#clojure – 2009-09-20

2009-09-20

00:36	danlei`	what would be a quick fix (if possible without getting down to the java level) for JComboBoxes double entry bug?
03:02	mortonJohnson	(defn hello [] "Hello Everybody")
03:30	CalJohn_	In clojure, is it true that STM types can be read without a transaction?
03:30	CalJohn_	unlike haskell's STM
03:39	Chousuke	CalJohn_: yes.
03:40	CalJohn_	can you atomically read while applying a non-atomic transformation?
03:42	Chousuke	the reference is conceptually something like a "pointer" to an immutable value
03:42	Chousuke	so "reading" it is just a dereferencing operation
03:42	Chousuke	and once you have the value, nothing can change it
03:42	CalJohn_	right, right
03:42	CalJohn_	ok
05:07	rafsoaken	How do I catch a say ArrayIndexOutOfBoundsException?
05:08	rafsoaken	never mind, found it..
05:30	jamesswift	hi folks, i was asking today about 'trie's and if anyone here could provide an example of how you would transform the inTree to the outTree http://paste.lisp.org/display/87340
05:30	jamesswift	the #haskell foks gave me a nice example in that language but i would like to have ine for clojure
06:28	ben_m	Hey there :) When I edit a file in vim, can I somehow run an interactive clj in another terminal with the file I'm editing and then just reload that when I change something?
06:29	ben_m	Nevermind, (load-file "foo.clj") works :)
07:38	cow-orker	will there be a non-private assert-args anytime soon?
07:39	Chousuke	you could use the pre- and postcondition support
07:39	Chousuke	I wonder if it's documented anywhere :P
07:40	cow-orker	hmm.... I haven't seen it, but that doesn't mean it's not documented somewhere :-)
07:42	Chousuke	the only mention I've seen of it is in the commit logs :)
07:42	cow-orker	I'll have a look there .... thanks!
07:43	Chousuke	search for ":pre" in the logs
07:43	Chousuke	that'll find it
07:43	cow-orker	thanks a lot!
07:58	cow-orker	:pre and :post cleaned up the code quite a bit! :-)
10:34	ankou	hi, the documentation says that the parameter of memoize should be refererentially transparent but is this a requirement?(I want to use it for loading a file which is not a pure function but a candidate for remembering the output)
10:42	durka42	ankou: as long as you don't care that the function's output won't change if a file's content changes behind its back
11:13	alinp	hi
11:13	alinp	is there a way to force evaluation for a function ?
11:14	alinp	I mean ... for map for instance
11:14	alinp	is it possible ?
11:14	alinp	,(doc map)
11:14	clojurebot	"([f coll] [f c1 c2] [f c1 c2 c3] [f c1 c2 c3 & colls]); Returns a lazy sequence consisting of the result of applying f to the set of first items of each coll, followed by applying f to the set of second items in each coll, until any one of the colls is exhausted. Any remaining items in other colls are ignored. Function f should accept number-of-colls arguments."
11:14	alinp	I don't want to return a lazy seq ...
11:14	alinp	I want to return a seq ... evaluated
11:16	alinp	the reason why I want that is ...
11:16	alinp	when calling time function for a map, it will not return the actual time took for the map to be executed
11:17	alinp	same for pmap
11:17	xdp	hello,drawString slow down my application, howto fix it?
11:17	danlei	alinp: why not wrap it in a doall?
11:18	alinp	danlei: thanks :)
11:18	alinp	this is what I tried to find out
11:18	danlei	ok. there's also dorun, if it's all about side effects ...
11:18	xdp	any alternative to drawString in java?
11:19	xdp	hmm
11:21	xdp	any swing wrapper in clojure by now?
11:25	xdp	or swt?
12:21	thesnowdog	At the risk of being jumped on, is there a list of "Clojure success stories"? As cheesy as it may be, management types love this stuff. I couldn't find it but my google foo is weak.
12:29	thesnowdog	ben_m: I gather you've found vim-clojure?
