Heyas. Is there a more succinct way of doing

(apply merge (map-indexed #(assoc {} %1 %2) ) ["a" "b" "c"])

(zipmap (range) [...])

ohhhhhhhhhhh nice

the beauty of laziness

that's perdy 🙂

😉

@bradford I should point out that for a lot of things, a vector is equivalent to such a map

Hey @ channel Where are the best places to post Clojure gigs?

Can I post in here?

I'll drop it in announcements

strike that, I dropped it in #jobs check it out!

is there an example somewhere for annotating and implementing an abstract class? does :gen-class provide that?

@gfredericks Oh, I totally agree, but it's for a cranky bad API

Am I using :prep-tasks correctly to run sass4clj? :prep-tasks [["cljsbuild" "once"] "javac" "compile" ["sass4clj" "once"]]. When I add sass4clj ti keeps on rebuilding ClojureScript over and over.

@richiardiandrea it might, but it'll get messy. You're probably better off writing a small clojure friendly java wrapper for it

Is there a macro that does this? (m a b c) ;=> {:a a :b b :c c}

@borkdude once I needed this too

(defmacro ->map [& symbols]
  `(hash-map ~@(interleave (map keyword symbols) symbols)))

I started playing with your previous example @residentsummer . Now I wonder why (zipmap (:a :b) '(1 2)) is an empty map

but thanks 🙂

you lost a quote on the first list

(zipmap '(:a :b) '(1 2))

lol ok yes

another possibility is then:

(defmacro ->map [& symbols]
  (let [keywords# (map keyword symbols)]
    `(zipmap (list ~@keywords#) (list ~@symbols))))

yep. don’t need hash for keywords# though

#(into {} (map (juxt keyword identity)) %) works too

Well as a macro... Not difficult to convert

Oh I see by using macroexpand what it’s doing

borkdude: it's just a list of symbols at compile time, so no evaluation happens

right of course

@residentsummer It’s a nice piece of code that fits in a tweet 🙂 https://twitter.com/borkdude/status/832269448539209733

(if I knew your twitter handle I would give you credit)

spread the knowledge! 🙂

I’m trying to run a compiled C script in my resources folder, does anyone know why I can’t slurp it and run it using (sh “bash” :in (slurp (io/resource “mycprogram”)))

@ccann So bash expects a bash script but a compile C program will be machine code (ELF). I'm pretty sure you can't just run machine code that you have in java memory like this, unless you go very low level. Easiest would be to spit it into a file (give it the executable bit) and then run it (sh "/tmp/your-program")

https://github.com/Raynes/conch has some interesting features

What’s the easiest way to go from qualified keywords to unqualified in a map

{:foo/a 1} to {:a 1}

In Clojure 1.8

@borkdude isn't that just more syntax than {:a 1 😛 2}? What is the benefit of using ->map?

(sp/transform [sp/ALL sp/FIRST] (comp keyword name) {:foo/bar 1}) if you use specter

(into {} (map (fn [[k v]] [(keyword (name k)) v])) {:foo/bar 1})

@thegeez I can now write:

(->map query-state
  database
  redis
  body)

{:query-state query-state
 :database database
 :redis redis
 :body body}

ah cool

@borkdude with next release of specter:

user=> (setval [ALL FIRST NAMESPACE] nil {:foo/a 1 :bar/b 2})
{:a 1, :b 2}

@bronsa the problems with that approach are that it's slow and it changes sorted maps to unsorted maps

I've been wanting k-v transducers for a while. They're easy to make in userspace

Nested keys destructuring isn’t possible?

