hi - i’m trying to write a run-tests function in my user.clj - but i don’t know how to get the regex to find the same tests as lein test

(require '[clojure.test :as t])
(t/run-all-tests #"_test*")

Dangling meta character '*' near index 0
*_test*
^

Have you tried #”.*_test.*”?

This could also be an in-ns question - i’m in the user namespace

user=> (t/run-all-tests #".*_test*")

Testing user

Ran 0 tests containing 0 assertions.
0 failures, 0 errors.
{:test 0, :pass 0, :fail 0, :error 0, :type :summary}

i’m not sure what that regex is supposed to match, actually - there are namespaces in my project like x.y.z_test and x.y.z-test, but switching in the dash in my regex still gives me the above output, just Testing user

Do you need the regex or can you just call the 0-arity run-all-tests?

huh - that prints out a bunch of namespaces, including things like clojure.core and clojure.walk (which i use in my project)

but still

Ran 0 tests containing 0 assertions.
0 failures, 0 errors.
{:test 0, :pass 0, :fail 0, :error 0, :type :summary}

but nothing ending in -test , might explain the regex not matching anything 🙂

Do you have your test ns loaded? run-all-tests just filters on every namespace loaded

is there an overarching namespace i can load? can i somehow load myproject.test.* or something?

You could do a file-seq over your test directory and load every file that matches

I recently wrote some code that might be similar:

(require '[clojure.tools.namespace.find :as find])
(require '[clojure.java.classpath :as classpath])

(defn require-clojure.*-namespaces []
  (let [nss (->> (find/find-namespaces (classpath/classpath))
                 (filter #(.startsWith (name %) "clojure.")))]
    (try
      (doseq [ns nss]
        (require ns))
      (catch Exception e
        (println e)))))

you'll need `[org.clojure/tools.namespace "1.1.0-SNAPSHOT"]` [org.clojure/tools.namespace "1.0.0"] as dependency

can i get that from clojars?

(sorry i’m being obtuse, gentlemen - deeply appreciate the help)

Why are you using a snapshot at all?

Just use 1.0.0

I'm pretty sure I just copy and pasted the wrong snippet when I was in a hurry 😬

yeahhhhh buddy - thanks @ddouglass @smith.adriane @alexmiller

So I have some basic multimethod code like this:

;; Dispatch on the type of each argument
(defn selection-dispatch [& args] (mapv type args))

(defmulti selection #'selection-dispatch)

(defmethod selection
  [PersistentVector PersistentVector js/Boolean]
  [[start-paragraph start-offset] [end-paragraph end-offset] backwards?]
  {:start {:paragraph start-paragraph
           :offset start-offset}
   :end {:paragraph end-paragraph
         :offset end-offset}
   :backwards backwards?})

;; Example:
(selection [:p1 1] [:p1 10] false)

(def selection-dispatch (partial mapv type))

Your original function took the args as varargs, your new one takes a collection

So, not the same

Ah, I understand. For some reason I had it in my head that what was being passed to the dispatch function was the list of arguments as a single vector (rather than one at a time)

Makes perfect sense now though, thanks for clearing that up

I've been confused and fearful for a while about certain idiom w.r.t. backquote. I've posed the https://clojureverse.org/t/backquote-tilde-in-and-outside-of-macro-definitions/6388?u=jim_newton.

question about destructuring: I see https://clojure.org/guides/destructuring how I can both destructure a sequence with & rest :as all . But it is not clear to me how both bind an destructure other sequences. For example

(let [[[a b] & more] some-data]
   ...)

(let [[[a b] & more] some-data
      ab-pair [a b]]
  ...)

(let [[ab-pair & more] some-data
       [a b] ab-pair]
  ...
)

I don't think you can do it in one expression. I'd be tempted to inline [a b] in the body of your let statement without giving it a name. Here's Clojure: The Essential Reference's take on what you can do with a vector in a destructure call:

[bind1 .. <& bindN> <:as sym>]

I've been going through 4clojure exercises and came across happy numbers http://www.4clojure.com/problem/86 I feel like I'm quite close to the solution, but instead of returning true at the easiest test case when I pass 7, my method starts an endless loop.

(defn happy? [number]
  (loop [ number number
         acc   []]
    ( let [digits (num->digits number)
           squared-sum  (reduce + (map (fn [number] (* number number)) digits))
           happy-number (= squared-sum 1)
           this-squared-sum-appeared-before  (and (not (empty? acc)) (contains? acc squared-sum))]
      (case [happy-number this-squared-sum-appeared-before]
        [true _]  true
        [_ true] false
        (do (println squared-sum acc)
           (recur squared-sum (conj acc squared-sum)))))))

I think you just can't use _ as a wildcard in the case expression like that

(case [true :something]
  [true _] :success
  [_ true] :fail
  :fallback)
;; => :fallback

