#clojure – 2008-07-01

2008-07-01

09:40	wlr	rhickey:apropos your recent identity/entity essay, this may interest you: http://arxiv.org/pdf/0806.4746
09:41	Lau_of_DK	wlr, where is that essay ?
09:41	notyouravgjoel	the jvm supports os level threads, and thus clojure will use all of my cores, correct?
09:45	wlr	Lau_of_DK: http://clojure.org/state
09:47	spacebat	notyouravgjoel: yes it can
09:49	Lau_of_DK	wlr, thanks
10:21	Lau_of_DK	Anybody here working with Chousers zip-filter-xml lib ?
12:20	JamesIry	Gang, if any of you happen to be in LA, Orange County, or San Diego I've formed a group called Southern California Functional Porgrammers: http://socalfp.org.
13:13	rhickey	Anyone ever gotten Shoal or Jxta to work with IKVM? Trying to do some Clojure/.Net interop
13:17	kotarak	These numbers in the compiler messages... Are these line numbers? Eg. monad.clj:906, but this file has only 70 lines...
13:18	rhickey	there are some instances where you'll get a line number from a macro
13:19	rhickey	can you paste a small reproducing case?
13:19	cemerick	rhickey: No, but what problems are you running into?
13:20	rhickey	ffailla can provide some details of the problem
13:22	kotarak	rhickey: the problem is a wrong defmethod call: (defmethod monad/bind [m k] (cond (is-ok? m) (k m) (is-nok? m) m)) It's missing the dispatch value.
13:30	rhickey	kotarak: when I put these 2 lines in a clj file and load, I get an error on line 2:
13:30	rhickey	(defmulti bind identity)
13:30	rhickey	(defmethod bind [m k] (cond (is-ok? m) (k m) (is-nok? m) m))
13:30	kotarak	I get one on line 906.
13:30	kotarak	From the REPL: clojure.lang.Compiler$CompilerException: NO_SOURCE_FILE:906: Unable to resolve symbol: m in this context
13:30	rhickey	just those 2 lines in a file?
13:31	rhickey	what version of Clojure?
13:31	kotarak	I'll try. Just a second
13:31	kotarak	20080612 zip
13:33	rhickey	rev 909, on 6/17, improved things in this area
13:34	ffailla	cemerick: I have compiled jxta to IL via IKVM and ported the DiscoveryClient/DiscoveryServer Java tutorial to .NET as a test. It seems that my discovery callback never gets executed that was wired up with DiscoveryService.addDicoveryListener. The client and server apps appear to be running with out error, but the communication between the two does not appear to function. The Java example works fine.
13:35	cemerick	ffailla: What version of ikvm are you using?
13:36	kotarak	rhickey: ok. Will try the svn version.
13:36	Lau_of_DK	Chouser: You in the house tonight ?
13:37	Chouser_	Lau_of_DK: I am.
13:41	ffailla	cemerick: ikvm-0.36.0.11
13:41	pjb3	In Clojure terminology, is there a difference between a Var and a Symbol?
13:41	rhickey	pjb3: definitely
13:42	rhickey	a symbol is just a name
13:42	rhickey	like a string except it has 2 parts, ns and name
13:43	cemerick	ffailla: the first thing I'd do is compile the java example to IL, and bootstrap that up to make sure the whole stack works.
13:43	ffailla	cmerick: will do... i'll let you knwo how it turns out
13:43	ffailla	thx
13:43	rhickey	a var is a reference
13:43	cemerick	no prob
13:44	pjb3	rhickey, so when you do (def x) you are assigning a Var to the Symbol x?
13:44	rhickey	there is no storage in a symbol, it is an immutable value, so no such thing as assigning to it
13:44	rhickey	we names vars in our programs using symbols
13:45	rhickey	so (def x) says create a var with the name x in the current namespace
13:46	rhickey	we could use the same symbol x to refer to something else in a different ns
13:46	rhickey	symbols don't have a 1:1 relationship with places
13:47	rhickey	pjb3: do you know CL?
