#clojure – 2016-05-03

2016-05-03

00:12	sdegutis	wait no
00:12	sdegutis	is that actually working?
00:12	sdegutis	ok yeah i think so
00:13	sdegutis	which is more efficient on cpu? apply max or reduce max?
00:13	sdegutis	how about memory?
00:13	sdegutis	oh wait
00:13	sdegutis	profile.
00:23	dysfun	i'm going to guess at 'apply max', however
00:23	dysfun	(just a hunch)
03:44	Valentijn	Hi, quick question:
03:47	Valentijn	I have a vector looking like this [{:id 1 :from "F" :to "T" :pricing atom([some pricings])}, more entries], how can I update the pricings atom of each entry of the vector? When using (map (function-to-update-single-atom) myvector), the vector doesn't get updated. What am I doing wrong?
03:54	Valentijn	Hmm, doall did the trick. Can anyone explain?
03:54	opqdonut	map is lazy
03:54	opqdonut	it returns a lazy sequence
03:54	opqdonut	the computation is only done when somebody starts looking at the sequence
03:54	opqdonut	for things with side-effects it's clearer to use https://clojuredocs.org/clojure.core/doseq
03:57	Valentijn	Thanks! I don't do IO or something in the update function (just an update of the :pricing of the map with swap!), is doall then equal to doseq, or does something happen behind the scenes.
03:57	opqdonut	well swap! is a side effect
03:57	opqdonut	of sorts
03:57	opqdonut	doall and doseq are different, doall takes a sequence and forces (evaluates) all the elements
03:58	opqdonut	doseq is a macro that you use like this: (doseq [el my-vector] (do-something el) (do-something-else el))
03:58	ridcully	lazyness?
04:04	pnor	what is the easiest way to groupby a map { x: .. y: ... }
04:04	pnor	by x and y at the same time
04:04	pnor	(group-by :x input) works fine for x only
04:05	ridcully	(group-by (juxt :x :y))
04:05	luma	(group-by (juxt :x :y) input)
04:06	pnor	ok thanks guys
04:33	Valentijn	hehe den dyl
05:04	sunset-shimmer	hi, clojurians!
05:06	sunset-shimmer	Can you recomend me some course or book or articles about concurrency? I want to know, what the difference between async/await and futures/promises, what the actors are, what the chans are, and so on.
05:08	dysfun	well we don't have actors if that helps a little :)
05:09	dysfun	futures are computed on a thread pool
05:10	dysfun	you can wait for them to complete if you need them and you can chain them together
05:11	dysfun	promises are like futures except that you get a function to deliver the result and it's up to you where it gets computed
05:11	pythys	Hi Folks. So issuing a simple command in repl like (require 'compojure.core :refer :all) would crash with java.lang.Exception: Unsupported option(s) supplied: :all
05:11	pythys	Reading through the official documentation, it does not mandate that you only use :refer inside (ns)
05:11	dysfun	pythys: add vector-parens
05:12	pythys	dysfun: to what? the whole expression? where to where?
05:12	dysfun	(require '[compojure.core :refer :all])
05:12	hiredman	(require '[...])
05:12	pythys	Oh ...
05:12	hiredman	just like it would be in a :require clause of an ns form
05:13	pythys	why do I need to quote the vector in here and not in (ns,,,)
05:13	dysfun	because ns is a macro
05:13	pythys	Ahhhh I see
05:13	dysfun	so it won't be evaluated and fail to find the symbols named
05:13	pythys	because you're passing in "data" that will eventually become "code" right?
05:14	pythys	Now it all makes sense. that's why it's a compiler exception!
05:14	dysfun	no, not really
05:14	dysfun	when you call (require '[compojure.core :refer :all
05:14	dysfun	the require function is passed that vector as data
05:15	pythys	which is then fed to the macro and converted to actual code ...
05:15	pythys	right?
05:15	clojurebot	right is not wrong
05:15	dysfun	it then goes and loads the code, which has the side effect of attaching the namespace vars
05:15	dysfun	(ns ...) actually expands to the (require '[..]) form (and not just for require, :use etc.)
05:16	pythys	oh I see I see
05:16	pythys	it's data to data
05:16	pythys	but in another form
05:17	dysfun	think of it more like when you execute some clojure in the repl you are asking it to evaluate data
05:17	pythys	okay
05:17	dysfun	and when it's not a list, it evaluates to itself
05:17	dysfun	when it's a list, after evaluating the subforms inside of it, the function gets called with the given parameters
05:17	pythys	the doc for require officially says (require & args) and lists some keywords below ...
05:18	pythys	How do I generally know when to quote and when not to quote?
05:18	dysfun	the quote simply stops it trying to evaluate the vector (which contains symbols which are nlt yet in the namespace)
05:18	dysfun	you almost never want to quote. for the specific case of require, use etc., when you have to put a : on the front because you're in ns, you don't quote. otherwise, you quote
05:19	dysfun	if you did not quote here, it would complain it could not find compojure.core because it hasn't been loaded (how could it? you're passing it as an argument to require!)
05:20	dysfun	a vector evaluates to itself, so we could also individually quote the symbols
05:20	dysfun	but most of us prefer to just quote the entire vector
05:21	dysfun	(a symbol is evaluated by looking up the value it names)
05:21	pythys	Sorry I'm not getting this ...
05:22	dysfun	when you 'run' clojure, you evaluate it one step at a time
05:22	pythys	as I understood, clojure only evaluates the first thing on the list, and the rest is data
05:22	pythys	so (1 2 3) would execute 1 on 2 and 3
05:22	dysfun	no. when you evaluate the list, you first evaluate the contents of the list, then you call the function
05:22	pythys	and therefore (run [a] [b] [c] ,,,) would just execute "run"
05:23	pythys	oh
05:23	dysfun	first it will execute [a] [b] [c]
05:23	dysfun	because it needs the values to pass
05:23	pythys	dysfun: does that also apply on maps?
05:23	dysfun	it will also evaluate run (because run is a symbol)
05:23	pythys	and sets?
05:23	dysfun	yes, it does
05:23	pythys	so any data structure executes unless quoted?
05:23	dysfun	yes. but bear in mind the quoting might be done by a macro
05:24	pythys	is the execution of a vector similar to a list? e.g. [a b c] would also apply a on b & c?
