#clojure – 2008-10-02

2008-10-02

01:24	scottj_	How come clojure doesn't figure out automatically what can be run in parallel and do that?
01:34	Chouser	is that easy to do?
01:36	scottj_	I think I've heard Haskell does it.
01:38	scottj_	But yeah, I was wondering if there was a reason other than "it's hard and we haven't gotten to it" that clojure doesn't have it.
01:38	walters	i think haskell's static typing makes that much easier for them
01:39	walters	clojure is dynamically typed with the advantages and disadvantages that typically entails
01:40	walters	i.e. you can run your app without going through cycles of staring at obscure type inference clash errors from the compiler, but you lose some smarts and checking that could be done at compile time
03:00	Lau_of_DK	Morning gents - Quick JAVA question: Where can I find an example of the mainloop in a swing application, so as to enable my clojure program to run from clojure.lang.Script ?
03:16	hoeck	Lau_of_DK: for all i know, there is no user-defined main loop in a swing application, the components just fire events which call the associated Listeners
03:17	hoeck	Lau_of_DK: so just setting up the Listeners and open a main swing window should do it
03:19	hoeck	Lau_of_DK: but im not a swing guru, just played with swing and clojure a while ago
04:08	Lau_of_DK	hoeck, im pretty sure that there's something simliar to c's main.c which needs to start some kind of loop, I vaguely remember RHickey pointing to an example and saying that I should mimic that behavior
04:08	Lau_of_DK	Of course, I lost the link
04:14	Lau_of_DK	Looking over Suns site, you might be right though
04:17	hoeck	mhh, maybe you have to check (in a loop) wether your main swing window is still open so that the script does not quit before
04:18	achim_p	Lau_of_DK: take a look at ants.clj: http://groups.google.com/group/clojure/files. no main loop. that's one of the differences between swing and swt.
04:22	Lau_of_DK	but achim_p, ants.clj wont run strictly from the command line either, you need to maintain a repl
04:27	achim_p	Lau_of_DK: i just tried with a clj file with this single line: "(doto (new javax.swing.JFrame) (show))". it didn't terminate when run as a script. does that work for you?
04:30	Lau_of_DK	gimme a few secs,colleague knocking on the door
04:46	Lau_of_DK	achim_p , yes that works, thanks :)
04:55	Lau_of_DK	Do you guys remember how to add the exit-listner so that the script terminates when the windows is closed? As I recall there was a one-liner posted somewhere
05:11	achim_p	Lau_of_DK: i think you'll have to extend a WindowAdapter for this and add it to the JFrame. there might be a shorter way ...
05:19	Lau_of_DK	achim_p, I worked out, that if you do this do your main JFrame, then it will exit when it closes
05:19	Lau_of_DK	(doto frame (setDefaultCloseOperation (. JFrame EXIT_ON_CLOSE)))
05:19	Lau_of_DK	(doto frame (setDefaultCloseOperation (. JFrame EXIT_ON_CLOSE)))
05:19	Lau_of_DK	(sorry, my paste putty/bitchx thing messed up on my screen, but I suppose you can read the bottom Line?
05:33	achim_p	yes, thanks! that's better.
08:42	drewr	I love seeing all the chatter on twitter about clojure.
08:42	abrooks	;-)
08:42	drewr	It's grown a lot in the past few weeks.
08:42	abrooks	It has.
08:42	drewr	"While I appreciate most of the ways clojure deviates from CL some things are just plain wrong. I mean, nil is (). Come on, people!" --appelberg
08:43	abrooks	Bzzt.
08:43	rhickey	why is nil () and not [] or {} ?
08:44	abrooks	rhickey: I was just about to note how you put that argument to rest in the recent talk.
08:45	rhickey	It made sense when there were only lists... but now, not so much. or you''d also have to have null
08:45	abrooks	When you're in a universe that has a single instance of something it's very hard to see the distinct attributes of that thing. An emtpy list may reasonably look like nothing when it's the only empty sort of thing that you have.
08:45	abrooks	Heh. Crosspost.
08:46	rhickey	heh
08:47	jdz	rhickey: you're my hero of the day!
08:47	jdz	(i smell some Java stuff will have to be done in near future, and this is a perfect time to start learning Clojure)
08:48	rhickey	jdz: great!
08:48	drewr	abrooks: How can OCaml have pointer misalignments??
08:48	jdz	i'm just looking through the website and wonder if there is a way to create .jar files from clojure sources...
08:49	jdz	rhickey: can Clojure dump it's generated bytecode?
08:50	abrooks	drewr: Heh. The compiler does...
08:50	abrooks	drewr: In theory this runs on IRIX6 but their avoidance of GNU autoconf is my pain.
08:51	drewr	...and their joy. :-)
08:51	jdz	rhickey: not that it is very important. but you know, i'm new to Clojure, and all newbies that come to #lisp ask about making executables :)
08:51	rhickey	jdz: not at present. You can jar up src with the normal Java jar tools
08:52	jdz	rhickey: ok, thanks. i won't take any more of your precious hacking time.
