#clojure – 2015-07-07

2015-07-07

02:42	tmtwd	so, I can write an app in clojure , put it into a jar, and then it can be deployed on any machine with a jvm?
02:42	justin_smith	tmtwd: yes, "lein uberjar" makes it pretty easy
02:42	tmtwd	that is sweet
02:43	tmtwd	so if I pass someone a jar to run, they needn't even know it was written in clojure?
02:44	justin_smith	tmtwd: not neccessarily, though it will contain clojure source code :)
02:44	tmtwd	thats really cool
02:44	justin_smith	tmtwd: I did have an issue with one client, where we couldn't use clojure any more because they discovered we were using clojure because they were trying to use static analysis tools, and those don't work on clojure.
02:45	justin_smith	that's was a weird way to say that
02:45	justin_smith	anyway, we secretly shipped clojure, and it was fine until they cound't run their SA tool
02:45	tmtwd	bummer
02:45	amalloy	justin_smith: their static analysis tools worked well enough to tell what language was being used. sounds good to me
02:46	justin_smith	amalloy: heh - they were source level analysis tools :P
02:46	justin_smith	but it wasn't until trying to run the tools that they noticed we were shipping .clj
04:19	J_A_Work	query about reagent and field focus: https://groups.google.com/forum/#!topic/reagent-project/RNk998XWxtw
04:24	joschka	What am I doing wrong that I have to evaluate my functions `in the correct order` after I do (cider-jack-in). A simple (cider-eval-buffer) doesn't do it, I always end up with an "Unable to resolve symbol x" error because some later on positioned function wasn't evaluated yet. The functions don't need to be in 'some order' in the file right?
04:24	joschka	I feel like such an idiot asking that question :D
04:27	joschka	upon starting using (cider-jack-in), (ns-publics) retuns an empty map, shouldn't all functions be evaluated anyway right from the beginning?
05:29	pyr	hi clojure!
05:30	pyr	is there a generally accepted way of using component when you need an arbitrary number of components for a specific functionality
05:30	pyr	e.g: your app may open one to n "input sinks" which will adhere to a specific protocol, but you can't know in advance how many
05:31	pyr	does component cater to this ?
07:20	magnars	joschka: Clojure is evaluated top-down, so you should define functions before they are used.
08:03	joschka	magnars: yes, thank you I already found (declare [&forms]) and all of the logic behind top down evaluation
08:50	elvis4526	hey, so i tried using H2 to mock a database, but my existing postgresql seem to not works right away with H2 :-()
08:50	elvis4526	I get this: "org.h2.jdbc.JdbcSQLException: Attempt to define a second primary key; SQL statement:"
08:51	elvis4526	Is there any specific way I need to handle references to other fields when using H2 compared to postgresql ?
08:53	elvis4526	uh, I think I just need to quote the identifiers
09:28	elvis4526	okay i just switched to sqlite instead lol
09:29	justin_smith	joschka: yes, in clojure functions need to be defined in order
09:29	justin_smith	joschka: amazing, but true
09:29	justin_smith	sorry, someone already said that
10:19	dstockto1	new videos seem to have been posted on clojuretv
10:21	puredanger	yeah, day 2 should be going up today
10:21	oddcully	woohoo
10:22	dstockto1	cool, still waiting for the om next one
10:22	puredanger	not sure they'll get to all of them today
10:40	nooga	anyone using manifold? I'm looking for a decent way to model a stream "valve"
10:49	Manaphy91	I have a big hash map that cause a stack overflow... I use it like an advice for a dynamic programming algorithm... how can I evaluate memory size of a data structure?
10:57	TimMc	Manaphy91: Three things.
10:57	expez	(ArrayList.) What is the .? I thought this was a reader macro?
10:58	TimMc	One, do you mean an out of memory error? I'm not sure how a hash map would cause stack overflow.
10:58	TimMc	Two, advice... is this like memoization? Not really important here, just curious.