12:29	clojurebot	Gesundheit!
13:29	manic12	is there any swing example code in clojure?
13:29	LauJensen	Is the JVM Video up somewhere yet ?
14:25	ben_m	thesnowdog: Why do you ask? :)
16:46	ordnungswidrig	How must a multimethod dispatch function be written? What are the params passed to it? The actual params that the multifunction is invoked with?
16:47	ordnungswidrig	I keep getting "Wrong number of args passed to: user$fn"
16:49	Chousuke	yes
16:49	ordnungswidrig	I used (defmulti foo first)
16:50	Chousuke	then you would call (foo [1 2 3 4]) or something
16:50	Chousuke	and the dispatch value would be "1"
16:50	ordnungswidrig	ok
16:50	ordnungswidrig	without the explicit seq would (defmulti foo (fn [&rest] (first rest))) do?
16:51	Chousuke	yes.
16:51	Chousuke	though I think you need a space after the & :)
16:52	ordnungswidrig	And with an explicit dispatch keyword: (defmulti foo [ type & rest] type) ?
16:52	Chousuke	yeah
16:52	ordnungswidrig	where type is a namespace keyword and I have a hierachy built using derive?
16:52	Chousuke	though both type and rest shadow core functions :P
16:53	Chousuke	ordnungswidrig: it can be anything
16:53	ordnungswidrig	ah the shadows.
16:54	ordnungswidrig	http://gist.github.com/189297
16:54	manic12	are there any good examples of using gen-class ?
16:55	Chousuke	ordnungswidrig: the defmethods need to take the shape parameter too
16:56	Chousuke	so (defmethod draw ::shape [_ x y] "shape") -> now you can call (draw ::shape x y)
16:58	ordnungswidrig	Now I see the light!
16:58	ordnungswidrig	:-) That makes sens as the method can now acces the dispatch value it was called for.
16:58	Chousuke	or you could do something like (defmulti draw type) and then (defmethod draw ::rect [rectangle] "rectangle") and ensure that rectangles have ::rect as their :tag metadata
16:59	ordnungswidrig	:tag metadata?
16:59	Chousuke	(doc type)
16:59	clojurebot	"([x]); Returns the :type metadata of x, or its Class if none"
16:59	Chousuke	oh wait, it was :type :P
17:01	Chousuke	anyway, (draw (with-meta something-representing-a-rectangle {:type ::rect}))
17:01	ordnungswidrig	ah, I see.
17:01	Chousuke	(or you can have a make-rect that attaches the metadata for you
17:01	Chousuke	) :P
17:02	ordnungswidrig	something like that, yes. I'll try. Designing a non-oo api is nothing I've done in the last 5 years.
17:03	Chousuke	well, defmethods used like this are quite a lot like OO in a sense.
17:03	Chousuke	but all your objects are immutable values, not something that can change so I guess the program ends up quite different :)
17:04	ordnungswidrig	Yes, actually I'm desiging a litte rest framework remotely resembling erlangs webmachine. Every resource is represented by a collection of functions (calculate etag, does-resource-exist etc.)
17:05	ordnungswidrig	What I'm doing is to provide reasonable default implementations and a single resource can take the defaults and decorate / replace them with the actual implementation for it
17:06	Chousuke	hmm
17:06	ordnungswidrig	I thought of making each decision point function a multimethod and dispatching on a namespace keyword representing the resource
17:07	Chousuke	that might work
17:07	Chousuke	though what will you do if you want to use functions from different namespaces?
17:07	ordnungswidrig	I though namespace keywords would do the trick?
17:08	Chousuke	I mean, if you want to dispatch to one namespace for one of the functions and to another for some other.
17:08	Chousuke	I guess that might just not happen :/
17:12	ordnungswidrig	Hmm, basically there will be a default dispatch value for the default implementation and I assume that all methods defined for a single disptach value are in the same namespace.
