#clojure – 2008-06-29

2008-06-29

00:09	spacebat_	so, I'd like to ask what environments people use, plain REPL, netbeans+enlojure, emacs+ilisp, emacs+slime, or something else?
00:11	spacebat_	hi craigoz, whereabouts in .au? I'm in adelaide
04:21	fanda_	hello!
04:22	fanda_	just trying IRC
05:03	spacebat_	hi fanda_
05:03	fanda_	hello spacebat_
05:04	spacebat_	new to clojure?
05:04	spacebat_	I am
05:04	fanda_	yes, me too
05:04	fanda_	just starting with it
05:04	fanda_	i used newLISP before
05:04	fanda_	but I know little about Java
05:05	spacebat_	knowing very little lisp and no functional programming, its a steep curve
05:05	spacebat_	but I can see the reasons to keep on with it
05:05	spacebat_	I used to work for a java shop, but that was years ago
05:06	spacebat_	my day job is perl
05:06	fanda_	yes, i love functional programming and LISP especially
05:06	spacebat_	newLISP, I haven't heard of that one
05:06	fanda_	i used it for explorative programming
05:06	fanda_	it is a small dialect of Scheme (LISP)
05:06	spacebat_	open or proprietary?
05:06	spacebat_	I tend to think that common lisp is a bit on the hulking side
05:07	fanda_	yes, common lips is too big
05:07	fanda_	http://www.newlisp.org/
05:07	spacebat_	but it does seem to be the most widely implemented standard
05:07	fanda_	clojure is more symetrical and more well thought in my eyes
05:07	spacebat_	I've liked that common lisp has been easy to start with
05:07	spacebat_	because it lets me code imperatively
05:08	fanda_	yes, exactly
05:08	spacebat_	but that doesn't fly here
05:08	fanda_	newlisp is similar
05:08	fanda_	(setq x 5) or (set! x 5) ;-)
05:08	fanda_	clojure is more pure
05:08	spacebat_	I saw an excellent post on the newsgroup today that spelled it out
05:09	spacebat_	if you make a new value, either give it a new variable, or pass it directly into a function
05:10	fanda_	yes, I also have problems with immutability
05:10	fanda_	i am thinking about creating some "cook book"
05:10	spacebat_	I've had similar ideas
05:10	fanda_	how to mutate or "looks-like-mutate" ;-)
05:11	spacebat_	gradually accumulating code snippets in a library, a modest general purpose collection at the moment
05:11	fanda_	i have been reading some code from contributions
05:11	fanda_	now i am trying to create my first useful something :-)
05:12	spacebat_	I haven't even looked into contrib yet
05:13	fanda_	here
05:13	fanda_	http://groups.google.com/group/clojure/files
05:13	fanda_	and here
05:13	fanda_	http://clojure-contrib.svn.sourceforge.net/viewvc/clojure-contrib/trunk/
05:13	spacebat_	I see yes I checked that out of svn but its just sitting on disk so far
05:14	spacebat_	looking at complete programs has been a bit confusing, trying to get the gist from gradually larger chunks of code
05:15	spacebat_	clojure just might be my gateway back to java
05:15	spacebat_	using an IDE to get past the static verbosity of java repulses me these days
05:16	spacebat_	I've been ruined and made anew by dynamic languages
05:17	spacebat_	rhickey was saying that there is a guy in sun who really gets lisp
05:17	spacebat_	and wants to put tail recursion and more functional support in the JVM
05:19	spacebat_	ok newlisp, I have seen that page before, like a year ago
05:19	spacebat_	I've been learning lisp about 3 weeks now
05:20	spacebat_	does it have threads?
05:21	fanda_	what do you mean - if newlisp has threads? no, it doesn't
05:21	spacebat_	ok
05:21	spacebat_	yes that's what I meant sorry
05:21	fanda_	newlisp is written in C
05:21	fanda_	runs on many platforms
05:21	spacebat_	what brings you from there to here?
05:21	spacebat_	yes portable threading isn't trivial
05:22	fanda_	but it has everything on its own - runtime - garbage collector, etc.
