#clojure – 2009-03-27

2009-03-27

02:08	yangsx	I have an extended assert that print some additional info for debug purpose, but sometimes there is an assertion failure without preventing any such info at all at repl if the assertion is buried in some depth.
02:08	yangsx	Is that expected behavior?
02:08	yangsx	s/printing/preventing
02:36	hiredman	what kind of try/catch stuff do you have around the assertion?
05:10	Raynes	Weee my Clojure text editor is almost complete. Ya know. Creating substitutes for the basic applications that come with Windows is a great way to learn a language let me tell ya.
05:16	antifuchs	Raynes: congratulations
05:47	AWizzArd	Raynes: sounds nice
06:13	antifuchs	now to hack some more on the 3d modeller plugin - I think I should be able to print a clojure-generated 3d model in very few days (:
07:27	durka42	antifuchs: awesome, what library are you using?
07:27	antifuchs	I'm writing a plugin for Art of Illusion. this lets me interactively (in slime) write code that creates 3d models
07:28	antifuchs	that's inspired by a friend's MetaCADEvaluator plugin for same
07:28	durka42	nice
07:29	antifuchs	it is! it's rewarding on its own already, but since it's for a 3d printer, I even get to play with the stuff this creates afterwards (:
07:30	durka42	3d printers are nearly as cool as clojure
07:31	durka42	silly me i figured you meant "print" to screen
07:31	antifuchs	heh. I'm not yet decided on the ordering on coolness; but both are pretty awesome (:
07:31	durka42	but you meant print to _reality_
07:31	antifuchs	oh no. print to toy (-:
07:57	noidi	is there a function like nth that counds from the end of the collection instead of the beginning?
07:58	noidi	counts
07:58	noidi	in python i could use my_list[-2] to get the second-to-last item from a list
07:59	Cark	i dion't think there is
08:01	Cark	actually this might be a good sign you need a vector rather than a list
08:02	noidi	i'm using a vector, actually
08:03	Cark	ah well tyhen it's (get my-vector (- (count my-vector) 2)
08:03	noidi	thanks!
08:04	Cark	,(let [v [1 2 3 4 5]] (v (- (count v) 2)))
08:04	clojurebot	4
08:06	noidi	i'd like (nth [1 2 3 4 5] -2) better :)
08:07	Cark	you may write a function to do this =)
08:07	noidi	yeah, i know
09:01	antifuchs	hm, is there a way to get a more meaningful backtrace from clojure than what I'm seeing in slime right now? the top frame is always clojure.lang.Compiler.eval, followed by similarly useless ones /-:
09:03	antifuchs	(I got the issue resolved eventually, but it would have helped enormously to know which function the breakage was in)
09:09	drewr	antifuchs: Hit 1 to see expand each cause.
09:10	antifuchs	OH. wow. (:
09:10	antifuchs	I was so used to seeing one useful and one useless restart from sbcl that I completely ignored the second one
09:10	antifuchs	thanks!
09:10	sellout	antifuchs: Zing!
09:11	antifuchs	hey sellout (-:
10:29	AWizzArd	Do we have an expert for regular expressions here?
10:30	AWizzArd	I want to know what follows an underscore, but only if the string contains exactly one underscore
10:30	AWizzArd	(re-find #"" "hello_world") ==> world
10:30	AWizzArd	(re-find #"" "hello_sweet_world") ==> nil
10:31	hiredman	,(re-find #"{^_]_[^_]" "hello_world")
10:31	clojurebot	Illegal repetition {^_]_[^_]
10:31	hiredman	,(re-find #"{^\_]\_[^\_]" "hello_world")
10:31	clojurebot	Illegal repetition {^\_]\_[^\_]
10:31	hiredman	,(re-find #"[^_]_[^_]" "hello_world")
10:31	clojurebot	"o_w"
10:32	hiredman	,(re-find #"[^_]+_[^_]+" "hello_world")
10:32	clojurebot	"hello_world"
10:32	hiredman	,(re-find #"[^_]+_[^_]+" "hello_world_sweet")
10:32	clojurebot	"hello_world"
10:33	AWizzArd	I was thinking about negative lookaheads: an _ not followed by an underscore (re-find #"_(?!_)" some-string), but that does not work out
10:38	hiredman	,(re-find #"_[^_]+" "hello_world_sweet")
10:38	clojurebot	"_world"
10:38	hiredman	,(re-find #"_[^_]+" "hello_world")
10:38	clojurebot	"_world"
10:39	AWizzArd	They are all pretty close.