17:13	Chousuke	right. though actually WHERE they are defined does not matter. :) just as long as there is a definition for a certain dispatch value
17:13	ordnungswidrig	...or a dispatch value that matches with isa?
17:13	Chousuke	yeah.
17:14	Chousuke	you can manually define a dispatch value "outside" your namespace if you just write it out in full. ie. (defmethod foo :some.external.namespace/dispatch-key [] ...)
17:15	ordnungswidrig	But (derive :orders :some.namespace/ressource) and (defmulti :orders) will do and pickup the defaults for .../ressource as well?
17:16	Chousuke	well, derivation doesn't "inherit" anything
17:17	Chousuke	it just provides the default in case there's no more specific implementation
17:17	ordnungswidrig	Yes, I meant the default implementaion
17:18	Chousuke	so in that case if you didn't do (defmethod :orders [] ...), it would use the fuction for :some.namespace/resource
17:18	duck11231	Is it possible to re-def a defmulti without losing the associated defmethods?
17:19	Chousuke	I don't think so :/
17:19	duck11231	I have some of my defmethods in other files, and when I re-eval the base file, I lose some of my handlers
17:21	Chousuke	duck11231: I suppose the solution to that would be to define the multimethod in some other file that doesn't need to be re-evaluated :P
17:22	ordnungswidrig	Chousuke: hehe, "header files"
17:22	Chousuke	I suppose you could do some hackery to get the methods currently defined for the multi and then set them up again manually after the multimethod has been redefined...
17:22	Chousuke	the MultiFn class has .getMethodTable and .getPreferTable and .addMethod and .preferMethod... :)
17:23	duck11231	I think I need to write an emacs keybinding to send a complete reload of my base namespace. I don't like using C-M-x because I lose linenumbers, so I usually C-c C-l
17:26	ordnungswidrig	ist there something like "underive" in the repl?
17:27	ordnungswidrig	slapmyhead underive
17:27	Chousuke	:)
17:28	pixelman	Trouble starting swank. Shouldn't I be able to do (start-swank) when i (use 'swank.swank) ?
17:33	pixelman	doh! it was called (start-server ...
17:37	ordnungswidrig	hmm, emacs shows the matching opening parent only when I'm on the character _after_ the closing parent. is this the default?
17:45	ben_m	What's the difference between an atom and a ref?
17:45	ben_m	(I'm reading 'Programming Clojure' and it wasn't explained yet)
17:47	hiredman	clojurebot: atom vs. ref?
17:47	clojurebot	I don't understand.
17:47	hiredman	clojurebot: atom vs. ref is <reply>http://groups.google.com/group/clojure/msg/fd0371eb7238e933
17:47	clojurebot	Ack. Ack.
17:47	Chousuke	ben_m: changes to refs are coordinated, changes to atoms are not
17:48	Chousuke	though that might be an oversimplification
17:48	ben_m	So atoms are not exactly threadsafe?
17:48	Chousuke	well, they are atomic
17:49	ben_m	Doesn't ring a bell, but I will look it up :)
17:49	Chousuke	it means that you won't see a "half-value"
17:51	Chousuke	but the point is that if you have two atoms, there's no way to get a consistent snapshot of them both "at the same time", so to speak
17:51	ben_m	I see
17:51	Chousuke	whereas with refs you can do the reads in a transaction and if anything changes the refs in the middle, the read gets retried until you get a consistent result
17:52	hiredman	if you have two queues, and those two queues are in atoms, if you take an item from one, and put it in the other, it is possible for other operations to be interleaved between the take and the push, so there is a time when the thing you are swapping is in neither queue
17:52	rafsoaken	How can i construct a hash-map from (1 \a 2 \b) ?
17:52	Chousuke	rafsoaken: apply hash-map :)
17:52	rafsoaken	obvious when you think about it :) thx
17:53	hiredman	if you do the same thing with queues in refs, the whole unit of work happens at once
17:53	ben_m	Chousuke: hiredman: Thanks, I think I understand :)
17:53	rafsoaken	,(apply hash-map (1 \a 2 \b))
17:53	clojurebot	java.lang.ClassCastException: java.lang.Integer cannot be cast to clojure.lang.IFn
17:53	manic12	where is an example of the use of the :constructors keyword in gen-class?