05:22	fanda_	libraries for one
05:22	fanda_	you can import only C libraries or write your own lisp libraries - so much time spent there
05:22	kotarak	did anyone encounter issues with agents and clojure.lang.Script?
05:22	fanda_	i have no idea about this one
05:23	spacebat_	me neither sorry
05:23	fanda_	don't be sorry
05:23	spacebat_	heh
05:23	fanda_	:)
05:23	fanda_	if you have any lisp questions, i might answer
05:23	fanda_	map, apply, filter...
05:23	fanda_	lambda (meaning fn) functions
05:24	spacebat_	is there something you don't like about newlisp?
05:24	spacebat_	not asking you to trash it or anything
05:24	kotarak	No. It's more about using agents for concurrency. In the REPL I see the agent output, calling the script "hangs". I'm not sure where or why.
05:24	fanda_	hi kotarak :-)
05:25	kotarak	hello fanda_
05:25	spacebat_	sounds like something a tad advanced
05:25	kotarak	ok. never mind
05:25	spacebat_	maybe the REPL is doing some sync that's needed and not in Script
05:26	fanda_	don't know why he left...
05:26	spacebat_	hunting rather than gathering
05:26	fanda_	hm
05:27	spacebat_	newlisp looks like it has potential
05:27	fanda_	yes, its cool in its own terms
05:27	spacebat_	if its fast, then with the right libs for coordinating processes it could be a real workhorse
05:28	fanda_	here are my creations:
05:28	fanda_	http://intricatevisions.com/index.cgi?page=newlisp
05:28	fanda_	just click on the left for code, code-tk, ...
05:28	spacebat_	does it generate binaries?
05:28	fanda_	no, it does not
05:28	fanda_	its only interpreted
05:28	spacebat_	what tipped lisp over the interest threshold recently was seeing Language::Lisp::ECL on the cpan
05:28	fanda_	but you can make wrappers - wrap newlisp.exe with your script
05:28	spacebat_	ok
05:29	spacebat_	ECL uses gcc as a backend and can compile standalone exes
05:30	fanda_	can be interesting
05:30	spacebat_	a small naive fibonacci program compiled to 24k on disk
05:30	spacebat_	its common lisp, so I guess it leaves out all the stuff that isn't being called
05:30	fanda_	ok, that's interesting!
05:30	spacebat_	it also makes it easy to embed, all common lisp functions are callable from C
05:31	spacebat_	the fib program ran about 10 times slower than a C program with the same gcc, for fib(39)
05:32	spacebat_	but it was still about 6 times faster than the fastest interpreter I tried, which was python
05:32	fanda_	quite interesting
05:33	spacebat_	time to give my boy a bath
05:33	spacebat_	nice chatting fanda_
05:34	fanda_	wait
05:34	spacebat_	yupo
05:34	fanda_	save this link
05:34	fanda_	http://groups.google.com/group/clojure/browse_thread/thread/69b781ffe805a7de/b60673e9d4436ce0
05:34	spacebat_	will do
05:34	fanda_	comparison CL - Clojure ;-)
05:34	fanda_	might use it
05:34	spacebat_	thanks, bye
05:34	fanda_	nice chatting!
05:34	fanda_	bye!
05:40	kotarak	sorry, got disconnected. maybe the output of the agent goes somewhere else in the Script compared to the REPL.
06:22	spacebat_	possibly, you said it hangs though
06:22	spacebat_	whereas it returns in the REPL?
08:31	Chouser	kotarak: you might just try adding (flush) after your print or prn
08:33	kotarak	Chouser: no, doesn't help.... Everything worked before, until a packed the output into an agent (since I have to some sync here). Then it stopped working. In the Script. In REPL it still works.
08:34	rhickey	kotarak: your script may be ending before your agent is done?
08:36	kotarak	huh? It can? Ok.... Hmmm... I (await) the agent, but let me add some sleep there.
08:37	rhickey	if you await in the same thread you sent, then it's done. Who flushes - - the agent or main?
08:37	kotarak	the agent
08:39	kotarak	also tried a (flush) in the main thread, didn't help
08:40	rhickey	can you paste a small case?