13:47	pjb3	rhickey: not really, coming from more of a Java/Ruby background
13:48	Chouser_	so "symbol" is almost synonymous with "identifier"?
13:49	rhickey	symbols can be used as identifiers, and are in program's code-as-data
13:49	rhickey	when you type a symbol into the repl, the evaluator tries to find the var associated with it
13:49	pjb3	gotta go, be back later
13:49	rhickey	ok
13:51	Chouser_	I always flail a bit trying to talk about clojure code. I keep reaching for the word "variable" which is clearly wrong, and am never sure what to say instead.
13:53	kotarak	"naming" maybe?
13:57	cemerick	rhickey: (conj (hash-set) 5) => #{5}, but (conj (sorted-set) 5) => IllegalArgumentException
13:57	rhickey	there's no substitute for owning up to symbols being first class objects, vs just names in program text...
13:58	cemerick	That's in svn r927.
13:59	rhickey	clean? what does (sorted-set) return?
14:01	Chouser_	I just got the same error on r926. ant clean and rebuild fixed it.
14:01	rhickey	Chouser: I've taken to calling let-bound locals just locals
14:01	cemerick	Yeah, I cleaned, updated, built. (sorted-set) => {}
14:01	cemerick	I'll try another wash and rinse. :-P
14:01	rhickey	user=> (sorted-set)
14:01	rhickey	#{}
14:02	Chouser_	cemerick: specifically it was java.lang.IllegalArgumentException: Don't know how to create ISeq from: Integer
14:02	cemerick	Chouser_: Yeah, that's what I'm getting too.
14:02	Chouser_	rhickey: "locals", nice.
14:02	rhickey	vars are much trickier, people have such presumptions
14:04	Chouser_	a global var pretty much is a global variable, isn't it? You can point it at a new value anytime you want, you're just not supposed to.
14:05	rhickey	it is until you distinguish def from set! and binding
14:05	Chouser_	binding them is a bit different, but elisp and perl do that, so there's some reference for it.
14:05	rhickey	CL too
14:06	Chouser_	perl's such an odd beast. it only had globals and dynamically-bound variables for a while, lexicals came later. Also has closures, but no named function arguments.
14:07	cemerick	wow, that was way harder than it should have been -- I cleaned 3x -- ended up checking out anew, all's well now.
14:07	Chouser_	rhickey: really? I don't see too much code on the groups with misused def
14:08	rhickey	not among the more experienced
14:08	rhickey	but re-def-ing is many people's first inclination
14:08	Chouser_	is there some reason you allow def inside functions?
14:09	rhickey	Sure, you might have a program that writes a program
14:09	Chouser_	surely you could detect it at compile time and error out. ...would stop it quick.
14:09	rhickey	dynamically
14:09	rhickey	stop redef? how will we fix bugs?
14:10	rhickey	or just non-top redef?
14:11	kotarak	I have my math point of view: a definition is something special, long lasting. Eg. N is the set of natural numbers. This won't change (in a given context). Namings are local to eg. a proof. Let f_x be the density of x blablabla. The (def) is something important, which won't change. And (let) gives local namings for a limited context.
14:11	Chouser_	no, I just meant when you see a def that's not at the top level of the expr
14:11	Chouser_	but your point about building a program dynamically stands.
14:12	rhickey	kotarak: that was the idea, defs are durable, lets transient, set!s dangerous and not allowed on globals
14:12	rhickey	but people see the effect of def and consider it assignment
14:13	rhickey	also, one tends to re-def dummy var names in the repl
14:13	Chouser_	hm, although allowing it via (eval '(def foo 5)) would still pass the "top-level" test and would be weird enough to perhaps discourage casual use.
14:13	rhickey	most code shouldn't ever eval
14:14	Chouser_	most code should also never call def from inside a function, right? so it lines up?
