@st3fan You can also set defaults

(defn string->integer [s & {:keys [base] :or {base 10}}]
    (Integer/parseInt s base))

I use this pattern a lot to take configuration on a function.

Though I'd say taking a map is probably more idiomatic, as it let's you continue to use overloaded function arity.

Like

(defn string->integer [s {:keys [base] :or {base 10}}]
    (Integer/parseInt s base))

What clojure library allows me to throw arbitrary clojure data as an exception ?

(throw (ex-info …))?

@qqq Slingshot? (but I'd suggest trying @xiongtx suggestion first -- before you stray too far off the reservation 🙂 )

@xiongtx is correct, ex-info suffices

totally forgot ex-info = arbitrary clojure data

actually, what can slingshot throw taht ex-nfo can't throw?

I believe Slingshot obviates exceptions altogether and lets you just "throw" arbitrary data? I'd have to go read the docs to be sure tho'...

I know it's pulled in by several projects I depend on but I've never used it directly!

I'm really liking hara.event

Hiya 🙂

I have a question, I have protocol and record and can call protocol functions on that record like so

(defprotocol IProtocol
    (foo [_]))

  (defrecord Record []
    IProtocol
    (foo [_]
      (println "hi from Record foo!")))

  (def record (->Record []))

  (foo record) ;; hi from record foo!

What I want is a way to get a ptr to a function foo that will work with record

from a keyword

so

(defn get-fn-ptr [protocol record-type key-word-fn]
    ;; What do I put here?
    ;; I can see func
    )

  (def xxx (get-fn-ptr IProtocol Record :foo ))

  (xxx record)  ;; calls foo for record

I can see the :method-builders has when I dump IProtocol

but don’t really know enough about java to understand what they are

And my clojure fu is poor, looking the clojure source on github isn’t elucidating me much 🙂

Any help greatfully received

FWIW I have a state machine and the states are keywords

I want to generate state entry / exit funcs based on the methods supported by a record or reified object

so state :game-start

would call on-game-start and exit-game-start if the functions were found at bind time

Phew!

😄

I need a doseq to keep some state around. Is there soething more efficient than an atom? It's thread local, so I'm willing to use weird hacks.

@qqq volatile!

thheller: is this faster than https://clojure.org/reference/vars ?

@thheller : ^

Changes to references made volatile are always "written through" CPU caches all the way to main memory (which is somewhat expensive), this means changes are guaranteed to propagate to other threads (nescessary in stateful transducers). 

@qqq Well there is nonvolatile versions:

Depending and how the state looks like, a transient also might work.

with transients, you ahve to "pass new var back"

we can't just 'bash in place"

true, but you can use a reduce on a transient for example

but then it's no longer doseq

if I give up doseq, both reduce + loop/recur would work

@thheller volatile! is the fastest reference type that clojure offers

err, @qqq

how does it compare with per thread binding ?

it seems like volatile has to write out to ram, whreas per thread things don't need to do that

in my limited understanding of computer arthiceture, it seems like bindings would be faster than volaltiles

to me, it seems like 'volaltile` here doens't mean fast -- it means "oh shit, another thread can change this behind my back"

@qqq (vswap! the-ref do-some-work)

will only cause one write after everything is done

yeah, but the right ahs to go all the way out to RAM

so it doesn't seem like a good idea for something neste withint two do-seq's

not sure what kind of performance you are going for here, if it matters that much use java (or just loop/recur)

it needs to be cljs compatible

java is out of the question

I'm writing indexing routines for a db, something like a mini-{datomic, datascript}

just use a volatile! and look into performance if that becomes an issue

performance between cljs and clj are completely different

Does volatile really have to write thru the cache?

they’re not thread safe

This looks like the code

https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/Volatile.java

it just wraps java volatile which is only supposed to be used thread locally

Hi folks, I've posted this question on #architecture but didn't got an answer, so I'll ask here: what libraries have you been using for PubSub/Presence? Also, thoughts on Pulsar? I’ve an Erlang/Elixir background so I’m trying to find similar tools. 🙂

oh I’m wrong 😄 it means the opposite

I already have:

(s/def ::entity (s/map-of keyword? any?))

use s/keys not s/map-of in that case

I think it's (s/and (s/map-of ....) (s/keys ... ))

s/keys for :db/eid and :db/table, s/map-of to assert the other fields

How do I easily get indicies with for? Best thing I have so far is

(for [[i v] (map vector (range) ['a 'b 'c])]
     ...)