17:53	rafsoaken	,(apply hash-map (list 1 \a 2 \b))
17:53	clojurebot	{1 \a, 2 \b}
17:53	hiredman	rafsoaken: whole 'nother problem
17:54	rafsoaken	yeah, sorry wanted to try clojurebot desperately
17:54	Chousuke	,(into {} (partition 2 '[a 1 b 2 c 3]))
17:54	clojurebot	java.lang.ClassCastException: clojure.lang.Symbol cannot be cast to java.util.Map$Entry
17:54	Chousuke	wait, what.
17:54	ben_m	(into {} works just like a cast, right?
17:54	hiredman	using numbers as keys in a map has issues
17:55	ben_m	In other languages.
17:55	Chousuke	ben_m: cast? no.
17:55	hiredman	eh?
17:55	Chousuke	ben_m: into actually builds the map
17:55	hiredman	~def into
17:55	Chousuke	,(into {} (partition 2 [1 2 3 4]))
17:55	clojurebot	java.lang.ClassCastException: java.lang.Integer cannot be cast to java.util.Map$Entry
17:55	Chousuke	why doesn't that work? :/
17:56	hiredman	,(partition 2 [1 2 3 4])
17:56	clojurebot	((1 2) (3 4))
17:56	Chousuke	,(into {} [[1 2] [3 4]])
17:56	clojurebot	{3 4, 1 2}
17:56	hiredman	,(int {} (map vec (partition 2 [1 2 3 4])))
17:56	clojurebot	java.lang.IllegalArgumentException: Wrong number of args passed to: core$fn
17:56	hiredman	,(into {} (map vec (partition 2 [1 2 3 4])))
17:56	clojurebot	{3 4, 1 2}
17:57	Chousuke	anyway, using into might be better if you're building a big map from a large seq
17:57	Chousuke	since IIRC apply holds on to the head of the sequence, while into does not.
17:59	manic12	where are some examples hiding of the use of gen-class, specifically the :constructor and :init keywords ?
17:59	rafsoaken	thanks Chousuke & hiredman~
17:59	rafsoaken	s/~/!
18:00	manic12	anyone?
18:04	manic12	should I just write my class in java and then use the java interop capabilities?
18:05	ben_m	How would the defmulti call look like if I want to use a meta tag as dispatch function? (My terminology might be wrong here)
18:06	ben_m	For example (doesn't work obviously): (defmulti sound ^{:animal-type}) (defmethod sound ^{:animal-type :dog} [] (println "Bark"))
18:08	Chousuke	ben_m: (defmulti sound (fn [thing] (:animal-type (meta thing))))
18:08	ben_m	Ooh :)
18:08	Chousuke	or (defmulti sound (comp :animal-type meta)) :)
18:09	Chousuke	and then (defmethod sound ::dog [thing] "bark")
18:09	ben_m	Now that confuses me :)
18:10	ben_m	What's the ::dog doing?
18:10	Chousuke	it's the type tag
18:10	Chousuke	similar to :dog, but ::dog is automatically namespace-qualified
18:10	ben_m	I should probably keep reading the book before I ask question :D
18:10	Chousuke	,'::foo
18:10	clojurebot	:sandbox/foo
18:10	ben_m	,':foo
18:10	clojurebot	:foo
18:13	ben_m	Thanks for your help :)
18:13	ben_m	Good night.
18:18	manic12	i want to override a constructor, how do i do that?
18:27	Chouser	manic12: you don't. just provide a function that will act as a factory
18:29	Chouser	hm, I guess gen-class can provide ctors
18:31	manic12	and provide a :factory keyword?
18:32	Chouser	manic12: you're using gen-class?
18:33	manic12	either gen-class or :gen-class of ns, I don't care
18:35	Chouser	ok, then you can use :constructors to create ctors with whatever signatures you need.
