#clojure – 2015-09-19

2015-09-19

04:34	Empperi	01:54 [rajaniemi] DCC SEND from crowgoose [37.187.79.138 port 43352]: virus.exe [13kB bytes] requested in channel #clojure
04:34	Empperi	01:59 [rajaniemi] DCC aborted receiving file virus.exe from crowgoose
04:34	Empperi	okey dokey
04:35	Empperi	got to say one has to be pretty desparate to try that on such a channel
04:55	ahoegh_	Empperi: crowgoose tried the same one me.
05:24	m1dnight_	Does anyone know how I can create .edn config files that can change after I created an uberjar? As it currently stands I have to recreate the uberjar each time I change the config.
05:31	mavbozo	m1dnight_, what's this config.edn file contains? can't you put the config.edn file somewhere outside the uberjar?
05:33	m1dnight_	Well, the thing I don't know exactly is, can I just put a relative path in the codebase then? So that, say, the foo.edn file is always in the root directory of the jar file?
05:34	m1dnight_	Maybe I can just play around with it. (edn/read-string (slurp (io/resource "servers.edn"))) This is how I read the config file at the moment.
05:36	mavbozo	you can run your uberjar with java -jar -Dconfig.location="/etc/my-app-config.edn"
05:36	mavbozo	and in your code, you can get the config.location with (System/getProperty "config.location")
05:37	TEttinger	m1dnight_: if it's a resource it's inside the jar. you can modify the jar to replace the resource I think
05:37	m1dnight_	oh that might be something Im interested in, mavbozo
05:37	m1dnight_	TEttinger: but the thing is that modifying/recompiling the jar takes some time and I would just like to stop and start it to re-read the config
05:37	m1dnight_	It doesnt have to be inside the jar.
05:37	m1dnight_	I will have a look at it right away!
05:37	TEttinger	or you can change it from a resource to just (edn/read-string (slurp "servers.edn"))
05:38	TEttinger	hm
05:38	TEttinger	if you had a resource called servers.edn and you tried to get a local file with the same name, it would prefer the resource I think?
05:38	TEttinger	not sure
05:39	m1dnight_	To the experimentation-mobile!
06:12	justin_smith	you need io/resource to get the resource inside the jar
06:12	justin_smith	then it finds the first one in the classpath
06:25	m1dnight_	I stranded on setting the system property and then reading in the files like this: (edn/read-string (slurp (io/file config-path file)))
06:25	m1dnight_	where config-path is the System/getProperty and file is the filename.
06:26	justin_smith	if you don't need to read anything inside the jar, that would work
06:27	m1dnight_	Exactly! If I want to change the path to a temporary database or w/e I dont have to recompile. Which is nice.
07:03	triss	there's not a function like swap! that returns the value before the function provided is applied is there?
07:11	m1dnight_	Afaik there is not, no.
07:12	Bronsa	triss: no, http://dev.clojure.org/jira/browse/CLJ-1454
07:13	m1dnight_	Does anyone know if its possible to fold with an index? I want to iterate over a list of integers and return the index (1-based) of the higherst value.
07:14	triss	okeydoke. keep a ref to previous value isn't too much hassle for now.... surprised how many times its been implemented tho
07:15	m1dnight_	Are refs not an option for the value as well?
07:15	m1dnight_	You could use (dosync (ensure x) (let [old-value @x] (ref-set! x new-value)))
07:15	m1dnight_	or somethiong
07:16	m1dnight_	You could use (dosync (let [old-value (ensure x)] (ref-set! x new-value))) even!
07:17	Bronsa	m1dnight_: using the STM for simple CAS semantics seems an overkill
07:17	m1dnight_	Well you can then store {:curr :old} in the atom and update the old in swap! function and read that out afterwards
07:17	Bronsa	m1dnight_: wrt your question, just use a tuple as acc value to your reducing function and keep track of the ids
07:18	Bronsa	and incur a map lookup everytime you need to access the value?
07:18	m1dnight_	and that would work in a concurrency setting as well as you get the new value returned and can read the "old" value from the result of swap
07:19	m1dnight_	a map lookup is about O(1).