08:41	kotarak	I'll try to strip it done. Just noticed, that the hitting ctrl-c gives me the output. Maybe a have to issue an explicit exit?
08:44	kotarak	Ahh. Got the problem!!! When using agents, the script doesn't terminate, when reaching the end. You have to explicit call a (. java.lang.System (exit 0)).
08:44	rhickey	heh, I used to do that for you, but GUI app devs complained...
08:46	kotarak	rhickey: well, I'm mostly a non-GUI guy, so I expect a script to exit, when it is end is reached. But that also comes from things like C or sh. There you also have a non-returning function for GUIs. So maybe I just have a differnt point of view.
08:47	kotarak	rhickey: btw. good job with clojure. It brought me back to the lispy side of life. :)
08:47	rhickey	thanks, glad you worked it out
09:11	Chouser	calls to the "rest" part of a lazy-cons are synchronized, but I suppose I still need to wrap them in sync if I want to use set! on a ref, right?
09:13	rhickey	you mean your rest expression manipulates a ref?
09:13	Chouser	right
09:13	rhickey	Clojure will force you to be in a transaction, else throws
09:14	Chouser	well, reads a ref, but yeah. Ok, that's what I thought.
09:14	rhickey	I though you said set
09:15	Chouser	I did! I'm sorry, I mis-typed.
09:15	Chouser	actually, I mis-thought.
09:16	Chouser	sorry, still sketching this out in my head. the rest expr will only need to read the ref (and perhaps block on something). so no sync there! cool.
09:16	rhickey	You can do non-transactional reads of refs
09:17	rhickey	as long as you don't require a relationship between that read and another
09:18	Chouser	I don't think so. I'm going to try to build a vector in a background thread, while providing a lazy-seq as access to it in the main thread.
09:20	rhickey	Don't ignore things like java.util.concurrent.ArrayBlockingQueue
09:25	Chouser	hard not to ignore things I've never heard of
09:26	rhickey	Clojure doesn't duplicate the workflow tools of java.util.concurrent because they are really good
09:27	rhickey	queues/barriers/latches/exchangers etc
09:29	meredydd	rhickey: Ahh...so, that's really the answer to my question a few days ago
09:29	rhickey	meredydd: which question?
09:30	meredydd	about thread pools in Clojure...but java.util.concurrent does one, so Clojure doesn't have its own
09:30	kotarak	that's my main problem with clojure: when you have to fallback to some java stuff, I pretty lost.... (I have no clue about java whatsoever)
09:30	meredydd	(so you just have to do the magic proxy fiddle to turn a (fn) into a Runnable)
09:30	rhickey	actually Clojure does abstract thread pools with agents
09:30	rhickey	fns are Runnable
09:30	rhickey	and Callable
09:31	meredydd	They are now? Oh, great!
09:31	meredydd	(Must have been looking at an old discussion...could have sworn I'd seen you saying that there was a good behind-the-scenes reason (fn)s weren't Runnable)
09:32	rhickey	there is some casting required now to disambiguate for the executor methods which are overloaded on both Callable and Runnable
09:33	rhickey	that hassle was the only reason, but the tradeoff is worth it since half the java library uses one, and half the other
09:33	meredydd	Ah, excellent.
09:34	meredydd	Thank-you, then.
09:34	meredydd	And, by the way, did you do any more thinking about the relational algebra stuff in set.clj?
09:34	meredydd	Because I've been thinking a little about that
09:35	rhickey	no, what are your thoughts?
09:35	meredydd	and how, of course, the nil-for-empty convention is fine, provided one uses seqs rather than sets
09:36	rhickey	you mean seqs of maps as rels?
09:36	meredydd	yeah
09:36	rhickey	but won't they have to keep being made into sets anyway?
09:36	meredydd	Just thinking that, if you were willing to forgo the mathematical warm-and-fuzzies of exact correspondence to the un-augmented relational algebra
09:36	meredydd	Well, for what purpose?
09:36	rhickey	efficiency
09:37	meredydd	Of which operations? (Sorry, haven't poked around enough in set.clj to see how you do this stuff)
09:37	meredydd	Joins, I suppose.