(let [{:keys [a {:keys [c] :as b}]} {:a {:c 2}}]
  [a b c]) ;;=> [{:c 2} nil nil]

nope

not with the keys short-cut

and it wouldn't make it through code review 😉

it'd be goofy because it'd only be allowed when you have :as and when the value of :as is a symbol

(let [{{bar :bar :as foo} :foo} ...])

yeah.... never did like the nested destructuring notation :c

(let [{{:keys [b]} :a} {:a {:b :ok}}] b) (let [{{b :b} :a} {:a {:b :ok}}] b)

@ghadi That works, thanks

i wouldn't recommend it @borkdude

why not? I use that style all the time

it's hard to read nested destructuring

doesn't scan well

I like core.match for this.

yeah core.match solves this problem pretty well

I like nested destructuring, it's one my favorite parts of Clojure's design

does core.match check for exhaustiveness? or at least is there a way to make it check for that?

it always exhausts

core.match does not and cannot check for exhaustiveness

but its because it adds a wildcard

^ yeah wildcards are the solution there

i guess you can simulate it with generative testing

is there a way to do something like this in clojure?

public class Foo {
  private String bar;
  public Foo(String bar) {
    this.bar = bar;
  }
}

i need it to be something I can construct dynamically

You can make anonymous vars, and there are now transient vals too

and the constructor variables need to be private and only accessible indirectly w/ methods I'm exposing

arrdem is there a way to do that with deftype?

not that I remember offhand.

actually it doesn't matter if it's deftype, just something that has that sort of functionality

I looked at gen-class, but I don't think it can do private variables

what problem are you actually trying to solve?

is it possible you've figured out a solution but there may be others out there?

So if this is really what you want then writing a custom Java class is probably the easy road. deftype doesn’t give you machinery for private mutable fields.

https://www.conj.io/store/v1/org.clojure/clojure/1.8.0/clj/clojure.core/deftype

@dpsutton Under pretty much any other circumstance I wouldn't care about it being private

I should reformat that text...

but it needs to be private for this particular use case

well that's easily done in closures

@risto: how are you trying to consume this … structure whatever it may turn out to be?

Is it a value? Are you expecting to consume functions of this value? Are you trying to transform / alter it?

it's going to basically be a macro that generates this data type

ideally it would be deftype but it's okay if I have to encapsulate it in an inner class of some kind. I'm not sure a java class would work because it needs to be constructed dynamically

right no but what problem are you trying to solve that this appears to be the solution to you.

You really don’t want to be generating Java classes truly dynamically.

That’s gonna be total garbage for performance and very strange code in general.

have a requirement that a field be private is fishy to me

it needs to be private because I need to restrict how the developer interacts with arguments passed into the data type

the jvms private is easily overridable using reflection, it is really just a comment showing intent that the compiler checks

they can't just fetch the inner member because it would break the encapsulation that I need

If you really want a hidden value that can be accomplished… but this seems like the wrong way to do this.

if they want to fetch it, you cannot stop them

What’s the library? wallhack?

sure wallhack

what's wallhack?

https://github.com/arohner/clj-wallhack

yeah

well the difference between just a property access vs using something like wallhack is that, you know you're already that you're trying to access something you aren't supposed to

but if it's just something you can easily access then you can easily accidentally do that if you aren't aware

you could do like sicp, encapsulate a value and return a dispatch function that dispatches on keywords

closed over data is in fields

@dpsutton how does that look like?

if the user could access the data directly, then the abstraction I'm trying to write would be leaky in pretty horrible ways

@risto what access model are you trying to accomplish? An opaque session object?

user=> (def f (let [x 1] (fn [] (+ x 1))))
#'user/f
user=> (f)
2
user=> (->> (class f) (.getDeclaredFields) (map (fn [field] (.setAccessible field true) [(.getName field) (.get field f)])) (into {}))
{"const__0" #'clojure.core/+, "const__1" 1, "x" 1}
user=> 

I think the const__ fields are already public, and closed overs are marked private

i don't think we're going for absolute secrecy but just a clear "don't touch that or else things can break" idea here

but i still think you don't need to worry about it

(defrecord Foo [dont-touch-this-or-things-can-break])

^ clear

and way less awkward than the "dispatch" function style

yeah that's not going to work

oh well

@zane > I use core.match for this Can you give an example that looks like mine? Not sure how you use it

(let [a {:a {:b 3}}] (match a {:a {:b x}} x :else nil))

9X% confident that’s the correct syntax, the match form has some magic for allowing either a single value or a vector of values to be matched against.

ah nice, I’m going to give it a try

If you wanna see some real core.match use, lib-grimoire is mostly core.match in a very Haskell style.