07:19	m1dnight_	about
07:20	Bronsa	m1dnight_: that's irrelevant, it's always a c more than no lookup & forces you to (comp :new-value deref) rather than simply deref every-time you need to get the value
07:21	m1dnight_	Thats true. But the point is that you have to work with swap! and that it can not do what triss wants so you have to work around that.
07:21	m1dnight_	How would you do it?
07:22	Bronsa	m1dnight_: sure but there are better workarounds than the one you proposed, see http://dev.clojure.org/jira/browse/CLJ-1454
07:22	Bronsa	https://github.com/flatland/useful/blob/develop/src/flatland/useful/state.clj#L43 this one solution I like the most
07:22	m1dnight_	oh I see. yes the compare and swap one is much better idd
07:23	m1dnight_	Allright Bronsa, I stand corrected! :)
07:23	triss	cheers Bronsa
07:23	triss	and m1dnight_ !
08:12	gko	If I want to create a parser library with a default "main", should I use lein new app (that can be 'require'd to be used as any other library) or lein new default (and add "main" stuff myself) ?
08:52	triss	is it possible to make fireplace put evaluations output in to a vim buffer so I can refer back to it?
08:52	triss	i'd love to have a pane open with the output of the last few commands in.
09:02	triss	oh it seems :Last is doing the job
10:54	monsta	What is the differenct from using (vec (1 2 3)) and (into [] (1 2 3))
10:57	lodin_	monsta: I don't know, but I always use vec if what I want to do is to "cast" a sequence to a vector.
11:27	kavkaz	What is the most preferrable SQL library for Clojure? Is there one that most people use for backend stuff?
11:35	justin_smith	kavkaz: clojure.java.jdbc is probably the most used
12:21	xtrntr	can i interrupt a doseq?
12:22	tcrayford____	xtrntr: you can throw an exception to interrupt I guess :/
12:23	tcrayford____	there's no `break` keyword or anything else like that in clojure though
12:23	xtrntr	alright
12:23	xtrntr	thanks
12:24	tcrayford____	generally you'd just use `filter` to remove the elems you don't want to iterate over though
12:26	xtrntr	no, there's some kind of animation loop.. i suppose if i wanted to kill the animation halfway, i should put some kind of flag in the function?
12:26	xtrntr	or is that bad clojure?
12:29	noncom	xtrntr: user (loop) with (recur) then
12:29	tcrayford____	yeah, I'd vote for loop/recur
12:30	xtrntr	oh, there's a company named such
12:30	xtrntr	:)
12:37	justin_smith	xtrntr: if your processing of a sequence needs to stop arbitrarily, use reduce and reduced
12:37	justin_smith	use loop if you are doing something more complex than just walking along a sequence
12:38	justin_smith	,(reduce (fn [acc el] (if (> el 10) (reduced acc) (conj acc el))) [] (range))
12:38	clojurebot	[0 1 2 3 4 ...]
12:38	justin_smith	anyway, range is infinite, that's our proof the reduce stopped
12:38	justin_smith	*indefinite
12:39	justin_smith	,(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (conj acc el))) [] (range))
12:39	clojurebot	[0 1 2]
12:39	justin_smith	,(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (conj acc el))) [] (range))
12:39	clojurebot	[0]
12:39	justin_smith	,(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (conj acc el))) [] (range))
12:39	clojurebot	[]
12:39	justin_smith	,(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (conj acc el))) [] (range))
12:39	clojurebot	[]
12:39	xtrntr	i'm going to need time to get used to this..
13:01	noncom	how do i convert between js Date and cljs-time date ?
14:00	tolstoy	Something like: (cljs-time.coerce/from-long (.getTime (js/Date.))) ?
14:00	m1dnight_	Cljtime uses a lot of different formats
14:00	justin_smith	,(frequencies (repeatedly 1000 #(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (+ acc el))) 0 (range))))
14:01	clojurebot	{0 754, 1 129, 15 8, 21 4, 36 3, ...}
14:01	tolstoy	Oh, from-date. ;)
14:02	justin_smith	,(str (frequencies (repeatedly 1000000 #(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (+ acc el))) 0 (range)))))
14:02	clojurebot	"{0 749935, 153 2, 1 125070, 55 219, 15 7802, ...}"
14:03	m1dnight_	justin_smith: i was just looking for the frequencies today. Damn.
