#clojure – 2009-01-17

2009-01-17

00:29	blbrown	are there any clojure oriented helpers for working with Java collections, e.g. is there a less verbose way of iterating over the key/values in a java hashtable
00:33	johan1	I'm trying to create an XmlRpc server using apache xmlrpc, but its addHandler method takes an object with public method that will be the callbacks, and proxy only seems suitable for instantiating an already defined class or interface. Anyone here who has tried xmlrcp with clojure?
00:36	johan1	or could tell me how to create an anonymous object without first having a class or interface in a jar file
00:37	Cark	isn't there an abstract class you could derive from ?
00:39	Cark	something like (proxy [org.apache.xmlrpc.XmlRpcHandler] [] (execute [pname, pvector] ....
00:39	johan1	perhaps I could find something with the arguments I need, but it doesn't feel very flexible. I think apache xmlrpc is using reflection to check if there is a method in the supplied object which has the same name as the method defined in the xmlrpc message, and calls it if it can be found
00:39	johan1	perhaps... I will check the API
00:40	danlarkin	Should I use (symbol (str (first (all-ns)))) or can I use (.getName (first (all-ns)))?
00:41	danlarkin	I suppose the line is that I can't trust that getName will be there in the future eh
00:41	Cark	(ns-name (first (all-ns)))
00:42	Cark	(doc ns-name)
00:42	clojurebot	Returns the name of the namespace, a symbol.; arglists ([ns])
00:42	danlarkin	:) perfect
00:42	danlarkin	thanks, Cark!
00:42	Cark	=)
02:36	danlarkin	Yesss, auto-reloading based purely on (all-ns) working!
09:12	edw	OK, after watching the Clojure videos, I'm way convinced that there's a there there.
09:14	Chouser	as in Clojure's not just a fad language?
09:15	edw	Yeah. Rich Hickey is not a 2nd year CS student.
09:30	edw	The transaction management stuff is very nice.
09:46	edw	Oh! I thought I was on #scheme!
10:03	edw	Is here a SLIME for Clojure for idiots guide somewhere?
10:03	edw	I use SLIME for Scheme48 for a while...
10:03	leafw	edw: google is your friend.
10:04	Cark	bill clementson has a couple blog articles on the subject
10:04	Cark	(morning)
10:05	edw	Yes, it is, but I'm going through a lot of pages that provide...incomplete information.
10:06	edw	It's sort of like reading posts by PHP programmers talking about Ruby on Rails. Or football players talking about feelings.
10:06	edw	Thanks Cark.
10:17	edw	leafw: Thanks for the sage advice. Finally found something usable that, after following a bunch of URLs, I discovered was actually somewhere in Google's result list. Now I realize that there all human knowledge is discoverable in principle through Google and I should therefore never ask any question if it takes less than an hour of random clicking through the web.
10:17	edw	s/there all/all/
10:18	Cark	tss, it's never a bad thing to ask a question
10:20	Cark	hum and btw did you check the getting started section on the wikibook ?
10:21	edw	Wikibook?
10:22	Cark	from the clojure official site, click on the wiki link
10:22	Cark	clojurebot : wiki
10:22	lisppaste8	edw pasted "A useful IRC topic" at http://paste.lisp.org/display/73757
10:22	Cark	clojurebot : wikibook
10:22	Cark	hum =/
10:22	edw	leafw: Over is #scheme, we try to be helpful.
10:23	edw	Cark: I heard there's a beta Clojure book that can be bought.
10:24	Cark	yes there is, i don't know where to find it though
10:24	arbscht_	clojurebot: book
10:24	clojurebot	book is http://www.pragprog.com/titles/shcloj/programming-clojure
10:24	arbscht_	clojurebot: wiki
10:24	clojurebot	wiki is http://en.wikibooks.org/wiki/Clojure_Programming
10:24	Cark	hey why is clojurenot answering to you ?