10:39	AWizzArd	These damn regexps ;)
10:43	hiredman	,(re-find #"_[^_]+$" "hello_world_sweet")
10:43	clojurebot	"_sweet"
10:43	hiredman	bah
10:43	hiredman	,(re-find #"[^_]_[^_]+$" "hello_world_sweet")
10:43	clojurebot	"d_sweet"
10:43	hiredman	snort
10:44	AWizzArd	I will do it manually
10:45	AWizzArd	hiredman: thanks for your suggestions
10:46	Chousuke	(re-find #"_[^_]([^_])*" "hello_word_test")
10:46	Chousuke	,(re-find #"_[^_]([^_])*" "hello_word_test")
10:46	clojurebot	["_word" "d"]
10:46	Chousuke	hm, interesting :P
10:48	Chousuke	,(re-find #"_[^_]([^_])+" "hello_word_test")
10:48	clojurebot	["_word" "d"]
10:52	Holcxjo	,(re-find #"^[^_]*_([^_]+)$" "hello_word")
10:52	clojurebot	["hello_word" "word"]
10:52	Holcxjo	,(re-find #"^[^_]*_([^_]+)$" "hello_word_test")
10:52	clojurebot	nil
10:52	Holcxjo	,(re-find #"^[^_]*_([^_]+)$" "helloword")
10:52	clojurebot	nil
10:53	Holcxjo	,(re-find #"^[^_]*_([^_]+)$" "_world")
10:53	clojurebot	["_world" "world"]
11:00	Holcxjo	,(map (fn [text] (let [match (re-find #"^[^_]*_([^_]+)$" text)] (list text (if match (nth match 1))))) (list "" "hello" "hello_" "hello_world" "hello__world" "hello_world_test"))
11:00	clojurebot	(("" nil) ("hello" nil) ("hello_" nil) ("hello_world" "world") ("hello__world" nil) ("hello_world_test" nil))
11:03	AWizzArd	This regexp which solves this "simple task" is protected against being found.
11:03	Holcxjo	AWizzArd?!?
11:04	AWizzArd	I mean, we can't find it.
11:04	Holcxjo	This one: #"^[^_]*_([^_]+)$" ?
11:04	AWizzArd	"Return what follows an underscore. Match only if the string contains exactly one underscore".
11:05	Holcxjo	That's what mine does. Or not?
11:05	AWizzArd	,(re-find #"^[^_]*_([^_]+)$" "hello_a_xyz")
11:05	clojurebot	nil
11:05	AWizzArd	,(re-find #"^[^_]*_([^_]+)$" "hello_a")
11:05	clojurebot	["hello_a" "a"]
11:06	AWizzArd	yes okay, this one is doing it, it seems
11:06	Holcxjo	Might want to make the last "+" a "*" in case the empty string is acceptable as being after the underscore
11:06	AWizzArd	,(re-find #"^[^_]_([^_])$" "hello_")
11:06	clojurebot	["hello_" ""]
11:07	AWizzArd	Holcxjo: grats :)
11:07	Holcxjo	np
11:14	AWizzArd	clojurebot: max people
11:14	clojurebot	max people is 164
12:05	tsdh	Does anyone have an example of :let in a for comprehension?
12:05	hiredman	,(for [x (range 10) :let [y (* x x)]] y)
12:05	clojurebot	(0 1 4 9 16 25 36 49 64 81)
12:06	tsdh	Thans, hiredman.