18:35	manic12	how do I provide the body of the ctor, and how do I call super?
18:37	Chouser	you use :init to provide a function that will be called before the object is created, and :post-init to provide a function that will be called after the object is created (and the super called).
18:38	manic12	ahh! i glossed over that post-init stuff
18:38	manic12	thank you
18:38	emacsen	what's the cannonoical clojure way to provide validation on an object (eg make sure the values conform to what they should be on a struct)?
18:39	Chouser	hm... there are validators for reference types, but not for structs as far as I know.
18:39	Chouser	probably best to provide a function that should be used for creating the struct, and do any checks there.
18:40	emacsen	k. I was doing that but then thought there might be a more clojureish way
18:40	emacsen	I'm doing something simple like stoing lat/longs and want to be sure that the numbers fall within the proper range always
18:44	emacsen	the other confusing thing is that for atoms, there's :validator
18:45	Chouser	emacsen: yeah, reference types have validators
18:45	Chouser	atoms, refs, agents, etc.
18:46	Chouser	more critical there, because any function could be used to change it.
18:46	emacsen	okay... similar dumb question... If I have a struct, is there a function to ask the struct its "structure basis object" name?
18:46	Chouser	not dumb -- comes up all the time.
18:47	Chouser	but a struct basis is not a class. a struct is just a simple optimization of a map.
18:47	emacsen	so what do I really want?
18:48	Chouser	if you want to attach a "type" to an object, it's common to use metadata
18:48	emacsen	oh that's a good idea
18:48	Chouser	,(type #^{:type ::Foo} {:a 1})
18:48	clojurebot	:sandbox/Foo
18:49	emacsen	heh
18:54	emacsen	thanks for the advice
18:57	Chouser	yet another reason to have a function to create the things
18:57	emacsen	right- makes sense
19:55	sfuentes	i'm a little confused here and i was hoping somebody could help me out here. It seems that some ppl in the clojure community see OOP as not really being a good way of modeling programs. Is this true?
19:55	emacsen	sfuentes: that's a very big simplification, but it's sort of true
19:56	dnolen	sfuentes: and pretty much impossible in Clojure anyway. Clojure doesn't support OO style programming very well. You'll have to explore other approaches.
19:56	emacsen	more accurately we'd say that the benefits of OO can be achieved other ways, and the OO model itself causes problems
19:56	technomancy	sfuentes: have you read http://clojure.org/state ?
19:56	emacsen	dnolen: Well, you can do it.. you can call java OOs, etc
19:56	emacsen	erm java objects
19:57	technomancy	Clojure people don't endorse conflating state and identity, which is something most mainstream OOP implementations do
19:57	emacsen	sfuentes: also, it's a big leap for some people who'd never used CLOS (the Common Lisp object system). if you have, it's a leap, but a smaller one
19:57	rlb	Also, some of the very common systems (Java, C++, etc.) are very narrow programming models..
19:58	rlb	(even as far as OOP goes)
19:58	emacsen	and now sfuentes, I'm afraid we're going to have to pelt stones at you...
19:59	sfuentes	my usual thinking is that prog languages are tools and obviously tools are designed for certain tasks. so the challenge for me here is to try to understand where a tool like clojure is better suited.
19:59	emacsen	sfuentes: it's better for data oriented problems
20:00	emacsen	(though it can do far, far more)
20:00	dnolen	sfuentes: I think the programming language == tool analogy to be very fragile. programming language == factory that generates tools to be a better one.
20:00	emacsen	sfuentes: have you ever used a lisp before?
20:02	dnolen	sfuentes: when you program in something like Java changing the factory is an expensive and sometimes impossible task. Clojure is a just in time factory where many parts are easily reconfigurable.
20:02	sfuentes	the only lisp (clisp) i know is from my programming languages cs class
20:02	emacsen	they never teach lisp right in school
20:02	sfuentes	but i wouldn't say i know the language
20:02	rlb	FWIW, quite a while back I found the Keene CLOS book to be a good way to see a broader perspective wrt OOP in fairly few pages. Although it may not be as easy if you're not yet familiar with lisp in general.
