#clojure – 2008-09-20

2008-09-20

13:00	Chouser	I think because JS is already dynamic, I can make calling clojurescript from java and vice-versa even more transparent.
13:01	Chouser	JS already unifies "package" and "class", as they're all just Objects, and sincs clojure namespaces will also just be an Object, they're all already unified.
13:51	rhickey	clojurescript from javascript?
13:54	Chouser	sure, probably most common will be to define a function in clojurescript and hand it off to the DOM to be called on an event.
13:58	Chouser	oh! yes, sorry, clojurescript from javaSCRIPT.
13:59	Chouser	I don't think I can write the Collections in cljs without corrupting clojure first. I need access to JS's "this" reserved word.
15:08	mhinchey	I'm having a problem with metadata. In the repl, (meta first) returns nil. Is that right?
15:10	rhickey	mhinchey: the metadata is on the var, not the function value, so (meta (var first)) will work
15:10	rhickey	(meta #'first) is a shorthand
15:10	mhinchey	got it, thanks
15:29	joubert	Hello
15:29	Chouser	joubert: hi
15:29	Chouser	mhinchey: or ^#'first for extra-short-hand
15:29	Chouser	I miss perl. sniff
15:30	rhickey	Chouser: now, now
15:30	joubert	I would like to call a method on a Java object. However, the method name is unknown to the caller code, and must be passed to it in a variable.
15:31	joubert	e.g.
15:31	joubert	(let [meth 'blahblahmeth] (. myObj meth "miau"))
15:32	joubert	(this code is only to illustrate the intentional use; it does not actually run)
15:33	leafw	joubert: you could solve it with reflection, but I am curious to hear what options clojure offers as well.
15:33	Chouser	(clojure.lang.Reflector/invokeInstanceMethod "foo" "replace" (to-array ["o" "x"]))
15:34	joubert	oooh uuuugly
15:34	joubert	:-)
15:34	Chouser	hmph.
15:34	leafw	joubert: make a macro for it.
15:34	Chouser	or design your code so you don't need it.
15:34	hoeck`	joubert: try using a closure: (let [m #(.blablameth % "miau")] (m myObj))
15:34	hoeck`
15:35	joubert	hoeck: that is similar to (memfn) isn't it?
15:36	hoeck`	joubert: yes, forgot that
15:37	joubert	hoeck: that means I need to pass in #(.blahblahmeth % "miau") as the param to my function, instead of just "blahblahmeth" or 'blahblahmeth
15:37	Chouser	#(.method obj arg1)
15:38	Chouser	you're putting % in the obj position, not allowing it to call a different method
15:38	joubert	Reflector/invokeInstanceMethod - kosher to call it from apps? Seems like an API that is not intended for use by programs?
15:39	lisppaste8	rhickey pasted "jcall jfn" at http://paste.lisp.org/display/67182
15:40	leafw	what does the '#' do to the (apply jcall ...) ?
15:40	leafw	new to me.
15:41	Chouser	#(+ 5 %) === (fn [i] (+ 5 i))
15:41	leafw	shorthand for a lambda?
15:41	Chouser	#(+ 5 %1 %2) === (fn [i j] (+ 5 i j))
15:41	Chouser	leafw: exactly
15:41	leafw	ok
15:41	leafw	thanks.
15:42	rhickey	#(apply jcall %1 name %&) => (fn [x & etc] (apply jcall x name etc))
15:43	leafw	but # is also used for defining a key in a hash set/table, right?
15:43	Chouser	looks like memfn might do it too, but I've never used it and am failing to get it to work for me
15:44	leafw	(if (some #{text} table) ...
15:44	Chouser	leafw: # is used for several things, all documented here: http://clojure.org/reader
15:44	leafw	thanks
15:44	joubert	memfn doesn't work for this instance, because you cannot pass a symbol to the Clojure syntax for Java member calling
15:46	Chouser	oh, I see -- memfn's a macro.
15:46	Chouser	ok, that make sense. It's been pretty much superceded by the #() syntax.