12:22	scottj_	Is anyone able to run the code from this genetic mona lisp solution? (http://npcontemplation.blogspot.com/2009/01/clojure-genetic-mona-lisa-problem-in.html) I get "java.lang.Exception: Unable to resolve symbol: draw-polygon in this context"
12:24	kefka	I asked this question last night and couldn't get a conclusive answer. Does Clojure have the problem of keywords and strings getting interned on reads, the way CL does?
12:24	kefka	The reason I'm asking is that I'm worried about memory leakage.
12:24	kefka	(Almost no one was on last night when I asked.)
12:25	scottj_	kefka: I think I remember Rich talking about that in one of his screencasts, probably the lisp one.
12:25	scottj_	strings are java strings, if that helps answer the question
12:28	scottj_	see fourth paragraph, http://netzhansa.blogspot.com/2008/10/trying-clojure.html
12:29	danlarkin	kefka: the reader does not intern
12:30	danlarkin	symbols, I know, at least
12:31	hiredman	depends what you mean by "intern"
12:32	hiredman	well
12:32	hiredman	hmm
12:35	brianh2	kefka: i've been poking around a little
12:35	brianh2	found this http://www.thesorensens.org/2006/09/09/java-permgen-space-stringintern-xml-parsing/
12:36	brianh2	which pointed to this http://www.javaworld.com/javaworld/javaqa/2003-12/01-qa-1212-intern.html
12:39	kefka	Ok, so it looks like there's nothing to worry about with symbols piling up and eating memory. Is the same true of keywords?
12:39	clojurebot	http://clojure.org/data_structures#toc10
12:40	brianh2	best i can tell, keywords are symbols & therefor interned in the permgen space
12:41	hiredman	erm
12:41	hiredman	I am pretty sure what gets interned is the string behind the keyword or symbol
12:41	hiredman	~def c.l.Keyword
12:44	cemerick	symbol and keyword strings are interned, and keywords themselves are interned as well (of course, using a separate facility from the standard lib's String.intern())
12:45	cemerick	Of course, there's nothing keeping you from creating a symbol whose string isn't interned.
12:45	cemerick	,(identical? 'foo 'foo)
12:45	clojurebot	false
12:45	brianh2	that's semantics. but ok. to be precise. it would appear that every keyword that is created generates a symbol that is then placed into a map as the key to the keyword itself
12:46	cemerick	yeah.
12:47	brianh2	that symbol causes the ns name & the keyword name to be interned into the permgen space
12:47	cemerick	The direct Keyword constructor is private right now, but if there was a compelling case for the non-interned keyword strings, I'll bet that could be changed.
12:47	clojurebot	for is not used often enough.
12:47	cemerick	Yes.
12:48	cemerick	I'd be surprised if that was somehow absolutely a requirement, though. Likely just a way to ensure good space/performance tradeoffs by default in maps, etc.
12:49	brianh2	& since the keyword table is private & nothing ever, as far as i can tell, removes anything from it, keyword strings will never be GCd
13:04	rsynnott	what do you want non-interned keyword strings for?
13:08	brianh2	rsynnott: i don't ;) i was just interested in the implications of using the String.intern() feature for keywords/symbols
14:26	Lau_of_DK	Good evening gents
14:28	pjstadig	good afternoon
14:29	mozinator	I would like to ask a question, I tried to search for it, but I couldn't find it.
14:29	mozinator	Is it possible to inherit a java class and override methods ?
14:29	hiredman	,(doc proxy)
14:29	clojurebot	"([class-and-interfaces args & fs]); class-and-interfaces - a vector of class names args - a (possibly empty) vector of arguments to the superclass constructor. f => (name [params] body) or (name ([params] body) ([params+] body) ...) Expands to code which creates a instance of a proxy class that implements the named class/interface(s) by calling the supplied fns. A single class, if provided, must be first. If not provid
14:30	hiredman	if you want to add new methods you need to use gen-class or gen-interface
14:30	mozinator	hiredman, thanks for the pointer!