08:52	rhickey	I think it's a viable question, there was a thread and some code for it here: http://groups.google.com/group/clojure/browse_frm/thread/3c2010cde7d87a6d
08:54	abrooks	drewr: I'm not about to defend GNU autoconf on any grounds of cleanliness. It's a horrific catastrophy of POSIX shell and M4. It's just that encapsulates so much knowledge about portability and cross-compiling that individual engineers simply don't have. It's necessary. GNu autoconf is the worst build configuration system ever... except for all the others.
08:54	drewr	So rhickey, did you pass the Xach test at the talk?
08:55	rhickey	drewr: I think so: http://xach.livejournal.com/191581.html
08:55	drewr	abrooks: Yeah, that's what I thought. I've mostly stayed on the user end of autotools.
08:57	jdz	rhickey: btw, one thing i missed from the videos (maybe it's just me): what is the result of (first empty-sequence)? (in the 'rest' case it's nil)
08:57	drewr	rhickey: Ah, that post just came up in my feed reader. If you impressed that group then Clojure has a bright future!
08:58	abrooks	jdz: (first empty-sequence) -> nil
08:58	abrooks	jdz: The reason is there is no empty sequence.
08:58	jdz	abrooks: yeah, that's quite natural. it's just that it was not mentioned in the presentation. and i'm not sure it should...
08:59	abrooks	jdz: (seq []) -> nil
08:59	jdz	abrooks: no, there is an empty sequenc. that's the whole point!
09:00	jdz	abrooks: it's just that there is nothing in the sequence, so you can't take neither the first nor the rest of it. but it still is a sequence.
09:00	abrooks	You never have an empty sequence. You may have an empty list/vector/set/hash but if you get it's sequence you have nothing.
09:00	jdz	(well you can take first and rest of it, and you get nil)
09:01	jdz	abrooks: oh, right. right.
09:02	rhickey	in Clojure, nil means "nothing", but first and rest are defined on nil to return nothing/nil too
09:02	abrooks	Er... s/it's/its/ ----^ (It's too early in the morning...)
09:11	andrewdotnich	g'day everyone
09:12	rhickey	andrewdotnich: hi
09:12	andrewdotnich	rhickey, watched your "Clojure for Lisp programmers" talk this afternoon
09:12	andrewdotnich	going to start playing around with it in my spare time, looks quite impressive
09:13	rhickey	great!
09:14	andrewdotnich	I'm a 3rd-year university student in Melbourne, Australia - we haven't had much FP teaching as part of our course
09:14	andrewdotnich	although we did go through Lambda Calculus for a languages subject
09:20	abrooks	andrewdotnich: If you've not come across http://projecteuler.net , it's a great way to learn a new language (particularly functional ones). Plus it's loads of fun.
09:20	abrooks	ER. I meant to have "I highly recommend it" in there some where. ---^
09:25	andrewdotnich	yeah, I've done a few Euler problems
09:26	abrooks	andrewdotnich: In Clojure or another language?
09:26	andrewdotnich	Python, mainly
09:26	andrewdotnich	another language I've had to teach myself
09:27	andrewdotnich	my university being quite traditional in its language selection (Pascal, then C# / Java, with some C++ thrown in)
09:31	andrewdotnich	rhickey: in your talk you mention that you use emacs to write in Clojure - are you aware of any work to create a Clojure bundle for TextMate (my editor of choice)?
09:32	rhickey	H4ns: nice blog post. http://netzhansa.blogspot.com/2008/10/trying-clojure.html Did you try debugging with JSwat or enclojure?
09:32	H4ns	rhickey: no, i've tried sticking to slime. i guess i should try to be more open :)
09:33	H4ns	rhickey: for the next project, i'll look into one of those, thanks!
09:33	rhickey	ah, there's not the same infrastructure to support Slime debugging, but Clojure follows all the rules for Java debugging and profiling. Should be able to debug with break points, line-stepping, locals etc
09:35	H4ns	rhickey: i'll look at that and post praise to my blog, promised :)
09:35	rhickey	H4ns: ok :)
09:36	rhickey	also, I've been working on error messages and will look at anything specific
09:38	H4ns	rhickey: for today, i need to return to good old common lisp, but i will come up with specific reports - should i post to the group?
09:38	rhickey	H4ns: yes please
09:38	H4ns	ok.
10:07	Chouser	earthvssoup: the new code looks beautiful
10:07	earthvssoup	Chouser: thanks to you
10:07	Chouser	I'm starting to get the feeling people want more or different documentation. ;-)
10:08	earthvssoup	For me... a little bit from column B and a lot from column A ;)
10:08	rhickey	I'd love to see a Clojure examples project get going somehow
10:08	earthvssoup	I am totally a n00b here, but I would be happy to help however I can
10:09	H4ns	planet.clojure.org and aggregate manually maybe?
10:10	Chouser	At this point there's a whole lot of example code floating around "out there" -- is google any good at collecting that?
