hello! can u help me to figure out how do design a simple thing? let's say that I've defined a simple map with configuration values as myns.core/conf. let's say also that I have a second namespace myns.other-ns where a function needs to use some values in myns.core/conf can I call, in myns.other-ns/my-function direct on that map inside the first namespace? or it is always better pass in the conf as a parameter to myns.other-n/my-funciton?

in another words, how is the 'best' way to share this conf map between namespaces?

I would always pass the configuration as a parameter.

Globals -- your def of myns.core/conf -- make testing and maintenance hard. You should try to avoid them altogether if you can.

(that's assuming configuration could potentially change from run to run)

yes... it changes... the values are read from a .edn file

Then it should not be a global def at all.

The value bound to a def is evaluated when the namespace is loaded and having side-effects occur during namespace loading is a Bad Thing(tm).

I should, then, read the conf file in core namespace and always pass the values as parameter to the functions?

Read the conf file at program startup, and always pass it as a parameter.

(it will make your life much easier in the long run)

but how to workaround that? I mean.. I need to read the conf file and 'keep' that value in memory to use on the subsequence calls to functions..

I should define an atom and swap it on loading the conf file?

or just use a 'load-conf function` just in time to call the "entry point function"?

The latter.

The former is just another global variable. And a mutable one at that.

ok

Have you looked at Component or Integrant?

another thing... I have several values inside this conf file...

and several of that are used in diferent functions

no... i'm not using that libraries..

They are designed for "global state" that has a lifecycle -- you could have a Configuration component that reads the EDN file when you start it up. And then pass that Configuration component into your entry point function.

Once the config is loaded, it should be treated as just another immutable map of data as you're passing it -- or parts of it -- around your app.

Can you depend on the ordering of a map? For example, if I were to do (vec {:first :foo :second :bar}) can I depend on it returning: [[:first :foo] [:second :bar]] ?

Versus returning [[:second :bar] [:first :foo]]

In certain special circumstances, yes, but those circumstances are likely to be so easily broken that I wouldn't recommend it.

Circumstance 1: You create an array-map using the function of that name. Down-side - as soon as you do other normal map operations on it like assoc, merge, etc., and it gets over a small size near 8 key/value pairs, it will return you a hash-map, where the order is gone.

Circumstance 2: You use a sorted-map, which sorts key/value pairs on the value of the key, a priority-map, which sorts them on the value of their values, or an ordering-map, which sorts them on the order that the key was last inserted.

sorted-maps come built into Clojure. The other 2 require libraries that are linked from the Clojure cheatsheet: https://clojure.org/api/cheatsheet

Circumstance 2 is a bit more robust than #1, but even that can be broken in unexpected ways, e.g. if you do a merge on two maps, you get back a map that has the sorting properties of the first argument, not the second one.

I see. I'll stick to vectors of pairs when I need order, then

Thanks!

Is there a neater way to create a map if the keys are same as variable names?

hi, what do you use or would recommend to use for stripe? Some clojure library or interop with stripe-java?

I've added [cljsjs/stripe "3.0-0"] to my project.clj, then in some.cljs file i requiere [cljsjs.stripe], try to compile the file and get " No such namespace: cljsjs.stripe, could not locate cljsjs/stripe.cljs"

I am working on a luminus app using mount. I want to define a constant list, but that list is stored in the db so needs to be loaded after mounting the db component, so I can’t just def it. I could define an atom then load it in an init function, but it seems wrong to use an atom for a data structure that should never change. Any suggestions for a better way?

You could use a promise instead of atom, it's basically an atom that can never change once it has been written.

I’ve found myself doing something like this quite a few times. Is there a more idiomatic way of writing this snippet that doesn’t involve a conversion between map and a list

Hi, please advice any data structure browsers for Emacs or REPL. something like in Intellij we have debuger's object browser.

@masta I use this https://github.com/timmolderez/inspector-jay

Good morning clojurians. lazy-seq question. I have always had difficulty wrapping my head around lazy sequences. I understand the simple examples fine but have difficulty trying to ramp up from there to more complicated data. Take the following poor example of a map of maps: {1 {101 :a 102 :b 103 :c} 2 {201 :aa 202 :bb}}. I want a seq function that will produce pairs of the form [outer-map-key inner-map-value] for each distinct bit of data. So on the example data set the seq would produce [1 :a] [1 :b] [1 :c] [2 :aa] [2:bb]. If I were simply mapping a function it would be:

(doseq [[k m] outer-map]
  (doseq [[_ v] m]
    (call-fun k v)

@dave.tenny Map works, but for this case for is your friend

Ah yes, forgot about for. I'm curious though how I would produce this if I were implementing a "producer fn" using lazy-seq.

for returns a lazy sequence (I am pretty sure)

Yes, I think you're spot on with for, and perhaps looking at the macro expansion will yield some clues for me about writing my own producer functions on data structures with lazy-seq, which is really what I'm trying to master with my question.