05:24	dysfun	(the 'calling' of a macro implicitly quotes the rest of the list)
05:25	dysfun	yes
05:25	pythys	ouch! why?
05:25	pythys	Why would I evaluate a vector as something to run!
05:25	dysfun	you wouldn't. only lists get 'run'
05:26	pythys	then why quote a vector in the first place?
05:26	dysfun	because it has the side effect of quoting everything in it recursively
05:26	dysfun	thus we trade one quote per symbol for one quote for the whole expression
05:26	pythys	and why quote everything inside?
05:26	TEttinger	not even side effect, it's kinda what quote does, right?
05:26	TEttinger	if you had to quote every thing individually it would be a pain
05:27	dysfun	because that vector contains symbols, the evaluation of which is looking up the value contained in the var named by the symbol
05:27	TEttinger	there's ~ to unquote and I can't remember if it only works in certain places
05:27	TEttinger	,(str '[hey ~Math/PI])
05:27	clojurebot	"[hey (clojure.core/unquote Math/PI)]"
05:27	luma	it only works inside syntax-quote
05:27	TEttinger	hm
05:27	pythys	dysfun: OH, so it's because there is "no value" for that symbol
05:27	TEttinger	thanks luma
05:27	luma	as does unquote-splicing
05:27	pythys	dysfun: and it is only needed by the macro to flag something
05:27	dysfun	you could for example (require [(symbol "compojure.core") :refer :all])
05:27	dysfun	that is valid, but it's annoying to write
05:28	dysfun	pythys: right. we don't care that it doesn't name anything yet, we still need to use a name to communicate the information about what we want to require
05:28	pythys	I seeeeee
05:28	pythys	damn, now it clicks
05:28	dysfun	clojure could in an alternate world take a string argument instead
05:29	dysfun	then there would be no need to quote and it would be marginally fuglier
05:30	pythys	yeah, :refer evaluates to itself, :all evaluated to itself, compojure.core evaluates to nil which crashes the thing
05:30	pythys	because no symbol called compojure.core is defined
05:30	dysfun	well no, it doesn't evaluate to nil so much as it doesn't evaluate - an error is thrown. clojure is upset.
05:30	pythys	I seeee ... sort of undefined
05:31	pythys	compiler getting pissed
05:31	jonathanj	what do Clojurians think of Racket?
05:31	dysfun	pythys: isn't it always? have you noticed the length of stacktraces?
05:32	pythys	uh-huh of course
05:32	dysfun	jonathanj: it's good if you like scheme more than clojure or if you want to learn something for the things it explores rather than to get work done
05:32	jonathanj	Typed Racket is pretty attractive and so is the ability to handily write a DSL
05:32	pythys	dysfun: by the way, how do you know that you need to pass a vector to require in the first place? the definition in the official documentation is just (require & args)
05:32	dysfun	DSL-writing comes for free with every lisp
05:32	pythys	do you have to look at the code for that?
05:32	luma	if you want to see what happens when a language allows you to "handily write a DSL", see scala
05:33	dysfun	pythys: because i saw other people do it on the internet, probably
05:33	jonathanj	well, Racket is a lot saner than Scala
05:33	jonathanj	Scala started at the deep end and went off whatever comes after the deep end
05:33	pythys	dysfun: yeah but I mean generally speaking, you access a new library and want to figure out what to pass. How do you do that?
05:33	dysfun	no argument here
05:33	jonathanj	anyway, Racket isn't an option for me, the main reason I use Clojure is because I need java interop
05:34	dysfun	pythys: i read the documentation (usually the README.md on github). if it isn't working then, i go read the test suite to see how they made it run
05:34	jonathanj	everytime i read something about Racket i leave finding myself wondering if i have a suitable project to use it for
05:34	pythys	dysfun: okay, so this is sort of a penalty of using a dynamic language
05:34	dysfun	well if you want to build a GUI app, javafx/swing/awt is the pits, so that could be a good domain for racket
05:35	dysfun	pythys: no. contrary to most scala programmers, i don't think a type signature constitutes the wholeness of documentation
05:35	jonathanj	John Carmack wrote a networked game server in Racket
05:35	jonathanj	and he had a lot of good things to say about the experience
05:35	pythys	dysfun: but you just mentioned yourself that you have to "dig out" how the thing works
05:35	pythys	dysfun: this is exactly why I was confused and joined the channel for help for example
05:36	pythys	I was trying to make sense of it
05:36	dysfun	pythys: right. and i also program haskell. the best button on hackage is the 'read source' link
05:36	pythys	dysfun: right, I see
05:36	pythys	dysfun: usually data validation is in the first few lines of (doc require) for example
05:36	pythys	so you would immediately know it's a vector
05:36	pythys	sorry I meant (source require)
05:36	dysfun	right
05:37	pythys	got that!
05:37	jonathanj	dysfun: you write Clojure and Haskell code?
05:37	dysfun	i write a lot of things
05:37	jonathanj	dysfun: you're not bipolar, are you?
05:37	dysfun	is there a type system joke in there?
05:37	pythys	hmmmm, leaving a sour taste in my mouth. I'm too addicted to type systems
05:37	jonathanj	Haskell people hiss and recoil when you talk about about dynamic languages
05:38	dysfun	yes, i know, but despite the community it's a great tool
05:38	dysfun	sadly many in the community are also tools
05:38	jonathanj	i can't get into it, i've tried a few times but i keep getting stuck on theory
05:39	pythys	dysfun: do you have a preference of dynamic vs static? cases where the sacrifice is worth it?
05:39	jonathanj	and the infix operator soup is really disheartening as a beginner
05:39	dysfun	well my view ("ignore the type theory and just write the code") isn't that popular
05:40	dysfun	pythys: for cases where incorrectness is catastrophic and difficult to spot, use a statically typed language. Otherwise, use whatever you think will enable you to get the job done
05:40	jonathanj	i read through the haskell-servant tutorial the other day, and it seems like a really great way to write (and test!) web services
05:41	pythys	dysfun: okay I see. Well the upside I guess is that you have a very focused dense effective code with clojure without too much ceremony
05:41	dysfun	clojure is one of my favourite tools to work with. It's very practical and easy to get things done with
05:41	pythys	but I need a repl all the time to see what's up.