But that ain’t pretty. Resorting to map-indexed is another option, but I like for 🙂

i think the canonical way to get the indicies is to use map-indexed

@grav for is really much for for list comprehension

I probably understand the difference between doing list comprehension and mapping over a list?

I personally only use for when I need to loop over a "deep" data structure

(for [xs coll
      y xs] 
...)

Yes, that’s a good case for for. I don’t know, I just think for is really easy to use in the context of Reagent

Where I need to create a vector of vectors (a component containing sub-components)

creating lists is exactly for's use case -- (not looping, which loop is good for)

so, do your thing man 😉 🙂

yeah looping was not the right term, it only make sense if you do something with the return value obviously

there are better alternative otherwise

doseq/run! etc

since for is a looping construct in most every language, people already come to clojure misusing it, not realizing it is for list comprehension, so my mission in life is to dispel the notion that for is for looping in clojure 😉 (j/k about the mission in life part)

@grav if you are using for to create nested structures, you can still do that, but use the appropriate map-indexed to create the indexed structure, right?

(for [[i v] (map-indexed #(vector %1 %2) '[a b c])
      sub-v '[x y z]]
  [i [v sub-v]])

@joshjones Yes, that’s kind of what I’m doing now, though I’m doing (map vector (range) ['a 'b 'c]) instead of (map-indexed ...

In my case, I’m creating nested data structures, so no worries 😉 I really like for for this purpose, it’s very clojuresce imho. But there should be a for-indexed 🙂

Hi all, I noticed clj-webdriver is no longer maintained as of Dec 2016. Anyone have a suggestion to succeed it?

I’ve found these two: https://github.com/jackrusher/sparkledriver https://github.com/tmarble/webica

@nfisher I’ve been using https://github.com/igrishaev/etaoin

(lightly)

and it’s been great

It’s not a Selenium wrapper, so it might not be exactly what you’re looking for, but if you need to drive a browser it is nails

@nwjsmith thanks! Will take a look. I was using clj-webdriver, but it means I’m pinned to an old version of FF (47) and selenium(2.x). 😕

I have project with integration tests that I would like to run locally as well as in other environments. When I put them in /test (which intuitively makes sense), they aren't added to the JAR so I can't run them in other environments (UAT, staging, etc). What is the best place for these?

The project is using Leiningen.

you could make another jar which when run runs the integration tests

have another project essentially

Is it possible to include namespaces that are in /test in the JAR?

Would I just at this to :source-paths in the uberjar profile?

You still wouldn't be able to run them using lein test without a main

I have (defn myfn [] (shouldnt-be-called)) and I want to stub it out with with-redefs, like this:

(with-redefs [myfn (constantly nil)] ...)

I've found I can successfully stub out shouldnt-be-called, but I don't think I should need to stub things down stream from myfn

where is your usage of myfn?

you may be accidentally capturing the value of myfn pre-redefs

somethings do cross namespaces, is that what you mean?

and shouldnt-be-called comes from a defd var

if you do a lazy sequence with (map myfn ....), and then redef myfn, the lazy sequence will use the old definition

(lots of gotcha with with-redefs -- it's not a recommended function, but an occassionally necessary evil -- lots of previous discussion on this)

hrm... thanks for helping me get out of this earlier!

i thought i was going crazy!

we'd need to see some context around where you are using myfn

i just need it for testing, but, perhaps i need to find another way

it's occasionally useful in testing

myfn lives in (def thing {:myfn myfn}) in another ns than the one getting tested...

yeah there's your problem

Just like in the map example, you're using myfn as a value.

ahh

Clojure will dereference the myfn value when that def happens

oh, that totally makes sense I think. not obviuos, but makes sense now 🙂

hi guys, quick question: why (= 1024 1024.0) returns false and (== 1024 1024.0) returns true, I thought that = compares values

For your case @josh.freckleton , better to parameterize your side effect:

(defn myfn [impl] (... use the impl))

Another quick hack that you can do is: (def thing {:myfn #'myfn}) but I recommend parameterizing 100 million times more

#' means the var itself, not the value inside the var

thanks @ghadi , I couldn't have solve that otherwise!