10:10	alec	no
10:10	earthvssoup	not really
10:11	Chouser	to be more useful, I think an examples project might have to work hard at being well organized -- start simple, build up a topic at a time.
10:11	earthvssoup	agreed
10:11	rhickey	we've imagined a structure with a page per function, with doc/example/test/tips
10:12	earthvssoup	For me, good examples are key
10:14	jdz	i miss interactive documentation. like (describe defstruct)
10:14	Chouser	doc
10:14	jdz	Chouser: oh thank you.
10:15	earthvssoup	Many examples projects fall into the trap of, "this is the bad way to do it... now look at the right way to do it"
10:15	Chouser	Also: (find-doc "struct")
10:15	blackdog	i think the best examples are in boot.clj, keeping it open at all times for reference is well worth it
10:15	Chouser	earthvssoup: I'm not quite sure what you mean.
10:16	Chouser	blackdog: that's certainly what I used, but you do have to be a bit careful -- at the top of boot.clj there's not enough clojure defined yet to do things the Right Way
10:17	earthvssoup	Well, for example On Lisp PG (at times) creates functions such as (bad-reverse) and then (good-reverse). I suppose that there is some value in that there are discussion points made about why (bad-reverse) is bad, but for me it is distracting
10:18	Chouser	ah, I see. That might make more sense if you've got a coherent narrative (such as in a book) -- for reference docs I would agree bad examples aren't very useful.
10:18	H4ns	earthvssoup: i think good examples must tell you not only why they are as they are, but also why other ways are not as good.
10:19	earthvssoup	BTW, I agree that boot.clj is great. Perhaps an annotated version explaining how it builds on itself would be useful?
10:19	earthvssoup	H4ns: agreed
10:19	H4ns	earthvssoup: i think good example code should be good enough that could copy and paste it, but one never should actually do it :)
10:21	earthvssoup	Of course my On Lisp -> Clojure project takes the (bad/good-reverse) approach, but that is only a product of my ignorance
10:22	Chouser	btw, the "else" part of "if" is optional. If you leave it out, it's as if you specified nil.
10:23	H4ns	Chouser: in common lisp, we prefer when over if without an else clause. same in clojure?
10:23	Chouser	H4ns: yes
10:24	Chouser	H4ns: yes
10:24	H4ns	Chouser: ok
10:25	drewr	rhickey's explanation of cons/seq is awesome.
10:28	Chouser	Having just spent 10 minutes looking at the problem, I think I'm the wrong person to set up a examples wiki. :-/
10:28	drewr	What's the behind-the-scenes difference of:
10:28	drewr	wm> (first {:foo 1 :bar 2})
10:28	drewr	[:bar 2]
10:28	drewr	wm> (first (seq {:foo 1 :bar 2}))
10:28	drewr	[:bar 2]
10:28	lisppaste8	rhickey pasted "make-adderb" at http://paste.lisp.org/display/67788
10:28	Chouser	drewr: first calls seq on its arg for you
10:28	drewr	Ahh.
10:29	rhickey	earthvssoup: that's the most straightforward make-adderb
10:31	Chouser	H4ns: that PDF is beautiful.
10:31	earthvssoup	rhickey: awesome. My v2 version wrapped the entire if in the dosync. I guess that was overkill. Also, I should have picked up on the @ deref Thanks
10:32	jdz	which pdf?
10:32	H4ns	Chouser: yep - it will propably be very helpful for when to just read it back to back.
10:33	H4ns	http://clojure.googlegroups.com/web/manual.pdf?gda=HTUM7jwAAABoLitVpBTEcNIQc_NHg39S6DeYQuwQGx9N3mteasxC_bb1z1jhUxpJojBve3FvCyr9Wm-ajmzVoAFUlE7c_fAt&gsc=IJhlFgsAAAB2uMKWD8zLj_ZrTVfKpqX8
10:33	H4ns	dunno about the gibberish in the end, sorry.
10:33	alec	rhickey: thanks again for speaking on Monday. Clojure has been the topic of more than a few conversations at ITA (the big area Common Lisp employer) in the past few days
10:33	H4ns	alec: the food sponsor, too!
10:34	rhickey	alec: you're welcome. what are the conversations like?
10:34	blackdog	thanks for that pdf, v. useful
10:35	rhickey	it was my pleasure to speak to an audience so deeply engaged in the concepts
10:37	alec	some cool Common Lisp code has come out of it, especially from discussion of the assertion "Common Lisp's standard library is very much tied to cons cells"
10:37	alec	we also dream about how easy it would be to parallelize our applications - that's a big selling point
10:38	alec	the "I don't care about consing 20GB/s" remark was also funny, since one of our applications cares especially about performance and we see better performance with less consing
10:39	alec	overall good reception
10:40	rhickey	alec: there certainly are times when I do care, but was more impressed by the Azul GC not breaking a sweat at those rates
10:40	blackdog	rhickey: what is ephemeral garbage? is that the first generation of garbage?
10:41	H4ns	rhickey: i suppose that they do have certain advantages due to the fact that they can change the hardware to suit their garbage collector, is that true?