Or ... not. Ugh, that's some expansion 🙂

(j/k, useful bits there)

I think the hard part is figuring out the function to generate the next item in your list, which is kind of like figuring out recursive solutions.

So basically code it as if I were producing a sequence recursively and insert lazy-seq before any recursive calls. Maybe that's how I should think of it.

I think that’s the basic idea — I’m trying to write a lazy seq for your nested map problem, but it’s been a while since I’ve done lazy seqs!

Ok, I have a solution, I’ll put it in a gist so as not to be a spoiler if you want to keep working at it.

https://gist.github.com/manutter51/3e000c8d19ea4ae17d64b17302a40975

I bet this would make a good 4clojure problem 😉

Probably should have pinged @jdt on that gist…

got it, will take a look

I just rant into java.lang.AbstractMethodError: Method linked/map/LinkedMap.isEmpty()Z is abstract, which I've never seen before. My instinct says dependency version conflict maybe? More context to follow...

Manifested when trying to access the /swagger.json endpoint in a compojure-api app, so I think it's coming from the process that generates swagger.json. Maybe a Jackson lib version conflict?

Anyone who used https://github.com/jarohen/chime? I've tried to start "Pollers" with it using core-asyncs go-loop but when I have too many go-loops running concurrently one is blocking all others.

Has anyone seen this warning? Using clojure 1.10-beta3

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by clojure.lang.Reflector (file:/Users/rick/.m2/repository/org/clojure/clojure/1.10.0-beta3/clojure-1.10.0-beta3.jar) to method com.sun.org.apache.xerces.internal.jaxp.datatype.XMLGregorianCalendarImpl.toGregorianCalendar()
WARNING: Please consider reporting this to the maintainers of clojure.lang.Reflector
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

looks like something that would happen with a recent jvm - downgrading to a 1.8 jvm should eliminate that

(not that that's necessarily the right fix...)

that was my thought

don’t see any reason to downgrade, just ignore the warning if there is not a newer version of the library out

Yeah, I agree & understand the message. I’m just following through on what the message suggests i.e. indirectly notifying the maintainers of clojure.lang.Reflector 🙂

though I thought I’d ask here first, rather than bother Alex etc directly with it at this stage; as they’re busy enough 🙂

ooooohh, I thought the issue was with the Apache library, didn’t read carefully enough!

my bad 🙂

well it might be… and it might be with my code too… or it could be the specific environment I’m running this in.

I hadn’t noticed this before, but basically I’m running an interactive rebase exec with lein test over a tonne of commits; but launched it via magit/emacs rather than from my shell. It’s still going, so it could be picking up a java 9 VM or something… not sure yet. I was expecting it to run with java 1.8… but it looks like it might be finding something different.

seems like it, the IllegalReflectiveAccess thing is for sure a JVM > 1.8 problem

yeah that was my thought… probably the new module system

I was assuming it’d pick up 1.8; but this is the first time I’ve run lein test through magit and interactive rebase, so it’s entirely possible it’s getting a different version of the jvm. I don’t want to rerun another process through magit whilst it’s going, as I suspect that will break things.

Its still going, and I’ll be packing up for the day when it finishes… but can look at it tomorrow

ok it’s actually just finished… looks like it is getting java 9 when run this way…

I didn’t give it much thought at the time, but was expecting java 8 when I first kicked off the process.

ok home for me! 👋

I found amalloys answer to "How to recur upon exception":

(defn try-times* [thunk times]
  (let [res (first (drop-while #{::fail}
                               (repeatedly times
                                           #(try (thunk)
                                                 (catch Throwable _ ::fail)))))]
    (when-not (= ::fail res)
      res)))

( https://stackoverflow.com/questions/1879885/clojure-how-to-to-recur-upon-exception )

ugh, no, use trampoline

(trampoline
 (fn f []
   (try
     ...
     (catch Throwable t
       f))))

@mrchance I don't know the exact semantics for lazy seq realization but I have a memory of a discussion about it meaning it isn't always one at a time in all situations for all kinds of lazy sequences

maybe checkout https://github.com/joegallo/robert-bruce

In general I would just avoid using lazy sequences for side effects

unless you are able to (doall ...) explicitly

https://markhneedham.com/blog/2014/04/06/clojure-not-so-lazy-sequences-a-k-a-chunking-behaviour/

@hiredman Thanks! That helps, and I saw a mosaic of Robert the Bruce recently, so that's a bonus 😉 I'll probably go with the trampoline though, finally a chance to use it, and one less dependency @emccue Yeah, precisely what I was worrying about, thank you too 🙂

Oh, so it does happen

outdated reference maybe though

but enough evidence to not rely on that behaviour

Exactly, wouldn't depend on it then

also, who is what is the meaning of the reference to robert the bruce

> It's named after Robert the Bruce, whose determination was inspired by the sight of a spider trying (and failing) many times to build a web. 😉

A Scottish King, I believe

and I learned something today

😄

Hooray for programmers struggling to name their libraries

Researching for an upcoming Clojure project for work. I will need to make oauth v1 authenticated requests to an existing API. Any recommended libraries?