I have an entire DB query engine implemented in core.match because bad reasons

https://github.com/clojure-grimoire/lib-grimoire/blob/develop/src/grimoire/api.clj#L441

</plug>

Why does this work:

(match {:a {:b 1}} {:a {:b x}} x)

(match {:a {:b 1}} {:a {x 1}} x)

if x were closed over from an outer scope I think that would work.

core.match does not do search for values which would match in a logic programming style.

Hi! Is there a more succinct way of counting occurrences of a vector of strings than

(apply merge (map #(let [mat (re-seq (Pattern/compile %1) "a a b b c c")]
               {(first mat) (count mat)}
               ) ["a" "b" "c"]))

whats the difference between core.match/match and core.match/matchm? I think there are some other ones in the code also

seems reduce-y

bradford: isn’t there a count-by

whaaa

> Same as match but supports IMatchLookup when matching maps.

hrm there's a frequencies

but the apply-merge-map still feels crufty, it's something I do a lot of

@bradford

(defn count-by [f coll]
  (reduce (fn [acc x]
            (update acc (f x) (fnil inc 0)))
          {} coll))

(def count-by (comp frequencies map))

oooo nice

quick question: is there a way to use alias (or similar) to remove an alias? in other words, make it as if the library was required without the :as keyword? using unalias seems to remove access to the library entirely, unless i'm confused and it's a matter of reloading it afterwards

unalias just removes the alias, so you must be confused

you can refer to a name in any loaded namespace using a fully qualified name

you are maybe looking for refer, not aliases

in the absence of an alias, you have to use the fully qualified names, you don't get the short names you get from refers

to explain the reason i'm interested in this, i want to toggle between two versions of functions in different namespaces and previously would be like (doto 'namespace2 require in-ns). someone suggest i instead require it from the start and then toggle the alias on and off, but i'm having trouble figuring out how to toggle if off...in other words, make it as if i had required it without an alias to begin with

you will need to reload code

So that’s not gonna do what you want.

vars are resolved at compile time, not runtime

The aliases table is used only when resolving Vars at compile time to find aliased namespaces. Once a function has been compiled, it is linked statically-ish against fully named Vars in the namespace where they are defined.

does that mean it doesn't make sense to even do it this way then?

perhaps i'm saving overhead when i toggle back to the first namespace

Yeah. If this is what you want, you’re gonna want some sort of API object or map of names to functions to pass around.

i'm not sure what you mean. wouldn't i want to simply want to require it only when i toggle it on and then remove the entire ns when i toggle it off? which would be a slight improvement over do-to since the initial namespace will remain loaded the entire time and just have its functions overriden

A namespace is a mechanism for resolving names to functions. So if you take a step back, if you have a function defined in terms of a thing you refer with an alias from a namespace, that’s a full application of a function which would accept the thing you’re referring as an argument and return a function that does the thing you want.

i wouldn't be aliasing them

Right

but it doesn't seem to override them unless i actually switch namespaces

I’m sorry you want functions that behave differently depending on what namespace you’re in?

i want to stay in the same namespace and be able to toggle whether they're overridden by those in an another one

i had the toggle functions switch namespaces to achieve this same effect effect before and someone suggested i try this instead

So what I’d do is I’d change my functions so that they take as an argument (probably the first argument) a map of keywords to functions, destructure it and call the functions which were destructured out. You can then define two API maps, one for the functions in the current namespace and one for the implementations elsewhere. This way you can switch back and forth between which implementations you’re using without any mucking with namespaces or compilation.

i think you're confused about what i'm doing here

the functions are (some-thing-off) and (some-thing-on). i don't know why i'd have a function where i pass it the names of ~100 other functions to achieve this

i already implemented it one way that's fine, but now i'm asking specific questions about how to implement it another way

specifically, how to have a function that requires a library so that it overrides functions

Because of Clojure’s namespace and compilation model as explained above, you can’t make such a function which doesn’t also (require :reload) the namespace you’re currently in.

i see. so then the best way is exactly as described before then right?