(case [true '_]
  [true _] :success
  [_ true] :fail
  :fallback)
;; => :success

cond is probably what you want here

Can anyone point me to a clear example of how parameters are passed through an application using ring and compojure? As a simple example, I have layout function in my handlers that would take a map of params as an argument. I want to set the title of each page in the handlers that render the content for each page. Subsequently I'll want to pass queries into those handlers for each page. TIA

Hi guys, here am I: a new clojure enthousiastic but still beginner (;p

another records/protocol question lol: i have a bunch of records and a protocol in a namespace A, and then i import the records explicitly and require :refer :all the protocol and record constructor functions into namespace B. in namespace B, I use extend-type to implement the protocol for the records. When I run lein repl and lein test, this works great. and when I run lein uberjar on my development machine, it works. but when I run lein uberjar on the server/target machine, it fails with: Caused by: java.lang.IllegalArgumentException: No implementation of method: :cost-name of protocol: #'game.cost-interfaces/CostFns found for class: game.cost_interfaces.Click is there any way to debug why it might be failing only when running uberjar?

i tried changing the extend-type calls to be defrecord calls, removing the import and definition of the records in the other namespace, and that works as well

kind of complicated, so my apologies if you try to understand it

Anyone have a nice solution for pretty printing JSON? I'd like to include some json in my documentation (source code) but without escaping quotes for example.

https://github.com/dakrone/cheshire has pretty printing

Yeah I'm using it now, but maybe I'm confused. I'm doing this:

(json/generate-string {:message-type :discovery
                       :device-id    (uuid)
                       :device-type  :example
                       }
                      {:pretty true})

"{
   \"message-type\" : \"discovery\",
   \"device-id\" : \"bafcaef0-2b66-49f1-bcb1-c66935ceb2ba\",
   \"device-type\" : \"example\"
 }"

I'd like my example to look like this in my docs later:

{
   "message-type" : "discovery",
   "device-id" : "bafcaef0-2b66-49f1-bcb1-c66935ceb2ba",
   "device-type" : "example"
}

try writing (println (json/generate-string ...))

doh 😄

cuz it looks like generate-string is returning a string object, which is getting "printed" as a string, vs getting printed

Yeah - thanks!

I tried pprint and some other stuff but never println 😃

I think I need to try to understand how the printing in the REPL works..

Is there a "non-strict" equality func in clojure.core eg. (equal-enough-for-me "3" 3) ;;returns true ? Or should I just be happy with (= (str 3) "3")?

clojure makes you be explicit about what you want. too many degrees of freedom in "non-strict"

(although sequences and vectors containing the same elements are equal)

Fair enough. But I still think such non-strict-eq might be useful sometimes.

you can write your own non-strict, because no one agrees on how to be non-strict

my non-strict eq has 3 and 4 as equal, everything else non-equal

hi, curious about clojure and memory, I have a large data set (`sequence of strings`) which i'd like to have a copy of - same data just separated to starts-with-chars-buckets(to later search on), while still maintaining a copy of the original.... a clojure map would do: A-> #{"A1", "A2", ..... "An"} B-> .... etc but assuming this would copy the original data once more (or not? does the JVM optimizes it?), i'd like to have some "pointers" pointing to each "allocation", so in a C++ world i'd allocate data (strings) once and point to them, each Character would have an array of pointers (or something else...) 1. does the strings are copied once more? or the JVM "takes care of that" what would be a clojure way to not copy the data once more? 2. does clojure has any "pointers" way of thinking? heap? stack? should I care about that? what if my original data is huge? 3. what would be a good source to look on? I read abit on atoms/refs/agents but not sure ? thanks 🙂

All of your data is immutable; you don’t need a copy

(def data-set ["A1" "A2" "B1" "C1"]) (def bucketed {:\A #{"A1" "A2"} :\B #{"B1"}....)

so my bucketed-version would "copy" the "memory-allocations" ? (not sure how this works under the hood)

Are you making these independently or making one from the other?

I create buckets from existing data-set (huge)

right now it's all in-memory,

In that case, buckets will be using a heap reference to the same string in data-set

(let [;; 'dataset' is someting like ["A1" "A2" "B1" "B2"]
      dataset (load-dataset)
      ;; 'bucketed' is something like {\A ["A1" "A2"] ...}
      bucketed (group-by first dataset)]
  ...

If some of the strings are duplicates, you can look into explicit string interning, or some garbage collectors do this automatically in the heap

so the group-by version would not "copy" anything?

No

awesome,

makes sense, didn't thought on group-by 🙂 just reduced and throwed it all to sets heh

Java stores objects on the heap and passes the reference

and what happens in a case like (def a "hello") (def b "hello")

how should I think on a,b

You will only get new string instances if you call String constructor or use a literal “abc”

In that case you made two literal strings

So there are two

got it,

The gc may dedupe them internally or you can explicitly intern with (.intern “hello”)

I generally wouldn’t recommend the latter unless you really understand what’s happening and why it would matter for you

Actually I think literal strings are automatically interned

i'm more curious how can I "know" what's going on? so group-by gives the feeling that stuff are not copied,

so in java world I can think on the stack/heap,

but with clojure?