14:03	justin_smith	,(apply str (frequencies (repeatedly 1000000 #(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (+ acc el))) 0 (range)))))
14:03	clojurebot	"[0 750190][153 2][1 124774][55 247][15 7791][21 3912][136 3][91 28][36 995][6 31478][28 1906][3 62449][66 120][45 496][78 73][120 7][10 15513][105 15][190 1]"
14:04	justin_smith	,(apply str (sort-by second (frequencies (repeatedly 1000000 #(reduce (fn [acc el] (if (> (rand) 0.5) (reduced acc) (+ acc el))) 0 (range))))))
14:04	clojurebot	"[171 1][190 1][153 2][136 5][120 10][105 10][91 32][78 64][66 112][55 238][45 492][36 976][28 1965][21 3914][15 7745][10 15816][6 31466][3 62785][1 124896][0 749470]"
14:20	csd_	what's the simplest way to replicate common lisp's progv in clojure? http://clhs.lisp.se/Body/s_progv.htm -- i.e. where you pass it a map and it sets up let bindings for all the k-v pairs in the map
14:21	justin_smith	csd_: flatland/useful has a macro that does that
14:23	csd_	any idea what it might be named?
14:24	justin_smith	one moment
14:27	justin_smith	csd_: I either lost it or misremembered
14:27	justin_smith	csd_: it would require calling eval unless the hash-map is a compile time literal
14:29	csd_	nah the bindings need to be made dynamically
14:29	justin_smith	csd_: the problem is you don't even know what keys (therefore what symbols) might be bound
14:29	justin_smith	that requires eval
14:29	justin_smith	unless you have a list of possible symbols somewhere...
14:31	csd_	i'm trying to port this over from CL http://norvig.com/paip/patmatch.lisp
14:32	csd_	i think i'd know the all the key-side symbols of the let, but not the value-side
14:32	justin_smith	I guess you could implement your own ad-hoc binding / resolution mechanism that does not use clojure eval
14:32	justin_smith	but it won't be proper local bindings either
14:33	csd_	this sounds outside my depths
14:33	justin_smith	oh, wait, if you know all the possible left-hand-sides this might be a case for with-local-vars
14:33	justin_smith	(doc with-local-vars)
14:33	clojurebot	"([name-vals-vec & body]); varbinding=> symbol init-expr Executes the exprs in a context in which the symbols are bound to vars with per-thread bindings to the init-exprs. The symbols refer to the var objects themselves, and must be accessed with var-get and var-set"
14:34	justin_smith	oh no, never mind
14:34	justin_smith	csd_: couldn't you convert that code to use a hash map and do explicit hash-map lookups to get the values?
14:36	csd_	i guess, although not sure how off hand
14:39	csd_	seems doable i suppose
15:12	amalloy	justin_smith: that's certainly not in useful. the closest thing to that i've done is write an answer on stackoverflow saying it's a bad idea
15:34	justin_smith	amalloy: on the surface level, I was factually wrong, on a more real level, I was correct that you had the right answer
15:34	amalloy	haha
15:34	amalloy	very deep indeed
15:36	gfredericks	~this is not a case for with-local-vars
15:36	clojurebot	Ack. Ack.
15:37	mungojelly	i don't really understand how these leiningen dependencies work i guess i need to read something about it, does it actually look at these urls to find the dependency or what is it looking in
15:37	mungojelly	how do i say a dependency on flatland/useful, like how do i know which version to say? :/
15:37	justin_smith	mungojelly: it searches your repositories
15:37	justin_smith	it starts with like maven central and clojars and maybe sonatype
15:38	mungojelly	oh ok it just seemed to magically know everything in the universe
15:38	justin_smith	haha
15:39	mungojelly	so is what i should do search on maven/clojars myself to find what versions i might want to tell it to depend on?