15:48	leafw	woah, this syntax with %1 %2 ... is really nice. Like using regex for function declarations.
15:49	joubert	What is the performance difference between Reflector/invokeInstanceMethod and just going (. meth obj var) ?
15:50	Chouser	joubert: I think the . syntax uses invokeInstanceMethod if it doesn't have sufficient type hints to produce a direct call.
15:51	joubert	chouser: OK.
15:53	joubert	It seems to me a nicety might be to "respect" bindings in invoking methods on objects, or no?
15:54	joubert	(when resolving the method names)
15:55	rhickey	joubert: no, it's not a dynamic name system, not duck naming. Clojure supports compiled name resolution.
15:56	joubert	rhickey: does that mean that the . syntax has performance characteristics different from Reflector/invokeInstanceMethod?
15:56	rhickey	. tries to make a direct call, if names were just values it couldn't
15:56	rhickey	much much faster if it can avoid reflection
15:57	joubert	OK. I know how to design my solution then. Thanks.
15:57	rhickey	the jcall/jfn I posted is dynamic calling
15:58	joubert	right. I'm not going to go with than.
15:58	joubert	that.
16:00	Chouser	joubert: that's good to hear. :-)
16:06	leafw	what is the equivalent of 'range' in python? Is there such function in clojure?
16:06	Chouser	you might try range
16:07	Chouser	:-)
16:07	leafw	xD
16:07	leafw	why do I ask.
16:07	Chouser	(doc range), if that helps
16:09	leafw	thanks.
16:12	joubert	chouser, rhickey, leafw: (defmacro runSetter [setterSym target value] `(. ~target ~setterSym ~value))
16:13	joubert	and then you can (runSetter methodName myObj val)
16:15	joubert	but still cannot pass a symbol, because its name cannot be resolved in the context.
16:15	joubert	anyway, just wanted to add this dimension to my initial Q.
16:20	leafw	how come doc throws an Exception for java methods? Why not just print nothing, or at least the signature of its arguments and return type?
16:20	leafw	that'd be useful.
16:22	Chouser	How would it know which class's method you're talking about?
16:23	rhickey	didn't someone do a javadoc that loaded the right page in the browser?
16:24	Chouser	I use this: http://paste.lisp.org/display/67122#1
16:25	leafw	Chouser: (show ij.IJ/log) fails ... fails for a static method
16:27	Chouser	start with the class (or an instance) to list all methods and fields.
16:27	Chouser	(show ij.IJ)
16:27	Chouser	then pick the method you want out of the list: (show ij.IJ 9)
16:28	leafw	got it.
16:28	leafw	will edit it to take the string and search it. Thanks for sharing.
16:30	leafw	a jdoc builtin function, or evne just doc with some magic on it, would be great. Just a suggestion.
16:31	rhickey	someone did it in a paste somewhere...
16:31	rhickey	http://clj-me.blogspot.com/2008/05/jumping-to-javadocs-from-repl.html
16:33	Chouser	wow
16:37	rhickey	yeah, cgrand rocks, I miss him
16:40	rhickey	if only Sun would cough up JWebPane...
16:40	rhickey	saw it at JavaOne, totally awesome Java wrapper on WebKit
16:41	Chouser	ah, interesting.
16:41	rhickey	then we could run ClojureScript in a Java hosted browser window :)
16:42	Chouser	Or perhaps run the ClojureScript as Clojure instead, and make V8 look like molasses
16:43	Chouser	<script type="test/clojurescript">...
16:43	Chouser	er, text
16:43	rhickey	yes, the access to the DOM etc from Java was great - they seemed to have all the right ideas
17:56	mhinchey	I'm working on adding the 1 vars to swank-clojure, which has its own repl. I think it would be helpful if evaluating 1 2 or 3 doesn't reset those vars. That way, if you don't loose the values by simply checking one of them. Does that make sense?
18:05	rhickey	mhinchey: I don't know, the CLs I've used have pushed the * evals too
18:12	mhinchey	rhickey: alright, I'll post to the group, see what others think
19:46	abrooks	:w
19:47	abrooks	er... hm. Not so much Vim.
