#clojure – 2009-05-16

2009-05-16

02:35	tsdh	Can anyone enlighten me when `var?' is useful? It seems it's true only for the return value of a `def'. (var? (def foo 17)) ==> true, but (do (def foo 17) (var? 'foo)) ==> false.
02:41	hoeck	,(let [x #'fn] (var? x))
02:41	clojurebot	true
02:42	hoeck	tsdh: but I haven't used it in 'real' code so far
02:42	hoeck	tsdh: maybe it's just for completeness sake, or to implement crazy macros ..
02:46	tsdh	What's #' for a reader macro?
02:47	tsdh	Ah, Var-quote. Thanks, now I've gotten it.
02:50	unlink	I wish lazy-seq were easier to type.
03:08	unlink	What's the best way to memoize a lazy-seq? (memoize #(nth (my-seq) %))?
03:08	unlink	+)
03:08	unlink	*for efficient random access
03:13	hoeck	unlink: putting it in a vector??
03:19	kli	if you hold on to the head of a seq, I think it will memoize it
03:19	kli	not 100% sure
04:20	Raynes	Wow, this is taking forever.
04:33	vy	Raynes: You should also try compiling Open Office. (Wine is a good candidate too.)
04:38	Raynes	vy: It's still going. o_o
04:38	Raynes	I can picture myself three days from now sitting her all starry eye'd while I watch the text fly in Bash.
04:50	Raynes	Yay it's done!
08:16	eee	does clj have a concept of generic infinity?
08:17	eee	no matter what type is being compared, it is always bigger?
08:31	marklar	Hi I'm trying to set up emacs + slime on a new machine. I getting a ClassNotFoundException: swank.swank whether I do it manually or using the clojure-mode clojure-install. Has anyone encountered this before?
08:38	eee	i just use clojure-dev eclipse plugin
08:50	achim_p	hi all! did anybody here try to define custom data structures in clojure? i'm playing around with a simple deque (http://gist.github.com/111147), which works with a custom set of ops, but i'm not sure how to best proceed if i wanted first/last/next/butlast to give sensible results
09:06	liebke	achim_p: I've only written custom clojure data structures in java, implementing the ISeq interface. I suppose you could use gen-class to do the same in pure clojure.
10:16	tmi	anyone working with compojure know sessions work (in recent compojure master branch)?
10:31	meredydd	tmi: Yeah
10:31	meredydd	tmi: You include the value of (session-set) or whatever in the return value
10:32	meredydd	The way to think of it is that your handler code returns "what I want to happen in response to this request"
10:32	meredydd	that includes content, headers, etc to return, as well as what changes to make to the session
10:33	meredydd	sorry - I mean (session-assoc) and friends
10:40	tmi	meredydd: ok, thanks, I'll give it a shot :)
11:56	eee	any clojure-dev users in here?
13:09	biilly	hi. anyone know how to pass expressions to swank-clojure in .emacs?
13:10	biilly	of how to read some expressions as a file to pass to swank-clojure-init-files?
14:28	dreish	I wonder whether this is real: http://www.google.com/trends?q=clojure%2Cjruby%2Cjython&ctab=0&geo=all&date=ytd&sort=0
14:28	dreish	And if so, why?
14:28	dreish	(Referring to the sudden surge in Clojure searches in the last data point.)
14:29	dreish	Because it went to 1.0, maybe?
14:30	danlarkin	http://www.google.com/trends?q=clojure%2Cruby%2Cpython&ctab=0&geo=all&date=ytd&sort=0
14:31	dreish	Man bites python. At 90, Ruby's fighting fit. Eric Idle adds an orchestra to Monty Python comedy.
14:32	dreish	Not really comparable.
14:32	danlarkin	mmmm
14:32	danlarkin	that's news items though, but yeah I get it
14:34	dreish	I think the surge is from 1.0. Looking at the 30 days chart, it settles back down after early May, though still above where it was before.
15:00	Chouser	I've got a map that's in theory is acting as an identity -- it's got values like an open socket, a thread or two, etc. But many of the values will never change (like the socket and thread).
15:01	Chouser	So, should I pass it around as a reference type, because it has identity, and then not need to use reference types for the mutable members?
15:01	cp2	ugh
15:01	Chouser	Or, should I pass it around as a map value, because it's largely immutable, and then have specific reference types for the mutable members?
15:02	Chouser	I've been doing the latter, I'm just not sure it's right.
15:02	danlarkin	reference type as in (ref )?