05:41	pythys	uh-huh I see
05:42	pythys	dysfun: so natually, less lines of code in comparison to any typed language I assume
05:42	pythys	naturally
05:42	dysfun	depends
05:43	dysfun	haskell gets pretty close until i start working with monads
05:43	pythys	which is where "real" work is anyway
05:43	pythys	otherwise it's just a hot CPI
05:43	pythys	CPU
05:44	dysfun	well there is definitely a point in solving modern problems with haskell that way too much code is in the IO monad
05:45	pythys	I see
05:45	pythys	Thank you so much, things are much clearer now overall
05:45	pythys	I hit small things but make big discoveries each time
06:18	jonathanj	searching on clojuredocs:
06:18	jonathanj	Search results for query: clojure.java.shell
06:18	jonathanj	1 to 1 of 1 results.
06:18	jonathanj	0 examples
06:18	jonathanj	but there are 0 results listed
06:19	jonathanj	is there something like `/usr/bin/which` in Clojure/Java?
06:19	jonathanj	ie. first discover whether something exists before trying to spawn it
06:19	dysfun	if you're going to shell out, you may as well shell out to `which`
06:19	jonathanj	that's a bit of a weird way of thinking about it
06:20	jonathanj	`which` doesn't exist on Windows, for example
06:22	dysfun	no, i'm not aware of anything that handles this
06:25	jonathanj	i guess you'd have to just implement which oneself (or deal with the exceptions)
06:25	ridcully	expect it's there, but capture stderr etc and make sure you get a rock solid error message out. try it with a missing binary or even add a test for it. this way some ops person (or future you) can handle it on OS level
06:25	ridcully	if its most likely not on PATH (windows?) then make it a mandatory config
06:26	ridcully	there is nothing worse then getting a 3trillion line stacktrace with an NPE for some missing binary ;)
06:29	ilevd	What's best modern clojurescript framework/lib except zelkova, reframe. Is zelkova production ready?
06:47	henderson	What is the most efficient way to find the map where :id = 2 in the following structure: ({:id 1 :otherVal "someval"},{:id 2 :otherVal "someOtherVal"}) ?
06:47	henderson	the structure is a list of maps
06:48	hamid	, ({:id 1 :otherVal "someval"},{:id 2 :otherVal "someOtherVal"})
06:49	clojurebot	nil
06:49	hamid	henderson, you have to filter
06:50	hamid	, (filter #(= 2 (:id %)) '({:id 1 :otherVal "someval"},{:id 2 :otherVal "someOtherVal"}))
06:50	clojurebot	({:id 2, :otherVal "someOtherVal"})
06:50	henderson	Oh, thanks man!
06:50	hamid	henderson, glad i could help! this channel is kinda sleep i guess!
06:52	henderson	haha, true
06:55	hamid	ilevd, what about Om.Next?
07:04	jonathanj	https://pb.codehash.net/c4f583de7927485cab94a8b2e3752afd
07:05	jonathanj	if anyone wants to code golf that :)
07:12	ridcully	path is unused?
07:59	mettekou	Say I have a data structure contained in an atom and I would first like to select an element of it and then update this element. I could do both operations inside a single swap!, which is correct with respect to race conditions and other nasty things, but does not allow for much concurrency. Is there a better solution?
08:00	mettekou	In other words: I'm looking to split up selecting the element and updating it without sacrificing safe concurrency.
08:05	ridcully	update-in ?
08:07	luma	,(let [a (atom {:foo 0, :bar 0})] (swap! a update :foo inc))
08:07	clojurebot	{:foo 1, :bar 0}
08:52	ilevd	hamid, I don't know, I'm considering return back to Elm
09:02	dysfun	mettekou: you always have to check when you update
09:02	dysfun	swap! is basically compare-and-set in a loop until it succeeds
09:03	mettekou	dysfun: I rewrote the code using a compare-and-set! in a loop, which indeed changed nothing.
09:04	dysfun	well this is how you do it
09:04	dysfun	turns out that optimistic CAS results in higher average throughput
09:07	dysfun	of course if the computation takes an unreasonably long time, you may wish to consider another strategy
09:08	ilevd	You want get a value from when you swap?
09:09	dysfun	i read it as he is concerned about the concurrency properties of using swap
09:19	mettekou	dysfun: Yeah, I'm concerned about the fact that most of my computation is a look-up which does not modify anything but does take place inside swap!.
09:33	dysfun	you mean like an update-in?
09:34	dysfun	i mean the simple way of writing it would be using update-in, were it not for your artificial separation?
09:35	pythys	Hey folks, (defn registration-page [& [id]] ,,,) what does the "[& [id]]" mean?
09:35	pythys	are we passing an optional vector inside a vector?
09:35	dysfun	& is rest args, [] is destructuring the rest args, id is the first item in the rest args
09:35	justin_smith	mettekou: refs are more general and allow access and update as separate steps if you are concerned about maximum concurrency
09:36	dysfun	so it's essentially just a single optional parameter
09:36	justin_smith	mettekou: also, they can coordinate update of multiple refs, which can significantly reduce the number of retries needed when changes are frequent
09:37	justin_smith	pythys: (fn [& [id]] ...) is the bad way to write (fn f ([] (f nil)) ([id] ...))
09:38	pythys	ok, I need a second to try and swallow this!
09:39	justin_smith	another way to say that, is that for a single optional arg, the right thing to do is multiple arities
09:39	pythys	justin_smith: what does multiple arities mean?
09:39	justin_smith	,((fn f ([] (f 2)) ([x] (* x x x))))
09:39	clojurebot	8
09:39	mettekou	Hmmm... Doesn't doall force the result of a for just like that of a map or other function that yields a lazy sequence?
09:40	justin_smith	pythys: that's a function that takes either 0 args or 1
09:40	justin_smith	mettekou: doall realizes a top level lazy sequence, yes
09:40	pythys	ok, i understood that part, but I don't get it syntactically
09:41	pythys	so [& [x]] means destructure the "rest" of the arguments passed and fetch the first one>
09:41	pythys	?
09:41	justin_smith	pythys: (f ([arg] (1 arg body)) ([two args] (two arg body))) etc.