@ghadi, so #' solved it easily, why do you recommend against it?

am I confused about it? the docs for = state that "Equality. Returns true if x equals y, false if not. Same as Java x.equals(y) except it also works for nil, and compares numbers and collections in a type-independent manner."

because the reason for #' here is to make the with-redefs work - there are better ways to mock things in Clojure (like making the implementation a passed in argument)

@piotr.owsiak I don't think you are confused. That's precisely what the doc says.

or at least the first half. > Clojure's immutable data structures define equals() (and thus =) as a value, not an identity, comparison

= also says > Same as Java x.equals(y) except it also works for nil, and compares numbers and collections in a type-independent manner

Yeah the verbiage is a little confusing

he had already quoted that so i just finished it out

The type-independent part of that sentence refers to collections

i was being snarky because he asked if he was confused and just pasted the doc string 🙂 (without stating what the potential confusion could be)

Not numbers and collections. It's an English ambiguity

user> (= [1 2] '(1 2))
true

^^^

== is type-independent around numbers and only numbers

and it doesn't use an epsilon factor

user> (== 0.3 (+ 0.1 0.2))
false

ok guys, thanks for clarification

Hello guys, can you give me some link of moder best practice in clojure/clojurescript. thanks

Without manually doing lots of transient/persistent management away, is there an easy way to: (1) do a bunch of assoc-in update-in on transients, then make the whole thing persistent ?

I know it's all personal preference generally speaking, but say I have a function whose purpose is to update/populate state in an atom and this function only runs once and on app startup. What would be an idiomatic return for that function? Is there a good design pattern for such a thing? Returning a reference to the atom in question? Returning true? Leaving it as a nil return?

We like to end the names of functions like that with a bang !, and have them return a keyword, e.g., :done-building-indexes. --- returning a keyword instead of, say, the contents of the entire index, tends to be friendlier on one's repl during development.

Agreed. Would you say that it is idiomatic for the returned keyword to be more informational like :done-building-indexes for the sake of the repl, or would you find yourself ever using that keyword for something? Again, obviously this is all relative and personal preference, I'm just trying to understand what "clean" or idiomatic Clojure would look like in the generic case.

I can't say too much for idiomatic, our team is perhaps a bit insular 😉, I can't think of a case where the actual value returned from a function like that was ever used. I guess I try to keep those keywords unique/grep'able in case they do end up in some log somewhere, but yeah, something friendly for development more than useful-as-a-value.

@mbcev ideally I write functions that update an atom such that they have no atom related logic in them - I write the function to take a foo, and return a foo, and then use the function as an argument to swap! on an atom containing a foo

Ahh, thanks guys. I like both of those ideas.

another way to say that is that I don't write functions that update atoms (ideally at least) and just write arguments to swap!

@noisesmith --- now that sounds idiomatic. ha! What does your function that calls swap! return? I think that's the question at hand...

your function to swap! must return the new value to put in the atom

that's the only correct result from such a function

Not the argument to swap! but the function that itself calls swap!.

^

oh, it should return the new value

So in other words, it should return what swap! returns, typically

the reason I called it is to swap! on something, so the reasonable return is the resulting data

right

I find that with realistic data I end up blowing up my repls when I do that. 😉 But, then we're back to personal preference/tools. 😄

your repl won't blow up if you stop using your editor as a repl btw

it might take a few moments to print, but not much

sorry, that's another topic

haha, no apologies needed. There's a joke in here about "Big Data" I think. 😛

"big data is when your application data is large enough to stall your debug console"

I appreciate the thought about factoring the pure functions used to swap!.

I have definitely had the case where my repl went unusable a bit because I looked at the data coming from kafka, for example

but I always had a usable repl again after a control-c or just waiting

I appreciate both of your responses and I will use your advice accordingly!

Thanks @harold and @noisesmith

to avoid blowing up your repl you can always set *print-level* and *print-length* in the repl profile

That's a good idea, I had that for a while, but then I copy/pasted some edn for a colleague and data was lost. 😐

Which #kafka clj library should I use? there appears to be a dozen

clj-kafka or kafka-clj. hrmmmmmmmmm 😉

clj-kafka has worked OK for me, haven't tried kafka-clj

a lot of my code is using direct interop with kafka itself though