15:03	danlarkin	If that's what you mean, I would put the whole map in a ref
15:03	danlarkin	IMO
15:03	danlarkin	but I guess it's just personal preference
15:05	Chouser	I mean reference type as in ref, atom or agent
15:05	kotarak	as in IRef?
15:05	Chouser	Um.. yeah, I guess so.
15:06	Chouser	I also generally have a closure or two. If the "object" is an IRef, then I need to make sure I close over the IRef, not the values it contained originally.
15:07	Chouser	If the "object" is immutable, then I can close over the values fine, but need to close over each of the internal IRefs as needed.
15:07	Chouser	hm.
15:21	Lau_of_DK	Good evening gents - Whats new in Clojureland?
15:24	kotarak	Hi Lau.
15:24	cp2	;)
15:24	cp2	i havent dropped in over 5 minutes, this must be a good sign
15:29	biilly	how come when i javadoc from my repl in emacs it hangs, but in the console script it launches the browser fine?
15:41	cp2	looks like a spoke too soon
15:42	rhickey	Chouser: could the closures take the value as an arg?
15:44	biilly	in repl-utils/javadoc, it uses "browse-url" which i know is an emacs command, is this in clojure.contrib as well?
15:44	kotarak	rhickey: did you read the thread about the latest ns macro changes on the list?
15:44	kotarak	I had problems with the anon fn there
15:44	rhickey	kotarak: yes, I'm working on that now
15:45	kotarak	ok :)
15:45	rhickey	I hae a workaround but would rather get the 'right thing' in there - which is unwrapping do at top level
15:55	Chouser	the only closures I have so far are for Threads -- but anyway, they can only take the object if its an IRef
15:56	Chouser	(def new-obj [a] (let [b (LinkedBlockingQueue.)] {:t (Thread. #(work a b)) :a a :b c}))
15:56	Chouser	should be defn
15:58	Chouser	(defn new-obj2 [a] (let [obj (atom {:a a :b (LinkedBlockingQueue.)})] (swap! obj assoc :t (Thread. #(work2 obj))) obj))
15:58	Chouser	I guess that's the other option?
16:00	Chouser	I like how the obj produced by new-obj can't be messed with -- I can't replace the LBQ with something else, because work is dealing with it directly and the map's immutable
16:01	Chouser	with new-obj2, I could swap in a new value for :a or :b, and depending on how work2 is written, it may or may not notice the change.
16:03	Chouser	or do I have that backwards, and being able to change it while running is actually a benefit?
16:19	cads	is there a clojure script that takes options and arguments for stuff like loading extra jars?
16:21	rhickey	kotarak: try 1370
16:21	kotarak	k, just a sec
16:25	stuhood	cads: to add jars, you add them to java's classpath. see http://clojure.org/repl_and_main
16:27	cads	I have written a bash script that takes these arguments: clojure [-j= & jars] [script file]
16:28	cads	it either runs a script with the or if the script argument is left blank, starts
16:28	cads	oh, wait
16:28	kotarak	rhickey: two thumbs up. Seems to work. :) At least I didn't get a failure up to now.
16:28	kotarak	thanks for quick fix!
16:29	cads	it'll start a repl if it has no script to run, but if you give it a script it also passes the remaining commandline arguments to the script
16:29	clojurebot	http://www.pigdog.org/auto/mr_bads_list/shortcolumn/1914.html
16:34	kotarak	rhickey: yep, works now.
16:43	cads	I love clojure, and how tiny it is
16:44	dnolen_	ditto.
16:44	cads	I can leisurely skim its sourcecode and get a good feeling of how whatever I want to know about works
16:44	kotarak	No 1000 page Spec. Phew...
16:47	cads	does scheme have unicode yet?
16:52	kotarak	cads: dunno, I didn't follow R6RS...
17:20	cads	hey, I'd like to use a clojure script as part of a unix pipe, but I'm not entirely sure how it is that pipes are able to control the processes that generate the data so as not to have to queue data up
17:21	kotarak	Just read from the pipe. The producer is stopped as soon as the buffer is full.
17:22	cads	say the producer is a clojure script writing stuff to standard io, then the whole java process is just stopped?
17:22	kotarak	Hmmm... I think the thread writing to the output buffer is stopped. The rest probably goes on.
17:24	cads	I'll have to test it
17:26	cads	one last thing, for io stream output, I'd like to write a special print function for a datastructure containing 3d particles. But I'd like the function to be called print, and in fact it would be neat for the actual print function to be able to print these structures specially, mixed in with normal printing for other things
17:26	cads	can I overload print like that?