10:41	jdz	blackdog: it's just recently generated garbage since last GC.
10:41	rhickey	blackdog: something you allocate and stop referencing almost immediately
10:41	blackdog	ok, thanks
10:43	rhickey	H4ns: I presume, but everyone is working on reducing GC costs, parallel GC etc. Bottom line is ephemeral garbage is relatively cheap, and eventually, with escape analysis, might often not even exist
10:44	jdz	in what ballpark those Azul systems cost?
10:44	rhickey	The Clojure seq abstraction couldn't exist without ephemeral garbage
10:45	rhickey	jdz: if you need to ask, you can't afford it :)
10:45	jdz	fair enough
10:46	jdz	i know i don't want one under my desk :)
10:46	jdz	(i don't have a desk that big)
10:46	rhickey	I do, they are very small (something like 200 cores in 5U)
10:47	jdz	sounds pretty awesome
10:47	rhickey	:)
11:15	jdz	or is it Symbolics ex-employees?
11:16	abrooks	It's hard to see but that's a non-breaking space. ;-)
11:16	jdz	nice one!
11:32	achim_p_	hi! re: examples blog/wiki - when i started with lisp/clojure, i did some project euler problems, which i put up here then: http://clojure-euler.wikispaces.com. quickly got fed up with number theory, though, and stopped. if anyone would like to contribute/discuss solutions, please do! access to the wiki should be completely open.
12:55	scottj_	how do you guys think enclojure would do at the benchmark game? about like groovy/jruby?
12:57	scottj_	I mean clojure. I was just installing enclojure :)
12:57	abrooks	Ruby is slow in its native install. I wouldn't expect JRuby to win any speed competitions but perhaps I'm wrong.
12:58	rhickey_	scottj_: should be able to get close to Java, perhaps not with the most idiomatic Clojure, but that's the game
12:58	abrooks	I know nothing of groovy's performance.
12:59	abrooks	I'd sort of expect Groovy to be significantly better than JRuby as Groovy is explicitly a language designed around the JVM.
13:00	rhickey_	abrooks: there's a tremendous amount of dynamism in both Groovy and JRuby getting in the way of perf
13:00	abrooks	rhickey_: I suspected as much of Groovy (I know that JRuby is hampered).
13:00	walters	though groovy does have the nice aspect that you can just replace "var" with "int"
13:01	abrooks	Does Groovy use unboxed numbers?
13:01	walters	i think currently when you declare types it doesn't do anything useful
13:02	scottj_	So maybe performance closer to Scala? http://shootout.alioth.debian.org/gp4/benchmark.php?test=all&lang=all is a summary including groovy and jruby
13:04	abrooks	This is one of the more fatuous language articles I've read recently: http://java.dzone.com/news/groovy-will-replace-java-langu
13:04	abrooks	Did you know that "Groovy is the only language together with Scala and of course Java that always compiles to true Java byte-code."
13:05	rhickey_	scottj_: statically typed langs should have best perf, but Clojure should be closer to Java than to Groovy, certainly
13:10	scottj_	abrooks: does Clojure use unboxed numbers?
13:13	abrooks	Not directly though within a function unboxed numbers can be used without reboxing them on recur calls if the proper type hinting is provided. I think I'm getting this right. rhickey_?
13:13	abrooks	^directly^directly,
13:15	rhickey_	abrooks: yes, it supports unboxed numbers (and arithmetic) locally, and in non-reflective calls to/from Java, given any needed hints
13:16	rhickey_	ditto arrays of primitives - see type hints and primitives sections here: http://clojure.org/java_interop
13:19	danlarkin	just read http://netzhansa.blogspot.com/2008/10/trying-clojure.html
13:20	H4ns	danlarkin: let me know if i wrote something silly
13:21	danlarkin	no no, I like it
13:21	scottj_	H4ns: I think those nbm files have dependencies that it will download from netbeans
13:22	H4ns	scottj_: the error message refers to the local file and complains about the network settings, so it does not seem to know the real url or something.
13:23	H4ns	"Networking problem in file:/C:/Users/hans..."
13:33	lisppaste8	danlarkin pasted "def def" at http://paste.lisp.org/display/67800
13:34	danlarkin	I'm confused about what happens in that snippet I pasted
13:35	Chouser	don't def def
13:36	Chouser	;-)
13:36	rhickey	danlarkin: right now there aren't prohibitions on redefinitions of special ops
13:36	rhickey	but invocation always resolves def to special op, so you haven't truly shadowed it
13:39	danlarkin	so special symbols get short-circuted in the evaluator?
13:39	danlarkin	would that be fair to say?
13:39	rhickey_	right, there aren't necessarily vars for them
13:41	danlarkin	right, since in a clean environment (resolve 'def) returns nil
13:41	rhickey_	I should lock them down...
13:42	H4ns	wow, slime with a working repl _is_ amazing! :)
13:43	H4ns	btw, does the repl have something like , , **?