20:28	Chouser	rhickey: do you have a CA from Erik Soehnel? I want to use his multimethod print.
20:29	rhickey	yes, I'm hoping to get that print into Clojure proper soon
20:34	Chouser	oh, well that would be even easier. :-)
21:15	alec	Is it expected for Clojure to take a long time starting up? I installed from svn using maven, and when I run 'java clojure.lang.Script <empty file>', it takes 6 seconds to finish
21:15	alec	(using openjdk-6)
21:16	Chouser	alec: I've heard reports approaching that. I don't know if my faster startup time is just due to a fast machine or something else.
21:18	alec	I don't see anything on the website about precompiling the Clojure source to bytecode; is that possible?
21:19	Chouser	no, not presently.
21:19	Chouser	you're using the release from this month?
21:19	alec	svn from the other day
21:19	rhickey	alec: what OS? anything on the classpath?
21:20	dudleyf	It's about 4 seconds on my MBP
21:20	alec	running Debian amd64
21:20	alec	nothing else in the classpath, but Debian's openjdk may load other things in, let me see if I can disable that
21:22	alec	no, setting $CLASSPATH to only the Clojure jar file didn't speed things up
21:23	abrooks	rhickey: By Cliff Click's megaboxen you mean Azul Systems Vega 3?
21:23	rhickey	there is a (non-Clojure) issue with JDK6 and ever increasing classloading times, which seems to impact Clojure on Linux/Windows
21:24	rhickey	abrooks: dunno the model
21:25	abrooks	Wow. The Vega 3 is spiffy: 864 processor cores and 768 GB of memory in a flat SMP configuration.
21:27	rhickey	He's asked for some non-Java programs, so I've got a parallel ant colony optimization of the traveling salesman problem - < 100 lines of Clojure, looking to see how it scales
21:31	abrooks	rhickey: Cool. I'd be interested to hear how that goes.
21:32	abrooks	rhickey: How did you get access to one of these?
21:32	rhickey	He's got one, not me :)
21:33	abrooks	Oh, this is directly via Cliff Click?
21:33	rhickey	yes
21:34	aking	See Cliff's blog about it: http://blogs.azulsystems.com/cliff/
21:34	abrooks	Cool. Do you know Cliff well?
21:34	rhickey	nope. We're both speaking at the JVM languages summit next week. We've only spoken on the group and his blog
21:37	abrooks	Oh, frick. I didn't realize cliffc was Cliff Click.
21:37	abrooks	Heh.
21:38	abrooks	rhickey: Sounds like he's skeptical about the scaling benefits of STMs.
21:39	abrooks	... hence your inerest in running a large scale Clojure app on his systems...
21:39	abrooks	^inerest^interest
21:43	rhickey	he's still in a pretty rarefied domain. No matter how many cores we get, most apps will have trouble thinking of more than a few dozen things to do at once. Using every core becomes the job of the next layer - VM/OS/whatever is running the multiple apps. I'm pretty sure STM will work where most apps are using locks, with greater ease and more robustness
21:45	rhickey	my ACO broke out of a local minimum after 10 minutes - woo hoo!
21:47	abrooks	rhickey: How big is the universe? (4-way connected?)
21:48	abrooks	Congrats, BTW. :)
21:48	Chouser	boot.js loads now
21:49	rhickey	abrooks: it's a 280 node (2-D) tour
22:14	abrooks	The Vega 3 looks quite interesting. We get 1458 (vs 864) cores and 1944GB (vs 768) in roughly the same rack space (a bit more with fans and power) but ours is across 243 (6 core) nodes. 864 cores seeing 768GB in flat SMP is impressive (and sadly useless for most applications).
22:15	abrooks	We = my employer, in this case.
22:15	rhickey	have you got Clojure running on that?
22:17	abrooks	No. We currently have a JVM half ported (running interpreted, non-JIT). Not enough serious HPC customers are out there. No one has asked for Java yet.
22:19	abrooks	It would be interesting to see how the JVM runs with slow cores with fast memory.