17:27	kotarak	cads: (defmethod print-method :your-dispatch ...) should do the trick
17:27	cads	is the dispatch method for print in clojure.core?
17:28	kotarak	cads: dispatch is type
17:35	StartsWithK	fyuryu: hi
18:01	danlarkin	Can't decide if I should return nil/error code or throw an exception when something goes wrong with this couchdb api
18:03	Chouser	both!
18:03	rsynnott	possibly best throw an exception; then the user can catch it and use error codes if they want to
18:03	rsynnott	the other way round is slightly more awkward for the user, IMO
18:04	danlarkin	or use error-kit!!!
18:10	danlarkin	yeah returning nil isn't really working out for me, because first you have to check for nil, then you have to either check for the error code or result, blah
18:28	quidnunc	What should "swank-clojure-extra-classpaths" be set to in emacs? I'm having trouble setting it to anything non-nil (can't find swank.clj anymore).
18:46	danlarkin	Chouser: first real use of error-kit... I love it :)
19:17	Chouser	danlarkin: hah, great.
19:19	danlarkin	Also looking at david nolen's spinoza, it's also really cool!
19:19	Chouser	that's an object system, right?
19:20	Chouser	I think error-kit incorrectly contains parts of an object system. :-/
19:21	danlarkin	yeah, it's an object system, which is why I passed it over initially when I saw it on the ML
19:21	clojurebot	why not?
19:22	danlarkin	but it integrates with multimethods "correctly" (IMO) and doesn't reinvent too much, it looks like
19:22	danlarkin	I think it might be just-enough of an object system
19:23	Chouser	I'm not sure what I think of "object systems" in clojure, but even if they're ok, I don't think having error-kit invent its own is acceptible.
19:24	danlarkin	objects are just struct-maps
19:24	danlarkin	with extra sauce on top, so it looks like you can take it or leave it
19:24	Chouser	sure, but it's what you do with them that makes or breaks it.
19:24	Chouser	right
19:24	danlarkin	(I'm saying all this without having used it yet :) )
19:25	Chouser	well, error-kit error objects are just maps, but they have types which have inheritence, and they have constructors, etc.
19:26	Chouser	It seems likely to me either error-kit doesn't need all that, or that other things do.
19:27	danlarkin	sorry, do you mean "...doesn't need all that, and that other things also don't"?
19:29	danlarkin	if so, I sortof agree initially, but I haven't made up my mind yet
19:30	danlarkin	it's all degrees anyway, as long as it's turing complete you can do whatever you want anyway, it's just how convenient it is to work with
19:49	tashafa	hello
19:49	tashafa	qq....
19:49	tashafa	how do i get the arglists of a function passed into another function
19:49	tashafa	>=?
19:49	tashafa	?
19:52	Chouser	I don't think there's any way to get that.
19:52	Chouser	You can get the arglists of a ver defined using defn, but even that's not 100% reliable.
19:53	tashafa	cool thanks
19:54	tashafa	now i have to figure out a workaround
19:58	danlarkin	tashafa: what do you need to accomplish? maybe there's another way we can help you think of
20:02	tashafa	sorr..im back
20:05	tashafa	i have a library that takes a function from a user and applies to 3 or 2 arguments
20:05	tashafa	i want the user to be able to provide a function with either 2 or 3 items in the arglist vector
20:06	tashafa	so i need to be able to tell how many arguments the function the user provides has
20:07	tashafa	sorry let me rephrase that last sentence
20:07	Chouser	a callback with an optional 3 arg
20:08	danlarkin	so if they pass in a two arg function, you take one code path, and if they pass in a 3 arg function you take another
20:08	tashafa	yup
20:09	tashafa	but i dont want them to pass a function with optional args
20:10	Chouser	yeah, that seems very reasonable. Functions could provide a way to find out what numbers of args they could take, they just don't currently.
20:10	dreish	What about passing a function and a number?
20:11	Chouser	and it wouldn't be as simple as in some langages -- javascript provides a single arity int, and that just wouldn't cut it in Clojure.
20:11	tashafa	Chouser: yeah it looks like so
20:11	dreish	or {:fn x :arity n}?
20:11	danlarkin	or try to call with 3 args and catch IllegalArgumentException, and then try with 2?
20:11	tashafa	dreish: seems a little to hacky for me
20:11	dreish	tashafa: Why?