10:25	Cark	oh i know
10:25	edw	I figured it was Pragmatic: they did the same thing with the DHH Rails book.
10:25	Cark	clojurebot: wiki
10:25	clojurebot	wiki is http://en.wikibooks.org/wiki/Clojure_Programming
10:25	Chousuke	Cark: you have a space between clojurebot and :
10:25	Cark	clojurebot : wiki
10:25	Cark	yes
10:25	Chousuke	it's very strict about that.
10:26	Chousuke	you're not even allowed to use , or any other delimiter
10:26	Chousuke	has to be : :)
10:26	edw	Colons are so formal.
10:28	Cark	clojurebot: you're too formal
10:28	clojurebot	Excuse me?
11:45	edw	Hmm. Strings should be callable. E.g. ("012" 1) -> 1
11:46	rhickey	edw: unlikely, for perf reasons
11:46	edw	And sliceable, along with vectors. E.g. ([0 1 2] 0 1) -> [0 1]
11:47	edw	Ah. Just doing an OCD generality audit.
11:47	rhickey	Clojure strives to be as general as is practical
11:48	edw	I'll try to restrain my some of my more Scheme-like personality traits. ;)
11:49	rhickey	edw: it's a fair question
11:49	edw	So how about the splicing? (Since you've emboldened me...)
11:50	rhickey	edw: saving those additional args for multiple dimension indexing
11:51	rhickey	there's subvec already
11:52	edw	Ah. OK. Just finished watching the two part video. I was thinking about the treating-a-vector-as-if-it-were-multi-dimensional feature.
11:52	rhickey	I don't think splicing is that important an operation
11:54	edw	I agree. But for a single-dimensional data structure, it's the most obvious use of a second argument. To me.
11:55	edw	And so that's where my mind went. I'm trying things and seeing if they do what I intuitively think they should and then looking them up when they don't work that way.
11:57	Chouser	edw: that's an interesting experiment, but the results will surely be highly dependent on your particular background, don't you think?
11:58	edw	Yes. I didn't mean to imply that a proper language should validate my intuition.
11:58	edw	Intuit is a plastic thing.
11:59	edw	Intuition, even. It's cold in this coffee shop.
11:59	Chouser	It's a very intruiging way to introduce yourself to a new language. Unfortunately, I'm in too deep already -- my intuition has now been almost entirely overtaken by what Clojure actually does.
12:03	edw	I've been doing little but Scheme for several years, but have gone from 6502 assembly to C to Perl to Java to Python previously. I'm sort of stuck thinking that Scheme is the programming language that God wrote the universe in, but I'd like something for practically-minded mortals.
12:05	Chouser	Yes, I'm sure He has no trouble keeping track of all His mutable state.
12:06	kotarak_	I was also a Scheme fan before (and still am). But Clojure replaced it almost immediately as my favourite.
12:07	blbrown	just wanted to say, clojure is really cool... I am having a blast with it
12:07	blbrown	funny that it is a lisp, but doesn't seem like it
12:08	Cark	blbrown : what do you mean ?
12:09	blbrown	Cark, well, I been using Common Lisp off and on for years, but it seemed a little cumbersome, but I seem to work better with Clojure. I think it is because I also work with Java
12:09	edw	Getting over the lack of TCO was the big stumbling block for me to get over, because I'm habituated to think of the procedure call as the only "real" looping construct.
12:10	kotarak_	blbrown: Or the changes rhickey did to "Lisp", were just the right things?
12:10	Cark	blbrown, CL was my first exposure to lisp so i guess it'll always have a place in my heart
12:10	blbrown	karmazilla, possibly that too
12:11	edw	Clojure represents to me a nice blend of the MIT and New Jersey schools.
12:11	gnuvince_	Better is the New Worse is Better
12:12	edw	A Better Worse
12:44	rhickey	Clojure group crossed 10000 messages today!