09:41	mettekou	,(doall (for [id (range 10)] {:id id :from "BRU" :to (nth destinations (mod id 10)) :pricing [[(+ (rand-int 200) 200) (+ (rand-int 100) 200) 0] [(+ (rand-int 400) 200) (+ (rand-int 100) 150) 0] [(+ (rand-int 600) 200) (+ (rand-int 100) 100) 0]]})))
09:41	clojurebot	#error {\n :cause "Unable to resolve symbol: destinations in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: destinations in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6688]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol:...
09:41	justin_smith	pythys: yes, and it accepts any number of args, only using the first (if present)
09:41	mettekou	,(doall (for [id (range 10)] {:id id :from "BRU" :to (nth [1 2 3 4 5 6 7 8 9 10] (mod id 10)) :pricing [[(+ (rand-int 200) 200) (+ (rand-int 100) 200) 0] [(+ (rand-int 400) 200) (+ (rand-int 100) 150) 0] [(+ (rand-int 600) 200) (+ (rand-int 100) 100) 0]]})))
09:41	clojurebot	({:id 0, :from "BRU", :to 1, :pricing [[296 298 0] [272 174 0] [714 180 0]]} {:id 1, :from "BRU", :to 2, :pricing [[339 222 0] [368 183 0] [318 198 0]]} {:id 2, :from "BRU", :to 3, :pricing [[227 230 0] [396 194 0] [258 173 0]]} {:id 3, :from "BRU", :to 4, :pricing [[295 264 0] [209 187 0] [287 147 0]]} {:id 4, :from "BRU", :to 5, :pricing [[310 219 0] [295 223 0] [593 163 0]]} ...)
09:42	pythys	justin_smith: but if I'm not mistaken, destructing happens with let
09:42	justin_smith	pythys: you are mistaken
09:42	justin_smith	pythys: destructuring is available in any binding context
09:42	pythys	destructuring sorry
09:42	pythys	justin_smith: what is a binding context?
09:42	justin_smith	pythys: you can destructure in function args, loop bindings, for bindings, doall bindings, etc. etc. etc.
09:43	justin_smith	pythys: a vector where you name an arg
09:43	mettekou	,(vec (doall (for [id (range 10)] {:id id :from "BRU" :to (nth [1 2 3 4 5 6 7 8 9 10] (mod id 10)) :pricing [[(+ (rand-int 200) 200) (+ (rand-int 100) 200) 0] [(+ (rand-int 400) 200) (+ (rand-int 100) 150) 0] [(+ (rand-int 600) 200) (+ (rand-int 100) 100) 0]]}))))
09:43	clojurebot	[{:id 0, :from "BRU", :to 1, :pricing [[226 224 0] [359 220 0] [566 149 0]]} {:id 1, :from "BRU", :to 2, :pricing [[372 253 0] [296 224 0] [704 108 0]]} {:id 2, :from "BRU", :to 3, :pricing [[390 275 0] [285 179 0] [722 123 0]]} {:id 3, :from "BRU", :to 4, :pricing [[225 215 0] [450 216 0] [432 136 0]]} {:id 4, :from "BRU", :to 5, :pricing [[207 255 0] [565 174 0] [274 186 0]]} ...]
09:43	justin_smith	pythys: or a value, more generally
09:43	mettekou	,(vec (for [id (range 10)] {:id id :from "BRU" :to (nth [1 2 3 4 5 6 7 8 9 10] (mod id 10)) :pricing [[(+ (rand-int 200) 200) (+ (rand-int 100) 200) 0] [(+ (rand-int 400) 200) (+ (rand-int 100) 150) 0] [(+ (rand-int 600) 200) (+ (rand-int 100) 100) 0]]})))
09:43	clojurebot	[{:id 0, :from "BRU", :to 1, :pricing [[261 285 0] [220 154 0] [339 104 0]]} {:id 1, :from "BRU", :to 2, :pricing [[356 229 0] [412 178 0] [482 129 0]]} {:id 2, :from "BRU", :to 3, :pricing [[280 250 0] [348 191 0] [370 157 0]]} {:id 3, :from "BRU", :to 4, :pricing [[336 227 0] [505 189 0] [417 110 0]]} {:id 4, :from "BRU", :to 5, :pricing [[223 203 0] [596 156 0] [277 154 0]]} ...]
09:43	justin_smith	mettekou: (vec (doall ...)) is never useful
09:43	mettekou	Yeah, I just found out. :P
09:44	pythys	justin_smith: sorry, not sure I understand. What do you mean by a vector where you name an arg or a value?
09:44	justin_smith	pythys: function args, let blocks, loop bindings, macro args
09:44	justin_smith	pythys: for bindings, doseq bindings
09:44	justin_smith	etc.
09:44	justin_smith	pythys: in all of them you have a vector, and assign names to values
09:44	pythys	justin_smith: so any place where you have []? or any place where you "assign" values?
09:45	justin_smith	pythys: where you assign symbols to values
09:45	pythys	ok
09:45	justin_smith	inside a vector, specifically
09:45	pythys	I think this is probably the most challenging part in clojure, destructuring. It's where I get majorly challenged
09:46	pythys	Too many variations on destructing with multiple different syntaxes
09:46	justin_smith	pythys: there's about 3
09:46	justin_smith	pythys: and they can be used in a bunch of contexts that are all very similar to each other
09:47	justin_smith	{foo :foo}, {:keys [foo]} [foo] [foo & bar], and then you can do nesting but not inside :keys
09:47	pythys	which three? I have let, defn, loop, recur, def, fn, plus the above example [& [x]]
09:47	pythys	seems to be too many
09:48	justin_smith	pythys: those are contexts
09:48	justin_smith	not syntaxes
09:48	pythys	oh oh
09:48	pythys	ok, then what are the three syntaxes you referred to?
09:48	justin_smith	pythys: they all use the same destructure syntax
09:48	justin_smith	pythys: two ways to do a hash-map, and one way to do a sequence
09:48	justin_smith	with optional :as and :or keys
09:50	pythys	justin_smith: aren't maps also sequences?