20:12	Chouser	(fn foo ([a] a) ([a b c] c) ([a b c d & e] d))
20:12	dreish	danlarkin: Exceptions take a long time to construct.
20:13	tashafa	because i'm trying to mimic how javascript
20:13	tashafa	dreish^
20:13	danlarkin	dreish: don't dismiss them flat out, though. maybe this isn't a critical code path
20:13	tashafa	it isnt
20:13	tashafa	the exception route seems like the forerunner
20:13	dreish	Yech.
20:13	dreish	That's the hackiest possible route, but whatever floats your boat.
20:14	tashafa	yeah but it hides the hack from the user
20:14	danlarkin	tashafa: are you relying on the user not to pass you a function on one argument, 4, 2 with an optional.. etc?
20:16	tashafa	im hoping the user passes a function with any number of arguments
20:16	tashafa	*a function that takes any number of arguments
20:17	quidnunc	Do .clj files need to (manually) compiled to Java byte-code or is it enough to have it in the classpath?
20:17	tashafa	but i just need to know how many arguments the function uses
20:18	danlarkin	quidnunc: it's enough to have it in the classpath
20:18	Chouser	tashafa: I think wanting to know that is reasonable, and this sounds like a solid use-case.
20:19	tashafa	python has this functionality i think
20:19	tashafa	i need to look it up though
20:19	Chouser	I can imagine wanting to be able to pass in general-purpose functions and have your fn look at them and do the right thing.
20:20	Chouser	So, you could certainly choose to pursue a feature request.
20:20	quidnunc	danlarkin: Thanks.
20:20	Chouser	...but that's not going to help you today. For today you need to find an acceptible work-around
20:20	dreish	I can't think of any good reason IFn couldn't have a .getArities()
20:21	Chouser	dreish: returning a set? plus a flag to indicate variadic?
20:21	dreish	I'd think a set.
20:22	tashafa	cool... i'll try and pursue a feature reauest and find a workaround. If i get anywhere i'll be sure to post back here
20:22	Chouser	one work-around would be a func that takes a 2-arg fn, and returns a 3-arg fn that ignores the 3rd arg
20:22	Chouser	(do-callback (fn [a b c] ...)) would just work.
20:22	tashafa	Chouser: you are a genius
20:23	Chouser	(do-callback (fix-it (fn [a b] ...))) would also work.
20:30	hiredman	I think .getArities would return a boolean IFn
20:31	dreish	How would you iterate over that?
20:31	hiredman	dreish: I am just thinking it would make handling & rest easier
20:32	dreish	Good point.
20:33	hiredman	hmmm
20:33	hiredman	I guess it could be some subclass of set
20:35	hiredman	that allows you to specificy some rule, like (> x 3) for set membership
20:42	hiredman	~def c.l.PersistentHashSet
20:46	danlarkin	Chouser: I can't call error-kit/raise with a sexp that returns the correct error because raise is a macro, so should I be using raise* for this?
20:52	Chouser	looks right
20:53	Chouser	appears to even be documented.
20:53	danlarkin	'doh!
20:53	danlarkin	where, do you mean the docstring?
20:53	Chouser	yes, just that.
20:53	hiredman	hmmmm
20:54	Chouser	I didn't mean to suggest you shouldn't have asked.
20:54	hiredman	IPersistentSet does not have a seq method, but the repl seems to call seq on it when trying to print it out
20:55	hiredman	java.lang.UnsupportedOperationException: seq
20:55	Chouser	,(seq #{:a :b :c})
20:55	clojurebot	(:a :c :b)
20:55	Chouser	?
20:55	hiredman	~def c.l.IPersistentSet
20:55	hiredman	if you proxy IPersistentSet, and try to print out the resulting object
20:55	hiredman	boom
20:57	Chouser	It's just and interface. You have to provide all the functions if you want them to do anything.
20:57	Chouser	s/and/an/
20:57	Chouser	(proxy [clojure.lang.IPersistentSet] [] (seq [] '(1 2 3)))
20:58	hiredman	Chouser: I don't want them to do anything
20:58	hiredman	I don't want a seq method, the interface does not contain one, but when the repl tries to print out my proxy object it tries to call a seq method on the object
20:59	hiredman	I imagine in some print function somewhere there is an IPersistentSet that should be an APersistentSet
21:00	hiredman	,(map #(.getName %) (.getMethods clojure.lang.IPersistentSet))
21:00	clojurebot	("disjoin" "get" "contains" "equiv" "count" "cons" "empty" "seq" "count")
21:00	hiredman	hmmm
21:00	hiredman	ah
21:00	hiredman	extends
21:00	hiredman	of course
21:03	danlarkin	for the records regarding error-kit and raise: yes I just ran macroexpand-1 on raise and substituted as necessary
21:03	danlarkin	Chouser: so thanks :)
21:04	Chouser	heh, ok.