12:45	rhickey	Google still says "low activity" :(
12:46	antifuchs	bah, google
12:47	antifuchs	if it's below a hundred billion, they don't even take notice.
12:48	gnuvince_	Give it time; the rise of Clojure is pretty impressie
12:48	gnuvince_	*impressive
12:48	gnuvince_	We're regularly at 100+ users connected to this channel
12:50	danlarkin	yeah but like only 30 people ever talk
12:50	danlarkin	70 lurkers freaks me out
12:52	antifuchs	you could call them programming language stalkers if that's better (:
13:03	blbrown	im active, sort of...silence is golden
13:10	Chousuke	an IRC channel is unhealthy without its share of lurkers.
14:12	danlarkin	lisppaste8: url
14:12	lisppaste8	To use the lisppaste bot, visit http://paste.lisp.org/new/clojure and enter your paste.
14:14	lisppaste8	danlarkin pasted "suitable for clojure.contrib.ns-utils ?" at http://paste.lisp.org/display/73772
14:15	danlarkin	that takes a string, although it could be modified to take a symbol too
14:16	danlarkin	so you pass it like "my.app.foo/bar"
14:17	danlarkin	and if my.app.foo is on your classpath it'll require it and resolve bar in that context and return it
14:37	Chouser	seems reasonable to me.
14:38	danlarkin	cool
14:39	Chouser	You might use 'symbol' to split the namespace from the name, rather than a regex
14:40	danlarkin	,(symbol "my.app.foo/bar")
14:40	clojurebot	my.app.foo/bar
14:40	Chouser	,(namespace (symbol "clojure.contrib.mmap/slurp"))
14:40	clojurebot	"clojure.contrib.mmap"
14:41	danlarkin	ah
14:41	Chouser	,(name (symbol "clojure.contrib.mmap/slurp"))
14:41	clojurebot	"slurp"
14:41	danlarkin	ahh ha
14:41	danlarkin	yes that is probably better
14:50	lisppaste8	danlarkin annotated #73772 with "dropped regex" at http://paste.lisp.org/display/73772#1
14:50	danlarkin	so that one takes a string or symbol
14:52	kotarak	A Java question: Is there a way to have a InputStream, that can be feed with additional input? So something like a Queue but in form of a InputStream?
14:56	Chousuke	sounds like a pipe
14:57	Chousuke	java.nio has it it seems. http://java.sun.com/j2se/1.4.2/docs/api/java/nio/channels/Pipe.html
14:57	kotarak	Exactly. I feed it on one end with characters, and the other end can read them as from a normal InputStream
14:57	kotarak	oh
14:58	Chousuke	it doesn't seem to use *Streams though.
14:58	kotarak	Yeah. :/ and it talks about "bytes"...
14:59	kotarak	But there is java.nio.channels.Channels! Hah!
14:59	Chousuke	http://java.sun.com/j2se/1.4.2/docs/api/java/io/PipedInputStream.html this if you don't want to use nio
15:00	Chousuke	but apparently nio is better... it wouldn't be "new io" if it weren't I guess
15:01	kotarak	Chousuke: thanks! Good pointers!
15:18	rowth	this may be a _really_ stupid idea, but...in some other jvm languages like groovy, you can use a clojure to implement a single method interface (i.e. if you're calling addActionListener etc.), would it be complete madness to ask if we could do something similar with clojure? Don't get me wrong, the (proxy ...) form is already much more terse than java, I'm just wondering...
15:19	rowth	also, since this is the first time I've actually said something to clojure folk, I might as well take the opportunity to say that Clojure rocks...thanks Rich!
15:20	rowth	damn, I meant "use a closure"
15:22	apage43	rowth: could it be implemented quickly enough as a macro? I don't see why not.
