#clojure – 2009-09-27

2009-09-27

02:58	ngoc	It seems a variable must be of one of the 4 reference types: Var, Atom, Agent and Ref. Is there a type other than these types?
03:02	jwhitlark	I'm trying to compile and run a jar via ant using instructions from: http://www.lithinos.com/Compiling-Clojure-applications-using-Ant.html
03:03	jwhitlark	I keep getting "Could not find the main class"
03:04	jwhitlark	Are there any other recommended resources? My google-fu seems to be failing me tonight.
03:13	ngoc	jwhitlark: Don't you want to use Maven? I use Maven to compile Clojure programs, it is very easy, just follow instructions on the Google group of Clojure.
03:14	jwhitlark	hmmm. is that the preferred way?
03:14	jwhitlark	ngoc: I'll take a look at maven then.
03:15	jwhitlark	The interesting thing is the class file is compiled properly, and I can run it that way, but it can't find it from the manifest file in the jar.
03:16	jwhitlark	I'm just trying to jar up the example on the clojure site, nothing fancy.
03:18	ngoc	Sorry I don't use Ant. But in my experience compiling Clojure with Maven is very easy because there is a convention, you can't be wrong.
03:21	fullets	Is there an easier way to distinguish a valid hash map from e.g. the result of (read-string "{:a 1 :b}") than trying to print it and seeing if an exception is thrown?
03:21	jwhitlark	ngoc: thanks for your help. I'll go read up on maven
03:27	_mst	jwhitlark: Just a tiny example of doing it manually if it helps: http://dishevelled.net/compile.txt
03:27	_mst	nice to know what ant/maven are doing behind the scenes I think :)
03:27	jwhitlark	thanks!
03:28	jwhitlark	I'll give it a spin.
03:33	jwhitlark	_mst: Thanks so much! I got it working with you instructions, now I can compare the two jars and see where it's going wrong.
03:34	_mst	excellent :)
03:50	hoeck1	fullets: you could just read the hashmap elements into a list and see if they are even
05:26	LauJensen	Notice #45 :) http://botd.wordpress.com/2009/09/26/top-posts-1247/
05:27	crios	jwhitlark: regarding maven, check stuartsierra's blog: http://stuartsierra.com/
05:28	konr	Guys, what could be wrong with my macro? It seems that the if in the anonymous function is always returning true: http://clojure.pastebin.com/m3bfea741
05:28	konr	*false
05:29	LauJensen	konr: No backquote
05:30	LauJensen	konr: Untested, by have a look at how I control the evaluation and use gensym http://clojure.pastebin.com/m75cb5358
05:42	spuz	How do I create a function that returns a sequence?
05:43	spuz	all the functions I've seen seem to rely on existing sequence funtions to do that
05:48	hoeck1	spuz: thats what lazy-seq and rest for
05:50	hoeck1	spuz: you may want to look at the definitions of repeat, drop-while etc. of core.clj
05:52	spuz	actually, for returns a sequence, so I don't think I need to create one myself
05:53	hoeck1	sorry, typo, I meant 'lazy-seq' and 'rest' are used to build lazy sequences
05:54	hoeck1	and yes, often you use only the helper functions like repeat, iterate or map to create lazy sequences
05:56	spuz	hoeck1: yeah, I understood what you meant. I'm just trying to figure out how to filter the sequence returned by 'for'. Is it possible to add a filter within the for expression, or do I need to wrap it around a call to 'filter'?
05:58	hoeck1	for has a :when clause
05:58	hoeck1	,(for [x (range 1 5) :when (even? x)] x)
05:58	clojurebot	(2 4)
06:09	spuz	hoeck1: is there any benefit in using the :when clause over a filter apart from concision?
06:10	spuz	it would seem to me to be potentially less efficient as you are evaluating x twice
06:12	spuz	for example: (for [x (range 1 5) :when (> 2 (Math/sqrt x))] (Math/sqrt x))
06:12	spuz	Is the square root not be calculated twice?
06:13	hoeck1	spuz: yes, but then a surrounding filter would be better
06:13	spuz	ok
06:15	hoeck1	spuz: or just a chain of map and filter: (filter #(> 2 %) (map #(Math/sqrt x) (range 1 5)))
06:16	spuz	hoeck1: yeah map makes more sense in this case. In my case I have two variables, x and y and two ranges.
