#clojure – 2008-05-02

2008-05-02

09:31	Chouser	"Downloads: not available" ... how often should I be clicking reload on that page?
09:31	Chouser	Is every 5 seconds too much?
09:31	rhickey	:)
09:31	jteo	emacs should be good enough for anyone
09:36	Chouser	because elisp is as good as Clojure?
09:38	jteo	let's not go there. :)
09:40	Chouser	:-)
09:41	Chouser	seriously though, the ancientness of elisp (and other parts of emacs) are major contriubtors to my failure so far to switch away from vim.
09:42	Chouser	Not that viml (vim's scripting "language") can even be mentioned with a straight face in this context...
10:01	rhickey	I'm working on:
10:01	rhickey	(gen-class
10:01	rhickey	package-qualified-name
10:01	rhickey	;all below are optional
10:01	rhickey	:extends aclass
10:01	rhickey	:implements [interface ...]
10:01	rhickey	:constructors {[param-types] [super-param-types], ...}
10:01	rhickey	:methods {name [return-type [param-types]], ...}
10:01	rhickey	:main boolean
10:01	rhickey	:factory name
10:01	rhickey	:exposes {protected-field {:get name :set name}, ...})
10:01	rhickey	will spit out bytecode you can load immediately or store as .class file
10:01	rhickey	Fully statically accessible name
10:02	rhickey	Fully dynamic implementation, code goes in clojure namespace with same name
10:05	rhickey	thoughts?
10:05	cgrand	Very nice! What does :factory stands for? A static method name?
10:05	Chouser	wow.
10:05	rhickey	cgrand: yees, set of static methods matching ctor sigs
10:06	rhickey	ctor calls will flow through clojure init fn, if provided, allows you to morph args to super ctor and supply a state for the class
10:07	Chouser	people are going to try to use this for more than just Java interop, as part of the design of the clojure apps.
10:07	rhickey	aah, but state is final
10:07	Chouser	hehe. ok, nice.
10:07	rhickey	but can be actor or ref, so resulting objects are Clojure-savvy
10:08	rhickey	transactional or asynch state for POJOs
10:09	Chouser	class name is required?
10:10	rhickey	yes, that is how the binding to Clojure code works - classname-->namespace-name
10:11	rhickey	The idea is you'll gen-class once, then proceed to implement incrementally/iteratively in Clojure
10:11	rhickey	The only part that's locked-down is what is supplied to gen-class
10:12	rhickey	changing that means restarting JVM
10:18	rhickey	cgrand: this is why I've held up on servlets, I'm hoping gen-class can be used to generate servlets and any other stubs that used to require Java
10:19	cgrand	rhickey: that was my first thought while reading this: no more hand-coded java stubs :-)
10:19	Chouser	rhickey: ah, so once you're done (gen-class foo ...), you can're reuse the name "foo" without restarting the JVM.
10:19	rhickey	chouser: yes,that's the static nature of Java I can't change
10:19	rhickey	I've tried in this design to maximize the dynamic parts
10:20	rhickey	but classnames are load-once-per-classloader
10:23	cgrand	what about providing an (optional) file name which would be loaded in static init? Or should all the init stuff be done in user.clj? (won't asnwer, must go)
10:23	Chouser	the methods list has no method bodies, does it -- just the interface description?
10:24	rhickey	methods is just for additional methods, the generated class will have all methods of superclasses, and yes, no code in gen-class at all
10:25	Chouser	ok, so you're generally do (gen-class Foo ...) and later (proxy [Foo] ...).
10:26	Chouser	Sorry if I'm a little slow on the uptake here.
10:27	rhickey	gen-class builds a class that redirects method calls to vars named classname/methodname
10:27	ericthorsen	rich: how close are u to putting up the work?
10:27	ericthorsen	I'm ready!
10:27	rhickey	it's in svn, but not done
10:28	Chouser	ohhh... gen-class links a Clojure namespace to a new Java class
10:29	ericthorsen	ok
10:29	rhickey	right
10:29	Chouser	which I now see you said up at the top.
10:29	Chouser	the method functions get an extra first param for the class instance?
10:30	rhickey	yes
10:30	rhickey	(gen-class org.clojure.MyComparator :implements [Comparator])
10:30	rhickey	(in-ns 'org.clojure.MyComparator)
10:30	rhickey	(defn compare [this x y] ...)
11:59	cgrand	rhickey: you mentioned that instances can hold state (as a final field?) how would one declare it and access it?