13:44	Chouser	H4ns: 1 2 *3 ?
13:45	H4ns	Chouser: java.lang.IllegalStateException: Var *1 is unbound. (NO_SOURCE_FILE:0)
13:45	H4ns	maybe the slime repl is not a repl thread in that sense.
13:46	H4ns	rhickey_: you should (i admit, this is kind of a selfish remark) :)
13:46	H4ns	"i wanted to enter the 21th century, but enclosure did not even want to install"
13:46	Chouser	H4ns: could be. I don't use emacs, so I can't say.
13:48	drewr	abrooks: I think JRuby has actually surpassed CRuby in speed, but I don't keep up with that stuff.
13:49	aking	H4ns: are you using clojure from svn or the release version? 1/2/*3 was added two days after the release
13:49	achim_p	the star vars don't work in slime
13:50	achim_p	another downside is the lack of input line numbering
13:50	H4ns	aking: svn
13:50	walters	drewr: it has yeah...but ruby 1.8 is a really bad VM
13:51	drewr	walters: :-)
13:51	H4ns	achim_p: input line numbering i don't miss so much. what do you use that for?
13:56	fyuryu	lazy-cat
13:56	abrooks	drewr: JRuby/CRuby -- interesting.
13:56	fyuryu	ups
13:56	fyuryu	wrong buffer
13:57	walters	drewr: also my impression is the jruby hackers are particularly good
13:57	H4ns	given a command-line repl, how do i load foo.clj into the running clojure? the getting started page does not tell.
13:58	Chouser	(doc load)
14:00	H4ns	java.lang.ClassCastException: java.lang.String cannot be cast to java.io.Reader when i type (load "foo.clj"), which is an empty file?
14:00	Chouser	rhickey: is there some reason you used fns-in-metadata instead of multimethods for clojure.zip?
14:01	abrooks	H4ns: You probably want (load-file )
14:01	abrooks	(load-file "foo.clj")
14:01	H4ns	abrooks: ah! damnit.
14:01	H4ns	thanks!
14:02	Chouser	huh. for me, (load "foo.clj") says Could not locate Clojure resource on classpath: user/foo.clj
14:02	abrooks	Chouser: load works in the classpath.
14:02	Chouser	if it finds foo.clj, but it's empty, I get nil
14:02	Chouser	abrooks: yes
14:03	abrooks	Oh, you're having a different problem.
14:03	Chouser	I'm not having a problem, I'm just failing to understand H4ns'
14:05	H4ns	i don't understand my problem either, but load-file works a little better.
14:05	rhickey	Chouser: those fns are supplied by users of the lib, it's composition. I guess the could have supplied a tag of some sort and then 3 multimethods, but much more verbose
14:06	Chouser	rhickey: ok, thanks.
14:09	achim_p	H4ns: never mind my comment about line numbers, i just checked, the standard repl doesn't seem to do it either. i could have sworn ... maybe i confused sth.
14:10	Chouser	^(def x) includes a :line number for me
14:12	achim_p	Chouser: ah, that's the difference i meant. in slime it's always 1
14:13	achim_p	i checked the error message on (/ 0 0), which states "NO_SOURCE_FILE:0" in both environments.
14:18	abrooks	user=> (/ 0 0)
14:18	abrooks	java.lang.ArithmeticException: Divide by zero (NO_SOURCE_FILE:0)
14:18	abrooks	user=> (def x (/ 0 0))
14:18	abrooks	java.lang.ArithmeticException: Divide by zero (NO_SOURCE_FILE:62)
14:19	abrooks	There's the difference. I think you must have something (such as a symbol) to associate the metadata with.
14:19	rhickey	Is there something useful about repl line #s?
14:21	abrooks	rhickey: I think so, particularly if you have the REPL joined to an editor or an IDE.
14:22	rhickey	I mean for source entered into the repl
14:23	rhickey	like above, line 62
14:24	abrooks	rhickey: Yes. If you have scroll back or prompt numbering or something managing the lines input to the REPL, I think that's useful.
14:31	abrooks	rhickey: I would eventually like to have enough to print the offending snippet with an indication of what's wrong. Being able to externally retrieve that snippet seems like a first step (of several possible).
14:33	rhickey	abrooks: understood, here with emacs + clojure-mode in inferior lisp I don't see any way to use those numbers
14:35	abrooks	At this point, I think it just runs against the users expectations when one sometimes gets an exception with a real line number sometimes and zero other times.
14:37	rhickey	Line numbers in a file mean one thing, in a repl..., but in any case, what you are seeing is that (/ 00) w/o the def is wrapped in a fn before eval, that fn having no line. I can change that to adopt the line of the wrapped expression - on todo list
14:43	abrooks	rhickey: I have the CA printed out and just need to fill it out and mail it. Perhaps I can express my wishes more helpfully/productively in diffs. ;-)
14:43	abrooks	IOW, don't bother yourself. ;-)
14:44	abrooks	I've been looking at datalog implementations. Which implementation were you thinking of using?