09:51	jonathanj	ridcully: ah, indeed, a remnant from a previous iteration
09:53	pythys	justin_smith: my bad, i got things confused
10:42	pythys	justin_smith: am I in the right place reading here for our discussion -> http://clojure-doc.org/articles/language/functions.html#extra-arguments-aka-named-parameters
10:49	zephalos	Hi, what is the best way to replace the thirdelement of a list by the third element of another list? E.g. [[1 2 100],[1 2 100],[1 2 100]] and [[4 5 200],[4 6 100],[4 7 200]] would then give [[4 5 100],[4 6 100],[4 7 100]]
10:56	ridcully	,(map (fn [[_ _ c] [a b _]] [a b c]) [[1 2 100],[1 2 100],[1 2 100]] [[4 5 200],[4 6 100],[4 7 200]])
10:56	clojurebot	([4 5 100] [4 6 100] [4 7 100])
10:56	zephalos	thanks man!
10:57	ridcully	to a certain definition of "best"
11:25	sdegutis	What's going on?
11:39	sdegutis	What's happening!?
11:45	justin_smith	zephalos: if you have a vector and not a list, (like in your example) you can use get and assoc (map (fn [a b] (assoc a 2 (get b 2))))
11:46	justin_smith	,(map (fn [a b] (assoc a 2 (get b 2))) [[1 2 100],[1 2 100],[1 2 100]] [[4 5 200],[4 6 100],[4 7 200]])
11:46	clojurebot	([1 2 200] [1 2 100] [1 2 200])
11:46	justin_smith	oh, that was backward
11:47	justin_smith	,(map (fn [b a] (assoc a 2 (get b 2))) [[1 2 100],[1 2 100],[1 2 100]] [[4 5 200],[4 6 100],[4 7 200]])
11:47	clojurebot	([4 5 100] [4 6 100] [4 7 100])
11:52	sdegutis	Pop quiz time!
11:52	sdegutis	It's someone else's turn to come up with it this time.
12:00	hfaafb	This US state is closest to Africa (if one were to fly a plane between the two)
12:01	luma	maine?
12:03	hfaafb	that's correct
12:28	mloveless	not florida?
12:29	sdegutis	I mean a Clojure pip quiz.
12:31	sdegutis	Oh here I got one.
12:31	sdegutis	(f [:a [:b [:c {:foo 1 :bar 2}] {:quux 3}]])
12:31	sdegutis	=> [[[:a :b :c] {:foo 1 :bar 2}] [[:a :b] {:quux 3}]]
12:31	sdegutis	What's f?
12:33	sdegutis	Bonus points for using Transducers.
12:46	ambrosebs	How do I eliminate reflection here? https://www.irccloud.com/pastebin/0IaxP9K6/
12:57	sdegutis	^Long maybe?
13:00	ambrosebs	sdegutis: ;!!CompilerException java.lang.UnsupportedOperationException: Can't type hint a local with a primitive initializer, compiling:(clojure/math/combinatorics.clj:311:3)
13:00	dysfun	ambrosebs:
13:00	sdegutis	Right.
13:00	dysfun	you need to use a let
13:00	dysfun	and type hint that
13:00	dysfun	ran across this the other day
13:00	ambrosebs	dysfun: let bind 1?
13:01	dysfun	well, 'acc'
13:01	ambrosebs	dysfun: I've tried lots of similar things I've had no luck
13:01	ambrosebs	other than doing something like (first [1]) to trick the compiler
13:02	ambrosebs	dysfun: can you share an example please?
13:02	dysfun	so my first instinct is that zero? is probably causing boxing
13:02	sdegutis	Right.
13:02	dysfun	(loop [acc l n n] (let [^long acc' acc ^long n] ...))
13:03	dysfun	that was enough to make my boxing problem go away
13:04	ambrosebs	dysfun: replacing zero? with (== 0 n) seemed to work :)
13:04	dysfun	yay!
13:04	ambrosebs	is there a difference between the two?
13:04	ambrosebs	I'm rusty on = vs ==
13:04	dysfun	== is int math, = is generic compare
13:04	dysfun	(usually .equals())
13:04	justin_smith	,(== 5.0 5 5M)
13:05	clojurebot	true
13:05	ambrosebs	dysfun: and I assume that never makes a difference for zero?
13:05	justin_smith	,(= 5.0 5)
13:05	clojurebot	false
13:05	justin_smith	,(= 0.0 0)
13:05	clojurebot	false
13:05	justin_smith	,(== 0.0 0)
13:05	clojurebot	true
13:06	dysfun	ambrosebs: no, it won't. but on the other hand = is much more complicated
13:06	ambrosebs	dysfun: makes sense thanks!
13:06	dysfun	yw
13:07	justin_smith	dysfun: == is not int math, it's generic across exact vs. inexact (while = is generic otherwise, but does not cross exact/inexact boundaries)
13:07	dysfun	i stand corrected
13:08	ambrosebs	wait no, I'm still stuck :)
13:08	ambrosebs	false alarm
13:08	justin_smith	ambrosebs: == if for when you want exact and inexact numbers to be potentially equal
13:09	ambrosebs	justin_smith: is there a preference for integer maths?
13:09	justin_smith	ambrosebs: I don't understand that question - if you know all the inputs are integral, you don't need == and = will suffice?
13:10	ambrosebs	Sorry. I just don't want to make this code any slower unnecessarily
13:10	ambrosebs	but yes, thats my question
13:11	ambrosebs	but for factorial it really doesn't matter
13:11	ambrosebs	thinking about it :)
13:13	ambrosebs	Apparently this solved my reflection errors. https://www.irccloud.com/pastebin/JUePI4NG/
13:14	ambrosebs	moving the loop into a function
13:14	ambrosebs	does that mean the reflection is gone? :/
13:21	felipedvorak	I'm installing Clojure and it asks if I want jdk7 or 8?
13:22	dysfun	jdk7 is EOL
13:23	felipedvorak	jdk8 then. Thanks dysfun.
13:23	TimMc	jdk1.2 4 lyfe
13:25	mettekou	I wish every? would work like map, allowing n-ary predicates on the elements of n collections.
13:26	mettekou	(every? true? (map predicate-2 ones twos)) is too clunky.
13:29	sdegutis	Be there a convenient function for adding to a list or if the thing isn't a list then making it into a list to add to?