10:59	oddcully	expez: ctor call
10:59	oddcully	expez: new ArrayList() in javanese
10:59	TimMc	Three, evaluating the size of a data structure in Clojure in particular and in the JVM in general is actually really difficult. Might be possible, but it basically isn't done.
10:59	Manaphy91	exactly memoization!!
10:59	expez	Manaphy91: the jvm doesn't have tail call elimination. You're likely using a recursive algorithm without using loop/recur. If you were actually running out of memory you'd get OutOfMemoryError and not StackOverflowError
10:59	TimMc	OK, cool. :-)
11:02	Manaphy91	exactly I obtain 'Exception in thread "main" java.lang.StackOverflowError, compiling:(/tmp/form-init8694410201665152526.clj:1:72)`
11:02	expez	oddcully: yes, but what is the '.'? I thought this was a reader macro, which would be replaced by a constructor call at read time, but the reader returns "(ArrayList.)". I suppose I've answered my own question, and the "." is another token the compiler reads and replaces with a call to the constructor.
11:05	expez	Manaphy91: You need to read about loop/recur. This might be an OK source if you don't have your favorite clojure book at hand: https://blog.8thlight.com/patrick-gombert/2015/03/23/tail-recursion-in-clojure.html
11:06	oddcully	expez: ah sorry, i took that for an less advanced question
11:07	Manaphy91	expez: I know what are loop and recur... I don't understand why I obtan stackoverflow and I think it is due to extreme memoization....
11:09	expez	Manaphy91: That won't give you a StackOverflow error but a OutOfMemoryError. Allocate more memory to your jvm and you'll get the same result. Allocate a bigger stack and your program might start to run, depending on how deep the recursion is.
11:41	justin_smith	Manaphy91: memoization does not cause StackOverflow
11:41	justin_smith	Manaphy91: manual recursion (self call not using "recur") will
11:41	justin_smith	Manaphy91: recur isn't just for loop, it is for functions too
11:42	justin_smith	,((fn [x] (if (> x 10) x (recur (+ x 3)))) 4)
11:42	clojurebot	13
11:44	justin_smith	Manaphy91: oh, I just scrolled up - in order to use a hash map to drive a dynamic programming algo, I would use trampoline
11:44	justin_smith	(doc trampoline)
11:44	clojurebot	"([f] [f & args]); trampoline can be used to convert algorithms requiring mutual recursion without stack consumption. Calls f with supplied args, if any. If f returns a fn, calls that fn with no arguments, and continues to repeat, until the return value is not a fn, then returns that non-fn value. Note that if you want to return a fn as a final value, you must wrap it in some data structure and unpack it after trampoline returns."
11:44	Manaphy91	Yes, you are right!! I'm try to debug it! Any advice about debug in clojure? Usually i do a lein run and simply redirect output!!
11:45	justin_smith	Manaphy91: there's a few options. A simple one is to define an atom (def debug (atom nil)) and somewhere in your code call (reset! debug x), then you can play with that data as captured at that point in your code
11:45	justin_smith	Manaphy91: there's also tools.trace
11:45	justin_smith	Manaphy91: depending on editor preference, there is good debugging support in cursive (intellij idea) and cider
11:48	Manaphy91	I use vim, sorry but i'm not in emacs church...
11:48	Manaphy91	I'm seeing tools.trace
11:50	justin_smith	Manaphy91: the atom based things has other variants too like (def debug (atom [])) ... (swap! debug conj {:context ... :values {...}})
11:52	Manaphy91	justin_smith: thanks!!
11:55	justin_smith	Manaphy91: my experience is that in a repl, if I can capture the values where the problem was happening, I can quickly sort out the answer (by rewriting interactively in the repl until I get the return value I want, or using those values as the basis for a unit test, or rewriting the code the generated those values...)
11:56	justin_smith	Manaphy91: one of the main things I have learned with Clojure is how sane values are. Functions and macros and Objects are so opaque and weird, but values are very straightforward.