06:16	hoeck1	spuz: :when in filter is like filtering the sequence before mapping a function over it
06:16	spuz	(for [x (range n m) y (range x m)] [x y])
06:27	vy	What is the alternative to "map" ignoring the results, just doing the job with side effects.
06:30	hoeck1	vy: look at doseq
06:30	hoeck1	vy: or use (dorun (map ...))
06:32	hoeck1	vy: dotimes and while are also useful sometimes
09:04	abbe	hi everyone
09:51	rhickey	abbe: hi
09:53	lisppaste8	rhickey pasted "more functional Ikeda" at http://paste.lisp.org/display/87799
09:54	abbe	rhickey: checking out your presentation :)
09:54	abbe	rhickey: i liked when you said: love jvm, not java :)
09:55	rhickey	abbe: in which talk?
09:55	abbe	rhickey: Part 1 of a presentation by Rich Hickey at the Boston Lisp meeting.
09:56	rhickey	ah
11:03	LauJensen	rhickey: Great contribution on my blog, thank you very much for showing the way :)
11:06	rhickey	LauJensen: np
11:13	hamza	hey guys, i have the following situation, i start at x=0 y=1 suplly these coordinates to a (point x y) function i get a new point. each call takes its prev. generated point as its argument. is it possible to get a sequence of it so that i can use (take 10 (repeate call)) like structure?
11:29	LauJensen	hamza: did you read my last blog post? that gives you the solution in 4 different flavors :)
11:31	Chousuke	Chouser: I have the sq-macro at http://github.com/Chousuke/clojure/tree/sq-macro in core.clj
11:31	Chousuke	though I think it doesn't handle namespace alias resolution yet
11:32	LauJensen	hamza: short version, see (iterate ...)
11:33	hamza	laujensen can give url to blog post?
11:34	LauJensen	hamza: http://bestinclass.wordpress.com/2009/09/24/chaos-theory-vs-clojure/
11:34	LauJensen	that's the one you want
11:37	hamza	thank you,
11:38	LauJensen	np
11:38	raek	question: do vars used inside agents live inside the agents or the in executing thread?
11:42	serp_	zomg :o
11:42	raek	two serps?
11:47	raek	anyway, serp_ and I was discussing whether one could hide java gui objects from other threads (since they're not thread safe) by keeping them in var
11:47	raek	you have any ideas, #clojure?
13:33	drhodes	found this neat introspection function @ http://travis-whitton.blogspot.com/2009/06/method-introspection.html#comment-form
14:04	hiredman	clojurebot: ping?
14:04	clojurebot	PONG!
14:15	Chouser	drhodes: that looks about like how repl-utils/show started
14:44	drhodes	Chouser: oh, thanks for the heads up, I'll check it out.
14:46	emacsen	when should I use (in-ns) and when should I make a new namespace and import the sub-namespaces?
14:59	hamza	hey guys, i have a function that returns a file from disk, i call (memoize serve-file) in order not to hit the disk each time, serve-file is called from compojure but output is not cached. if i change the file to check i get changes reflected on the browser output?
15:05	lisppaste8	hamza pasted "memoize" at http://paste.lisp.org/display/87806
15:05	hamza	i also wrote a simple test case it always executes the function.
15:06	Chousuke	hamza: memoize doesn't change the function, it returns a new one
15:06	Chousuke	hamza: so you need (def mem-atest (memoize atest))
15:07	hamza	kk now i get it :P.
15:09	hamza	if i want to reset the cache, is there a better way to do it besides calling def.
15:11	hamza	again
15:11	hiredman	if you want control over the cache, I would take the source to memoize, paste it into your app, and add the ability to clear the catch
15:11	hamza	kk
15:21	hamza	wasn't there a set! function for re deffing a var or am i mistaken?
15:24	hiredman	you might have my-memoize return a proxy of AFn, and keep the cache in under the :cache key in the metadata, so you could flush the cache by mucking with the metadata
15:25	emacsen	Chousuke: any opinion on in-ns vs importing? I am just looking for general guidelines
15:26	hiredman	in-ns has nothing to do with importing
15:26	hiredman	it does no importing or namespace loading
15:26	emacsen	hiredman: erm, I meant use
15:27	emacsen	hiredman: right the guideline is when to make a new sub-namespace
15:28	hamza	hiredman: can you explain it a little further?
15:31	hiredman	hmmm
15:33	hiredman	,(alter-meta! (proxy [clojure.lang.AFn] []) assoc :cache {})
15:33	clojurebot	java.lang.RuntimeException: java.lang.IllegalStateException: Var null/null is unbound.