15:39	justin_smith	there's a default config that sets up the first repositories for you (but it is possible to replace it)
15:39	justin_smith	mungojelly: if you are not sure what version to get, sure. Sometimes I just look at the version tag / readme on github too.
15:40	justin_smith	mungojelly: there is also "lein search" which takes a long time to build the index though...
15:40	justin_smith	mungojelly: another interesting thing to check is http://crossclj.info which shows who is using what version of what library (in open source at least)
15:41	mungojelly	that's what i had been doing was entering the lein dependencies line it tells you to on github readmes but when things didn't tell me what to say i discovered i didn't know how that magic worked
15:43	mungojelly	someone linked to crossclj.info and it was too interesting for me to have the bandwidth to understand it, that's so much information
16:03	noncom	what's the best way to get the 2 dates representing the beginning and the end of the current month?
16:05	gfredericks	with clj-time?
16:06	justin_smith	gfredericks: is there a reason not to use Calendar?
16:07	gfredericks	I don't know, I was just trying to figure out the background for the question
16:08	justin_smith	I mean I've only used the API a little, but I never see people recommending using it, and wonder why
16:10	Intey	jsutin_smith: Calendar is native and correspond to clojure.instant ?
16:11	justin_smith	Intey: the instant reader in clojure is java.util.Date, but things like "date for first and last days of a month" would be done with the Calendar api and not the Date api
16:11	justin_smith	and maybe that unintuitive split is part of why nobody likes those apis...
16:12	Intey	In clj-time, i see 3 funcs, for noncom question: now, start, end. I don't know, but with those can be done.
16:13	noncom	ah, sorry, yes, in clj-time (cljs-time to be precise, but there is not much difference)
16:13	noncom	in the emantime, i found the way - i take (now), make a new date with year and month - that's the start and then make the end with +1 month
16:14	justin_smith	,java.util.Calendar/UNDECEMBER ; 13th month of the year
16:14	clojurebot	#error {\n :cause "Unable to find static field: UNDECEMBER in class java.util.Calendar"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to find static field: UNDECEMBER in class java.util.Calendar, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6704]}\n {:type java.lang.RuntimeException\n :message ...
16:14	noncom	ahhaha :D
16:14	noncom	13th monh
16:14	noncom	java can do this
16:14	justin_smith	,java.util.Calendar/UNDECIMBER ; 13th month of the year
16:14	clojurebot	12
16:14	justin_smith	haha, spelled it wrong the first time
16:14	noncom	is it an easter egg?
16:14	justin_smith	no, it's a documented part of the api
16:15	noncom	:/
16:15	noncom	:D
16:15	justin_smith	,java.util.Calendar/WEDNESDAY
16:15	clojurebot	4
16:16	justin_smith	,java.util.Calendar/HOUR
16:16	clojurebot	10
16:16	justin_smith	OK, this is a weird API
16:16	noncom	really :)
16:18	justin_smith	noncom: OK, undecimber is there because localized calendars are supported, and the Hebrew calendar, among others, there is sometimes a 13th month
16:18	noncom	this makes sence
16:19	noncom	but the name is funny nevertheless :)
16:19	justin_smith	it is a weird name
16:19	justin_smith	https://en.wikipedia.org/wiki/Undecimber
16:19	justin_smith	but it's real
16:20	noncom	huh, so all this is serious..
16:20	noncom	good to know
16:21	justin_smith	it's justin_smith 's rule of locales: anything localized will support things you find hilarious
16:22	justin_smith	(see also unicode snowman)
17:46	rary	Okay, I've switched to idea+cursive. It is really nice, I like it!
17:46	rary	justin_smith: thank you for your advice again.
17:47	rary	rainbow parentheses are beautiful :)
17:51	rary	I am reading the Joy of Clojure now and authors write that if there would be a strong request to publisher, they will write a separate book about Clojure compiler implementation details
17:52	rary	Lets create a strong request, ha? :-) it will be definitely interesting reading.