20:02	emacsen	or... I shouldn't say never... but they usually teach it poorly and too quickly
20:04	emacsen	sfuentes: it's hard to discuss the benefits of Clojure without someone understanding the benefits of Lisp in general. Lisp isn't easily compatable to other languages because it's a very different style of programming
20:04	emacsen	different than say Python or Ruby, or C
20:04	emacsen	( I should say "Lisps aren't" rather than "Lisp isn't")
20:05	technomancy	sfuentes: there are real unavoidable problems with concurrency when you mix state and identity like how most OOP does
20:06	technomancy	you should read the "State and Identity" essay I linked to
20:07	dnolen	emacsen: Lisps really are not so different then Python Ruby IMHO. Those are Lispy languages. Clojure's emphasis on FP and concurrency are the more distinguishing traits.
20:07	emacsen	dnolen: we'll have to agree to disagree :)
20:07	dnolen	emacsen: haha, sure.
20:08	sfuentes	my dilemma is in trying to decide on what "tools" to invest my time in
20:08	dnolen	sfuentes: what "tools" are you using now?
20:09	sfuentes	mostly php :/
20:09	dnolen	well Clojure will be serious upgrade for you then ;)
20:09	sfuentes	not really by choice, as that knowledge is widely requested
20:10	emacsen	it's widely requested that you know Clojure?
20:11	sfuentes	emacsen: no. clojure appears to me as being a newer skill/tool that has potential ... so obviously it would suit me to get a head start
20:12	emacsen	sfuentes: it's a big jump from PHP. I might suggest trying something like going through technomancy's peepcode video
20:12	emacsen	and watching the Rich Hickey videos
20:12	emacsen	and then deciding
20:12	sfuentes	i did watch one of hickey's videos.
20:13	emacsen	The problem is right now there aren't many gentle introductions
20:13	sfuentes	i even purchased the peepcode video last night.
20:15	dnolen	sfuentes: in order to ease your introduction I would use NetBeans + Enclojure. Though I'm Emacs person myself- I wouldn't recommend it as your introduction to Clojure. If you're doing web dev, you should definitely check out Compojure and/or Ring.
20:17	sfuentes	i remember fiddling with clisp in college and wondered why it wasn't more widely used in industry. the problem seemed to be centered on standard libraries. Clojure seems to have alleviated this by targeting the jvm, so it seems like there's a strong case for a lisp dialect now. That's how I feel now, and that's why i'm thinking about learning clojure.
20:19	sfuentes	dnolen: Netbeans+Enclojure is what I'm working with right now. Haven't really developed anything meaningful, but that's my dev env
20:19	dnolen	sfuentes: well then you're all set. Learn some Clojure! :)
20:20	sfuentes	i got one more question
20:23	sfuentes	before i heard of clojure, scala appeared to be the lang to learn from the rest. so now i'm wondering if scala and clojure are alternatives or whether they complement each other in larger systems. I think if I knew more about lisp I would know this, but I don't.
20:25	dnolen	sfuentes: not too many scala people here I don't think. however the my reductive generalization would be: Clojure is a simpler language than Scala but probably just as powerful for writing applications.
20:27	sfuentes	alot of what i'm hearing seems to be centered around FP vs OOP, and if that's the case, can you say that other functional languages are simple and perhaps even more powerful than OOP languages?
20:28	dnolen	sfuentes: that would be too reductive of a generalization :) not all FP languages are "simple". nor are all OO languages "powerful", PHP case in point.
20:30	sfuentes	i see. so haskell would not be considered simple, right?
20:31	sfuentes	but i'm not sure i would say php is naturally oop
20:31	sfuentes	by the way, i appreciate you guys taking time to answer my silly questions
20:36	Chouser	I think the combination of syntax and type system would be enough to consider Haskell more complex than Clojure.