14:30	clojurebot	for is not a loop
14:33	durka42	why did clojurebot start speaking when he is not being spoken to
14:33	durka42	test:
14:34	durka42	he suddenly became sentient!
14:34	durka42	~he suddenly became sentient!
14:34	clojurebot	CLABANGO!
14:34	durka42	so just "for"
14:34	sellout	durka42, I think it's the comma
14:34	sellout	eh, guess not
14:34	pjstadig	hiredman, suddenly he became sentient!
14:34	pjstadig	huh
14:35	cmvkk_	~
14:35	clojurebot	BDFL is Benevolent Dictator For Life (a.k.a. Rich Hickey)
14:35	cmvkk_	hmm
14:36	cemerick	he says something without prompting once every 20 messages or something now
14:36	sellout	That's a long time!
14:36	hiredman	everytime (= 1 (rand-int 20))
14:36	cmvkk_	just anything? or something relating to the last message
14:37	hiredman	it treats the last message as if it was addressed to it
14:37	clojurebot	it is too
14:37	hiredman	^-
14:37	cemerick	hiredman == crazy mad social scientist ;-)
14:41	p_l	markov model, eh?
14:41	pjstadig	sorry
14:41	pjstadig	i was trying to teach clojurebot to argue with me
14:41	pjstadig	it is too/it is not/it is too
14:42	pjstadig	but everytime i tried to get it to learn to respond to "it is too" he thought (= 'it 'too)
14:42	hiredman	heh
14:42	hiredman	clojurebot: it is too?
14:42	clojurebot	it is too
14:48	Lau_of_DK	mozinator...
14:48	Lau_of_DK	~proxy?
14:48	clojurebot	proxy is <Chouser> proxy teases with its ease of use, then suddenly betrays.
14:48	Lau_of_DK	Consider reading up on gen-class instead :)
14:48	hiredman	shrug
14:48	mozinator	Lau_of_DK, will do, thanks
14:48	hiredman	~works on my machine
14:48	clojurebot	http://haacked.com/images/haacked_com/WindowsLiveWriter/IConfigMapPathIsInaccessibleDueToItsProt_1446B/works-on-my-machine-starburst.png
14:50	pjstadig	~is too!
14:50	clojurebot	is not!
14:50	pjstadig	~is not!
14:50	clojurebot	is too!
14:50	pjstadig	sweet
14:51	pjstadig	clojurebot has sass
14:53	pjstadig	~is not!
14:53	clojurebot	is too!
14:53	pjstadig	~is not!
14:53	clojurebot	is too!
14:53	pjstadig	~is not infinity!
14:53	clojurebot	is too infinity +1!
14:53	pjstadig	d'oh
14:54	pjstadig	beaten by a bot
15:11	AWizzArd	Some days ago Rich gave a talk. A lot of twitter users were writing about it. Is there an audio/video file available?
15:11	sellout	AWizzArd: It was definitely recorded.
15:12	sellout	Don't know when/where the video will be available.
15:12	hiredman	the infoq is not yet, it maybe a while before they put it up, the skillsmatters is up
15:12	sellout	It was (I think) 5 hours.
15:12	hiredman	clojurebot: skillsmatter?
15:12	clojurebot	Titim gan �ir� ort.
15:12	pjstadig	infoq will probably release video from qcon, but they dribble it out
15:13	pjstadig	may not be months
15:13	sellout	hiredman: I think he's referring to the ILC one, but not sure.
15:13	hiredman	oh
15:13	pjstadig	oh ILC would be nice
15:13	hiredman	what?
15:13	clojurebot	?Que?
