Clojurians Log v2

I'm looking for a resource that can help me learn how to parse arbitrary binary data. Given a description along the lines of "Offset 0000, 32 bit integer, magic number. Offset 0004, 32 bit integer, number of rows. etc...", It would be a huge help to see an example of a simple program that parses a custom binary data structure and... kind of like http://www.gigamonkeys.com/book/practical-parsing-binary-files.html but in Clojure. Actually, I think I might just go with that and try translating it to Clojure.

They are definitely implementation details, but i still want to test them independently of the public api.

Is there a nice way to do the following? I feel there is too much repetition going on …

(defn should-add-label [settings issue]
  (and
   (check-issue-status settings issue)
   (check-issue-assignee settings issue)
   (check-issue-milestone settings issue)
   (check-issue-labels settings issue)))

(every? #(% settings issue) [#'check-status #'check-assignee #'check-milestone])

Another possibility then is to use with-test to provide tests with the defn of the private function itself. http://clojure.github.io/clojure/clojure.test-api.html#clojure.test/with-test That way the tests "stay private" too, in a way, since they are right there with the "implementation detail".

interesting

there is so much in the core 😕

Sometimes it helps to think out loud

There may be an every-fn or every-pred already in core

ah yes but the predicates take only one argument

Not according to the source https://github.com/clojure/clojure/blob/clojure-1.10.1/src/clj/clojure/core.clj#L7396

Oh, wait it takes multiple args, but as ands to the predicate weird

Nope, confusing myself with all the anonymous functions, the returned predicates takes multiple args as expected

Ok I need to re-read that

Me too

I have POST /parse-reply {body :body} (compojure-api) The content of (str(slurp body)) is along the lines of:

"--xYzZY
Content-Disposition: form-data; name=\"attachments\"


--xYzZY
Content-Disposition: form-data; name=\"dkim\"

{<http://x-com.y.gappssmtp.com|x-com.y.gappssmtp.com> : pass}
--xYzZY
Content-Disposition: form-data; name=\"subject\"

Re: TEST RESPONSE
--xYzZY
Content-Disposition: form-data; name=\"to\"

<mailto:x@y.com|x@y.com>
--xYzZY
Content-Disposition: form-data; name=\"spam_score\"

0.011
"

There is a ring middleware to decode form data

Yeah. Referring the last comment response of: https://stackoverflow.com/questions/33824124/multipart-params-are-not-extracted-by-ring-middleware#comment56033214_33829549 Went through: <https://github.com/ring-clojure/ring-defaults> but not sure how to get it working. Especially the handler:

(require '[ring.middleware.defaults :refer :all])

(def site
  (wrap-defaults handler site-defaults))

Hi. I’m trying to create a clojurescript library that makes use of some javascript files. I”m using leiningen and :foreign-libs under :cljsbuild in order to bundle the js into the library. However, that doesn’t seem to make the js code available to the application code consuming the library. Could anyone point out to me the proper way to incorporate javascript files into clojurescript libraries?

Is there someway in clojurescript to define constant values during compile-time, like the https://webpack.js.org/plugins/environment-plugin/ plugin?

Euh... What does that plugin do?

You can define constants with ^:const which will inline the value if its EDN

Otherwise, you can use macros to perform whatever compile time things you want

I was trying to do it with macro just now but the compiler wasn’t happy about it

# .clj
(ns my.core)
(defmacro getenv [key]
  (System/getenv key))

# .cljs
(ns my.core 
  [:require-marcors my.core])

(def ENV (getenv))
(defn hi [] env)

WARNING: Can't take value of macro my.core/getenv at line 4
WARNING: Can't take value of macro my.core/getenv at line 5

I wouldn't say the use of a macro for this is hacky. Like if you want this functionality, macros are a great way to get it. Much better than the JS pre-processing that webpack plugin must have to do. Now, that error normally means you are passing a macro to something that expects a function. I assume that's not the real code.you try, cause you have typos and all in it. Macros in ClojureScript can be a bit tricky to setup right, and then I'd just double check you don't have a dumb mistake, like missing a parens or forgetting to pass an arg, etc.

Also seems you might be hitting this bug: https://github.com/bhauman/figwheel-main/issues/165

So it could be a false positive warning. Apparently is fixed in a newer version of figwheel

thanks for the link, I wasn’t using figwheel, but I’ll double check the macro usage

is there a way to load into a default namespace with deps.edn?

in lein's project.clj, I can say :repl-options {:init-ns default.core} and when the repl starts, it loads the file and enters the namespace so I don't have to do anything extra

in my project's root directory, when i enter clj, it loads into the repl with my dependencies in the classpath, but it doesn't load the current project's files, and I have to call (load "default/core") to load them before I can call (in-ns 'default.core)

you can use the -e features of clojure.main to evaluate expressions before you start the repl:

% clj -M -e "(require 'clojure.set)(in-ns 'clojure.set)" -r
#object[clojure.lang.Namespace 0x5bf22f18 "clojure.set"]
clojure.set=>

that can be bundled into an alias in deps.edn as well (requires a , instead of spaces to avoid some word splitting through the shell):

{:aliases
 {:repl {:main-opts ["-e" "(require,'clojure.set)(in-ns,'clojure.set)" "-r"]}}}

cool, thank you. i don't see -e noted anywhere in https://clojure.org/guides/deps_and_cli or https://clojure.org/reference/deps_and_cli. oh, it's in https://clojure.org/reference/repl_and_main okay

didn't look at that page

yeah, -i can be useful to load a .clj file containing whatever in advance too

There’s a typo in your require macros expression. Is that present in the source or just in slack?