14:14	Chouser_	I'm just musing here. Don't let me keep you from something important. ;-)
14:14	kotarak	OCaml got me cured of re-defing things. However one these it also in introductory code: (define some-state ...)
14:14	rhickey	no, when I call evel I think "there must be a better way"
14:14	rhickey	eval
14:15	kotarak	s/these/sees/
14:16	rhickey	in OCaml are subsequent defines (with the same name) different bindings?
14:17	kotarak	Just let me check, but if remember correctly, your are not allowed to re-def things. Doing this like let x = f 5 in let x = g x in let x = h x in x are always "new" x's.
14:18	kotarak	Hmm... Ok. you can re-def.
14:19	rhickey	right but def x 5, write code using x, def x 6, code using x still sees 5 unless recompiled?
14:20	kotarak	Yes. Eg.: let x = 5;; let f () = x;; let x = 6;; f ();; will give 5.
14:31	kotarak	Hmmm. Is it bad to modify the meta-data of a "foreign" object?
14:32	rhickey	what do you mean by foreign?
14:33	kotarak	I'm a library and the user passed in
14:33	kotarak	oops.
14:34	kotarak	the user passes in something. Then I will most likely use with-meta, I suppose. Then I get a copy.
14:35	rhickey	you can merge metadata safely using namespace-qualified symbols as keys - `my-key will become 'my-ns/my-key
14:36	kotarak	o.O Uh? Nice.
14:37	rhickey	also note, recently symbols became fns of maps like keywords (`my-key ^blah) works
15:31	kotarak	hmmm..., x and y not def'd, I expect ^x = nil and ^y = {:Foo :Bar} and x and y = "Hello": (def x "Hello") (def y (with-meta x (assoc ^x :Foo :Bar))), but I get an IncompatibleClassChangeError. Where is my mistake?
15:33	StartsWithK	i'm trying to clojure applet, so i was reading this http://is.gd/JRW and using gen-and-save-class created my class that extends clojureapplet class http://pastebin.com/d7efff553 but i'm still geting this error http://pastebin.com/d48033846
15:33	StartsWithK	can someone tell me what that means
15:33	StartsWithK	*to make
15:36	rhickey	kotarak: strings can't have metadata
15:37	kotarak	-.- Ok.
15:37	rhickey	StartsWithK: ClojureApplet is not public
15:42	StartsWithK	rhickey, tnx that was it :) so just a quick question http://pastebin.com/d66048d8c means that i have to sign my applet?
15:43	StartsWithK	and clojure.jar hmm..
15:44	kotarak	doh, "symbols and collections support metadata". Those who can read shall have a clear advantage.
15:44	rhickey	StartsWithK: it may not work even when signed - Clojure needs a classloader which may be disallowed, but that story could be different with the latest plugin stuff
15:45	StartsWithK	i use JNLPAppletLaucher, and on that thread he used web start too, so i was thinking it sould work as applet if it can be made to work as web start application
15:46	StartsWithK	https://applet-launcher.dev.java.net/
15:46	rhickey	forgot he did that, looks promising
15:47	blackdog	StartsWithK, did you try without creating a main class? I was hoping that it would pick up user.clj auto, but it doesn't seem to want to work
15:48	StartsWithK	blackdog, i don't know how to make applet run without some class extendind javax.swing.JApplet or java.awt.Applet
15:48	blackdog	duh, i'm getting mixed up with webstart
15:48	StartsWithK	i don't think it can be done any other way
15:49	blackdog	i was trying to run it auto from a jar,
15:49	blackdog	without a main class
15:50	StartsWithK	i don't think that could work, jnlp needs entrypoint class
15:50	blackdog	yea i was giving it a stub main,
15:51	StartsWithK	i'm using this http://pastebin.com/m5e817f05 as applet launcher
15:51	blackdog	but user.clj still didn't kickj in
15:51	blackdog	thanks that's useful
15:51	blackdog	apparently with the new update n jdk 6, applet and webstart stuff is unified to a degree
15:52	blackdog	you can drag an applet of the page and have it run stand alone (apparently)
15:52	StartsWithK	yes, and my line of thinkis is - if web start can launch clojure then applet should too
15:52	StartsWithK	ill have to run my applet first :)
15:53	StartsWithK	and i think there is some option for that, i'm not sure, still reading the docs
15:53	StartsWithK	but i found you can force it to use separate jvm, maybe that is it
15:53	blackdog	i thought that was one of the innovations in updaten
15:54	blackdog	updateN (or whatever it's called)
15:54	StartsWithK	i think it was update5 or 10..