09:37	rhickey	right
09:37	meredydd	Ah, bugger. The man has a point.
09:37	meredydd	Damn it - it's just that I was thinking
09:37	rhickey	also I like the rel is a set of maps rule, i.e. no dupes
09:38	meredydd	yep. As I say, nice mathematical warm-and-fuzzies with the exact correspondence to the RA
09:38	rhickey	with the twist of a non-fixed set of columns
09:39	meredydd	yeah, well...it's that, or a set of vectors, which wouldn't be as nice to work with.
09:39	rhickey	that's the special sauce of Clojure rels - non rectangular/sparse
09:39	meredydd	indeed.
09:40	meredydd	Anyway - I was just musing that if you were to work with seqs, you could create a nice hack to use a proper SQL back-end for these things
09:40	meredydd	and, because the seqs are lazy, you could have ops like joins, pi, sigma, etc fold themselves into the SQL statement
09:40	rhickey	seq->set once on load seem not too bad
09:40	rhickey	seems
09:41	meredydd	which is only actually executed when (first) is actually called on the seq
09:41	meredydd	which would, neatly, allow you to keep all the relational operations Clojure-idiomatic.
09:42	meredydd	(at the cost of some "Is it a bird? Is it a plane? Is it a seq, or an SQL wrapper?" hackery in the back-end.)
09:44	kotarak	Hmmm... Is there something in using agents, which turns off flushing? Suddenly I have to add (flush)es all over the place.
09:44	kotarak	Or is java.lang.System.exit discarding unflushed stuff?
09:45	meredydd	kotarak: I think java.lang.System.exit is just killing the VM before the agents get a chance to run what you've sent them
09:45	rhickey	If you have multiple thread writing to the same stream you're likely to get a mess at some point. Maybe confine your I/O to a single place and have the agents just create the to-be-output values?
09:47	kotarak	I have one agent, which does the output stuff. So this is in sync. It's also (await)ed by the main thread. So there should be no problem here. I think exit just kills the VM, with flushing. Give me a second.
09:48	kotarak	Yep. It's java.lang.System.exit. Is there some way of a sane shutdown? (Ie. doing things like flushing output.)
09:48	rhickey	await/flush/exit doesn't work?
09:49	kotarak	it does.
09:49	kotarak	The flush is a bit anoying
09:49	kotarak	But maybe this is again my different background. Just have to get used to it.
09:50	rhickey	there have been requests that the pr* fns flush
09:52	kotarak	I'm used to "newlines flush" and also exit() flushes. So flush is somehow the default for me. Now java.lang.System.exit does not flush. poof I have problem. But that's simply the wrong default on my side.
12:19	Chouser	tomhickey_: on clojure.org's left-hand menu, the clickable area for each link extends the full width of the menu. Top notch!
13:15	rhickey	new essay: http://clojure.org/state
15:40	abrooks_	Chouser: Good observation regarding tomhickey_ 's good UI. Nicely done tomhickey_!
16:20	scgilardi	pjb3: I liked the picture of Rich you posted the other day captioned "State: You're doing it Wrong"
16:26	scgilardi	I have a thought about the flushing issue: it's often a good thing to flush on newline, but sometimes the inefficiency matters. How about a var flush-on-newline whose global binding is to "true" which is used to control whether or not some subset of the "pr*" functions flush on newline (or flush with each call).
16:28	scgilardi	I also like the idea I saw for "dbg*" functions that auto-flush as debugging is often a case where flushing matters
16:46	rhickey	scgilardi: flush-on-newline whose global binding is to "true" works for me
16:51	scgilardi	cool, thanks.
17:39	rhickey	user=> flush-on-newline
17:39	rhickey	true
18:17	Chouser	hmph. can't properly store nulls in an ArrayBlockingQueue
18:18	rhickey	aargh
18:31	Chouser	but false works fine, so using that as an end sentinel, this does what I want:
18:31	Chouser	(for [e (repeatedly #(.take q)) :while e] e)
19:40	rhickey	gotta love repeatedly