11:59	justin_smith	Manaphy91: also, about the stack overflow / hashmap size thing - Clojure won't store a hash-map on the stack as far as I know
12:02	amalloy	it can't. objects are all on the heap, with only pointers on the stack
12:03	justin_smith	amalloy: I suspected that, but lacked proof / motivation to research right now :)
12:03	amalloy	the JIT may be able to move some stuff to the stack via escape analysis or something, i dunno
12:04	justin_smith	right, but the JIT is not about to "optimize" by blowing the stack
12:49	br0tat0chip	hi! i just started playing around with clojure and i got a little program working that updates some values in redis. does anyone have a good resource on websockets or how to get that to stream real time to a front end? ive done some research but not sure which is the simplest/straight forward way to go
12:58	elvis4526	I'm trying to understand clojure hiearchy system. I'm not sure I understand what you can use with (derive) ?
12:58	elvis4526	can you use something else than ::keyword ?
12:58	justin_smith	elvis4526: it creates heirarchies that will effect isa? and multimethod dispatch
12:59	justin_smith	elvis4526: you can use regular :keywords, or namespaced ::keywords, and use those keywords to mark more complex objects like records or maps
12:59	justin_smith	,::foo ; just a shorthand
12:59	clojurebot	:sandbox/foo
13:00	justin_smith	elvis4526: the idea is that it creates an abstract heirarchy, decomposed from any concept of implementation or datatype
13:01	justin_smith	you can even create purely functional anonymous local heirarchies (though derive uses the mutable global heirarchy by default)
13:02	elvis4526	okay but then why something like (derive :user ::record) doesn't work ?
13:03	justin_smith	elvis4526: oh, right - you do need to use namespaced keywords
13:03	justin_smith	I forgot
13:03	justin_smith	,(derive :foo/bar :foo/baz)
13:03	clojurebot	nil
13:07	elvis4526	Oh okay - then i guess what I don't understand is namespaced keywords. What's the default namespace of :keyword ?
13:07	justin_smith	elvis4526: ##(namespace :foo)
13:07	lazybot	⇒ nil
13:07	elvis4526	yep that's what I get in a fn
13:07	justin_smith	,(namespace :foo/bar)
13:07	clojurebot	"foo"
13:07	elvis4526	why ?
13:07	justin_smith	,(namespace ::foo)
13:07	clojurebot	"sandbox"
13:08	justin_smith	elvis4526: because :foo has no namespace, ::foo has your current namespace, and :bar/foo has "bar" as a namespace
13:08	justin_smith	maybe that doesn't really answer why though
13:53	amalloy	justin_smith: since you're listing valid namespace forms: do you remember what the rarely-seen ::foo/bar does?
13:54	justin_smith	amalloy: expands the alias in the current namespace for foo
13:54	justin_smith	eg if you had (require '[clojure.string :as s]) ::s/bar would be :clojure.string/bar
13:54	justin_smith	iirc
13:54	Bronsa	yup
13:54	amalloy	dangit nobody ever remembers that. how am i ever gonna get to be the joker if everyone gets my riddles
13:55	justin_smith	amalloy: you might be conflating your batman villians
13:59	elvis4526	okay, I'm trying to imitate the concept of "parent constructor" in an OOP paradigm
13:59	elvis4526	maybe this will be more clear
14:00	elvis4526	but I'm really confused with what exactly is the relation with (derive) and the multimethods system
14:00	justin_smith	elvis4526: there is no relationship of functionality, only a relationship of identity
14:01	justin_smith	elvis4526: if there is no extension of a multimethod to ::foo, but ::foo is derived from ::bar and the multimethod is extented to ::bar, the method for ::bar will be called
14:01	justin_smith	if that helps
14:02	puredanger	it allows you to create an arbitrary hierarchy, that will be used to find method matches as with the Java OO hierarchy
14:03	justin_smith	yeah, I think that's a better way to put it, thanks
14:06	puredanger	I believe that there is a section covering multimethod hierarchies in Joy of Clojure, although I don't have the second edition to verify
14:07	justin_smith	I fleshed out some multimethod / heirarchy examples on http://conj.io too
14:09	lvh	Is it okay to read resource files in project.clj? I have a few SSL certs/keys for testing (pem files), I need them as strings in env (using weavejester's environ)
14:09	lvh	The obvious way to add things to env is through project.clj
14:09	justin_smith	elvis4526: my examples here http://conj.io/store/v1/org.clojure/clojure/1.7.0-beta3/clj/clojure.core/defmulti/
14:11	justin_smith	elvis4526: specifically example 4 is all that is relevant here I guess
14:24	chomwitt	why (str ["3"]) => "[\"3\"]" ? why do we quote? doublequotes?