15:56	blackdog	i hope sun don't fu on the new applet stuff it would be nice to write everything in clojure from back to front
15:56	StartsWithK	yes, i would like to run my jogl apps as applets :)
15:56	StartsWithK	https://jdk6.dev.java.net/plugin2/jnlp/
15:56	blackdog	i was suprised to see applet usage on facebook, but that's a hopeful sign
15:57	StartsWithK	i tested it with some demos from jogl and it runs really nice and fast.
16:10	StartsWithK	ok, i certified clojure.jar and my helloworld.jar as show in http://is.gd/JTG
16:11	StartsWithK	it no longer is bothering me with security, it just asked do i trust this untrusted certificate
16:11	blackdog	nice
16:11	StartsWithK	now i have this http://pastebin.com/m5e1ebdeb
16:12	StartsWithK	but that looks like i just don't know how to use genclass
16:12	Chouser_	no, you're doing it right.
16:13	Chouser_	you have a (refer) inside your genclass namespace, right?
16:13	Chouser_	You either have to do a bunch of :exclude, :only, or :rename.
16:13	StartsWithK	yes
16:14	Chouser_	or skip the refer entirely and use clojure/defn and such everywhere.
16:14	StartsWithK	ok ill try that (this is how it looks at the moment http://pastebin.com/m43685eff)
16:18	Chouser_	it's pretty annoying, because either way you generally screw up and leave something out of your :exclude or :only list, and just have to try again, note the exception, and add the name to the list.
16:18	Chouser_	on the other hand, it's hard to think of how it ought to work instead.
16:19	rhickey	one possibility is to have all of the 'method' names be munged in some fixed way
16:20	Chouser_	another would be if you could define names in a namespace without having to be in that namespace. (defn classns/init [this] ...)
16:22	rhickey	since most namespaces will be long com.blah.ClassName seems like a -method suffix or m- prefix would be shorter
16:22	StartsWithK	changet it to http://pastebin.com/d37cd7943 but now i get "unable to resolve clasname : Graphics"
16:24	Chouser_	yeah, although with namespace aliasing that problem would go away too.
16:25	Chouser_	hm, with munging you could have a handy macro to do the right munging for you. (defmethod foo [this]...)
16:25	Chouser_	well, no defmethod, but something. def-genclass-method. ;-)
16:26	rhickey	defhandler?
16:26	Chouser_	yeah
16:27	StartsWithK	how will that help with the need to use clojure/let and others?
16:27	Chouser_	that way the actual munging could be entirely internal to clojure and not show up in the user's code at all.
16:28	rhickey	and with munged names you could (refer 'clojure) without conflicts
16:29	Chouser_	I suppose the names manually given to genclass would remain unmunged? :factory, :state, etc?
16:30	rhickey	right
16:30	Chouser_	yeah, this would be a lot better than how it is now.
16:32	StartsWithK	ok, i think it will work.. now i get no matching field found: getSize
16:32	StartsWithK	so applet must be running
16:32	Chouser_	defhandler could even add the "this" arg for you, like proxy does
16:33	Chouser_	hm, except some of the unmunged names probably still take "this", which might be confusing
16:33	Chouser_	ha!