13:29	sdegutis	So that (f 1 2) and (f 1 [2]) both return [1 2] ?
13:32	sdegutis	Ah, yes. Found it.
13:40	sdegutis	,(let [f #(->> (vector %2) (cons %1) (flatten))] (= (f 1 2) (f 1 [2]) [1 2]))
13:40	clojurebot	true
13:40	sdegutis	:D
13:40	sdegutis	I have 2 uses of clojure.core/flatten in production.
13:41	ambrosebs	quite a feat
13:41	luma	that's probably two uses too many...
13:46	sdegutis	The one above is one of them.
13:47	luma	that one's broken if you feed it a vector as the first parameter
13:48	luma	(f [1] 2) isn't [[1] 2] but [1 2]
13:54	sdegutis	luma: right, only strings are ever needed
13:54	sdegutis	luma: it's a convenience thing for building a list of strings; it can accept a string or a coll of strings
15:19	bsamorim	guys, I have a few questions regarding the usage of java classes in clojure, regarding the mutability
15:19	bsamorim	could any1 help me out a bit?
15:19	bsamorim	it's pretty vanilla stuff, I s'ppose
15:20	bsamorim	suppose I have a nested clojure structure, with one of its elements being a java object
15:20	bsamorim	how does clojure handle that?
15:21	bsamorim	is this structure partially mutable? totally? or not at all?
15:25	justin_smith	bsamorim: the structure is not mutable, the object inside the structure is
15:26	justin_smith	bsamorim: this can be a real gotcha if you used the object as a key in a hash-map - because you could have changed its hash-code, which as you might expect, makes hash-maps much less useful and sane
15:26	bsamorim	justin_smith: why would the hash-code change?
15:26	justin_smith	bsamorim: see also clojure's concurrency safe containers, which are the opposite - a mutable box meant to hold something immutable
15:27	justin_smith	bsamorim: because objects that are mutable can use their state to determine their hash-code - I mean they don't always do that, but they could
15:27	sdegutis	Right.
15:28	bsamorim	justin_smith: oh, sure, but a different binding wouldn't change it, right?
15:28	bsamorim	I mean, that's all clojure does with a mutable object, right?
15:28	justin_smith	bsamorim: absolutely not
15:28	justin_smith	if you mutate a java object, it is mutated
15:29	justin_smith	clojure does not hide or prevent this in any way
15:29	bsamorim	justin_smith: yeah, I know....sry, I was explaining my doubt as shit
15:29	bsamorim	justin_smith: I'll rephrase it
15:30	justin_smith	,(let [d (java.util.Date.) h (.hashCode d) _ (.setTime d 0) h' (.hashCode d)] [h h'])
15:30	clojurebot	[2014932744 0]
15:30	justin_smith	bsamorim: if you use a java.util.Date as a key in a hash map, then mutated it, you would break lookup in the map
15:30	justin_smith	because it's hash would no longer be relevant to its bin
15:30	bsamorim	suppose I have a class Foo, with one public attribute x
15:31	bsamorim	if I do the following commands:
15:31	bsamorim	(def a (new Foo))
15:31	bsamorim	(. x a 1)
15:31	justin_smith	maybe you want (set (.x a) 1) ?
15:32	justin_smith	err, set!
15:32	sdegutis	I often do (. date before end-date)
15:33	justin_smith	bsamorim: but what's your question?
15:39	justin_smith	,(defprotocol IFoo (getX [this]) (setX [this x]))
15:39	clojurebot	IFoo
15:40	justin_smith	,(deftype Foo [^:volatile-mutable x] IFoo (getX [this] x) (setX [this v] (set! x v)))
15:40	clojurebot	sandbox.Foo
15:40	justin_smith	,(def f (Foo. 1))
15:40	clojurebot	#error {\n :cause "Unable to resolve classname: Foo"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.IllegalArgumentException: Unable to resolve classname: Foo, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyzeSeq "Compiler.java" 6875]}\n {:type java.lang.IllegalArgumentException\n :message "Unable to resolve classname: Foo"\n :at [clojure...
15:40	justin_smith	,(deftype Foo [^:volatile-mutable x] IFoo (getX [this] x) (setX [this v] (set! x v)))
15:40	clojurebot	#error {\n :cause "Unable to resolve symbol: IFoo in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: IFoo in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyzeSeq "Compiler.java" 6875]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol: IFoo in this...
15:40	justin_smith	,(defprotocol IFoo (getX [this]) (setX [this x]))
15:40	clojurebot	IFoo
15:40	justin_smith	,(deftype Foo [^:volatile-mutable x] IFoo (getX [this] x) (setX [this v] (set! x v)))
15:40	clojurebot	sandbox.Foo
15:40	justin_smith	,(def f (Foo. 1))
15:40	clojurebot	#'sandbox/f
15:40	justin_smith	,(.getX f)
15:40	clojurebot	1
15:41	justin_smith	,(.setX f "whatever")
15:41	clojurebot	"whatever"
15:41	justin_smith	,(.getX f)
15:41	clojurebot	"whatever"
15:41	justin_smith	bsamorim: anyway, if you still have a quesiton, the above might help us
15:41	stisti	what's the easiest way to get a working lein? I have Oracle JDK 1.8 on Mac + brew install clojure lein but I can't get it to work
15:41	stisti	lein new app x; cd x; lein install
15:41	justin_smith	stisti: don't use a package manager to install lein, just download the file from leiningen.org
15:41	stisti	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.
15:42	justin_smith	stisti: that just means your project doesn't have a valid main, that's not a lein problem
15:42	justin_smith	stisti: easiest thing is to take out the part of project.clj that claims you have a main that isn't actually there
15:44	stisti	shouldn't I have a main if I'm making an app?