12:01	rhickey	was hardwired (to __state) when we last spoke, now there is a :state key, and an :init key which name the state and constructor initializer respectively
12:02	rhickey	access like a normal field, will be public like all members in these classes
12:02	rhickey	if :state not supplied, no state
12:04	rhickey	init takes ctor-args and returns [[super-ctor-args] state]
12:05	rhickey	s/returns/must return
12:05	cgrand	ok I understand now
12:14	cgrand	So, prior to instantiation the namespace and its functions must be defined. This means that when the user doesn't control object creation (because he's using some framework) everything must be initialized as soon as Clojure ends initializing (eg through user.clj). Am I right?
12:18	rhickey	Partially. The generated class will create the namespace as a side-effect of having static Var fields. If there is no init, then objects can be created right away. Code will need to be loaded prior to method calls in order to avoid UnsupportedOperation. But in general, yes, user.clj is the path to pre-loading.
12:25	rhickey	cgrand: I'm not averse to your suggestion of an option for the class to load its own code, need to think about any circularities
14:13	leafw	is there any way to set stdout in clojure?
14:13	leafw	(with-out-str ...) works inconsistently
14:14	rhickey	leafw: bind out
14:22	lisppaste8	Chouser pasted "exception trying to implement a Map" at http://paste.lisp.org/display/60112
14:24	Chouser	How could I do dissoc correctly, but mess up assoc? Anyone have any ideas?
14:25	leafw	'bind' is not a keyword in boot.clj
14:25	leafw	'binding'?
14:25	rhickey	yes, bind out with 'binding'
14:26	rhickey	like with-out-str does
14:28	leafw	I a using with-out-str
14:28	leafw	but half the times it ends up not printing anything ,i.e. "prn" calls don't print anywhere
14:28	rhickey	with-out-str prints to a string
14:29	rhickey	what do you do with the string it returns?
14:29	leafw	Ijust print it
14:29	leafw	prints with quoed newline and quoted quotes chars
14:30	leafw	I know this may not sound ver yhelpful.
14:31	leafw	code is at http://pacific.mpi-cbg.de/cgi-bin/gitweb.cgi?p=fiji.git;a=blob;f=src-plugins/Clojure/Clojure_Interpreter.java;h=8f664da07b8424cccdb1d38d746cc3c0b632927c;hb=1435e05539abc332386b515f7a4aa2df1f1236ac#l144
14:32	leafw	I created an interpreter, consisting of two JTextArea
14:32	leafw	exists in superclass AbstractInterpreter.
14:32	leafw	the ListThread is called via 'eval(String text)' method
14:33	abrooks	rhickey: I'd suggest that your respectable mop of hair may make up for lack of facial hair but you may want to consider growing a beard for good measure: http://blogs.microsoft.co.il/blogs/tamir/archive/2008/04/28/computer-languages-and-facial-hair-take-two.aspx
14:33	abrooks	;-)
14:33	rhickey	leafw: could you post a small example of your problem to paste.lisp.org?
14:34	leafw	I think I saw part of the problem
14:34	leafw	certainly on my side
14:34	leafw	I am returning from the while loop ... not ok if the parsing is not done.
14:36	leafw	yes, fixed. Oh well. thanks anyway.
14:40	rhickey	enclojure got dzoned - better get a download up soon :)
14:41	leafw	as long as java exists, there'll be those who bypass the pain by using clojure.
14:41	rhickey	Chouser: I can reproduce, looking at it now
14:48	rhickey	Chouser: I'm guessing it has to do with the covariant return type
14:49	rhickey	Associative.assoc returns Associative and IPersistentMap.assoc returns IPersistentMap
14:52	abrooks	rhickey: Going back to the awaiting a set of agents which mutually send to eachother. No, I don't know the number of jobs a priori. CountDownLatch isn't going to help me. Since almost exclusively all the jobs set to an agent are not originating from a thread outside of the agent pool, I don't have any way (that I can think of) to know when all queued jobs are done.
14:53	abrooks	Agents feel like a good fit for the problem but I don't know how to know when they're done.
14:54	rhickey	how do you know to stop creating jobs?
14:54	leafw	After much testing, I remain clueless: the fallowing fails. (binding out (. System out)) -- but with-out-str never fails, and uses a similar construct
14:54	leafw	oh Isee
14:54	leafw	binding is like a let.
14:55	Chouser	rhickey: thanks. I'll try to turn that nugget into a fix.
14:58	abrooks	rhickey: An agent only adds jobs when it sees work to do. Eventually, there's no more work todo. The problem is finding the lowest cost path across a the matrix (where nodes have cost and edges are free).