The “best” way is not to do this at all as I’ve been trying to say, but if this is specifically what you want to do and what you desire to improve, no there isn’t a better way.

yeah...i do actually need to meet specifications

and it seems like the worst possible solution to have a function that's 100s of words long

i guess there's a question of whether i's better to do (doto 'namespace2 require in-ns) or (ns namespace2 (:require [namespace2]))

Hello! I need some help… I am getting this error

main   │ Caused by: java.lang.NoClassDefFoundError: snow_client/core/Tabel
main   │ 	at service_now_bot.service$evs_for_tag.invokeStatic(service.clj:100)
main   │ 	at service_now_bot.service$evs_for_tag.invoke(service.clj:97)
main   │ 	at service_now_bot.service$fetch_and_enrich.invokeStatic(service.clj:138)
main   │ 	at service_now_bot.service$fetch_and_enrich.invoke(service.clj:133)
main   │ 	at service_now_bot.service$snow_page.invokeStatic(service.clj:150)
main   │ 	at service_now_bot.service$snow_page.invoke(service.clj:146)
main   │ 	at io.pedestal.interceptor$fn__1366$fn__1367.invoke(interceptor.clj:41)
main   │ 	at io.pedestal.interceptor.chain$try_f.invokeStatic(chain.clj:52)
main   │ 	... 39 common frames omitted
main   │ Caused by: java.lang.ClassNotFoundException: snow_client.core.Tabel
main   │ 	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
main   │ 	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
main   │ 	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
main   │ 	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
main   │ 	... 47 common frames omitted

If anyone has any ideas i would really love some 🙂

@ericfode Hi! After running lein uberjar which one of the jar files generated do you run? I don't know why but I've always been lucky running the jar file that doesn't have my version number in the name, if you now what I mean, as an example: mygreatapp-0.1.1-SNAPSHOT.jar wouldn't run but mygreatapp.jar would.

The one taht ends with SNAPSHOT-standalone

Give the other one a try

🙂

I get

main   │ Exception in thread "main" java.lang.NoClassDefFoundError: clojure/lang/Var
main   │ 	at service_now_bot.server.<clinit>(Unknown Source)
main   │ Caused by: java.lang.ClassNotFoundException: clojure.lang.Var
main   │ 	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
main   │ 	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
main   │ 	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
main   │ 	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
main   │ 	... 1 more
➜  service-now-bot git:(master) ✗

When i do that

It’s possible i constructed my library wrong when i released it

So that’s easy… Clojure itself isn’t on your classpath somehow.

https://github.com/ericfode/service-now-client

@arrdem that makes sense. I am trying to get it into an uberjar so i can put it in a docker file

the -standalone jar is the one you want....

https://github.com/technomancy/leiningen/blob/master/doc/TUTORIAL.md#uberjar

The first stacktrace you posted is an AOT problem, you’re referencing a class (`snow-client.core` contains a deftype or something it looks like) before the Clojure code which defines it has been executed.

Orly? how do i fix

https://github.com/hiredman/clojure-site/blob/df56aef005d5d867213a51c2d3bbec5a86b0acad/content/guides/running_a_clojure_program.adoc first step is to turn off aot

also do a lein clean

(that doc explains starting a clojure programming with aot compilation, which is 95% of the reason people give for needing to aot compile)

ok i got it to work with lein run, but not lein uberjar, that now gives me this Warning: The Main-Class specified does not exist within the jar. It may not be executable as expected. A gen-class directive may be missing in the namespace which contains the main method.

right, you didn't remove :main

ohh

now, turning off aot compilation won't necessarily immediately fix things, but it will unmask underlying issues