Mexico (México, actually) los of people have accented letters in their name but bank websites (and many other websites) often don't support diacritics. I've seen messages like: "Your name must consist of letters"! It does, you stupid webpage! I call the version of my name without accents, my "bank name". According to the rules of Spanish it is pronounced differently from my actual name...

@jbaty I've done that too!

@amszmidt Really? You think the claim that the vast majority of Mastodon posts with the hastag #Emacs are about GNU Emacs is "absolute nonsense"? You and I must not be seeing the same posts! :D That's exciting to me because I am curious to read more about non-Gnu Emacsen.

@amszmidt That's interesting. Can you share an example of Gnu Emacs going against the idea of Emacs? I would have no clue about this, since the only Emacs I know is Gnu Emacs.

@amszmidt Also you should probably take into account that empirically speaking the hastag #Emacs on Mastodon means GNU Emacs specifically (at least the vast, vast majority of the time).

@amszmidt Ah, OK. I apologize for misspeaking. I meant GNU Emacs everytime I said Emacs and have never used any other Emacs.

@amszmidt I agree with everything you said except for "Emacs is not a Lisp environment", since I can readily evaluate Emacs Lisp code and use it to modify the behavior of Emacs. The rest I agree with and believe it does not contradict anything I've said.

@amszmidt (1) The reddit user meant "Emacs" when he or she said "Lisp Machine", I understood this and answered accordingly.

(2) It does have something to do with having a Lisp Machine at your fingertips! While Emacs is definitely not a Lisp Machine it seems wrong to me to say it is completely unrelated ("nothing to do") to Lisp Machines. Certainly of all the software I have installed on my computer the only program for which the experience of using it is even remotely close to what I imagine the experience of using a Lisp Machine is Emacs, even if people who have used such a machine feel it is far. (And those people probably agree that, say, Firefox is even further).

(3) It is not just having Lisp! I didn't just program in Lisp, I used the integration with the environment I was working in (Emacs). This is not automatic. I've written programs in Lisp which are not interactive, and not easily extensible (you can say it was stupid of me to write such useless programs but I had my reasons at the time, like wanting to know the result of some computation). There is something special about Emacs beyond having Lisp.

On the #Emacs subreddit someone asked: "What exactly is the advantage of having a LISP machine at my fingertips?". I gave an example, which I reproduce here:

One time I organized a conference session. I had to select among submitted talks and schedule them. The conference had a website I could log into to see all the submitted abstracts, so I wrote some elisp code to download all the abstracts and create a nicely formatted #OrgMode file with all the information —Emacs comes with functions to make HTTP requests and with a full HTML parser!

Once I chose the talks to accept (which I tagged in the Org mode file), I wrote a quick bit of elisp to write emails to all the talk applicants notifying them of their acceptance or rejection. This code used Org's parsing functions to go through the talks, get the applicant information and to pick either the acceptance or rejection template as appropriate. The code didn't actually send the emails, it just created and pre-populated message-mode buffers so I could review and customize the messages before sending.

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@runlevelrobot @slomosapien I mainly use Emacs for writing prose (emails, papers, course notes, homework assignments, todo lists, committee reports, recommendation letters, etc.) and I still get a ton of mileage out of keyboard macros. You certainly don't need to be using emacs for programming to find keyboard macros useful!

There are a couple of features of #orgmode links in #Emacs that I think are underappreciated:

1. They work in all buffers, not just org-mode buffers! Bind org-open-at-point-global to a globally accessible key binding and enjoy org-links everywhere. For example, I like putting info links in comments in Emacs Lisp files, like info:calc#Graphics. Remember too, that file links can include a search string, for example file:~/.emacs.d/init.el::eshell takes me right to my eshell configuration. Shell links, that execute commands, are pretty useful too, for example <shell:zip source *.c *.h>.

2. It's super easy to create new link types (if you know how to program). For example, here's a new type of link for keyboard macros:

(org-link-set-parameters "kbd"
:follow (lambda (macro arg)
(kmacro-call-macro arg t nil (kbd macro))))

With that definition you can write keyboard macros like <kbd:M-a M-f M-t> and execute them with org-open-at-point-global.

I got a weight off my chest: I turned down an invitation to a math conference in the US and cancelled another I had already accepted. I know I'm probably overreacting, but I was worried about being deported since I've read many news stories about this happening to people with valid visas —including Europeans, so I don't like my chances as a brown Mexican! And even though I know it was unlikely to happen to me (it probably only happens to a small fraction of visitors), I'm happy to stop the nagging worry in the back of my mind. It's a shame: both events would have been great and I would have seen many American friends I don't get to see often.