18:47	obliviasimplex	hey, I seem to be having some trouble with Cider. M-x cider-jack-in gives me these errors and stack traces: https://bpaste.net/show/fcd37a267ba5
18:48	obliviasimplex	Anyone know what the trouble is here, and how to fix it?
18:57	domokato	is it possible to get the value of a var of a symbol passed into a macro? or does the value not exist yet?
19:00	domokato	this is in a namespace file to be compiled, not the repl
19:01	amalloy	domokato: you can do it, but it's more often a bad idea than a good one. what is the big picture?
19:05	domokato	maybe i'm trying to do something dumb, but I'm trying to write a macro that allows me to inherit fields between records. I don't intend to ever use the base record, so I've just defined it as a vector of symbols of fields and I'm trying to pass it into the macro, which would expand it into a call to defrecord
19:08	domokato	along with the additional fields
19:09	amalloy	inheriting fields between multiple records sounds like a bad way to get composite data. if you have N records which all need fields x,y,z, why not (defrecord Q [x y z]) and then just give those N records a single q field?
19:13	domokato	in my model, it just seems like a is-a relationship rather than a has-a
19:13	justin_smith	domokato: clojure really doesn't do is-a (at least not concretely)
19:13	domokato	alright, i'll just go with the has-a then :)
19:13	domokato	thx
19:14	justin_smith	it does is-a for interfaces (is-a thing that you can run this function on) but not data (no is-a thing that has these fields)
19:15	domokato	yeah, that's why i was trying to implement it, but seems to not be worth the effort
19:16	domokato	i guess it's a little bit annoying to do it the has-a way because I have to instantiate the inner record manually in every case
19:16	domokato	maybe it's okay...
19:17	justin_smith	domokato: using prismatic/schema you can do "has these fields" as an insertion, and using clojure.core/merge you can "inherit" it
19:17	justin_smith	s/insertion/assertion
19:21	domokato	i can't find any insertion
19:24	justin_smith	domokato: see my correction - I meant assertion
19:25	justin_smith	also, off topic but wow, I found a URL that can't be resolved, but if you paste it into chrome's browser bar it crashes the entire browser (not just one tab, the whole browser)
19:27	domokato	hm...don't see assertion either :(
19:27	domokato	https://github.com/Prismatic/schema ?
19:27	domokato	or do you just mean...do an assert?
19:27	justin_smith	yes, you can use s/defn for example to make a defn which asserts certain keys are present in some arg
19:28	justin_smith	domokato: sorry, I am talking about s/validate (and the other things which use that)
19:29	domokato	sorry, i'm unfamiliar with this library
19:31	domokato	yeah, i'm trying to use merge but i still have the issue of getting the value of a var from its symbol
19:32	justin_smith	in a macro?
19:32	domokato	yeah
19:32	justin_smith	in a macro, getting the symbol means too many layers of quoting
19:32	justin_smith	so if you are using ` you need ~ somewhere
19:33	domokato	i have a var like (def body-state ['sprite 'sprite-info]) and i'm passing body-state into the macro call, but when i unquote the the value passed in i get a var, i believe, not the actual vector
19:36	justin_smith	,(= ['sprite 'sprite-info] '[sprite sprite-info]) ; btw
19:36	clojurebot	true
19:36	domokato	ah
19:37	domokato	yeah, i noticed that
19:37	domokato	anyway, here's my macro right now: (defmacro pseudo-extend [name parent fields & remainder] `(defrecord ~name ~(apply merge parent fields) ~@remainder))
19:37	domokato	it works when passing in a vector literal, but not when passing in a vector var
19:38	justin_smith	,(apply merge [:a :b :c] [:d :e :f])
19:38	clojurebot	[:a :b :c :d :e ...]
19:38	justin_smith	weird
19:38	justin_smith	,(into [:a :b :c] [:d :e :f]) ; this is the normal way to do that
19:38	clojurebot	[:a :b :c :d :e ...]
19:40	domokato	oh okay nice
19:41	justin_smith	,(let [name 'n parent '[a b c] fields '[d e f]] `(defrecord ~name ~(into parent fields)))
19:41	clojurebot	(clojure.core/defrecord n [a b c d e ...])