14:45	rhickey	abrooks: IRIS Reasoner: http://iris-reasoner.org/
14:46	abrooks	Every once in a while I find myself really missing CLIPS and then I know how sad things are...
14:51	abrooks	IRIS looks very complete and well constructed.
14:52	rhickey	yes, nice set of interfaces for extension
14:56	earthvssoup	My first job out of college was CLIPS
14:56	earthvssoup	I look back on it fondly (although doesn't everyone with their first?)
14:58	Chouser	rhickey: is LGPL a problem with IRIS?
15:00	rhickey	Chouser: it means if we provide fixes to IRIS, they must be LGPL, but we should be able to consume IRIS by linking to it without tainting. It may be an issue for consumers of Clojure who want no LGPL
15:00	Chouser	ok, doesn't sound too bad.
15:03	rhickey	The idea would be to provide a datalog library for Clojure that encapsulated the use of IRIS, in case someone ambitious later wanted to implement datalog directly in Clojure - I've had a lot of difficulty finding all of the details needed to do the latter with Query/SubQuery/Recursive + negation, otherwise I would have tackled it
15:03	abrooks	rhickey: Are you thinking of pulling IRIS sources into Clojure and tracking upstream or are you thinking that we'd have a Clojure glue library that links with a user provided IRIS jar?
15:04	rhickey	abrooks: the latter
15:06	rhickey	IRIS is doing magic sets and stratified negation already, so if it is fast enough, why reinvent the wheel?
15:07	abrooks	rhickey: I think there's some value to the Pythonic "Batteries Included" model. If you know that standard distributions will have X it becomes much more useful.
15:08	rhickey	abrooks: we can battery-include the jar
15:08	abrooks	Ah, okay. My latter case was a user provided jar.
15:08	rhickey	right, you only gave me 2 choices :)
15:09	rhickey	I don't want to track the source
15:09	abrooks	;-)
15:09	abrooks	rhickey: That's wise, particularly with Subversion which goes out of its way to be sucky at tracking third-party changesets.
15:11	abrooks	Ullman has a presentation "Semantics of Datalog With Negation" among other things: http://www.google.com/search?q=site%3Ainfolab.stanford.edu%2F~ullman%2F+datalog
15:11	walters	though the fact that there's no standard mechanism for system jar installation sucks badly
15:13	rhickey	abrooks: I'm not at home with my materials, but I've read that, 2 other Ullman books, a book that specializes on Datalog and a bunch of other papers so far. I can post to the group with those details to start a discussion on this to see if there's sufficient interest/expertise
15:15	rhickey	what I've found so far is, lots of talk about the semantics, very little discussion of implementation, and when there is, it is always for simple datalog - no negation/built-ins or functions
15:16	rhickey	sometimes it seems as easy as - if you can stratify first, it goes back to the simple case, but everyone talks about implementation before they talk about negation
15:16	abrooks	Simple datalog is certainly the place to start, IMO.
15:17	abrooks	Can't it be incorporated without negation at first?
15:17	rhickey	but yes, should start simply
15:17	abrooks	Right.
15:18	rhickey	Where I'm at is the "buy" vs build point - IRIS is sitting there, with nice interfaces
15:18	rhickey	OTOH, I have my own ideas about purely functional dbs, with indexes
15:18	abrooks	rhickey: Don't we all. ;-)
15:20	abrooks	I think IRIS looks like a very reasonable starting place. Nobody's forced to use it. There's no reason why another reasoning system couldn't be added (or replace it) at some point in the future.
15:21	rhickey	What I imagine is this: create maps in memory or pull them from a db, pour them into a Clojure 'db', where they get tripletized. Tell the db which attributes to index. Then, attach a rule set to it and run queries. Both the rule set and db support non-destructive functional enhancement
15:21	abrooks	Chouser: Is noiski nearly done? We could just go with that? ;-D
15:22	Chouser	abrooks: noiski will use this feature, not the other way around.
15:22	abrooks	rhickey: That would be grand.
15:23	abrooks	Chouser: Silly - noiski has had this feature forever -- it's just missing from the current implementation.
15:31	abrooks	rhickey: I'm assuming that we wouldn't use the IRIS parser (primarily/at all?) in favor of using a native Clojure interface.
15:33	rhickey	abrooks: right - native Clojure
15:33	Chouser	woohoo! prn works, which proves multimethods at least kinda work, which proves isa? kinda works, which proves the type system is close enough.
15:34	rhickey	go Chouser !
15:34	abrooks	Chouser: Congrats!
15:34	Chouser	I gotta get this to a useful state soon -- I'm afraid I'm approaching burn out.
15:34	Chouser	I don't even remember why I wanted it anymore.
15:35	abrooks	Heh.
16:12	danlarkin	can I flip ([1 2 3] 0) around like I can with a map?
16:13	Chouser	keywords look themselves up in a collection, numbers don't.
16:17	danlarkin	why not?
16:17	lisppaste8	H4ns pasted "Backtrace for the swank-clojure maintainer" at http://paste.lisp.org/display/67814
16:18	abrooks	danlarkin: Keywords are functions of maps and maps are functions of keywords (both in the logical sense and in the Ifn interface sense).