14:26	lvh	Can I use the contents of a file in project.clj? I'd prefer to not have to copy-paste a big blob, but it seems like everything's quoted and I can't actually eval a thing.
14:31	oddcully	chomwitt: have you meant ,(apply str ["1"]) maybe?
14:32	snowell	lvh: You can wrap your `defproject` in a `let` and eval things up there to use inside
14:32	snowell	Whether or not that's a good idea in practice I'll leave up to the experts :)
14:32	lvh	snowell: oh, I didn't realize that worked
14:32	lvh	I guess it makes sense that it would :)
14:44	arrdem	hyPiRion: can I make lein use a file other than project.clj for the same purpose as project.clj?
14:56	chomwitt	oddcully: nop
14:58	amalloy	arrdem: `ln -s my-dumb-file.xml project.clj`
15:07	arrdem	amalloy: I thought not
15:08	amalloy	arrdem: there was that april fools joke lein-xml
15:08	amalloy	but it is not really what you want
15:09	the-kenny	well if lein-xml can read project.xml as xml we can at least represent the xml as sxml :)
15:29	{blake}	OK, I'm opening a DB connection like (def connection (up-connect)). But I want to put that in a function I can call at startup. Is possible? Or am I missing the boat/convention?
15:29	TimMc	something something component
15:30	{blake}	something something what? Is that what components are for? (Speaking of boats/conventions missed.)
15:31	TimMc	{blake}: https://github.com/stuartsierra/component might be appropriate for you
15:31	TimMc	I've not used it myself, mind.
15:32	lodin_	Is it recommended to prefix a library's core namespaces with libraryname.core, where the core namespaces would be those that define public protocols, functions using those protocols, etc, and non-core would be data structures that implement the interfaces in the core?
15:32	{blake}	TimMc: Yeah, I've stared at it more than once. I somehow didn't think of it in this context.
15:32	{blake}	But I guess that's "Database access: query and insert functions sharing a database connection" right there. :-/
15:34	TimMc	lodin_: "core" is just a default that lein uses because it needs something -- you don't want single-segment namespaces.
15:35	TimMc	As for the overall pattern (ignoring the actual name), that's not a pattern I've seen, I think. Maybe a good idea, though!
15:35	lodin_	TimMc: Yeah, I know. I want to distinguish between the necessary parts of the library, and the "batteries included" part.
15:36	{blake}	Are there local statics?
15:37	lodin_	TimMc: The alternative would be to just have the core namespace in the library, and have all actual implementations in other libraries, but that doesn't feel quite right. (At it would e.g. make testing harder.)
15:37	amalloy	{blake}: in...what? clojure? java? some weird library? certainly not in the first two cases
15:37	amalloy	but it's not 100% clear what you mean by local statics anyway. if you mean like in C, those are just sugar over a global static
15:38	jkni	lodin_: there's mention of that sort of organization using something like an impl namespace in Joy of Clojure 2e p. 199 but you won't really see it a lot at large
15:39	{blake}	amalloy: In an OO context, I would have a function that referenced a property. Like a DB connection. When you said "myconn := DB connection", the DB class would go look at connection, and return the value if the connection had been made, or make it, then return it, if not.
15:39	{blake}	Even in a non OO context, I would have a function with a local static that did the same thing.