15:14	Raynes	<3
15:14	rhickey_	in past 2 weeks - 2 talks + 1 interview at QCon, a talk at Java group in London, a short talk at semantic web meetup in NYC, 5 hour tutorial and a panel at ILC
15:14	pjstadig	http://skillsmatter.com/podcast/java-jee/clojure-for-java-programmers
15:15	hiredman	zouch
15:15	Raynes	Been busy.
15:17	Raynes	\o/
15:17	rhickey_	Raynes: awesome!
15:17	Raynes	We all know, Java totally needs moar IDE's.
15:18	Raynes	:D
15:19	mrsolo_	well eclipse clojure plug in is badly needed :-)
15:20	Raynes	mrsolo_: Clojure-dev already exists.
15:20	pjstadig	http://www.swnyc.org/index.php?title=AllegroGraph%2C_the_Semantic_Web_%26_Clojure_Updates
15:20	AWizzArd	Raynes: very good, you make my point. I am argumenting since months that Clojure will open job opportunities. Clojurists will sneak into Java companies, probably Startups, who will be willing to trade "cryptic code" (Clojure g) for the increased productivity.
15:20	mrsolo_	raynes: exists last time i checked few months back it is still not working too good
15:20	mrsolo_	slime is sufficient imho if you stay inside clojure
15:20	mrsolo_	but when you start doing java interop stuffs....
15:20	clojurebot	?
15:21	Raynes	mrsolo_: It's working better now, but with no offense to Laurent as I know he tries hard, Enclojure is better.
15:21	AWizzArd	pjstadig: thanks for this video link
15:21	pjstadig	AWizzArd: np
15:22	AWizzArd	Raynes: Enclojure still has to fight with the enormous complexity of NetBeans.
15:22	dysinger	There already is a clojure IDE - it's called emacs + slime :P
15:23	Raynes	Enclojure works for me. That's my disclaimer.
15:23	AWizzArd	it's what I am using too
15:23	mrsolo_	raynes: it takes resources to get plug in working; i don't envy him :-)
15:23	AWizzArd	but Enclojure will hopefully catch up over time
15:23	mrsolo_	as for enclojure that is the thing
15:23	mrsolo_	i don't use netbeans and really don't want to learn another ide
15:23	mrsolo_	again
15:23	dysinger	I tried both the eclipse & netbeans flavors yesterday - no thanks
15:24	dysinger	I can appreciate they are good for the java crowd though
15:24	dysinger	emacs + slime + jswat is all I need for now.
15:24	brianh2	rhickey_: how were you and Clojure received at ILC?
15:24	AWizzArd	dysinger: after using slime+CL for some years it is difficult to use something else, but I think sooner or later Enclojure will be able to do all that nice stuff too, and then even more.
15:25	hiredman	durka42 has edged out cconstantine url wise
15:25	dysinger	yeah - I won't give up emacs' awesome for now.
15:25	dysinger	but I can see how a Java IDE _could_ do better on the java parts.
15:25	dysinger	(debugging etc)
15:26	AWizzArd	the nice thing is that the debugger is already included in NetBeans, as well as the Gui builder.
15:26	dysinger	jswat is the netbeans debugging AFAIK
15:26	dysinger	true - I guess I'll be happy to play with it all.
15:28	AWizzArd	It is just very very complicated to program NetBeans. The guys who implement plugins for emails or vi for Clojure editing have a way easier job.
15:28	clojurebot	for is not a loop
15:34	jwinter_1	What am I doing wrong with loop/recur here http://gist.github.com/86841 ?
15:35	cmvkk_	your recur is inside a vector, so it's not in tail-call position.
15:36	pjstadig	http://gist.github.com/86844
15:36	jwinter_1	ah, thx very much
15:37	sellout	jwinter_1: You can't just wrap [] to put a block in your if branch
15:37	cmvkk_	well you can, provided you don't care about the return value...and provided you aren't trying to recur
15:37	sellout	If that did do something, I don't think it's what you'd want.
15:38	sellout	cmvkk_: ah, true enough
15:38	sellout	is that a common idiom in clojure?