19:41	justin_smith	that looks legit (if your args are of the types you think...)
19:42	justin_smith	but what I meant by using merge was not defining a record that has the merged field vectors, but using a map (or record) and using merge to get the default field key / values for things that you don't explicitly override in the hash-map
19:43	justin_smith	since defrecord is already using a hash-map like thing instead of an object, why not use hash-map merge to get default key / value pairs
19:44	domokato	i think your implementation that worked above isn't quite analogous to using defmacro
19:45	domokato	i just got it to work using: (defmacro pseudo-extend [name parent fields & remainder] `(defrecord ~name ~(into @(resolve parent) fields) ~@remainder))
19:47	justin_smith	domokato: that's a fair bit of work to do something records allowed already (you can merge an instance of a defrecord class with a normal hash-map)
19:49	domokato	right but i'm trying to inherit fields from another record. Not their values, just their declarations. I will use merge with normal hash-maps later to instantiate those fields
19:50	justin_smith	what good does inheriting declared fields do when defrecord allows associating any field you want to a record instance?
19:50	justin_smith	,(defrecord Foo [bar baz])
19:50	clojurebot	sandbox.Foo
19:50	justin_smith	,(assoc (->Foo 1 2) :quux 42)
19:50	clojurebot	#sandbox.Foo{:bar 1, :baz 2, :quux 42}
19:50	rhg135	performance if there's many instances with the extended fields
19:51	domokato	yeah, performance
19:51	rhg135	you did profile this right?
19:51	domokato	yeah
19:51	domokato	it's slowing down my draw loop considerably
19:51	domokato	keyword lookups in hash maps
19:52	domokato	that's why i'm changing everything over to use records instead of maps
19:53	rhg135	something about this feels wrong, but I can't think of anything better
19:53	domokato	tell me about it
19:53	domokato	:)
19:53	justin_smith	domokato: why not make those fields the render loop needs be the record fields, and associate other records into it (not just their fields)
19:57	domokato	if I have a bunch of records with BodyState as a field, every time I instantiate one of those I need to do (map->Thingy {:body-state (map->BodyState ...) ...}) rather than just (map->Thingy ...)
20:00	domokato	in my case i generally do (map->Thingy nil) first then merge in the data later
20:00	justin_smith	domokato: when you do that, you don't get any of the perf benefit
20:01	justin_smith	,(type (assoc (->Foo nil) :a 1 :b 2))
20:01	clojurebot	#error {\n :cause "Unable to resolve symbol: ->Foo in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: ->Foo in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6704]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol: ->Foo in this...
20:01	justin_smith	,(defrecord Foo [bar baz])
20:01	clojurebot	sandbox.Foo
20:01	justin_smith	,(type (assoc (->Foo nil) :bar 1 :baz 2))
20:01	clojurebot	#error {\n :cause "Wrong number of args (1) passed to: sandbox/eval49/->Foo--64"\n :via\n [{:type clojure.lang.ArityException\n :message "Wrong number of args (1) passed to: sandbox/eval49/->Foo--64"\n :at [clojure.lang.AFn throwArity "AFn.java" 429]}]\n :trace\n [[clojure.lang.AFn throwArity "AFn.java" 429]\n [clojure.lang.AFn invoke "AFn.java" 32]\n [sandbox$eval91 invokeStatic "NO_SOURCE_...
20:01	justin_smith	oops
20:01	justin_smith	,(type (assoc (map->Foo nil) :bar 1 :baz 2))
20:01	clojurebot	sandbox.Foo
20:01	justin_smith	oh, wait...
20:02	justin_smith	never mind, that only happens with dissoc
20:02	domokato	what does?