15:33	hiredman	~def alter-meta!
15:35	hamza	ok thanks,
15:39	emma	Hi.
15:39	emma	I am forming a study group which will meet here on Freenode to work through SICP (the canonical text on CS)
15:39	emma	If anyone is interested our first meeting is beginning now. It's a text available online.
15:43	emacsen	SICP redone with clj or just SICP?
15:43	emma	emacsen: it's SICP.
15:44	kwertii	I thought Knuth was the canonical text ;)
15:46	metvop	#j /sicp
15:49	emma	We are having our first meeting in ##club-classroom
16:37	kmurph79	i'm going through this http://bestinclass.wordpress.com/2009/09/24/chaos-theory-vs-clojure/ can someone explain exactly what (iterate #(* 2 %) 1)) does?
16:42	arbscht	kmurph79: it returns a lazy sequence of the powers of 2
16:42	arbscht	,(take 10 (iterate #(* 2 %) 1))
16:42	clojurebot	(1 2 4 8 16 32 64 128 256 512)
16:43	kmurph79	arbscht: thanks. what does the # and % do ?
16:44	arbscht	#(* 2 %) is effectively identical to (fn [x] (* 2 x))
16:45	arbscht	it's shorthand for anonymous functions
16:45	Chousuke	you can also have more parameters with %n where n can be anything from 1 to 20, or %& for the "rest" arg
16:46	Chousuke	just % is equal to %1
16:47	kmurph79	interesting. thank you.
16:49	arbscht	,(take 10 (iterate (partial * 2) 1))
16:49	clojurebot	(1 2 4 8 16 32 64 128 256 512)
16:58	somnium``	how would you write a macro to create a number of seperate function calls, like (mymac fun & args) -> (fun arg0) ... (fun argn)
16:58	somnium``	trying to do it recursively but not getting it
16:59	LauJensen	~@(for [a# ~args] (~fun a#)) - something like that I believe
16:59	clojurebot	for is a loop...in Java
16:59	Chousuke	hmm
16:59	arbscht	somnium``: what are you really trying to do?
17:00	Chousuke	(doseq [a args] (f a))
17:00	Chousuke	:P
17:00	somnium``	in an xml builder, I have helper functions that return vectors, but splicing sequences adds complications
17:01	somnium``	they work as expected as individual calls, but kind of repetitive to write (fun a) (fun b) (fun c) ...
17:05	somnium``	with side effects?
17:05	somnium``	hadn't considered that
17:05	Chousuke	well, hm
17:06	somnium``	its wrapped around html lib in compojure, so in something like [:tag1 [:tag2 (myhelper "foo")]] -> [:tag1 [:tag2 [:sometag "foo"]]]
17:07	Chousuke	(defmacro foo [f argv] `(do ~@(for [a argv] (list f a))) or something?
17:07	somnium``	want to be able to do [:tag1 [:tag2 (myhelpers "foo" "bar" "baz")]] -> [:tag1 [:tag2 (myhelper "foo") (myhelper "bar") etc...
17:08	somnium``	will try that
17:10	Chousuke	remember though that you can only return one expression from a macro
17:10	somnium``	yeah...
17:10	Chousuke	perhaps you could do `[:tag2 ~@(myhelpers whatever)]?
17:11	somnium``	may have to wrap the whole builder in a macro
17:12	somnium``	why only one expression form a macro? seems like a non-first class special form
17:13	Chousuke	you can only return one thing from ANY function :)
17:14	somnium``	maybe I should just teach the builder to auto-splice sequences...
17:14	Chouser	you're sure it doesn't do that already?
17:14	Chousuke	I mean, sure you can return multiple things wrapped in a (do ...) but then the (do ...) makes it a single expression :P
17:14	somnium``	not in my tests
17:15	Chouser	this is compojure?