16:18	Chouser	danlarkin: I can't answer that kind of "why" with authority, but I suppose it has something to do with Clojure numbers being Java numbers, and Java numbers not implementing IFn, Callable, or Runnable.
16:20	danlarkin	it seems like it would be nice to have the same syntax rules for a map no matter what one's keys are
16:20	danlarkin	although if it's not possible, it's not possible
16:21	Chouser	well it couldn't work for everything, since a fn is a perfectly valid map key, but if it's named in functional position you'd want to pass the map to the fn, not the other way around.
16:23	abrooks	danlarkin: You'll never have that symmetry as you can have a key be an IFn but putting an IFn in the callable position of the list will result in it being called, not being looked up in a subsequent map.
16:23	abrooks	i.e. (def x #(println "foo"))
16:24	abrooks	user=> (x {:foo :bar})
16:24	abrooks	java.lang.IllegalArgumentException: Wrong number of args passed to: x (NO_SOURCE_FILE:0)
16:24	danlarkin	would it be unreasonable to suggest that the (:a {:a 0}) syntax be deprecated? in favor of uniformity? or is using a non-keyword hash key such an edge case as to make it not a huge issue
16:24	abrooks	user=> ({:foo :bar} x)
16:24	abrooks	nil
16:24	abrooks	user=> ({x :bar} x)
16:24	abrooks	:bar
16:24	abrooks	danlarkin: I think because of the special nature and usage patterns around keywords, that reversed structure is very reasonable.
16:25	abrooks	A keyword never has a value or other functionallity other than referring to itself. Looking itself up is a pretty close concept.
16:47	danlarkin	is there a function to return the arity of another function? I looked but could not find anything appropriate
16:48	smoofra	can someone help to enlighten me please: what's the diffirence between alter and commute?
16:50	danlarkin	not only does commute set the in-transaction-value of ref, it also sets the current value
16:51	ozzilee	smoofra: Commute means the order doesn't matter, so Clojure is free to apply commute calls in whatever order it pleases.
16:58	smoofra	ah
16:58	abrooks	Okay, I'm baffled. I would think that I could get the function's metadata:
16:58	abrooks	user=> ^(defn x [a b c] (println "foo"))
16:58	abrooks	{:line 11, :arglists ([a b c]), :name x, :file "NO_SOURCE_FILE", :ns #<Namespace: user>}
16:58	abrooks	user=> (defn x [a b c] (println "foo"))
16:58	abrooks	#'user/x
16:58	abrooks	user=> ^x
16:58	abrooks	nil
16:59	wwmorgan	function can't have metadata. Try ^#'x
17:00	abrooks	Arg. Of course. I tried ^'x but forgot the sharp.
17:01	danlarkin	is #'foo shorthand for (resolve 'foo)?
17:02	smoofra	so is there any way to get mutable datastructures in clojure without going to refs or java?
17:02	wwmorgan	http://clojure.org/reader #'foo is short for (var foo)
17:03	H4ns	smoofra: what are you trying to achive?
17:04	abrooks	danlarkin: (map count ((meta (var x)) :arglists)) or (map count (^#'x :arglists)), depending on your taste, will give you a list of the arities of the function.
17:05	smoofra	H4ns: something like a haskell stref i suppose. a nice little ref you can read and write from without doing a transaction.
17:05	danlarkin	abrooks: thanks! didn't think of looking at the metadata, d'oh
17:06	H4ns	smoofra: why can't you use a ref and transaction for that? performance issue?
17:07	abrooks	danlarkin: np
17:10	smoofra	H4ns: im not trying to do something at the moment. just trying to understand. it just seems pretty incomplete to leave nakid refs entirely out of the language. and yea, performance is always a concern. i presume that the performance hit for using stm refs is not entirely negligable.
17:11	smoofra	er. naked even.
17:12	H4ns	smoofra: i'd say: don't worry. if you want to mutate, use other languages :)
17:13	Chouser	smoofra: you could use a var with binding and set!
17:14	Chouser	smoofra: I believe the overhead of a transaction when there is no contention is pretty small.
17:14	smoofra	H4ns: that's a bit silly. what with haskell having ST and all.
17:15	H4ns	smoofra: you need to talk to rhickey and have him convince you that you just don't want that.
17:15	Chouser	smoofra: but otherwise, if you're really sure you want to do unsafe mutation, using a Java array or some such isn't terribly hard.
17:15	Chouser	or right, what H4ns said. :-)
17:15	rhickey	just hopping on - don't want what?
17:15	H4ns	rhickey: mutate data.
17:16	rhickey	you have refs, vars, agents and java.util.concurrent.atomic for mutating data
17:17	ozzilee	rhickey: AFn.java line 169 has "Object... args)" at the end of the method signature. gcj doesn't like it, what is it?
17:17	rhickey	ozzilee: java variadics
17:17	walters	ozzilee: your best best is going to be to use openjdk
17:18	ozzilee	rhickey: Hmm ok.