15:40	{blake}	But if I say in Clojure (def connection)...and then later try to put something in connection? That's not even a thing, is it?
15:40	amalloy	{blake}: so, that is kinda dangerous to do carelessly because of multithreading
15:40	amalloy	but you can easily enough define a delay that you deref every time, or a memoized function that you call or whatever
15:41	lodin_	TimMc, jkni: I'm going for this then. lib.core.X I mean.
15:41	{blake}	amalloy: Oh, a memoized function...yeah, that sounds right. That's what I'm trying to do, and I'd just forgotten how.
15:41	justin_smith	{blake}: an option I have done lately is to use an agent for things like that (agent instead of atom because atoms retry, and I wouldn't really want to retry db connection process)
15:41	TimMc	amalloy: Oho, C-M-SPC leaves the point where it is. This is better than my approach for copying sexps. :-P
15:42	justin_smith	{blake}: though if it won't be altered or redefined at runtime, a delay or memoize makes sense, yeah
15:42	amalloy	TimMc: it even lets you copy multiple sexps easily!!1!
15:42	TimMc	yeah
15:42	{blake}	justin_smith: I'll check it out. Yeah, I don't want to use delay.
15:43	justin_smith	{blake}: why not a delay? you would want to alter it later?
15:43	{blake}	I mean, the larger situation is that I have "(def connection (up-connect user pass))" and that gets called when I making the WAR, which upsets my dev-ops guys.
15:43	{blake}	er, no "I" there.
15:43	justin_smith	{blake}: right, and a delay prevents that
15:44	justin_smith	though it requires a deref, but so would eg. an agent
15:44	justin_smith	and a deref vs. needing to call a memoized fn is like, 6 of one half dozen of hte other
15:45	{blake}	Oh, sorry. I think of delay as "delay(milliseconds)". =P
15:45	justin_smith	,(def d (delay (println "FORCED!")))
15:45	clojurebot	#'sandbox/d
15:45	justin_smith	,d
15:45	clojurebot	#object[clojure.lang.Delay 0x5d27ad7d {:status :pending, :val nil}]
15:45	justin_smith	,@d
15:45	clojurebot	FORCED!\n
15:45	justin_smith	,d
15:45	clojurebot	#object[clojure.lang.Delay 0x5d27ad7d {:status :ready, :val nil}]
15:45	justin_smith	,@d
15:45	clojurebot	nil
15:46	{blake}	justin_smith: Groovy. Thanks!
15:46	{blake}	(inc justin_smith)
15:46	lazybot	⇒ 271
15:46	justin_smith	I like delay for things that won't be rebound, it's simpler (weaker) than the other reference types
15:46	justin_smith	which means I can trust it more
15:46	{blake}	Well, I'm gonna make my own reference type. With blackjack and hookers. In fact, forget the referencing!
15:57	amalloy	justin_smith: there was a fun bug in the error-handling for delay in versions earlier than like 1.4 or so
15:57	justin_smith	oh?
15:58	amalloy	eg, consider (let [s "whatever", t nil] (delay [(.length s) (.length t)]))
15:59	amalloy	well, actually, it is better like this: (let [s "whatever"] (delay [(.length s) (/ 1 0)]))
15:59	amalloy	the first time you dereference that delay, you get an aritmeticexception about divide by zero, as you'd expect
15:59	amalloy	if you dereference it a second time, you get a null pointer exception on s
16:00	TimMc	hah, right
16:00	amalloy	(this isn't true anymore, but it was then)
16:00	TimMc	This is the :once thing.
16:00	amalloy	yes
16:01	amalloy	the macroexpansion of delay promises to call the thunk only once, but if the thunk threw an exception it would actually be called multiple times
16:01	Bronsa	amalloy: how was it fixed? by caching the exception?
16:01	amalloy	yes
16:01	amalloy	you could also imagine fixing it by throwing a BrokenPromiseException or whatever
16:02	{blake}	Why would there be a null pointer exception on s the second time?