15:38	cmvkk_	no
15:38	sellout	phew
15:38	cmvkk_	it's bad practice of course, and i've never seen anyone do it before...i was just pointing out that it does technically work
15:39	jwinter_1	the do block was what I was looking for, I just stumbled onto the fact that that vector would execute what's inside
15:40	sellout	cmvkk_: I thought it was a mistake akin to the CL newbie one of (if foo bar ((print baz) quux))
15:40	sellout	but it seems to be of a different kind
15:41	cmvkk_	yeah, although that example at least doesn't work at all
15:42	sellout	cmvkk_: Yeah, thankfully.
15:48	arohner	more and more, I find myself using refs of maps instead of plain maps, just so I can validate them
15:48	arohner	validators are awesome
15:49	AWizzArd	arohner: do you have a minimal example?
15:50	arohner	hrm, not a short one
15:50	AWizzArd	What is a validator?
15:51	arohner	it is a function that can be attached to a ref
15:51	arohner	if you try to change the ref, the validator is called
15:51	hiredman	arohner: you could write a validating version of assoc
15:51	hiredman	that uses a validator from the maps metadata
15:51	arohner	if the validator throws an exception or returns false, the transaction fails
15:52	arohner	hiredman: that's interesting. I was thinking of a validating struct-map
15:52	arohner	,(doc ref)
15:52	clojurebot	"([x] [x & options]); Creates and returns a Ref with an initial value of x and zero or more options (in any order): :meta metadata-map :validator validate-fn If metadata-map is supplied, it will be come the metadata on the ref. validate-fn must be nil or a side-effect-free fn of one argument, which will be passed the intended new state on any state change. If the new state is unacceptable, the validate-fn should return fa
15:53	sellout	arohner: But you don't need a validator if you're not going to modify the map, so why would you use a ref rather than the map directly?
15:54	hiredman	metadata and map destructuring are my features of the week
15:54	sellout	Rather, in which cases where you would have used the map directly in the past do you now use a ref?
15:55	arohner	I have a few different places where I create instances of the same kind of struct map
15:55	arohner	and I sometimes I find bugs where one fn that creates the struct map was doing it incorrectly
15:56	arohner	so maybe I want a validating struct-map
15:56	hiredman	very interesting
15:59	antifuchs	so - here's my finished 3d-printable part: http://github.com/antifuchs/aoi-swank-plugin/blob/1987fb6d3477fc5835d1c37b2762ac2cf82c5696/examples/dishwasher-part.clj (the exact same thing was printed before, as http://reprap.soup.io/post/15859377 (:
15:59	hiredman	~def defstruct
16:00	AWizzArd	antifuchs: sounds nice
16:00	AWizzArd	apropos bugs, please check out my posting in the Google Group: http://groups.google.com/group/clojure/browse_frm/thread/7a48f48e4b197a15/bcaf06d233cde839
16:00	antifuchs	I'm still not entirely happy with the surface syntax and the repeated need to transform by (90 0 0), but I'm optimistic that this will be very nice soon (:
16:00	AWizzArd	wow
16:02	sellout	antifuchs: You integrated with aol to make a dishwasher knob?
16:02	sellout	antifuchs: And you have a RepRap?
16:02	antifuchs	sellout: we have one at the metalab (:
16:02	AWizzArd	arohner: if rhickey decide to implement gradual typing, then you could catch some hard to find bugs
16:03	sellout	antifuchs: I'd ask you to print me one if I was near Austria.
16:03	arohner	AWizzArd: what is gradual typing?
16:03	sellout	arohner: see Typed Scheme
16:03	antifuchs	sellout: sure thing! new york may be easier for you (:
16:03	antifuchs	sellout: nyc resistor sell kits with space for 10x10x10cm models for $750
16:04	sellout	Nice, danke.
16:04	AWizzArd	arohner: it is mentioned in that Google Posting. But the basic idea is: it is extremly granular static typing. You can have as few or as much you want.
