How to deliver a exception, like datomic.api/transact?

QUESTION: Is there a partition-by which has f taking the previous or all already created partitions as well as the next element?

For context, I'm trying to partition every time next element is smaller then previous element

Like this:

(let [prev (atom nil)]
  (partition-by (fn [e]
                  (when (or (nil? @prev)
                            (< e @prev))
                    (reset! prev e)
                    e)) '(9 8 6 3 5 6 7 10)))

@didibus what do you expect for (8 4 7 6 10)?

(that code returns ((8) (4 7 6 10)))

Is there a list of "transducer producing functions" somewhere, like map, filter, keep, remove...? Tried to google but I just get general posts on transducers.

(find-doc "transducer")

@sundarj oh, cool!

Thanks, also @noisesmith

@noisesmith sorry for the ninja 😁

actually I bet the best result would come from transduc which would match transduce transducing transducer etc.

good point

@vinai there is a list at https://clojure.org/reference/transducers

@alexmiller Oh, thanks, I missed that. I was scanning the page for a list, not a paragraph.

Hey folks, I've used the #= reader macro in the past to evaluate a form at read time (ex: #=(* 24 60)), but I can't find a reference to it in the official docs. Is that something that is missing documentation, or might support for it go away in the future?

I'd say using it is a very bad idea

it's not a general purpose read-eval like common lisp's

I consider it an implementation detail

OK, that makes sense. thank you.

I'm trying to add the result of a simple expression like (str *ns* "/" "some-fn") to metadata that will become a Java annotation, and #= worked for that use case. Do you know of an alternative that would work for that use case?

you could likely use a tagged literal to achieve that

a bit of a hack

but I'd rather do that than use #=

How do I proxy an interface method that has type m(A, B…)? ISTR the B… is syntactic sugar, but that clojure’s dot interop syntax knows how to deal with it. When I define a proxy with signature [x ys] or [x & ys], in either case I get No matching method found: m for class $myproxy.

@lvh the ellipsis is just syntactic sugar for a primitive java array, so you want a method where the last argument is a primitive java array

@bfabry do you happen to know if Clojure’s dot syntax allows you to type it as one would in Java, that is, with an implicit array?

(ISTR calling it worked fine)

what's ISTR? No, clojure's dot syntax requires you to pass a java primitive array as the last argument afaik

Sorry, I seem to remember/recall

OK, so I’m going to do something gnarly like (type (into-array Logging$WriteOption [])) and then type annotate with that?

boot.user=> (import '(java.util Collections ArrayList))
java.util.ArrayList
boot.user=> (Collections/addAll (ArrayList.) 1 2 3)

clojure.lang.Compiler$CompilerException: java.lang.IllegalArgumentException: No matching method: addAll, compiling:(/var/folders/42/zcfb2hds38l3shl7lqnjw2gh0000gp/T/boot.user7697464369495271650.clj:1:1)
     java.lang.IllegalArgumentException: No matching method: addAll
boot.user=> (Collections/addAll (ArrayList.) (into-array [1 2 3]))
true

I suppose that's not actually dot syntax... but I'd be surprised if the rules were different

boot.user=> (. Collections addAll (ArrayList.) (into-array [1 2 3]))
true
boot.user=> (. Collections addAll (ArrayList.) 1 2 3)

clojure.lang.Compiler$CompilerException: java.lang.IllegalArgumentException: No matching method: addAll, compiling:(/var/folders/42/zcfb2hds38l3shl7lqnjw2gh0000gp/T/boot.user7697464369495271650.clj:1:1)
     java.lang.IllegalArgumentException: No matching method: addAll
boot.user=>

ah, there we go

thanks 🙂

so, to proxy that

I honestly can't think of a proxyable java interface/class off the top of my head. my belief is it would just work but I don't know for sure

java/interface with an ellipsis method sig.

define “just work”? as in you’d expect the signature to just be (m [x ys] …)?

where ys is a primitive java array yes

why can't I think of anything that uses ellipsis...

ugh I think I figured out the problem; the exc is just because I’m calling it with the way I thought dot syntax worked, that is — allowing varargs

so the error is in fact 100% accurate because I’m passing 3 args and it only takes 2