15:44	justin_smith	stisti: then make sure your main actually exists
15:44	justin_smith	also why lein install an app? I would uberjar an app, and lein install for libs
15:44	justin_smith	lein install isn't
15:44	justin_smith	err
15:45	justin_smith	it isn't "install globally so you can run" it's "add to your local library dependency cache"
15:45	stisti	ok, I'm new to clojure and lein, trying to learn them. Could you just point me to some tutorial that allows me to get Hello World off the ground? Thanks
15:48	justin_smith	lein new foo; cd foo; lein run
15:48	justin_smith	after that you start by finding foo.core/-main, and editing it
15:48	justin_smith	stisti: have you seen this? https://github.com/technomancy/leiningen/blob/master/doc/TUTORIAL.md
15:51	stisti	been checking that out but I thought "lein new app foo" would create a something that would run. It seems to but I'm newbie enough to now see what it is missing
15:52	stisti	lein new foo; cd foo; lein run says there is no main
15:52	ridcully	it does. lein run, runs it
15:52	stisti	for me it says
15:52	stisti	No :main namespace specified in project.clj.
15:52	justin_smith	stisti: I think you need "lein new app foo" maybe?
15:52	justin_smith	one moment, double checking
15:52	ridcully	also a lein uberjar gives you something runable
15:53	justin_smith	stisti: that was my bad 'lein new app foo; cd foo; lein run' will work
15:54	justin_smith	then you can paly with foo.core, modify -main, add more namespaces, etc.
15:54	justin_smith	but it's a working starting point
15:54	stisti	yes, and when I do: lein new app foo2; cd foo2; lein run
15:54	stisti	Can't find 'foo2.core' as .class or .clj for lein run: please check the spelling.
15:55	ridcully	stisti: just for the record, whats your lein -version?
15:56	stisti	> lein -version Leiningen 2.6.1 on Java 1.8.0_74 Java HotSpot(TM) 64-Bit Server VM
15:56	justin_smith	stisti: lein new app foo2; cd foo2; lein run works locally
15:56	ridcully	dito (2.6.1, jdk 1.8.92)
15:57	justin_smith	stisti: did you try making foo2 from within foo? that might do something funky
15:57	justin_smith	stisti: since lein would try to load your project if present I bet...
15:58	stisti	I deleted all foo*
15:58	justin_smith	OK
15:58	stisti	lein new app abc; cd abc; lein run
15:58	stisti	Can't find 'abc.core' as .class or .clj for lein run: please check the spelling.
15:58	justin_smith	then something is severely wrong, my first course of action would be deleting lein from homebrew and just installing the shell script
15:59	justin_smith	package-managing lein tends not to work so nicely in my experience
15:59	stisti	ok, thanks
16:01	sdegutis	I found this funny.
16:02	sdegutis	https://github.com/xsc/lein-ancient
16:02	sdegutis	"A Leiningen plugin to check your project for outdated dependencies and plugins."
16:02	sdegutis	"dependencies: out of date"
16:03	justin_smith	sdegutis: clearly we need to make a lein-ancient-ancient plugin, to see if the deps of lein-ancient are up to date
16:03	sdegutis	:D
16:03	ridcully	but then would need to create lein-ancient-ancient-ancient'
16:04	justin_smith	ridcully: we could use a new naming scheme, lein-ancient, lein-ancient', lein-ancient'' etc.
16:04	sdegutis	Not if we just keep lein-ancient-ancient's dependencies up todate.
16:04	justin_smith	sdegutis: if we were capable of "just keeping dependencies up to date" we wouldn't need lein-ancient, now would we?
16:05	ridcully	that is impossible. why else is there a tool for it?
16:05	ridcully	that said, lein-ancient is a mighty fine tool
16:05	justin_smith	yes, it is
16:07	ystael	justin_smith: i'd prefer lein-heroic, lein-prehistoric, lein-hominin
16:15	sdegutis	lein-outdated
16:15	sdegutis	lein-outmoded
16:15	sdegutis	lein-can-upgrade
16:17	xemdetia	lein-can-lean
16:18	hxegon	lein-with-it-then-wreq-with-it
18:33	mettekou	((resolve (symbol "Math/random")))
18:33	mettekou	,((resolve (symbol "Math/random")))
18:33	clojurebot	#error {\n :cause nil\n :via\n [{:type java.lang.NullPointerException\n :message nil\n :at [sandbox$eval25 invokeStatic "NO_SOURCE_FILE" 0]}]\n :trace\n [[sandbox$eval25 invokeStatic "NO_SOURCE_FILE" 0]\n [sandbox$eval25 invoke "NO_SOURCE_FILE" -1]\n [clojure.lang.Compiler eval "Compiler.java" 6927]\n [clojure.lang.Compiler eval "Compiler.java" 6890]\n [clojure.core$eval invokeStatic "core...
18:33	mettekou	,((resolve (symbol "Math" "random")))
18:33	clojurebot	#error {\n :cause nil\n :via\n [{:type java.lang.NullPointerException\n :message nil\n :at [sandbox$eval49 invokeStatic "NO_SOURCE_FILE" 0]}]\n :trace\n [[sandbox$eval49 invokeStatic "NO_SOURCE_FILE" 0]\n [sandbox$eval49 invoke "NO_SOURCE_FILE" -1]\n [clojure.lang.Compiler eval "Compiler.java" 6927]\n [clojure.lang.Compiler eval "Compiler.java" 6890]\n [clojure.core$eval invokeStatic "core...
18:35	mettekou	,(symbol "Math" "random")
18:35	clojurebot	Math/random
18:37	justin_smith	mettekou: resolve is for namespaces containing vars, not for classes and static methods
18:38	mettekou	justin_smith: Thanks. That's what I needed it for anyway, but no way of quickly doing that here came to mind.
19:11	WorldsEndless	What's the long form of the #"" regexp macro? My function needs to compose a regexp pattern from a pair of strings
19:12	justin_smith	WorldsEndless: (re-compile s)
19:12	WorldsEndless	Thanks
19:12	justin_smith	you probably need to call str on the strings to get one string for re-compile
19:12	WorldsEndless	Google was not helping me much
19:13	justin_smith	WorldsEndless: conj.io / cheatsheet has this under the regex section last I checked
19:13	WorldsEndless	What namespace is re-compile?
19:14	justin_smith	sorry!
19:14	justin_smith	it's re-pattern
19:14	WorldsEndless	ah
19:14	justin_smith	,(re-pattern ".*")
19:14	clojurebot	#".*"
19:14	justin_smith	the source of that function reveals the source of my confusion (. java.util.regex.Pattern (compile s))
19:16	TEttinger	,(java.util.regex.Pattern/compile ".*")
19:16	clojurebot	#".*"
19:16	TEttinger	I like re-pattern better :)
19:16	WorldsEndless	:)
19:17	jonathanj	,(macroexpand-1 '#".")
