1. I have an existing java application. 2. I have launched a nrepl from it via (clojure.tools.nrepl.server/start-server ...) 3. I can connect to this repl via "boot repl --client --port 5555" 4. I want to run (require 'foo.bar) 5. how do I set the src path that clojure searches for foo/bar.clj in ?

@qqq Are you trying to load code that is external to the application?

https://clojuredocs.org/clojure.core/add-classpath <-- this is marked as Deprecated. What is it replaced with ?

@seancorfield: I want to specify a path ~/blahblah-src/ then I want (require 'foo.bar) to search ~/blahblah-src/foo/bar.clj

You could load files via their file system path using load-file...

Unless you start the application with a classpath that includes your src directory perhaps?

Deprecated just means "there are better ways". It doesn't mean "removed".

is there a split-when function? split-with is almost never what i want

Does anyone know of a bounded prn function? I want to print an arbitrarily large data structure, but only the first (say) 100 characters of it, and don't want to spend the CPU to print the whole thing out.

how do I "continuously" interleave two colls? e.g. if I have:

[:a :b :c] [1 2]

@ag use for, (for [x [:a :b :c] y [1 2]] [x y])

oh, yeah that works... thanks @schmee

(then do (apply concat ...) on that to get the whole thing)

now, this works for me. I'm still curious what if I have more than 2 colls?

you can keep going in the same fashion: (for [x ... y ... z ...] [x y z]) and so on

no, I mean if I have "infinitely" many 🙂 then I'm gonna have to use math.combinatorics I guess

Which method of function argument validations is considered more idiomatic in Clojure - using :pre and :post checks or perhaps using s/assert in the function body instead? Or perhaps something else instead?

Hello all, I have a question regarding the "cat" transducer... why does it need to double wrap reduced (i.e. why does it use the preserving-reduced wrapper for rf). Could anyone give me an example of why that's needed?

@boogie666 Do you see how it calls (reduce rrf result input)? If it didn't "double wrap" a (reduced ...) call inside your transduction the reduce would just return the value. And the reduction of the transducer wouldn't honor the reduced.

Basically it makes sure that if the rf function does a reduced call it will propagate to the transduction (which is again a reduce)

so that means that if the inner reduce stops the whole chain stops.

right?

Right

the thing is, i can't think of an example where not stoping the whole chain would be a problem

for that matter, i can't think of an example in which i could stop the whole thing...

(with cat in composition with something else)

@boogie666 :

(defn cat-wrong
  [rf]
  (fn
    ([] (rf))
    ([result] (rf result))
    ([result input]
     (reduce rf result input))))

(into [] (comp cat-wrong (take-while odd?)) [[1 2] [3]])

Compare with "fixed" cat

aha

thanks...

i get it now

The wrong cat just ignored the reduced from take-while and kept going

thanks

i understand

Note, you can't get that to work with (take x) transducer since it will properly guard that (it's more robust)

i know

that's i could not think of an example 😛 (i was just thinking of regular take)

Yeah take will still work since it keeps internal state. So it would just waste CPU cycles. But still be correct...

i remember seeing a presentation online about funnel / spc charts in clojure, possibly to do with healthcare? anyone know what im talking about and have a link?

hi all! I’m looking at a defmethod implementation in clj-http and I don’t fully recognise the form… http://leo-mt-prod-app07.aslan.local:8306/accountretention/admin/metrics?pretty=true — what is that extra arg none-cookie-policy that sits between the dispatch-value and the fn-parameter declaration?

Is it some sort of syntax for “naming” the defmethod?

are you talking about something like https://github.com/dakrone/clj-http/blob/eca25dd8cb66a1e909a712037b28cf1fe09d9a42/src/clj_http/core.clj#L149 ?

in that case, yes - the “none-cookie-policy” is a function name for the specific defmethod (which you’ll really only see in stack traces typically)

defmethods technically take the “function tail” which is “all the args you’d pass to fn” which includes the (optional) function name

Anyone here using parinfer-mode in emacs? I'm curious what everyone is using for the parinfer-mode-toggle key, Is it something you use often?

Why do some clojure functions that take arbitrary arguments provide several signatures to handle a known number of arguments before just taking arbitrary ones and applying the rest of the args to them? Is it just for performance and common case handling? for example https://github.com/clojure/clojure/blob/master/src/clj/clojure/core.clj#L6123

@theeternalpulse performance, but also for easier code writing

Often the arity that has & rest at the end calls into the other arities

I see. I'm often a little thrown off by them, I recognize the pattern but I generally wouldn't write arbitrary args like that, then agian I don't write languages 🙂

@theeternalpulse check out Erlang sometime 😄 They take it to a whole new level ,and use that pattern instead of if statement:

while(L) -> while(L,0). 
while([], Acc) -> Acc;

while([_|T], Acc) ->
   io:fwrite("~w~n",[Acc]), 
   while(T,Acc+1).

Not sure that it's better than other methods, just a different way of doing it

If I wanted to implement a “clojure lite” on the EVM, purely to learn more about compilers and clojure internals, where should I start? Is there any good reading on how clojure and the JVM play together?

well there's https://github.com/kanaka/mal - not sure if that's what you're looking for

These look like they are implementations in a language, not in a VM. Does Clojure compile to the JVM or Java first?

It compiles to bytecode, not Java source if that's what you mean.

hey guys, what is the best mongodb client for Clojure?

Monger seems the most up2dated one, what do you guys think?

ugh i'm really bad at slack sorry

so... assuming the coll is an instance of PersitentHashMap, it looks like there is no cons method for that object, but it extends APersistentMap, which has the following code:

yes, that’s all correct

I think this is where cons would be called from

for a map

where I get lost is where the actually addition to the map happens

the call to assoc

I just see it pulling out values from the passed argument x but not the joining to the map

assoc is only passed the elements of the x arg though right?

I'm sure my lack of Java knowledge is causing some confusion

what you said is correct - what’s confusing about it?

x in RT.conj is a map entry like [k v] if this is a map

in PAM.cons() that becomes o

the key and value parts of o get pulled apart and used to invoke assoc, which returns an updated map

the final part is where i got lost

i see assoc called with the two arguments

i don't see how it's added to original coll (map in this case) since it's only passed the two args from x

oh, this is an instance method on the map instance

oh

so you are implicitly “in” the map and calling assoc on it

the invocation looks like a function call

diff than i'm use to from my limited OO experience in Python

it is, but it’s call on the current object

got it

which is the map

all instance method calls in Java have an implicit first argument which is the instance

ahhhh

no self everywhere

which Java uses for dispatch

you can get that instance with this in Java

but you typically don’t need to do that explicitly

OK thx for clarifying... btw are these type of questions reasonable here or is that more beginner channel?

don't want to litter the thread but this channel is extremely helpful so far

generally, people in this slack are happy to answer questions anywhere :)

thanks alex!

yw

this could easily be #beginners or #java or even #clojure-dev since you’re looking at internals

here’s fine too