@aviv I think that the awnser is "you don't need to think about it" All operations in clojure are "immutable" In general they only create a "new index" without copy anything

clojure is using everything you know from java, so keep thinking that way :) there are no wrappers around anything - Clojure strings are Java strings, etc

the place where it diverges is that Clojure collections are immutable and "changing" a Clojure collection creates a new collection that typically shares most of the data with the prior collection

certainly the values, and often much of the internal structure as well

awesome, thanks for you both

Quick question, if one was starting a project to build an API, would you recommend using something like Pedestal or a plumbing together a slew of libraries like Ring+Compojure?

I used reitit to create a very usable API

it's my go-to these days, esp combined with malli to check the inputs conform to specs

Hello all, just a quick question is there a way to do this without flatten ?

(merge-with
   (fn [a b] (flatten (list a b)))
   {:a 1} {:a 2} {:a 3}) => {:a (1 2 3)}

not without somehting ugly using coll?, or an extra step to create {:a ()} first

do you care about list/vector and order?

@lukasmoench1113 also if the first input was {:a 1 :b 2} should we get {:a (1 2 3) :b (2)} ?

one approach: (reduce (fn [m [k v]] (update m k (fnil conj []) v)) [{:a 1} ...])

what about just using group-by instead?

is there other stuff in these maps?

yes

the types are different

(from the values)

Thank you guys ❤️ always a pleasure

Tbh to find my solution took me pretty long:joy: I hope one day I'm as good as your are

I've written this function a number of times, it's just small enough that it never ends up in a lib

it's a few very common idioms concatenated together

the double reduce makes me sad

ye i find it especially hard to write reducers, my version did only join the last keys in the map ...

to cheer up @hiredman

user=> (reduce (fn [m [k v]]
                 (update m k (fnil conj []) v))
               {} (concat {:a 1} {:a 2} {:a 3}))
{:a [1 2 3]}

What is the problem with double reduce?

it's less readable for one

"unnecessary multiplication of entities"

the second reduce was really a hidden concat, which is silly

you can view reduce as final operation to make something concrete (this is explicit in transducers), so when you see reduce used twice like that in my mind it sort of implies a seam

you can write a transducer that just kind of does sort of thing, I don't know of any off the shelf libraries

but something that takes a reducing operation, and runs it per value of each keyin a collection of maps instead of per map is something I've seen called faceting

but the double reduce may just be intrinsic

(defn facet [f]
  (fn
    ([]
     (f))
    ([accum]
     (f accum))
    ([accum value]
     (reduce
      (fn [accum [k v]]
        (assoc accum k (f (get accum k) v)))
      accum
      value))))

(transduce
 facet
 (fnil conj [])
 {}
 [{:a 1} {:a 2} {:a 3}])

and facet is neat because you can pass in other reducing functions

(transduce
 facet
 (fnil + 0)
 {}
 [{:a 1} {:a 2} {:a 3}])

facet sort of splits the two reduces at the seam, facet itself is very much the inner reduce and the outter reduce is replaced by whatever reducing context you use the transducer in

pretty cool thanks a lot

may be worth a blog post 😊

I'm happy to know a name for that

I think several reducing operations in Java Streams would be considered "faceted"

like the groupingBy variant

https://docs.oracle.com/en/java/javase/14/docs/api/java.base/java/util/stream/Collectors.html#groupingBy(java.util.function.Function)

https://github.com/aphyr/tesser is where I got that name

public static <T,​ K,​ A,​ D> Collector<T,​?,​Map<K,​D>> groupingBy​(Function<? super T,​? extends K> classifier,
Collector<? super T,​A,​D> downstream)

ugh, the generics make it so annoying to read

returns a collector that contains a "downstream" collector, where collector == reducing fn

I was wondering if I could pick your brain about a personal game project that I alluded to here yesterday. It’s the 4x4 grid of the keys :a : b :c :d by :w :x :y :z. So, I now have a vector of 16 “tiles”, each with 2 of these unique key pairs. So far, so good. I wanted to see how many possibilities exist of how we can shuffle the tiles, and came up with about 21 TRILLION. 2.09 x 10 ^ 23. That’s a hella-lotta possibilities. (16 Factorial) “Sure,” I said, “Let’s throw them into a defined sequence and do some research on it.”

(def tperm (combo/permutations tiles))
(nth tperm 0)
=> ([:a :w]
   [:a :x]
   [:a :y]
   [:a :z] ; ...(and a bunch more)…
   [:d :z]

(def tpermf (remove any-rc-match? tperm)) ; removes any 3-of-a-kind row/column match
=> #'game.core/tpermf
(first tpermf)
OutOfMemoryError GC overhead limit exceeded  clojure.core/take (core.clj:2752)