16:38	Chouser_	so you can define .foo, and you can refer to it, but you can't call it. in the context of a genclass ns, though, I suppose you could do (.foo this ...) and have it refer to the .foo you just def'ed.
17:49	StartsWithK	it was silly mistake on my part Graphics has no getSize method, JApplet has it.
17:49	StartsWithK	so (.getSize this) works
17:49	StartsWithK	and i can say applet works :)
17:50	Chouser_	very cool! how hard was it to sign the various bits?
17:50	Chouser_	you should write it up and send it to the google group.
17:50	blackdog	ii'm interested :)
17:50	StartsWithK	i will do it sometime tomorow, ill try to find ant tasks to automate signing the jars.
17:51	StartsWithK	so for now i can only say it works on jre 1.6_05 under xp
17:52	Chouser_	if you've got it up somewhere I can point linux with jre 1.6_06 at it.
17:53	StartsWithK	for now i think it should be at http://rekram.homelinux/neman/neman.html
17:53	Chouser_	is there a .net or .org in there somewhere?
17:54	StartsWithK	uff sorry, jer org
17:54	StartsWithK	*yes
17:54	Chouser_	Publisher: sun microsystems
17:54	blackdog	i get the blank gray applet box :)
17:55	StartsWithK	hmm
17:55	blackdog	not asking me for anything
17:55	StartsWithK	can you open java console to see the output?
17:55	Chouser_	ah, another auth box for published by K-something. ;-)
17:55	StartsWithK	thats me
17:55	Chouser_	yeah, I figured. and now a grey box. :-(
17:55	StartsWithK	it could take some time, i included jogl jars inthere too
17:55	blackdog	i;m on openjdk ubuntu here
17:56	blackdog	ok maybe it's stilldownloading here
17:56	StartsWithK	hmm.. i used openjdk on arch (64bit) and it didn't work for jogl textures..
17:56	blackdog	i'm on 64 too
17:56	blackdog	:/
17:56	blackdog	no worries
17:57	StartsWithK	icedtea6 worked with applets, but didn't display jogl correctly.. ill try it with 1.7
17:58	blackdog	where do i find the java console in ff3
17:58	StartsWithK	under xp in control panel there is java icon, i checked java console from there
17:59	StartsWithK	but i don't know under linux :/
17:59	StartsWithK	http://www.java.com/en/download/help/5000021200.xml
17:59	blackdog	my java is enabled but i'm not seeing any console optipon maybe it's another extension or so
18:00	Chouser_	did it open a new window?
18:01	blackdog	no, i'm getting the gray box and nothing else right now, i'll check my install
18:01	StartsWithK	i can say that it work on another xp box with jre 1.6_06
18:07	StartsWithK	blackdog, if dcc is working on freenode i can send you the files so you can try localy?
18:07	blackdog	sure, i'll give it a try, but i think it's my setup
18:08	blackdog	woops
18:08	blackdog	can you do that again
18:10	StartsWithK	ill send you the sources too, but they are just a mess at the moment, there is a ant task "ant dist-helloworld-applet"
18:11	StartsWithK	and you should sign helloworld after each modification
18:11	blackdog	ok, no joy locally either
18:12	blackdog	but i seems ubuntu is carrying a jdk7 gck web plugin, so i don't think it's entirely standard :)
18:13	blackdog	gcj
18:13	StartsWithK	im just happy it works under xp :) it it will not be fun to work with applets if i can't test them on my box
18:13	Chouser_	Hello World
18:14	blackdog	for real,
18:14	Chouser_	It just worked for me here.
18:14	blackdog	anything to stop having to write flash :)
18:14	StartsWithK	Chouser_, under linux?
18:14	Chouser_	linux ubuntu java 6
18:14	StartsWithK	cool
18:14	StartsWithK	thats 32bit?
18:15	blackdog	i'm 64bit
18:15	Chouser_	something about it doesn't like my window manager -- I think that's why I was getting a new window popping up.
18:15	Chouser_	but in a "normal" window manager, it worked just fine.