17:15	somnium``	yeah
17:15	somnium``	Im wrapping it with some stuff that operates on the vectors before html gets called
17:19	somnium``	I was working out a way to do layouts and partials with one context, so I came up (defview [& args] [some content]) -> (fn [context] (let [arg1 (context :arg1) ... argn (context :argn)]), so now they compose with (render {:initial bindings} :views.foo :views.bar views.zonk)
17:19	somnium``	but my helpers broke :(
17:20	Chouser	somnium``: use a seq instead of a vector. it works
17:20	Chouser	(html-tree [:html 1 (list 2 3 4) 5]) ==> "<html>12345</html>"
17:21	somnium``	ah
17:21	clojurebot	Paul Graham is the creator of the other new lisp
17:21	somnium``	strings are ok
17:21	somnium``	that may make things much easier
17:21	somnium``	thanks
17:21	somnium``	seqs of strings
17:21	Chouser	I think seqs of anything should work
17:22	somnium``	hmm
17:22	Chouser	user=> (html-tree [:html [:p 1] (list [:p 2] 3 4) [:p 5]])
17:22	Chouser	"<html><p>1</p><p>2</p>34<p>5</p></html>"
17:23	Chouser	that's the most I've ever used Compojure. :-D
17:27	somnium``	.. I found a simple solution, just have the helpers evaluate the tag and return a string .. thanks all
17:48	somnium``	is there a pred like string? for functions? or an idiomatic way to test?
17:54	LauJensen	,(string? "is there?")
17:54	clojurebot	true
17:55	LauJensen	,(ifn? #(println "foo"))
17:55	clojurebot	true
17:55	LauJensen	,(ifn? (println "foo"))
17:55	clojurebot	foo
18:06	LauJensen	somnium``: You got that? :)
18:07	rafsoaken	,(ifn? ifn?)
18:07	clojurebot	true
18:17	somnium``	got it
18:17	somnium``	thanks
18:18	somnium``	still finding the names of some core functions to be rather obscure
18:35	Makoryu	,(ifn? defn)
18:35	clojurebot	java.lang.Exception: Can't take value of a macro: #'clojure.core/defn
18:44	Chouser	,(fn? fn?)
18:44	clojurebot	true
18:45	Chouser	,(fn? fn*)
18:45	clojurebot	java.lang.Exception: Unable to resolve symbol: fn* in this context
18:50	Chouser	,(fn? (fn* []))
18:50	clojurebot	true
18:50	Makoryu	,(bound? 'foo)
18:50	clojurebot	java.lang.Exception: Unable to resolve symbol: bound? in this context
18:51	Makoryu	Whoops
19:04	hamza	hey guys, i have two sets such as the following #{{:tag "key" , :url "test"}} #{{:tag "key" , :url "test"}} how can i create a set that has the same item twice?
19:05	Makoryu	"how can i create a set that has the same item twice?" <- Think about this for a moment.
19:06	Makoryu	I don't think what you want is a set.
19:06	Makoryu	, #{"pizza" "pizza"}
19:06	clojurebot	#{"pizza"}
19:07	Makoryu	, ["pizza" "pizza"]
19:07	clojurebot	["pizza" "pizza"]
19:08	hamza	well my plan was to create a set of :tag :url values then select url's based on tags..
19:10	Makoryu	, #{{:tag 'foo :url "slashdot"} {:tag 'foo :url "reddit"}}
19:10	clojurebot	#{{:tag foo, :url "slashdot"} {:tag foo, :url "reddit"}}
19:11	Makoryu	hamza: As long as the URLs are different, you're all set
19:11	Makoryu	hamza: I'm really curious why you're using a set if you actually want them to be identical, though
19:11	Makoryu	hamza: If you need duplicate elements, use another container! Like, say, a vector....
19:11	hamza	my bad, i should get some sleep. i thouth about it wrong url's are different so there should not be any problems.
19:16	hamza	question, is it possible to get a list of distinct tags?
19:18	licoresse	(reduce ...) = inject:into: in Smalltalk?
19:42	jwhitlark	I have a swing application where I want a pop up menu to update according to the value of a ref (or atom, not sure which to use). Any suggestions? Perhaps someway to setup a callback for when a value changes? Or do I need to go further and implement some sort of hooks/advice system?
19:47	jwhitlark	hmmm. doseq with fill-queue looks like it might have potential..
19:49	Chouser	hm, that doesn't sound quite right.
19:49	licoresse	,(doc proxy)
19:49	clojurebot	"([class-and-interfaces args & fs]); class-and-interfaces - a vector of class names args - a (possibly empty) vector of arguments to the superclass constructor. f => (name [params] body) or (name ([params] body) ([params+] body) ...) Expands to code which creates a instance of a proxy class that implements the named class/interface(s) by calling the supplied fns. A single class, if provided, must be first. If not provid
19:51	jwhitlark	Chouser: no?
19:51	jwhitlark	I was looking at http://infolace.blogspot.com/2009/08/simple-webhooks-with-clojure-and-ring.html, but it was just off the top of my head.
