#clojure – 2008-09-23

2008-09-23

09:34	StartsWithK	should i call (agent-errors) periodicaly just to flush list of exceptions?
09:34	rhickey__	aren't the exceptions telling you something isn't working?
09:35	rhickey__	or just to detect the error?
09:35	StartsWithK	just to detect errors while developing
09:37	rhickey__	that or dereferencing will do it, the latter throwing
09:40	StartsWithK	(def a (agent nil)) (send a (fn [& args] (throw (Exception. "test"))) (deref a) (agent-errors a)
09:41	StartsWithK	agent-errors still show list with "test" exception
09:41	rhickey__	they'll be there until you clear them
09:42	yangsx	hi, what is the best match for Common Lisp's assoc in clojure?
09:43	rhickey__	yangsx: use maps instead of alists
09:43	rhickey__	{:a 1 :b 2}
09:44	yangsx	rhickey__: yeah, thanks, just trying to learn clojure by porting PAIP code
09:45	rhickey__	one of the problems with straight ports of PAIP or SICP is that you miss out on a lot of Clojure's benefits
09:47	StartsWithK	why are (symbol "test test") and (keyword "test test") legal?
09:47	yangsx	sure, but I can gain better insight the difference between the two, and clojure specific features can be left for the next turn
09:48	leafw	yangsx: clojure looks like lisp, but it's not lisp in many regards. leaving clojure features for the next turn doesn't strike me as wise.
09:48	rhickey__	yangsx: I disagree, pretty strongly. lots of that code is imperative and you'll just struggle trying to emulate it
09:49	yangsx	so I should change the order :)
09:50	yangsx	porting PAIP code is challenging
09:50	rhickey__	yangsx: The real challenge is functional programming, not the minor syntax differences
09:51	yangsx	rhickey__: I can program in functional style, but haven't try the pure way yet
09:53	rhickey__	yangsx: that's good, then it shouldn't be too bad. But at each point where Clojure differs, it pays off to learn why. For instance, it would be easy to do alists in Clojure, but I don't recommend it because they don't scale. You can use maps right from the start and they will.
10:00	yangsx	besides reading the wikibook and the official website and Stuart's blog porting PCL, are there any other resources helping me (from CL) to learn Clojure?
10:01	Chouser_	rhickey__: have you considered adding watchers to refs, similar to the new agent watchers?
10:03	Chouser	I sometimes think I want that, although then I often realize I want more than just the new value -- I also want some kind of delta or diff with the old value.
10:03	Chouser	...in which case it's probably more appropriate to write my own hash-map class or something to log the changes.
10:06	drewr	yangsx: At this point, it's best just to start with a problem and try to write the code to solve it.
10:09	yangsx	drewr: OK
11:01	rhickey__	Chouser: I have, not sure about old/new value. I've left it out for now. I think it is a violation of encapsulation in some ways - watchers could/should be calling functions to get at parts of the state they care about.
11:21	aking	Any chance that clojure would work under Android? It works fine (though slow) with jamvm on the iphone.
11:23	rhickey__	aking: that would require AOT compilation, since there is no dynamic bytecode loading on Dalvik. I've been looking at AOT compilation recently and getting on Android would be one of the reasons to do it
11:24	aking	that'd be cool. One the iphone with jamvm, it seems to be running about 150-200x slower with the one benchmark I tried.
11:25	rhickey__	are all java things 150x slower?
11:26	aking	godd question. I'll try a quick benchmark from the shootout
11:27	aking	good* .. ugh.. my typing is bad this morning... more coffee
11:33	aking	running 'time java binarytrees 14' gives 0.487s on my system and 40.804s on the iphone
11:34	cemerick	rhickey__: speaking of AOT compilation, you mentioned line numbers being an issue last week -- wouldn't emitting all of the java source corresponding to a line of clojure on a single line give you the desired result?