15:22	apage43	or wait, no
15:22	apage43	i see what you mean
15:29	rowth	I suppose you could try and do something like that, but then you end up with extra stuff wrapping the method you're calling and the closure you're passing in, which would defeat the point since the (proxy) syntax is already pretty terse. I suppose it may not be worth the potential extra complexity in the compiler, it's just that single method interfaces in java are basically the languages way of implementing a poor mans closure, so it would be nice if we coul
15:32	rowth	I like the idea of being able to do (.addActionListener button #(.setText label "you clicked zee button!")) or whatever
15:33	rowth	and if you use frameworks like Spring, there are an absolute shedload of methods that take single line Callback interfaces (doWithMethods, RowMapper, validators and all that caper)
15:33	rhickey	rowth: that would require compiler support, yes. I remember hearing about the Groovy feature and thinking there was some wart in it, but can't recall - something with overloading?
15:35	rowth	yeah...if the interface declares more than one method you have to use a closure that takes an array of objects
15:35	kotarak	(defn add-action-listener [widget callback] (.addActionListener widget (proxy [ActionThingyClassIDontRemember] []�(actionPerformed [e] (callback e))))) (add-action-listener button #(..)), not general though...
15:36	rowth	but (IMHO) groovy tries too hard to make things (supposedly) easy with a whole slew of random syntax / conventions
15:36	rowth	I was thinking of something a bit more clean cut
15:39	rowth	kotarak: yes it's easy to deal with individual cases; I suppose that might be the best way to deal with it rather than overcomplicating the core language
15:48	gnuvince_	,(some even? [1 2 3])
15:48	clojurebot	true
15:48	gnuvince_	,(some identity [nil 2 3])
15:48	clojurebot	2
16:04	LARefugee	clojurebot: logs?
16:04	clojurebot	logs is http://clojure-log.n01se.net/
16:13	lisppaste8	fanda pasted "Error in partition?" at http://paste.lisp.org/display/73778
16:14	fanda	(partition 0 [1 2 3]) returns infinite seq of nil
16:14	fanda	would you consider that an error?
16:15	fanda	see the above paste for all test cases
16:16	hiredman	interesting
16:17	hiredman	you'd think it would be (cycle `())
16:17	fanda	,(cycle ())
16:17	clojurebot	nil
16:18	fanda	yes, that's what I am suggesting - plain old nil :-)
16:18	hiredman	no, not (cycle ()), (cycle '())
16:18	hiredman	"Returns a lazy sequence of lists of n items each"
16:18	hiredman	from the partition doc string
16:19	hiredman	if n is 0, '()
16:19	fanda	i see... sequence of lists
16:19	hiredman	weird
16:19	rhickey	hiredman: you mean (repeat ())
16:20	hiredman	rhickey: I am sure I do
16:21	rhickey	or just change doc to: "Returns a lazy sequence of sequences of n items each", and leave behavior as is
16:21	fanda	(partition 0 [1 2 3]) => (() () ()) ??
16:21	fanda	(partition 0 [1 2 3]) => (nil nil nil) ??
16:22	rhickey	fanda: it will be infinite, as you never consume the input
16:24	hiredman	you win
16:26	fanda	ok, fine with me then
16:30	fanda	it is hard to break Clojure, I tell you :-)
16:30	fanda	it looks that people use it so much that many bugs are gone at this point
16:35	fanda	,(+ 1.1 2)
16:35	clojurebot	3.1
16:35	fanda	,(+ 1.1 2.2)
16:35	clojurebot	3.3000000000000003
16:36	danlarkin	fanda: bugs are never gone
16:36	danlarkin	that is to say, there will always be more
16:36	fanda	yes, but I have to say I have not had any luck finding them :-)
16:37	fanda	I am writing some function tests for clojure.core - none so far...
16:37	fanda	,(list (+ 1.1 2) (+ 1.1 2.1) (+ 1.1 2.2) (+ 1.1 2.3) (+ 1.1 2.4) (+ 1.1 2.5))
16:37	clojurebot	(3.1 3.2 3.3000000000000003 3.4 3.5 3.6)
16:38	fanda	this is consistent with numbers in Java, but strange anyway
16:38	Chousuke	you can use ratios if you don't want to lose precision
16:38	karmazilla	,(+ 1.1M 2.2M)
16:38	clojurebot	Huh?