19:17	clojurebot	#"."
19:17	jonathanj	can you expand reader macros?
19:17	justin_smith	,'#(depends)
19:17	clojurebot	(fn* [] (depends))
19:17	TEttinger	that may be how it prints
19:21	justin_smith	is there something in plumatic/schema that turns off checks globally?
19:48	TimMc	I think regex literals are maybe special because they are cached statically in whatever class they end up as part of?
19:49	TimMc	Unlike #( they don't just expand to more Clojure.
19:51	TimMc	Hmm, can't back up that claim from reading code.
20:50	Trioxin	idk whether to keep learning clojure or just give in and use something like scala. I want to leverage the JVM and functional programming but clojure is so difficult to get used to coming from the likes of C#, javascript, and PHP
20:54	TEttinger	Scala's uh not that easy, having used both that and Clojure. Clojure's definitely different though
20:55	TEttinger	Scala seems like it should be simple to transition to from Java or C#, but there's a sort of internal conflict in the language between "should this be functional" or "should this be traditionally OOP"
20:56	Trioxin	hm
20:56	TEttinger	most developers in it seem to go the functional route even when OOP could be considered a better choice (for their application in Scala)
20:57	TEttinger	and the inheritance-swamped standard library is not terribly easy to navigate
20:58	Trioxin	meh
20:58	TEttinger	see the inheritance diagram for the List type. http://nurkiewicz.github.io/talks/2014/scalar/img/list-scala.png
20:58	Trioxin	why can't there just be a suffiently abstract cross development language that has horsepower and concurrency without having to jump into some awkward paradigm
20:58	TEttinger	concurrency seems to be the problem there
20:59	TEttinger	an unsolved problem. although depending on what you're doing, maybe consider IBM's X10 language, the winner of the DOD's challenge to make a better big-data-handling language
21:00	TEttinger	it's basically Java with good solutions for datacenter woes, like the locality of a computation (what machine is doing it and where) and of course the standard java++ things, like first-class functions and a lib that understands them
21:01	Trioxin	hm
21:01	TEttinger	it compiles to Java or C++ IIRC
21:01	TEttinger	which is nice, since it can be made to use either group of libs for the two platforms
21:01	TEttinger	it is bad for distributable applications.
21:01	TEttinger	it is not meant for that, it's meant for deployment on servers
21:01	Trioxin	meh
21:02	Trioxin	lol
21:02	TEttinger	its competitor in the last round was Chapel, by Cray and now open source
21:04	TEttinger	https://github.com/chapel-lang/chapel
21:04	Trioxin	i only need a new language for computationally expensive components. The rest I do in node and electron.
21:05	TEttinger	IMO chapel is a vastly better language design than X10, but because it doesn't have interop with any VMs, it's kinda limited compared to X10
21:05	Trioxin	so the jvm makes sense. i can package it in an installer if need be
21:05	TEttinger	hm
21:06	TEttinger	so if you're aiming for commodity-desktop-scale concurrency, I don't really know anyone targeting that currently, other than clojure to an extent
21:07	TEttinger	clojure can do well there, but with "only 4" or "only 8" threads, the speedup is not especially major compared to GPGPU stuff
21:08	Trioxin	I'll be forced to c++. i know it and then i'll have to code for each platform
21:13	Trioxin	maybe node can do it. there is forking and the cluster api. of course I have to consider mobile as well. maybe one day I'll create my own language.
21:21	tolstoy	Clojure seems so much more tractable, and much simpler than Scala (or similar). If you can see it as foo(a, b) rather than (foo a b) you'd think there's nothing to it.
21:21	tolstoy	But there's Frege for Haskell-likeness, or Groovy for dynamic-like, and Kotlin, for a simpler Java (I think).
21:22	TEttinger	yeah, I see more and more Kotlin projects
21:22	TEttinger	seen some interesting Frege stuff, I think it compiles to Java source
21:23	tolstoy	Kotlin has the Swiftian ?. suffix for nullable types? Huh.
21:24	tolstoy	TEttinger: Frege's compiled to byte code. Says so right on Wikipedia! :)
21:27	justin_smith	TEttinger: sadly, frege can neither implement nor define interfaces
21:27	justin_smith	(that was the deal breaker for me)
21:28	TEttinger	The compiler reads Frege source files and produces Java source files that are normally subsequently compiled to class files.
21:28	TEttinger	https://github.com/Frege/frege/wiki/Compiler-Manpage
21:28	Trioxin	I'm a big fan of jetbrains. I'd seen kotlin but question how much of following and contribution it will have.
21:28	tolstoy	Oh.
21:28	TEttinger	mwahaha
21:29	TEttinger	Trioxin: in the java circles I've been in people are switching fairly often
21:29	TEttinger	it helps that IntelliJ can convert java to kotlin
21:30	Trioxin	one thing missing I see.. ios
21:30	TEttinger	now that RoboVM is out for the count, that's a tricky one
21:30	TEttinger	Multi-OS Engine from Intel is the current thing in the works
21:31	Trioxin	hmm. kotlin might be the answer
21:31	Trioxin	if interop is super good
21:32	tolstoy	This seemed kinda interesting: some sort of Compile Clojure to ObjC or something: https://github.com/galdolber/clojure-objc
21:32	TEttinger	https://software.intel.com/en-us/multi-os-engine
21:33	Trioxin	yeah was just reading there
21:33	TEttinger	yeah from what I can tell kotlin can be translated to and from java automatically
21:33	TEttinger	not sure how well it does
21:33	TEttinger	they seem close for interop
21:33	TEttinger	I've considered changing some stuff towards it
21:39	TEttinger	oh, and jtransc I looked into, it seems very capable of an "interesting" build cycle.
21:40	TEttinger	it compiles jvm .class files to haxe source, where it can be compiled to many platforms including native stuff for phones (iOS and Android)
21:41	TEttinger	but it can also, if your haxe libraries of choice are roughly compatible with your java libs, run without the lengthy C++ compilation step and go directly run from the .class files
21:42	TEttinger	so in theory you only need to compile from (in clojure, it would probably be an uberjar) when you deploy or test on a device