17:18	ozzilee	walters: Any idea if that will work on the PPC?
17:18	walters	ozzilee: it's a better match particularly for a dynamic language, and really what we want is hotspot to have a native code compilation cache
17:18	walters	ozzilee: work on a zero-assembler version is in icedtea from some Red Hat hackers
17:19	walters	ozzilee: there is also an ongoing port to LLVM but that's not ready yet
17:20	ozzilee	walters: So it looks like no dice for running Clojure on Debian PPC today. Bummer.
17:20	walters	ozzilee: is debian's openjdk pulled from icedtea? if so and it's recent enough i think it should work
17:21	drewr	H4ns: You can send your swank problem to jochu0@gmail.com. Jeffrey is very helpful.
17:21	walters	it will not be blazingly fast but it should work
17:21	alec	walters: I run svn clojure with Debian's openjdk 6
17:22	alec	(amd64, not ppc)
17:22	alec	works fine
17:22	H4ns	drewr: he's already looking at it, but thanks!
17:22	ozzilee	walters: Not in stable, anyway. I'll have to look around a bit.
17:22	walters	alec: yeah, the main pain point is ppc since hotspot is a highly tuned and custom JIT for x86/x86_64/sparc
17:23	walters	ozzilee: you might ask on OFTC #openjdk
17:24	ozzilee	walters: I'll do that, thanks.
17:30	rhickey	danlarkin: you asked earlier about keywords as functions. Not everything can be a fn, I can't change numbers for instance. If you want consistency, always use the map itself as the fn - that will always work. Keywords were made fns too because they are often used as keys, and when doing so tend to 'feel' like properties, in which case reading (:name x) as 'the name of x' works well.
17:30	rhickey	I don;t think it would work as well for numbers and strings, even if I could support that
17:30	rhickey	but I wouldn't take it out for keywords
17:33	danlarkin	rhickey: thanks for the explanation... I guess I will just stick to using the map/vector as the function, for consistency's sake
17:44	smoofra	is there a document anywhere that explains how closure maps to java? things like the calling convention, boxing, etc
17:44	wwmorgan	smoofra: http://clojure.org/java_interop
17:49	Chouser	rhickey: clojurescript/avoid-java-in-boot.patch moves some references to java from boot.clj into RT.java
17:50	Chouser	Any remaining references in boot.clj are skipped by clojurescript when compiling boot.clj, either because they don't make sense in javascript or because they'll need to be written in js by hand.
19:41	H4ns	can anyone recommend a fast, small java http server that i could use to run clojure applications in? i'm looking for something that can handle a lot (>1000) of persistent connections.
20:31	ozzilee	Good news everybody! Turns out openjdk6 runs on PPC Debian Lenny. So I've now got Clojure running on my 700mhz iBook :-)
20:45	arohner	what is the idiomatic way to see if an item is in a list?
20:45	arohner	like contains? for a seq/list/vector
20:48	arohner	I could use filter or some, but it seems like there should be a shorter way
20:52	H4ns	(take-while (partial = <elem>) <seq>) would work, but doesn't look quite idiomatic (and also cons)
20:53	H4ns	can someone explain how i would instantiate a class from a random .jar containing java classes that i have downloaded? i seem to be totally confused
20:55	fyuryu	H4ns: you have to add the .jar to you classpath, then import it in Clojure, and then instantiate like this: (ClassName. ...)
20:56	H4ns	fyuryu: import would work like what? can you give me an example?
20:57	danlarkin	H4ns: you can find examples of importin in the clojure-contrib repo
20:57	danlarkin	AFAIR it's (import '(java.whatever.whatever))
20:58	H4ns	wow.
20:58	H4ns	i must have tried almost everything almost like that :) thanks!
21:00	fyuryu	H4ns: http://github.com/rosado/clj-processing/tree/master/rosado/processing/processing.clj
21:01	H4ns	thanks - the import itself does not seem to check its arguments, so i'll need to learn more
21:05	H4ns	fyuryu: success, thanks!
21:55	danlarkin	H4ns: wow thanks for sharing, jconsole is really cool
21:57	H4ns	danlarkin: i'm only beginning to recognize what "leveraging the platform" really implies. there is just a hell of a lot of enterprise class infrastructure that comes along with the jvm.
21:57	H4ns	xlightweb also looks very good, both for client and server side http
23:46	arohner	is there a way to convert a java.util.Set into a clojure data structure?
23:48	danlarkin	perhaps call set on it?
23:48	arohner	I'm trying that
23:48	arohner	I get "Don't know how to create ISeq from:"
23:48	danlarkin	does (set (seq x)) work?
23:50	arohner	nope
23:51	arohner	the (seq x) fails
23:54	danlarkin	I'm sure there's a way
23:55	danlarkin	you could always do it manually
23:55	arohner	yeah, I'm surprised because set implements java.util.Collection
23:55	arohner	yeah
23:55	arohner	I thought Collection was what seqs used