Any feedback on using javascript files in cljs library code? https://clojurians.slack.com/archives/C053AK3F9/p1605769012476600

What is the idiomatic Clojure equivalent of Python's if "foo" in ("foo", "bar", "baz"): ?

(or (contains? {"foo" "bar"} "foo") ({"foo" "bar"} "foo")) you can use the function contains? or use the fact that sets are callable themselves

eval both of those expressions at the repl to see the different values they return

oh sets are callable 🙂

Beware of contains? because it trips most new people up at some point. It's behaviour is sometimes different to what you expect!

https://lambdaisland.com/blog/2017-10-02-clojure-gotchas-associative-contains

contains? checks for the presence of a key, for sets it does what you would expect, since keys=values, and for vectors it checks whether the index is present (contains? #{:a :b} :a)            ;;=> true (contains? #{:a :b} :c)            ;;=> false (contains? {:a :b} :a)             ;;=> true (contains? {:a :b} :b)             ;;=> false (contains? [1 2] 1)              ;;=> true (contains? [1 2] 2)              ;;=> false

Right so you need a # in your example @dpsutton 🙂

yep! (contains? {"foo" "bar"} "foo") => true (contains? {"foo" "bar"} "bar") => false

but if you used a set instead of a map:

(contains? #{"foo" "bar"} "bar")
=> true

oh right. my bad 🙂

(some #{:some :things :to :check :are :contained} [:some :vec :of :things]) I quite like this pattern, uses the fact that sets can be called and lets you check for more than one thing (if needed) existing in the coll, no idea on the performance but it's never been my bottleneck

that's a great tip

Yeah that is nice - because right now I do (some #(contains? (set labels) (:name %)) (:labels issue))

Oh I can't directly translate that but i can shorten it with that trick

(some (set ignored-labels) (map :name (:labels issue)))

I'd usually just define ignored-labels as a set

also consider: (some (comp (set ignored-labels) :name) (:labels issue)) - some already traverses, you don't need to map too

✨

That is really cool

you can even do something like (def ignored-issue (comp (set ignored-labels) :name)) then do (some ignored-issue (:labels issue))

or maybe "ignored-label" is a better name there

I find a tendency to reduce line / definition count as if that were meaningful simplicity, where giving the right things the right names is the clearest approach

"more smaller functions" ?

Also there are caveats if the set can contain false or nil when invoking the set

not just that - because the one liner has the same number of functions - the question is what is exposed as a name

right

I have some data with timestamps like "2020-11-19T17:32:32.277Z" and I think it would be a little nicer to transform that to our time zone, and/or "time ago" format. Near as I can tell the move is to use java.time directly, instead of the various wrappers I can find (which seem to be for Java 8 ). There are a rather overwhelming number of classes and I cannot figure out which one, if any, has a constructor that will take a string like I've got. Any tips?

ZonedDateTime/parse

Instant/parse would also work, but if you are messing with timezones the first thing you'd probably do from there is convert to a ZonedDateTime

I think you want this yeah https://docs.oracle.com/javase/8/docs/api/java/time/LocalDateTime.html#parse-java.lang.CharSequence-

there's multiple classes usable, but they each have parse methods

you may also be seeing the instant tagged literal in a print out

I don't think so, hiredman, the data I've got is not coming from a Clojure program

thanks folks! i thought I'd be using a constructor (Like. so) instead of a method

@mathpunk If you would prefer a wrapper, the clj-time README links to several (as part of trying to stop people using clj-time these days!).

the difference is that the parse methods make you specify the format you are parsing, where a constructor wouldn't (not that it couldn't, that would just be weird...)