21:07	danlarkin	clojurebot: exceptions?
21:07	clojurebot	http://paste.lisp.org/display/74305
21:07	danlarkin	clojurebot: thanks :)
21:07	clojurebot	Pardon?
21:11	hiredman	~def clojure.set/union
21:12	hiredman	that reduce is a drag
21:16	hiredman	I don't see how clojure.set/union can be made to work with rule defined sets
21:20	hiredman	~paste
21:20	clojurebot	lisppaste8, url
21:20	lisppaste8	To use the lisppaste bot, visit http://paste.lisp.org/new/clojure and enter your paste.
21:22	lisppaste8	hiredman pasted "rule set" at http://paste.lisp.org/display/80355
21:57	unlink	Is there any way to access what type of struct a struct instance is?
22:01	Chouser	it's a map. that should be enough. :-)
22:01	danlarkin_	you can have a :type key
22:01	danlarkin_	and then call clojure.core/type on it
22:01	danlarkin_	if you must
22:02	danlarkin_	or at least I thought you could
22:02	unlink	It's in there as a private field `def`, so tantalizingly inaccessible...
22:02	danlarkin_	oh, :type key on the metadata
22:03	unlink	user=> (meta (struct a 1 2))
22:03	unlink	nil
22:03	danlarkin_	it doesn't put it there for you :)
22:05	unlink	So I can't access it?
22:06	danlarkin_	a struct-map is just an optimized map
22:06	danlarkin_	it isn't a special thing
22:07	unlink	It is a clojure.lang.PersistentStructMap
22:07	unlink	Which has knowledge of what struct type it is.
22:08	danlarkin_	implementation detail
22:09	unlink	Except for the fact that it might be useful to know what kind of struct you are.
22:09	danlarkin_	the point is that you shouldn't be trying to use structs like classes
22:10	unlink	What's the right way to have a typed structure, then?
22:13	danlarkin_	put a :type key in the metadata
22:13	hiredman	(type #^{:type :foo} {:a 1})
22:13	hiredman	,(type #^{:type :foo} {:a 1})
22:13	clojurebot	:foo
22:17	mattdw	does anyone know if there's a way to provide class/interface names to 'proxy' at runtime?
22:18	mattdw	say (defn mk-proxy [cls] (proxy [cls] [])) ?
22:19	Chouser	get-proxy-class
22:19	Chouser	init-proxy
22:20	mattdw	ah sweet
22:20	mattdw	so proxy is just a wrapper around those two?
22:21	unlink	danlarkin_: I found what I was looking for. clojure.contrib.types/deftype
22:22	danlarkin_	clojurebot: def deftype
22:34	danlarkin_	Hm. couchdb returns the same status code & error message when you try to access a database that doesn't exist and try to access a document that doesn't exist
22:34	danlarkin_	so (document-get "foo" "bar") doesn't know if it's the DB or document that doesn't exist... in its current incarnation, at least
22:35	mattdw	Chouser: sweet, that's working great
23:07	Chouser	does anyone have a link for the blog that listed various ways to bundle data and functions in clojure?
23:07	Chouser	it talked about namespaces, mapfulls of closures, etc.
23:27	cads	hey chouser, you about?
23:27	Chouser	a bit -- on the phone too
23:28	cads	cool, lemme know when you got a sec, want to ask about your work with jscript and c, wrt clojure
23:44	danlarkin_	aw darn, and I can't even have multimethods like get and list that'd work on a server and database map, because clojure.core already defines them.
23:50	stuhood	danlarkin_: i thought namespaces handle that?
23:50	danlarkin_	stuhood: well all of clojure.core is refer'ed into the current namespace by default
23:51	danlarkin_	you can exclude specific functions and then write your own of the same name, but it breaks anyone use "use"ing your library
23:52	stuhood	danlarkin_: gotcha... so they'd have to rename the functions themselves during (use) anyway
23:53	danlarkin_	yep :-/
23:57	Chouser	cads: ok, anything quick? gotta run soon.