11:35	rhickey__	cemerick: there is JSR 45, it's just a post compilation step to add that info to the classfiles
11:36	rhickey__	might be some issues with tracking classes generated by inner classes
11:45	ozzilee	Ok, not my problem or business, but it bugs me. Shouldn't experimental things like agent watchers be added in a branch of the repository, rather than in trunk?
11:47	blackdog	or stick to the release version
11:49	rhickey__	branches are time-drains
11:50	ozzilee	I suppose.
11:50	cemerick	there'd probably be dozens of branches if things were allowed to bifurcate due to newness at this point
11:50	rhickey__	most new features are in the, don't use it, don't care category
11:50	rhickey__	and if there are repercussions, I want to know asap
11:51	blackdog	also, i think git or mercurial make branching easier- to beat abrooks drum :P
11:52	rhickey__	I'll put my productivity in developing Clojure up against any other model
11:54	rhickey__	it works for me, not advocating for anyone else
11:55	rhickey__	but the branching vs usage is important, if only the few people who were interested in agents were running that code, it would be far less tested than by having it in head
11:58	ozzilee	Makes sense to me.
12:34	shoover	StartsWithK: I didn't see an answer to your question from a couple hours ago. clear-agent-errors is the other way to get rid of them
12:36	shoover	Chouser: clojure-log seems to be missing Next/Previous in Chrome :(
12:45	drewr	Yet another browser to check. :-(
12:47	ozzilee	I don't see Next/Previous in Safari either. Same engine.
12:47	drewr	Oh, well that's good.
12:47	ozzilee	(web rendering engine I mean)
12:47	drewr	So are Chrome tabs basically a bunch of Safari processes?
12:48	ozzilee	Well, webkit processes I guess.
12:48	ozzilee	Chrome has its own Javascript engine though, separate from Webkit/Safari's.
12:49	drewr	Yeah, V8.
12:49	ozzilee	Yeah. The rendering is webkit though. I don't know much of the details.
12:49	ozzilee	I do know it's an older version of webkit than the current Safari uses.
13:30	Chouser	shoover: try the site again?
13:30	Chouser	it should be fixed
13:31	shoover	Chouser: indeed
14:03	StartsWithK	shoover: thanks
14:16	StartsWithK	agent is bind to current agent, and you can (send) to agent?
14:19	StartsWithK	i'm reading http://is.gd/318H producer-consumer example, and agent is used in example but i can't fint it on clojure.org in documentation
14:22	Chouser	StartsWithK: I think you're right, but agent's never been particularly documented.
14:43	fyuryu	StartsWithK: agent is the current agent, I remember rhickey mentioning it in the concurrency talk
16:43	StartsWithK	is it ok if i do (send (agent nil) action), i mean, is agent cheap or should i store him somewhere?
16:45	StartsWithK	or.. hmm, could i merge producer and consumer and remove ref in a way that same agent gets two action that like in that example call themselfs, and both operate on agents state?
16:46	StartsWithK	(let [a (agent nil)] (send-off a produce) (send-off a consume))
16:55	shoover	StartsWithK: you could, but you need two agents if you want the actions to run in parallel
22:05	yangsx	no documentation for recur in http://clojure.org/api though it's mentioned in clojure.markdown, a bug?
22:25	arohner	(reduce (fn [x y]) [])
22:25	arohner	java.lang.IllegalArgumentException: Wrong number of args passed to: eval--4705$fn (NO_SOURCE_FILE:0)
22:25	arohner	is that expected? it seems like a better error message could be thrown
23:00	Chouser	yangsx: recur is a special form, and thus is not on the api page
23:00	Chouser	yangsx: (doc recur)
23:53	yangsx	Chouser: special forms are special? :) but (doc recur) does not work here: Unable to resolve var: recur in this context
23:53	arohner	what version of clojure are you running?
23:53	yangsx	though I've understand recur now
23:54	arohner	yangsx: (doc recur) was added in svn r1034
23:55	yangsx	arohner: I see, my current copy's not updated