Hi, html5 audio element needs my server to send "Accept-Ranges" "bytes" and while the default ring file-response sends "Content-Length" $len the audio element still says Live Broadcast as opposed to showing the seek bar as needed

I guess the header is supposed to read "Content-Range" ? hrm

Apparently it needs 3 headers set:

Accept-Ranges:bytes
Content-Length:7437847
Content-Range:bytes 0-7437846/7437847

this might be relevant - each response still uses Content-Lenth, which just describes that payload not the resource https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/206

So basically it looks like I gotta add the "Content-Range" header... but i'm not sure how to get the byte length of a file

oh. looks like (.length ) does the trick with http://java.io

(defn format-when [zdt-str]
  (let [zdt (ZonedDateTime/parse zdt-str)
        dur (Duration/between zdt (ZonedDateTime/now))
        secs (.getSeconds dur)]
    (if (< secs (* 5 60 60))
      (let [[v a b] (->>
                      [[(quot secs (* 60 60 24)) "day" "days"]
                       [(quot (rem secs (* 60 60 24)) (* 60 60)) "hour" "hours"]
                       [(quot (rem secs (* 60 60)) 60) "minute" "minutes"]
                       [(rem secs 60) "second" "seconds"]]
                      (filter (comp (complement zero?) first))
                      first)]
        (if v (format "%s %s ago" v (if (= 1 v) a b))
              "now"))
      (str (.toLocalDateTime (.withZoneSameInstant zdt (ZoneId/systemDefault)))))))
=> #'user/format-when
(format-when "2020-11-18T17:32:32.277Z[Australia/Sydney]")
=> "2020-11-18T06:32:32.277"
(format-when "2020-11-19T17:32:32.277Z")
=> "2 hours ago"
(format-when (str (Instant/now)))
=> "now"

opened a new issue @ ring ^_^

Maybe I am overthinking this, but what is preferred in Clojure land? pr / pr-number or pull-request / pull-request-number ?

"pr" is a pretty common term in github speak of course

Oh hm their API calls it pull_number actually .. interesting

as far as I know "pull request" is a github UI concept, it's been adopted elsewhere but isn't part of git itself

I think this is off topic though

@st3fan for example the clojure.core project uses github as a mirror, but it's not how contributions are accepted, you'd use JIRA instead

Sorry my question is about naming not about contributing to Clojure 🙂

right, OK - regarding naming, pull-request is the name of a github UI feature

i'm working on a github client - so that is ok, i don't have to hide that detail

https://lore.kernel.org/git/1113577744.27227.53.camel@hades.cambridge.redhat.com/ the first instance of "pull request" on the git mailing list predates github by 3 years

I'm writing a small application which models populations changing over time - a sort of zero player game, similar to game of life. I want to draw the output of the steps on a canvas (a grid with squares on it that fill and empty) with the output being redrawn with each step. Is there a go-to Clojure library for this? I was thinking of quil, but only because it's the only one I've heard of. Are there alternatives I should be thinking about?

have you seen rich's ants simulation?

I've heard about it in the context of core.async, i didn't realize it had a drawing component

it predates core.async by a lot

Oh, not async, state management

I am not sure if the original is around any more https://gist.github.com/michiakig/1093917 is maybe a copy, it renders using java's built in 2d canvas stuff

the rendering looks something like https://img.linuxfr.org/img/687474703a2f2f6a756c69616e67616d626c652e636f6d2f626c6f672f77702d636f6e74656e742f75706c6f6164732f323031312f31322f616e74732e706e67/ants.png when it is run

That looks good enough to do what I want, thanks!

Neato

There's an awesome story in Surely You're Joking Mr. Feynman about how Richard Feynman had a line of ants in his apartment and bathroom. Rather than try and get rid of them, he started experimenting. For example, he put some sugar on a table and then used a coaster to "elevate/teleport" ants to the table. Sure enough, ants were able to figure out there was an elevator and they would start waiting on the coaster to get a ride. But they couldn't really figure out that the elevator went 2 ways. Very interesting. Also he used chalk to draw a line for each ant's path to the sugar in his bathroom. It was like a newton's linear approximation. First it was curvy and clunky, and over time each ant successively did a straighter-and-straighter line towards the sugar.

Love that book!

it's not a mirror

the github repo is the repo

this seems to be a pervasive thing people believe but I'm not really sure why as it has always been this way (since moving to git)

I'm a really happy camper right now. I rewrote the backend for http://devbots.xyz in Clojure (from Go) and it is really nice compact code and ... 10x less LoC 7000 vs 700

ooh, i did work out how to use ZoneId/systemDefault but i didn't know about Duration/between, thank you

Is it possible to programatically "load" a namespace? for example my bots nicely organized in their own namespace and right now I have code like this:

(def apps [needs-triage/bot needs-review/bot lock-issue/bot lock-pull-request/bot])
(def apps-by-id (into {} (map #(vector (:id %) %) apps)))

They do contain multimethods, so I think I need to fully "load" them before the multimethod dispatch works.

(not sure what the right terminology is)

load is the right word

you can load dynamically via require (or load, but that's considered lower level), but discovery is not generally a thing you can ask a jvm to do

you can inspect parts of your classpath as files/jar paths to "discover" things like that (and there are java libs that have support for that kind of thing)

probably best way to handle is with some kind of runtime config that lists the ns'es to load

these namespaces are embedded in my app, so i can also require them in core and then iterate over available namespaces and filter on devbots.bots. - maybe that is a simple start