16:02	Bronsa	:once can be really tricky
16:02	Bronsa	{blake}: the local is set to null after it's used
16:03	Bronsa	{blake}: a memory optimization that clojure uses to avoid blowing up the heap in certain situations
16:03	{blake}	Right, but--okay, so that's what gets cached, the null.
16:03	justin_smith	any votes for best kafka wrapper for clojure?
16:03	{blake}	samsa/core?
16:04	{blake}	(I'm kidding. Don't go looking for that.)
16:04	justin_smith	{blake}: if I ever make a kafka wrapper for clojure I will name it starvation-artist
16:05	dnolen	Bronsa: on my work machine ~40ms for clojure.tools.reader to read cljs.core, ~70ms for cljs.tools.reader
16:05	TimMc	Hey, can someone remind me of the common problem people encounter with protocols where they implement the wrong thing? Like, the interface or something?
16:05	dnolen	I believe my work here is done :D
16:05	justin_smith	TimMc: like they import the protocol as a class but don't require the ns?
16:06	justin_smith	that's common enough an error
16:06	amalloy	TimMc: implementing the interface is fine. a problem is using the interface via (.m x) instead of the protocol function via (m x)
16:06	TimMc	No, something that causes Foo != Foo errors.
16:06	amalloy	TimMc: reloading
16:06	justin_smith	TimMc: reloading
16:06	TimMc	amalloy: Hmm, maybe that was it.
16:06	{blake}	Nice. I think I would make one called "Gatekeeper" that didn't work but just lagged and lagged and lagged, and then finally said "This was assigned only to you".
16:06	dnolen	Bronsa: nearing 2 orders of magnitude speed improvement over master
16:06	TimMc	I think this one wasn't about reloading.
16:07	Bronsa	(inc dnolen)
16:07	lazybot	⇒ 22
16:07	Bronsa	dnolen: can't wait for a patch :)
16:07	dnolen	Bronsa: question is when/how you want it
16:07	dnolen	it relies on ns being present, which requires ClojureScript master
16:07	dnolen	and resolve-ns, things like that
16:08	Bronsa	dnolen: right. As I said a while ago, we need to release the new t.r at the same time as the new cljs
16:09	Bronsa	dnolen: I'll take the patch whenever it's ready and you tell me when you're ready to release cljs, I'm in no hurry
16:09	dnolen	Bronsa: OK it might be a while then - switching to analyzer/compiler perf work now
16:28	expez	Is cljs in cljs going to eliminate :refer-macros?
16:29	Bronsa	expez: IUC there will be no changes to how ns/macros work
16:43	nemelex	i'm new to clojure, can anyone tell me why i'm being silly by expecting this to work? ... http://pastebin.com/xKvzLVNa
16:45	justin_smith	nemelex: where is the entry namespace? why is it referred to but not required?
16:46	justin_smith	wait, that's probably just a small mistake in simplifying the code
16:46	nemelex	sorry, i skipped that ns off, but it is there - it's my internal thing
16:46	justin_smith	"Wrong number of args (0) passed to: PersistentArrayMap" means "too many parens around a hashmap"
16:46	justin_smith	,({})
16:46	clojurebot	#error {\n :cause "Wrong number of args (0) passed to: PersistentArrayMap"\n :via\n [{:type clojure.lang.ArityException\n :message "Wrong number of args (0) passed to: PersistentArrayMap"\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" 28]\n [sandbox$eval25 invoke "NO_SOURCE_FILE" 0]\n [cloju...
16:46	justin_smith	viz
16:47	justin_smith	you'd have to look at the code for create to see where that is happening I guess
16:47	nemelex	ah ok, i assumed it was happening when i was passing body to create
16:48	nemelex	i'll have another look -- thanks
16:57	markmm	Is there a emacs shortcut to sync the cider repl with a buffer you have changed
16:57	markmm	?
16:58	arrdem	markmm: with or without saving the buffer?