20:37	Chouser	Though I don't think Clojure's STM could be called simple.
20:38	rlb	sfuentes: also, in my experience, clojure tries to avoid being too pedantic. If you need mutation, fine. If you want to work in a more java/c++-esque object oriented fashion, you can (to some extent), that's just a very limited application of clojure's multimethods.
20:39	rlb	(There I'm speaking mostly about dispatch...)
20:40	Makoryu	Haskell is certainly simple compared to its peers in the imperative world. It has fewer rules with fewer exceptions... Of course, that allows libraries to implement a certain amount of syntax as ordinary functions
20:43	sfuentes	again. thank you all for your time and insights.
20:55	dthomas	If I do something like (doseq [x (new-huge-lazy-seq)] (stuff-with x)) will the whole sequence end up materialized in memory when iteration terminates? Or are the head elements eligible for the GC after they are operated upon and then forgotten?
20:56	dthomas	I suspect there is an easy way to test this involving top and (repeatedly).
20:59	hiredman	…
20:59	dthomas	Yeah, I think this is a stupid question.
21:00	dthomas	Lazy sequences still confuse me.
21:20	emacsen	dthomas: lazy sequences still confuse you why
21:20	emacsen	that is, what about them confuses you
21:20	Makoryu	dthomas: If you generate a lazy data structure and then explore the structure without letting the reference to the root go out of scope, the whole thing will remain in memory.
21:21	Makoryu	dthomas: Half the point of lazy sequences is that you can recreate them at will if you need them for different purposes, and it won't matter how big the entire thing would be.
21:34	dthomas	Makoryu: Presumably built-ins like (map) and (for) are not written in such a way that they keep the root around?
21:34	dthomas	(doseq [x (iterate inc 1)]) doesn't start accumulating memory in my box as it presumably would if something was holding on to the root of the lazy seq made by iterate.
21:36	dthomas	That's what was confusing me today.
21:42	Chouser	doseq itself won't hold onto the head, so the JVM garbage collection will clean it up as it goes.
21:43	Chouser	if you did (let [xs (iterate inc 1)] (doseq [x xs])) it would consume memory.
21:58	sfuentes	i'm embarrased to ask, but can somebody explain this snippet to me: http://pastie.org/624107
21:58	sfuentes	i'm hung up on the last line
21:59	dnolen	sfuentes: functions (fns) can have multiple arities.
21:59	durka42	the indentation is done confusingly, but it's a function with multiple arities
22:00	durka42	so you can call it with no arguments or with one
22:00	durka42	and if you call it with none, it calls itself with one, namely the String "world"
22:00	sfuentes	awww i see
22:01	sfuentes	is there a reason to use hyphex prefix to the function name though?
22:01	sfuentes	err hyphen
22:01	durka42	for gen-classing i believe
22:03	sfuentes	what is that if you don't mind me asking
22:03	sfuentes	nm. i'll look it up
22:03	durka42	making a java class from a clojure namespace
22:04	hiredman	~compile
22:04	clojurebot	the unit of compilation in clojure is the namespace. namespaces are compiled (not files). to compile a namspace the namespace needs to be on the classpath and so does ./classes/ (and the directory needs to exist) because clojure writes the class files to that directory. http://clojure.org/compilation
22:05	sfuentes	got it. thank you.
22:58	interferon	can i convert a struct-map to a vanilla map?
22:59	Chouser	(into {} my-struct-map)
23:03	interferon	thanks!
23:05	prospero_	if I use map over a hash-map, what's the simplest way for that to generate a new hash-map?
23:07	prospero_	it seems like there should be a simpler way than (apply hash-map (apply concat (map (fn ...) {...})))
23:08	dnolen	prospero: (into {} ...)
23:08	dnolen	,(into {} [[:foo 'x] [:bar 'y]])
23:08	clojurebot	{:bar y, :foo x}
23:09	prospero_	I knew there was something I was forgetting
23:09	prospero_	thanks