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Hey, not sure if this is the right place to ask: I'm using pedestals response-for function:

(test/response-for (:io.pedestal.http/service-fn @lhrb.server/server)
                     :post "/q"
                     :headers {"Content-Type" "application/edn"}
                     :body "(+ 2 2)")
After the first eval, changes to the request body do not have any effect and I always get the first request returned. Could anyone help me resolve this Issue?


Okay seems like it's not an issue with the response-for fn, since I observe the same behavior with curl


Oh gosh my bad ... I had a var in the repl which I used instead of the argument passed by the function. 🙈 Sry

Timofey Sitnikov11:05:11

Good morning, I am puzzled by the, which is the following:

(defn send-message
  ([{:keys [host] :as server}
    {:keys [from to bcc subject body] :or {to "" subject ""} :as msg}]
     (when-not (or (and from to)
                   (and from bcc))
       (throw (Exception. "message needs at least :from and :to or :from and :bcc")))
     (if host
       (smtp-send server msg)
       (sendmail-send msg)))
     (send-message (meta msg) msg)))
In the function definition, after the function name there is is a function call, where are the function parameters?


They're not actually function calls, although they're written similarly. The function has two arities (see defined for it, so there are two distinct function bodies, one for arity of two (server, msg) and the latter for arity of one (msg).

Timofey Sitnikov12:05:03

@tvirolai, thank you for clarifying, I did read about it, but for some reason it did not register as such.


Altering a data structure (map) multiple times (in a stateful way) with one line (without loop/recur) A simple question here regarding basic techniques. The case of 'altering stuff one single time' is page-3-stuff of any book, of course:

(let [cat-v [:data :content :objects]
	  dim-app-db (assoc-in app-db cat-v {})]
  ;; Process dim-app-db
Now I want to alter the target structure multiple times. My imperative mind set keeps producing this code:
(let [categories '([:data :content :objects]
     			   [:data :content :media :objects])
	  dim-app-db (let [func (fn [db categories]
				                (if (empty? categories)
				                  (recur (assoc-in db (first categories) {})
				                         (rest categories))))]
				        (func app-db categories))]
  ;; Process dim-app-db
But this is quite some clutter. I was thinking of a more lispy/functional way of altering the target structure (app-db) multiple times. Stateful transducers came to my mind. I read about it, but couldn't pattern match it into my needs so far. Is there a one-liner that does the job more graciously?

Noah Bogart13:05:40

why do you want to avoid loop/recur? it does what you want

Noah Bogart13:05:06

lemme see if i can rewrite what you have

Noah Bogart13:05:43

(let [categories '([:data :content :objects]
                   [:data :content :media :objects])
      dim-app-db (loop [db app-db categories categories]
                   (if (empty? categories)
                     (recur (assoc-in db (first categories) {})
                            (rest categories))))]
  ;; Process dim-app-db

🙌 3

Hi @nbtheduke . I don't want to avoid it at all cost. It's fine with me. (I LOVE loop/recur, in fact). I was just wondering if I do total beginner's mistakes. Maybe there is a way shorter technique and I just don't know it. This is a standard case, and I write this code quite often. (And it's lenghy and requires a new fn all the time.)


Ah, yeah, that's better code for sure. About the same lenght, and the approach has not changed. But certainly more elegant. Thanks!

Noah Bogart13:05:03

there’s also reduce

Noah Bogart13:05:12

dim-app-db (reduce #(assoc-in %1 %2 {}) db categories) i think (haven’t run that)

Noah Bogart13:05:10

first arg to the reducing function is the accumulator, second is the current value from the sequence, and the accumulator (which starts as the db) is returned at the end

🙌 3
👍 3

Hrm... you sure this works? If so this is exactly what I was looking for. 1 millions thanks, man!!!


Yeah, just reading this! 🙂 I knew reduce but wasn't aware it's capable of such things also. Awesome. Only downside is, I have to change A LOT of code now, lol. No, seriously, thanks. I had a moment of epiphany.

😂 3
🎉 3
Noah Bogart13:05:48

so glad to help!


I expected (map (comp (map inc) vector) [1 2 3] [1 2 3]) will give me ((2 2) (3 3) (4 4)) But it give me (#object[c] #object[c] #object[c]) instead. Is there anyone know how to explain this or what keywords should I look for? Thanks !


(map inc) is a transducer. If you switch to (partial map inc) you'll get your intended behavior


Thanks! I'll go search for related concepts. 🍻


When you’re doing simple conversions from one coll type to another, do you prefer to use set/`vec`/`list*` or (into #{}/[]/())? Or when would you prefer one or the other?


converting to a concrete list/seq isn't usually necessary


I use set/vec if it's a simple coercion, if there are more transformations I consider using (into [] transducer collection)


Yeah for me this comes up most often when I need the specific properties of a particular collection, for example using a set to check membership or a vec to ensure end-appending with conj in a reduce or something


Can I use clojure sets as a key in a hash-map, using a value within that set key as a lookup to get the value associated with the key? For example, I have a set of pet types that are collectively called pets. If I call get on the hash-map with "Cat" as an argument, then I would like to get "Pet" as the result. Instead I get nil, so it seems I am missing something. (assume I have a long list of sets and associated group names I want to call them, which I'd like to use as a lookup)

(get {#{"Cat" "Dog" "Rabbit" "Hamster"} "Pet"} "Cat")


no you cannot. and in general that wouldn't be well-defined (get {#{:a :b} :foo #{:a} :bar} :a) would have two valid choices for lookup


but if your domain has disjoint sets you could roll your own deftype that had the sets and then "unrolled" the sets into a regular map with each key in the set attached to the value for the set. and when you dissoc you drop all of the keys from that set




I want to detect customer country by ip address and show a handful of nations one page and have a default for the others... any reasonable index of ip prefixes to countries one can use?


@sova Not really. IP address groups aren’t all that geographic in nature and they’re very fragmented. Best option is to use a service like


clj-http: status 404 {:status 404, :headers {"referrer-policy" "strict-origin-when-cross-origin", ... I'm not sure what's up, if I run this locally the client/post works fine, but from the live box it returns an error


Does doing a curl of the same request from the live box work?


I switched to client/get and it works


would this be my middleware preventing a clj-http.client/post ?