20:02	amalloy	well, it's still true you don't get much benefit if you're building records out of maps
20:02	justin_smith	,(type (assoc (dissoc (map->Foo nil) :bar) :bar 1 :baz 2))
20:02	clojurebot	clojure.lang.PersistentArrayMap
20:02	justin_smith	the dissoc makes it not be a record instance, even if you attach the field later
20:03	domokato	ah, good to know
20:03	amalloy	if you are using records for performance, which is rare but not unheard of, you should probably call the constructor yourself, or at least the ->Foo constructor rather than map->Foo
20:03	domokato	it's the access i'm worried about, not so much the instantation
20:06	domokato	the field accesses happen in the draw loop every frame. the instantiation happens at the beginning of the game or just once every few frames
20:07	justin_smith	domokato: another option to consider is ECS where instead of iterating over objects and accessing fields, you can directly iterate the fields
20:11	justin_smith	domokato: or a protocol, where you provide the data / functionality via protocol functions rather than via direct field access
20:12	phaseNi	is (swap! blah (fn [x] nil)) the same as (reset! blah nil)?
20:12	rhg135	how is polymorphic method dispatch faster than field access?
20:12	rhg135	in theory, yes, phaseNi
20:13	rhg135	semantically, rather
20:13	justin_smith	phaseNi: not quite, swap! retries if there is concurrent modification, reset! does not
20:14	justin_smith	rhg135: now I wonder, maybe it's not faster than hash lookup, that's a good point
20:15	phaseNi	justin_smith: Out of curiosity, in this case, would it really matter?
20:15	domokato	justin_smith: thanks, and everyone else too :)
20:15	phaseNi	justin_smith: it just changes the timing a bit
20:15	rhg135	you can't now if it'll matter
20:15	justin_smith	phaseNi: not just timing, also the resulting value if there is concurrent modification
20:15	rhg135	not without the rest of the things touching it
20:16	mungojelly	cache what the painter needs and make updates to that only as there are changes in the model
20:16	phaseNi	justin_smith: i mean if the other thread happened slightly slower the value would still be changed
20:16	phaseNi	s/slower/later/
20:16	justin_smith	phaseNi: if the other thread did a reset! this is not true
20:17	rhg135	~mutable state
20:17	clojurebot	mutable state is bad
20:17	phaseNi	heh
20:17	rhg135	it becomes dependant on the order of thiings
20:18	amalloy	justin_smith: i don't think you can ever tell (reset! a x) and (swap! a (constantly x)) apart, if no concurrent swap! function has side effects (other than the swap of course)
20:18	phaseNi	yes, what amalloy said is what i was thinking
20:20	justin_smith	hmm
20:27	justin_smith	rhg135: in my criterium test, polymorphic method access is much faster than defrecord field access, trying the tests again with type hints (tried unhinted first) and will paste the results
20:28	justin_smith	and hinted field access is pretty much identical to unhinted polymorphic method via defprotocol
20:29	rhg135	that is strange
20:29	rhg135	way to go jit
20:30	amalloy	hinting doesn't matter to protocols at all
20:30	justin_smith	and when hinted, the protocol method call is unchanged (uploading to refpheap now)
20:30	justin_smith	amalloy: haha, so I discovered
20:31	justin_smith	https://www.refheap.com/109749
20:32	justin_smith	rhg135: domokato: so, turns out where JIT applies, a protocol method is as good as field access on a record, and you can do composition of protocols much more cleanly than composition / "inheritance" of base record fields
20:33	rhg135	that is very strange
20:33	rhg135	I love the jvm
20:33	amalloy	justin_smith: fwiw the jit isn't the only thing optimizing those protocol method calls. if you had the same line of code dispatching to two different implementations in alternation, the inline cache would never hit
20:34	justin_smith	hmm, OK
20:34	amalloy	oh, and it makes a big difference whether the record implements the protocol inilne or was extended to it
20:34	justin_smith	oh yes, that is definitely true, I knew that one
20:35	rhg135	is the cache that big a factor?
20:37	amalloy	probably. avoids map lookup and hierarchy dispatch i would think
20:45	rhg135	it seems not to for me
20:49	justin_smith	rhg135: seems not to?
20:50	rhg135	https://www.refheap.com/109750
20:51	rhg135	not a huge difference per 100 iterations where one is a cycle of two types and the other is of one type
20:55	domokato	my records store changing state and are kept in atoms, so i don't think protocols would work here?