19:58	jwhitlark	Do I need to go read up on java events? Would that be a reasonable way to do it?
20:05	jwhitlark	I guess what I'm really asking is if the java event model extends (is extendable?) beyond GUIs.
20:15	ambient	it's a bit troubling to me that i have to have such an intimate knowledge with java also if i want to use clojure :\
20:15	hamza	why is this not working {:t 'v {:u 'u :m 't}}
20:15	hamza	,{:t 'v {:u 'u :m 't}}
20:15	clojurebot	java.lang.ArrayIndexOutOfBoundsException: 3
20:16	hiredman	hamza: maps need pairs of elements
20:17	hiredman	you have three things there
20:17	hamza	what i am trying to do is a map of map's
20:17	hiredman	entirely possible
20:17	hamza	{:t 'v :y {:u 'u :m 't}}
20:18	licoresse	you still need a key
20:18	hiredman	that will work fine
20:18	hamza	,{:t 'v :y {:u 'u :m 't}}
20:18	clojurebot	{:t v, :y {:u u, :m t}}
20:28	Makoryu	That should really throw a more useful error than ArrayIndexOutOfBoundsException
20:30	icey	So... for you guys on osx- how are you managing your classpath / dependencies? just putting everything in a jar folder? something else
20:30	icey	?
20:31	Makoryu	icey: Well, on OS X, the default classpath is something like .:/Library/Java/Extensions
20:31	Makoryu	I keep all my libraries in the latter location
20:31	icey	hmmm, thanks Makoryu!
20:42	lisppaste8	hiredman annotated #87611 "infinite seq of swing events" at http://paste.lisp.org/display/87611#2
21:26	licoresse	how can I pretty-print automatically the output of lists in the repl?
21:26	licoresse	I am using slime
21:27	licoresse	,pretty print
21:27	clojurebot	java.lang.Exception: Unable to resolve symbol: pretty in this context
21:27	licoresse	,prettyprint
21:27	clojurebot	java.lang.Exception: Unable to resolve symbol: prettyprint in this context
21:27	licoresse	clojurebot: pretty print
21:27	clojurebot	Huh?
21:28	licoresse	right...
21:33	Chouser	licoresse: there's a pretty printer in contrib, but I don't know how to hook it into slime
21:34	kylesmith	is there any equivalent to update-in but with functions? something like (update-with m [fn & fns] f & args)
21:36	Chouser	yes, I just can't think of the name.
21:36	licoresse	Chouser: ok
21:37	kylesmith	I could replace fns with (apply comp fns) of course.
21:37	Chouser	oh, wait.
21:38	Chouser	sorry, I misread
21:38	Chouser	you want to provide a list of fns?
21:39	kylesmith	yes. I'm trying to incrementally build up an arbitrarily nested structure. When I recur, I can either keep a list of fns or compose them.
21:40	Chouser	ok, you'll have to do (apply comp fns) or equiv.
21:40	kylesmith	I could probably restrict myself to nested vectors, then I could just use update-in with a list of ints, but fns would be more convenient.
21:44	kylesmith	I'm basically composing first's and last's, which won't have a fixed index on each iteration, hence the problem.
21:56	licoresse	pprint was the pretty printer I was looking for
22:06	kylesmith	I can't access paste. is it down?
22:29	Makoryu	kylesmith: There's always another paste.
22:29	Makoryu	http://gist.github.com/
22:31	kylesmith	http://gist.github.com/195087
22:36	Raynes	snipt.org is a pretty neat pastebin.
22:37	hiredman	kylesmith: saying update-with works on an associative structure seems like a misnomer
22:38	kylesmith	ahh, I didn't change the docstring
22:38	hiredman	,(update-in [1 2 [[3 4 5]]] [2] (comp #(conj % 6) first))
22:38	clojurebot	[1 2 [3 4 5 6]]
22:38	hiredman	,(update-in [1 2 [[3 4 5]]] [2 1] conj 6)
22:38	clojurebot	[1 2 [[3 4 5] (6)]]
22:39	hiredman	anyway
22:39	kylesmith	hmm
22:39	hiredman	it seems like you want to apply a function to the nth item in something
22:40	hiredman	what happens if a collection contains multiple copies of [[3 4 5]]
22:41	kylesmith	probably bad things. I'm still thinking through this.
23:53	hamza	is there any documantation on how to use the complex numbers lib in contrib?