16:58	arrdem	markmm: C-c C-k will reload a file
16:58	markmm	arrdem: Ok thanks
16:59	arrdem	I think C-c C-l will evaluate the buffer whether it's saved or not but I'm not sure
17:04	markmm	arrdem: Yes it does do that, just tested it thanks
17:29	cfleming	amalloy: Sorry, I've been offline at a conference. The expiration is only for the beta, once it's stable upgrades will not be required.
19:35	whodevil	hello, I'm using lein ring uberwar then deploying it to tomcat which is running in debug mode, for some reason when I connect cursive to tomcat, it is not finding the namespaces. Is there something special I have to do to get cursive to pick up the bread crumbs?
19:40	whodevil	ok, I'm dumb, nevermind nothing to see here.
20:00	tolstoy	When using datomic free in-memory, is there a way to remove all the AWS dependencies other than exclude each and every one of them?
20:04	arrdem	Nope. Welcome to raw Maven.
20:04	tolstoy	Oy. ;)
20:05	arrdem	That'd actually be an interesting project, define logical groups of dependencies and write a Maven wrapper that can describe exclusions and replacements...
20:05	tolstoy	Seems like of datomic-free doesn't support aws, etc, it ought not to depend on it.
21:20	jefelante	#/python
21:20	jefelante	oops
22:37	puredanger	arrdem: you can do that in Maven with profiles
23:27	gfredericks	has anybody implemented a clojure collection that can keep arbitrary updated aggregations about itself?
23:27	gfredericks	I think finger trees can do that, but might be too general?
23:28	TEttinger	updated aggregations?
23:28	TEttinger	like remembering history?
23:28	gfredericks	no
23:29	gfredericks	like a map-reduce for arbitrary functions
23:29	gfredericks	I want to say just reduce but you wouldn't want it to be order sensitive
23:30	gfredericks	so the same kind of thing the hipster datastores use
23:30	TEttinger	I have no idea what you mean
23:30	gfredericks	word count!
23:30	TEttinger	do you mean a storage for transducers or something?
23:30	gfredericks	[{:sentence "hello there"} {:sentence "some more words"}]
23:30	gfredericks	^ the collection would have precomputed the word count to be 5
23:30	TEttinger	ahhhhh
23:31	gfredericks	and as you add/update items in the collection it efficiently updates the word count
23:31	amalloy	i think such a thing is too general to have an efficient implementation really, aside from one that says "you do all the work yourself"
23:31	gfredericks	really? what about the hipster databases?
23:31	amalloy	you need some constraints on what the function can do
23:32	gfredericks	yeah it'd have to be whatchamacallit
23:32	gfredericks	commutative
23:32	turbofail	and associative
23:32	gfredericks	the reduce part I mean
23:32	gfredericks	yeah
23:32	gfredericks	reducers already has this kind of logic does it not?
23:32	amalloy	it also has to be invertible, or something like it
23:32	gfredericks	I don't think so; maybe I didn't explain it well
23:33	gfredericks	if an item changes you just recompute the function for that item
23:33	amalloy	gfredericks: but then you need some properties for the function "combining" all this stuff at the top level
23:34	gfredericks	just the commutative/associative part, right?
23:34	amalloy	no
23:34	gfredericks	if you store a tree of values
23:34	gfredericks	then you just walk up to the root
23:34	gfredericks	doing your log(n) work
23:34	ttt_fff	are the slides from https://www.youtube.com/watch?v=ByNs9TG30E8& available anywhere? I want to know what om next isa bout without watching 46 minutes of video
23:35	amalloy	gfredericks: that is basically what finger trees do, and the thing you're storing is the measure, as i recall
23:35	amalloy	if you make the measure be something or other, then finger trees can efficiently concat/split
23:35	gfredericks	amalloy: yeah I figured finger trees could, I just didn't know off the top of my head if they were so general that you'd have to do manual work to wire it up
23:35	amalloy	but you can make it be something else and then you can keep a running sum of (f x)
23:39	ttt_fff	WTF IS OMNEXT about ?