18:15	StartsWithK	:)
18:16	Chouser_	yes, I believe I'm all 32 bit here (although probably on a 64 bit cpu)
18:17	blackdog	yea, i was a bit hasty with my install :/ should have kept it standard,
18:17	blackdog	the worst thing i found was that the mem consumption of java is even worse than usual
18:18	StartsWithK	blackdog, i think standard jdk6 under 64bit linux can't display applets at all
18:18	StartsWithK	icedtea6 can
18:18	blackdog	so for my dev i use the 32 bit updateN under my login which works fine
18:19	blackdog	ah, wonder if appletviewer works
18:19	blackdog	the update n version
18:23	blackdog	nopes
18:23	blackdog	~/usr/jdk1.6.0_10/bin/appletviewer http://www.rekram.homelinux.org/neman/neman.html
18:23	blackdog	java.security.AccessControlException: access denied (java.net.SocketPermission download.java.net connect,accept,resolve)
18:23	StartsWithK	yes i get that one too, but i can't say why
18:23	blackdog	maybe appletviewer doesn't deal with the secirty stuff
18:23	blackdog	no worries
18:24	blackdog	thanks for the src,
18:24	StartsWithK	random link http://www.innovation.ch/java/security.html
18:25	StartsWithK	with something about appletviewer and how to setup security
18:26	blackdog	k
21:02	Chouser	(defn f [] (let [x {:a #(...) :b #(...)}] ...))
21:03	Chouser	Is x built each time I call f?
21:03	rhickey	yes, but the fns are not recompiled
21:04	Chouser	I'm thinking of use x like this instead of a (cond) ... is that bad idea for style or speed reasons?
21:06	rhickey	what that really is is case - value dispatch. The resulting dispatch, especially if there are many cases, will be much faster...
21:06	rhickey	but - if you only dispatch once, you will have instantiated all the fns
21:07	rhickey	a fn compiles into a class that implements IFn
21:07	Chouser	I have 3 or 4 cases ... right, ok. probably not worth it just for speed.
21:07	rhickey	creating an instance is a simple ctor that passes any closed-over values
21:07	Chouser	ah, ok.
21:08	Chouser	my #() fns all close over args of f, so I can keep old instances. And then f will do a single lookup of x. So this is probably quite inefficient compared to a cond.
21:09	Chouser	...which is a pity because the hash look implementation is more terse.
21:10	Chouser	does java bytecode have goto?
21:10	rhickey	I need to add case just so you don't have to (cond (= x :a) ... (= x :b) ...)
21:11	rhickey	recur is goto
21:11	rhickey	there's also a table switch, for numeric cases
21:11	Chouser	ah, yes. I looked that up once.
21:12	Chouser	hm, hash values are numeric... oh, sequential?
21:12	rhickey	you need to know the values at compile time
21:12	Chouser	ah, never mind. I'm way off in the weeds now. I'll just go write my cond expression. :-)
21:12	rhickey	sort them
21:13	rhickey	case would be (case x :a ... :b ...)
21:14	Chouser	that would fully solve my terseness issue. I guess I can write a case macro that produces a cond
21:15	Chouser	would you provide an else for case?
21:15	rhickey	(case x :a ... :b ... x ...)
21:16	Chouser	oh! nice.
21:16	rhickey	CL has ecase where no match throws
21:17	rhickey	case with no match should return nil
21:33	slava	you can do interesting optimizations with a case macro
21:36	Chouser	slava: like what?
21:37	slava	well, if your keys are integers, you can turn it into a binary search or a table switch, depending on how closely packed they are
21:37	slava	for other types you can look at the hashcode, then only compare against the keys having that same hashcode modulo n, where n is the size of a dispatch table
21:39	Chouser	slava: if you have constant test values.
21:40	slava	yes
22:10	lisppaste8	Chouser pasted "naive case macro" at http://paste.lisp.org/display/63135
23:06	sterling	motd