Are stable internal links at https://htdp.org possible so that if a kata at http://codewars.com is based on a particular htdp exercise, a link directly to that exercise can be included in the kata description? Currently there are internal names. For example, as of 2019–07–28, Exercise 490 can be found at https://htdp.org/2019-02-24/part_six.html#(counter._(exercise._ex~3arel-abs-.O)). Does anyone know if this link will be unchanged over a period of years?

By the way, I didn’t add the “codewars” advert that slack seems to have appended to my message.

Not an advert. It’s just displays previews of a link in the text.

It reads like an advertisement…

Thanks for the heads up. I’m new to slack.

It does - but it’s just the text of their landing page.

What is the right thing to do with different versions of binaries?

https://github.com/soegaard/poppler-libs https://github.com/soegaard/poppler-libs-3

This repositories contains packages that contain binaries for poppler. The binaries depend on the libraries distributed with racket. The problem is the best thing to do when the racket binaries are updated. The poppler-libs contains binaries linked with the old binaries and poppler-libs–3 are linked with the new (“draw–3” libraries).

Should I just remove poppler-libs (and rename poppler-libs–3 to poppler-libs)?

If I keep both, how can I get raco to use the new package?

Currently when I install racket-poppler, it will use the package poppler-x86–64-macosx from poppler-libs — but I need the one from poppler-libs–3 ?

The information page: https://pkgd.racket-lang.org/pkgn/package/poppler-x86-64-macosx shows the package server uses the one rom poppler-libs.

@alexknauth: Your understanding of the word “deprecated” is indeed in line with the Racket meaning. My understanding at the time was not. I don’t think there was ever a plan to remove them, but rather a desire to steer people away from the older way of doing things and towards the new one. There needs to be a word for that, but deprecated isn’t it.

“discouraged”?

Hi all, been a while

A long while ago, someone from IU invited me to come check out the facility there and say hi. I don’t remember who that was, but I would like to. I am signed up to be a student at large and was interested in taking a class on LISP.

Perhaps a stupid question: is it possible to determine if a file is being run as the “main” file?

(I.e., not the result of an include)

actually, now that I think about this, the reason I’m asking is that I want to use this for testing purposes and I should probably just be adding things to the test module and then running those tests instead..

@stamourv I’ve heard the term “soft deprecation” used for that kind of thing

Although I think deprecating prop:equal+hash and prop:custom-write means we need a way for make-struct-type to support adding generic interface implementations

I forgot how beautiful this language is.

can anyone simplify O({2^n \choose \floor{n / 2}}) for me? I promise its not a homework question

wait nevermind, thats the wrong question

the “numerator” should be n not 2^n

It’s O({2^n \over \sqrt n}).

You can use Stirling’s formula: n! ~ (n/e)^n \sqrt{2 \pi n}.

I am trying to setup the Handin server package on an AWS Ubuntu 16.04 instance for a class that I am teaching this fall. Has anyone had any success doing this? Currently I am running into a problem running this command: racket -l handin-server ; I tried setting the DISPLAY environment variable to :0.0 but I get an error: “Gtk initialization failed for display "localhost:0.0”" I wonder if this is even possible since handin-server appears to have some dependencies to the GUI

Transducers are working!