I've been reading about print-dup a bit and I'm wondering about their relationship to tagged data literals and printing via pr/prn and reading back through read-string. To have a concrete example - https://github.com/clj-time/clj-time/commit/e5c9cce321e923464a3480ae04e4a43abdd4fc7e so it can be printed and read easily :

(pr-str (org.joda.time.DateTime.))
;;=> "#clj-time/date-time \"2022-04-07T09:35:13.158Z\""

(read-string "#clj-time/date-time \"2022-04-07T09:35:13.158Z\"")
;;=> #clj-time/date-time "2022-04-07T09:35:13.158Z"

(binding [*print-dup* true] (pr-str (org.joda.time.DateTime.)))
Execution error (IllegalArgumentException) at codescene-cloud-web.sign-up.routes/eval128869 (form-init6498231345551227843.clj:118).
No method in multimethod 'print-dup' for dispatch value: class org.joda.time.DateTime

Which one would you use (conditional add to map) and why: (merge {:a 1} (when true {:b 2})) or (into {:a 1} (when true {:b 2}))

I am using datomic cloud. I have a list of eids, I want to pull all of them in one query. How do I do that?

You might get more relevant responses in #datomic

So just how magic is the transducing arity of map? Like how does it make sense for there to be a transducer that takes multiple arguments per step? Is that something that only map can do? Or can other transducers do that too?

I think reading the source of the transducer arity of map, filter and cat can be illustrative and remove the magic

Yeah, I've read them, and it seems like there's just special magic about using sequence and map together.

I don't see any particular reason why map in particular should be so magic, like you could conceivably do like (filter <) or something followed by a map that takes multiple items.

map and sequence are the only paths into multi-source transducers

was there a particular rationale as to why

(comp (filter <)
      (map vector))

note that there is no variadic non-transducer filter

< doesn't take 1 vector though, it takes N args

there is space here for future work. we haven't tried to do that work.

Well yeah, you would call it like (sequence xf [1 2 3] [4 5 6]) and the output would include each pair because the right one is always greater than the left.

it's the same as the multi-source map transducer more or less

The only thing that seems to be missing here is an allegorical arity of filter that takes multiple sequences, mostly because it's unclear how you could return the value without wrapping it into a vector or similar.

and perhaps the wiring for allowing multiple sources to be maintained between steps in a transducer

that wiring exists in clojure.lang.TransformerIterator

fair enough

it's really an api problem in applying the transducing function

symmetry or something being missing is not necessarily a strong motivating problem statement

there is also some magic for map entries that probably conflicts with some of this

Yeah, I'm not proposing effort be put into this, I have no problem this solves, I was just curious if there was specific thought put into why filter can't work similarly, just calling the wrapped reducing function with the extra arguments as with apply, which would allow it to work with the reducing function produced with map nicely.

transducers extend the history of deciding not to solve this generically with sequences :)

but at some point something may put pressure on this and then we'll figure it out :)

Was there an article somewhere about different strategies for adapting one protocol to another?

I’m getting back into dev and Clojure/Script. I’m pretty sure I’m into a lot of ineffective anti-patterns in how I’m approaching developing (and always have been, I’m sure). Basic concepts aside (which I definitely need to keep working on) I don’t think I’m working with the repl correctly. I think a set of eyes would immediately identify some major missteps in how I’m going about things. I am wondering if anyone might be willing to look over my approach via Zoom screenshare for any amount of time (even just 10 minutes would be probably really helpful)… I’m camera shy so would just be my editor and voice, probably, and I don’t expect any more than that from you; you wouldn’t even need to share anything from your side. I seem to be addicted to Emacs and Cider but I’m not at all against trying other editors. I know that other editors are quite capable now… I’m still addicted to the fast Emacs bindings. I mention this because I’m also interested in Emacs workflows if anyone has that set up I’d love to learn. The proper thing is for me to post problems and I try my best, but I think what I might be missing at times is the amazing amount one can get if one is in an office where a coworker can notice ridiculous things I’m doing and point them out. These are things I can’t properly ask about since I’m unaware of them. I’m getting into front and back end dev and would be happy if anyone looked at any part of that. I could and will go to live events but I’m taking care of the ailing folks right now so a bit unable to do that, in case you’re wondering why I’m reaching out here. Mentioning this in #cider too, but open to any editor approach. Feel free to DM me here if this would be something you’d be up for… and thanks for the time reading this!

I’m open to other thoughts for getting unstuck, btw!

Hey, I'm trying to bind a Java class to a var, so that I can inject it in a function, but for some reason I'm not having success. What I'm doing:

(def my-class MyClass)
(. my-class someStaticMethod) ;; it doesn't work
(. MyClass someStaticMethod) ;; it works