16:04	antifuchs	they're very good, apparently (and I am pondering buying one of their extruders) (:
16:04	AWizzArd	Between 100% dynamic typing and a 100% statically typed program everything is possible.
16:04	arohner	AWizzArd: interesting. thanks
16:04	AWizzArd	And with a global switch one could even turn it off, if one really does not like static typing and a lib one is using supports it.
16:05	AWizzArd	Clojure could simply use metadata for communicating what it wants the compiler to treat as static code
16:05	AWizzArd	You could for example have one function in your whole code base which can perform type checks for one of its 4 parameters
16:06	AWizzArd	This would allow the compiler to let you know that you made a type error at some point or not. You would do this only for code that you want to be static (= not changeable during runtime).
16:08	AWizzArd	and this is also nice for editing source code
16:08	AWizzArd	The IDE could access the type information as well, and allow you several nice completions/checks during edit time.
16:09	arohner	very cool
19:52	zakwilson	I'm trying to use contrib.json.read. There seems to be no documentation. If I have a URL and want a PushbackReader, what's the standard way to get one?
19:53	danlarkin	you know what /is/ documented... :-o
19:55	zakwilson	I know the Java API has lots of docs, but I'm not finding what I need because I don't know where to look. I'm trying to use the URL class, but that doesn't seem do what I need.
19:57	zakwilson	Ahh... I think I figured it out. That has to go through way too many classes.
20:04	danlarkin	oh, nah I was just plugging clojure-json
20:04	danlarkin	but I'm glad you got it working
20:04	slashus2	danlarkin: I do like your json library.
20:06	danlarkin	cool
20:06	danlarkin	thanks
20:07	lpetit	Hello, is the fact that thread-local bindings are not propagated to child threads a design choice, a tradeoff made for performance considerations, both ?
20:08	lpetit	I meant thread local bindings of vars, of course
20:08	zakwilson	I think it's because they wouldn't be thread-local if they were.
20:08	slashus2	danlarkin: The decode-from-string is a nice feature to have.
20:10	lpetit	I meant thread-local values, with the same property a thread-local binding has towards the stack of bindings : changes done via new 'binding or set! calls would not affect threads higher on the stack call
20:10	rhickey_	lpetit: it's a design choice - closures in general are created without knowing the context in which the thread that will run them has been created - there are perf issues too
20:18	lpetit	rhickey_: what is the expected set of use cases for global vars ? A recent post on the ml made what I have considered a valid point. Say I'm the user of an interesting library's function called foo. foo accepts a closure. For debugging purposes, I place some (println) calls in my closure, and create in my thread a thread local binding for out to a proper value. Now if the next version of...
20:18	lpetit	...the library has optimized its foo function for using several threads (maybe replacing a call to map by a call to pmap ...), suddenly I loose some traces in my log.
20:19	rhickey_	lpetit: you can always create a closure that includes whatever bindings you need
20:21	rhickey_	but every closure creation can't capture every dynamic binding
20:23	lpetit	rhickey_: yes, and I remember Christophe Grand already posted such a solution (macroified for ease of use) in his blog. But then one has to know in advance which bindings to further propagate. That may be impractical with a big code base, or code written by big teams ?
20:25	lpetit	rhickey_: again, please: when you write "but every closure creation can't capture every dynamic binding", are you saying "that would be ideal solution, but it is just impossible to do it efficiently", or are you saying "it is not affordable to impose to users that each closure creation capture the current dynamic binding" ?
20:26	rhickey_	there are as many reasons why you might want to return a closure that leverages the dynamic context in which it is run - threads are not really relevant - dynamic context is just that - the context in which you are run, not the one in which you are created
20:27	rhickey_	i.e. any function that prints would capture the state of out at its definition point
20:27	rhickey_	not what you want
20:28	grosours	hi
20:29	lpetit	rhickey_: yes, my concern is about making the vars behavior recursive among the thread hierarchy, not only between the thread that holds the root bindings (but is there one anyway that can be distinguished as such), and a thread where I rebind the var.