14:59	rhickey	abrooks: are the agents in a list somewhere?
15:00	rhickey	abrooks: could you countdown agent idleness rather than jobs?
15:02	abrooks	rhickey: I have the agents in a map. How can I detect their idleness?
15:04	rhickey	abrooks: nothing automatic here, just brainstorming, they would have to report their idleness somehow
15:04	abrooks	Ah. Gotcha.
15:06	abrooks	What about some sort of barrier that you could send off to a set of agents wait for?
15:07	rhickey	there is CyclicBarrier
15:07	abrooks	Is that a Java object?
15:07	rhickey	yeah in java.util.concurrent
15:08	rhickey	if you have a fixed number of agents and they each know when they are done, that could work
15:08	abrooks	I'll take a look at that. Thanks.
15:08	rhickey	shame you can't increment CountDownLatch...
15:09	abrooks	Ah, here's the catch. A particular job knows when it's done but the agent does not.
15:09	rhickey	that's what I mant about incrementing countdownlatch, then each job issued would increment, each completed would decrement
15:10	abrooks	I could track the number of jobs going to zero but that would create a lot of contention on a single object.
15:10	abrooks	(i.e. count up on send, count down on job completion)
15:11	rhickey	right
15:11	rhickey	the problem isn't contention - AtomicInteger is plenty fast, the problem is polling for done
15:11	abrooks	Right.
15:11	rhickey	vs blocking for done
15:14	rhickey	got it - use atomicinteger and exchanger - job setting count to zero enters exchanger, master waits on exchanger
15:14	abrooks	Right, but jobs could check the value before they exit and perhaps trigger some thread wakeup.
15:14	rhickey	?
15:16	abrooks	If the "master" thread were to sleep or enter some sort of Java blocking primitive that I know nothing about but imagine it exists, the jobs could do the count up and count down. A job, before exiting could check the counter and unblock the master thread if the count was zero.
15:16	rhickey	every job issuer increments and every completing job decrements
15:16	rhickey	See AtomicInteger and Exchanger
15:17	abrooks	Right. And following that decrement the completing job could wake up the master so the master can block instead of be polling.
15:17	rhickey	no peeking, decrementAndGet
15:17	rhickey	when 0, exchange
15:18	abrooks	Okay, that. :) I don't know what Java offers. I've largely avoided Java for other languages when possible...
15:18	rhickey	java.util.concurrent rocks
15:20	abrooks	rhickey: I'll familiarize myself with it (and try to stop asking ignorant questions). Thanks!
15:21	rhickey	abrooks: you're welcome
15:56	abrooks	rhickey: java.util.concurrent does have some nifty tools. FutureTask is something I've wanted on a number of occasions and needed to fall back on periodic polling in the work thread on a cancellation flag.
15:57	ericthorsen	1st alpha of enclojure is up. Please read the Getting Started page before you begin.
16:11	rhickey	abrooks: and remember Clojure fns are Callable, so plug right into that framework
16:11	abrooks	abrooks: Duly noted. :)
16:13	rhickey	ericthorsen: congrats! and thanks
16:14	abrooks	rhickey: Hm. I really need to stop talking to myself in IRC. The above was, of course, meant for you. :-/
16:50	rhickey	Chouser: your proxy problem is fixed
16:51	Chouser	rhickey: oh! I thought the problem was on my end.
16:52	rhickey	no, proxy needed to gen 2 methods when returns types are covariant
16:52	rhickey	now it does
16:54	Chouser	beautiful.
16:59	bgeron	can take some time, though ;)
17:01	Chouser	oh! Yes, git is also beautiful, but I meant rhickey's fix.
17:01	bgeron	oh okay ;)
17:01	Chouser	abrooks: you saw my paste earlier? That's (the beginning of) that default-hash you wanted.
17:02	abrooks	Chouser: I didn't. Thanks for pointing that out.
17:05	abrooks	Just as an FYI. Sourceforge can host Mercurial projects. I'm not sure about git but suspect that it's doable. Public (free) git hosting is also available here: http://repo.or.cz/
17:05	abrooks	... if Clojure would ever want to be hosted in either DVCS. %coughs%
17:06	abrooks	Is there anything blocking that?
17:06	rhickey	not sure about IntelliJ support
17:06	rhickey	lack of spare time
17:07	rhickey	improve Clojure vs fiddle with VCS
17:08	abrooks	rhickey: Good reason. We don't want to distract you from Clojure. :)
17:18	rhickey	for the intrepid, if you want to play with gen-class in progress, what I just put up supports :extends, :implements, :state, :init, and :constructors