16:39	karmazilla	I wonder why that didn't work
16:40	fanda	,(+ (bigdec 1.1) (bigdec 2.2))
16:40	clojurebot	3.3M
16:52	lpetit	Hello all. Is it possible to create from clojure an array of primitive bytes ? I've seen function int-array, float-array, ... but there does not seem to be an byte-array ?
16:53	kotarak	lpetit: some combination of make-array with Byte/TYPE
16:54	lpetit	will this create a java.lang.Byte[] , or a byte[] ?
16:54	lpetit	I'm in the quest of performance
16:55	kotarak	I would expect byte.
16:55	lpetit	,(class (make-array Byte 3))
16:55	clojurebot	[Ljava.lang.Byte;
16:55	lpetit	,(class (make-array Byte/TYPE 3))
16:55	clojurebot	[B
16:56	lpetit	Is it this, the difference ?
16:56	lpetit	I'm not sure how to interpret [B . But I'm sure it's different from [Ljava.lang.Byte; ?
16:56	dreish	,(make-array Byte/TYPE 3)
16:56	clojurebot	#<byte[] [B@16095fc>
16:56	dreish	if that's any clearer.
16:56	lpetit	ok, thank you guys !
16:57	dreish	Just don't prematurely optimize.
16:58	lpetit	Yeah, I know. I've encountered a weird bug with the implementation of the JDK. Using a more "high-level" inputstream : DataInputStream, I've used writeUTF , but it does not work if your String representation as UTF-8 is bigger than 65535 bytes !
16:59	dreish	Interesting.
16:59	lpetit	And for the communication between a client and a server, I needed to pass big Strings ... so I have to make my hands dirty and use the old way : write(byte [] bytes, int offset, int length)
17:00	lpetit	I've seen the code of the JDK, I can see where the exception is thrown :-(
17:37	alex_____	apparently durka is taken
17:39	danlarkin	gotta register with nickserv
18:24	TD	are there any docs comparing the space complexity of clojure programs vs the equivalent java progams?
18:36	TD	actually space/time complexity
18:36	TD	i want to know what the efficiency hit of using clojure is, but the website doesn't seem to discuss it
18:43	hiredman	TD: what is your exact use case?
18:43	TD	just resource-constrained environments in general. desktop use or mobile. java has very poor memory usage, but i at least understand the cost of what i do.
18:44	hiredman	the general consesus is clojure is a. good enough b. can be optimized to spit out almost/the exact same bytecode as java
18:44	TD	i'm looking at JVM compatible languages for future projects, and see scala and clojure. but the problem is the costs of the features are never spelled out.
18:45	hiredman	sounds like you're doing premature optimization :P
18:45	TD	bytecode is only part of the story right. for instance the website says, use an immutable/persistant map instead of an object. fine. what is the cost of that, in bytes.
18:46	hiredman	if you are looking for "future" projects, in the future phones will have a gig or more of ram
18:46	TD	no, understanding the cost of your constructs is fundamental. people who don't write software that is unpleasant to use (or, on the server side, just expensive)
18:46	hiredman	currently, most phones have j2me, which really blows
18:46	Chousuke	TD: you could do the community a favour and find out.
18:48	Chousuke	space complexity for the immutable structures is not an issue for most clojure users I think, because they're used for things where the cost, whatever it is, is dwarfed by the benefits.
18:49	hiredman	and stuff that is not referenced is GC'ed
18:51	hiredman	whoops
18:53	TD_	did i miss an answer? looks like i got disconnected
23:18	danlarkin	Interesting, java crashed with a Bus Error when I rebuilt clojure.jar while it was running
23:20	Chouser	I think that's my most common java crash. Perhaps the only one, actually.
23:26	gnuvince_	sigh