20:30	lpetit	rhickey_;ok concerning closures and the capture of values of global variables, because then it would just be lexical binding considering that global vars are in the "outermost" lexical scope. And I agree they would certainly not deserve the "dynamic" qualificative then :-)
20:32	rhickey_	lpetit: what thread hierarchy?
20:32	rhickey_	thread pool threads aren't 'under' specific application threads
20:33	lpetit	rhickey_: argh, you're right
20:33	rhickey_	it's best to leave threads out when thinking about this
20:33	rhickey_	it has to do with the meaning of dynamic scope
20:34	rhickey_	which is a runtime, not definition-time, thing
20:37	lpetit	Sorry I don't understand, the main concern of my question is precisely to think about this thread stuff. Considering that threads created e.g. by pmap aren't technically child threads of the application thread, one might still consider they can be "logically" considered child threads, and inherit for their vars the bindings of the "logically" parent thread ? Technical and performance...
20:38	lpetit	...problems set apart, would it make sense if such a change could be made possible ?
20:39	rhickey_	no - imagine you create a closure that prints, and return it to someone that later binds out and calls it - what do you expect to happen? it has nothing to do with threads or pmap
20:40	cmvkk_	i thought you meant like (binding [foo true] (send-off ag some-fn)) then expecting some-fn to see foo as true.
20:43	rhickey_	(send-off ag #(binding [foo true] (some-fn %)))
21:01	lpetit	rhickey_: if as the closure creator I write it so that it prints, then at the time I write the closure, I'm OK to go with the normal behavior of dynamic variables: I don't know what the binding will be at call time, it will be set by the context. Now, as the user of the closure, I may want to specify a binding. As you just posted, I then have the possibility to add a clojure above the...
21:01	lpetit	...function to rebind the value. But please admit it's far from ideal for at least 3 reasons:
21:01	lpetit	1) I must repeat (and think about it) every time I have to make such a call. Even with some macro it's subject to errors. And if I have the value in a global already, I think I must write this if I want it to work : (send-off ag (let [let-foo
21:01	lpetit	foo] #(binding [foo let-foo] (some-fn %))))
21:01	lpetit	2) Sometimes I guess it will be difficult to remember all the bindings that must be passed as in the example aboe with send-off. And I fear things may get worse with big code base where one uses a closure created by lib B, passing it to lib C ...
21:01	lpetit	3) sort of leaky abstraction: if a user of a function provided by a lib must know if it is possible the function will split the work in separate threads for performance reasons or not, then I guess the technique of enclosing in a closure that will rebind before ... may well become "the way" to be sure it will work as expected.
21:01	lpetit	So then again: if closures or even classic functions should not rely on global vars because the user of the closure or the function call can't be sure the binding it placed on the needed vars went away for a good reason and in a predictable way, how to blindlessly rely on them on my code ? And if the answer to be systematically certain that I will not have surprises is to rebind in a...
21:01	lpetit	...wrapper closure, would propagating the global vars values to "logical" child threads (if ideally possible) be a good thing compared to the current state of the art (technical, performance considerations set apart)
21:05	lpetit	rhickey_: a final word and I go to sleep and don't bother you more tonight : I'm asking that because I wanted to play with clojure java code, trying some implementations ideas that could solve the technical and performance problems. But then, if at the end of the road it is not interesting for design considerations I haven't understood yet, I'll be a little bit disappointed by myself...
21:09	lpetit	rhickey_: anyway, thanks for having exchanged ideas and knowledge with me, regards, Laurent.
21:55	duderdo	Hi
21:57	duderdo	What would be the best way to let slime know my CLASSPATH? The function in the clojure wiki seems a bit verbose
22:07	sudoer	hi all,if i want to start on some web programming for clojure ,should I use compojure/other library or just do my own thing? I am learning clojure currently