#clojure – 2009-11-08

2009-11-08

02:52	somnium	(.size (MongoProxy.))
02:52	somnium	oops
03:05	stephenj	~def ->
04:57	ttmrichter	What's the command set for the 'bot here?
05:01	hiredman	clojurebot: how much do you know?
05:01	clojurebot	I know 467 things
05:01	ttmrichter	clojurebot: help
05:01	clojurebot	http://www.khanacademy.org/
05:02	ttmrichter	Ah.
05:02	hiredman	:D
05:02	ttmrichter	And I'm assuming , and ~ are special prefixes?
05:02	hiredman	~ is equivilant to clojurebot:
05:02	clojurebot	clojurebot is not a benchmarking platform
05:02	ttmrichter	~ commands
05:02	clojurebot	excusez-moi
05:02	ttmrichter	And the ,?
05:03	ttmrichter	,(add 1 1)
05:03	clojurebot	java.lang.Exception: Unable to resolve symbol: add in this context
05:03	ttmrichter	Oops.
05:03	ttmrichter	,(+ 1 1 )
05:03	clojurebot	2
05:03	hiredman	actually
05:03	hiredman	(+ 1 1)
05:03	clojurebot	2
05:03	ttmrichter	Beat you to it. :D
05:03	hiredman	notice the lack of ,
05:03	ttmrichter	Oh, no I didn't notice that.
05:04	ttmrichter	So why is everybody putting , in front (including you)?
05:04	hiredman	(+ 2 3)
05:04	clojurebot	suffusion of yellow
05:04	ttmrichter	,(+ 2 3)
05:04	clojurebot	5
05:04	ttmrichter	Somebody is an Adams fan, I see.
05:04	ttmrichter	(/ 2 3)
05:04	clojurebot	2/3
05:04	ttmrichter	(/ 2.0 3)
05:05	ttmrichter	,(/ 2.0 3)
05:05	clojurebot	0.6666666666666666
05:05	ttmrichter	,(/ 2 30)
05:05	clojurebot	1/15
05:05	ttmrichter	So is there a way to get a full set of instructions for clojurebot?
05:05	hiredman	not so much
05:06	hiredman	clojurebot: where are you?
05:06	clojurebot	http://github.com/hiredman/clojurebot/tree/master
05:07	hiredman	clojurebot: git 1c8e76b1a0e6616c780902a317a7ab9a8423288b
05:07	clojurebot	newnew is now reify
07:55	spuz	,(filter seq '("abc" "" "def" "" "ghi"))
07:55	clojurebot	("abc" "def" "ghi")
07:55	spuz	is that a good way to filter out empty strings from a seqence?
07:57	rhickey	,(remove empty? ["abc" "" "def" "" "ghi"])
07:57	clojurebot	("abc" "def" "ghi")
07:57	rhickey	might be clearer
07:57	rhickey	also, quoted lists are not idiomatic, use vectors
07:58	tomoj	seems like remove empty? is a bit slower for some reason
07:58	rhickey	tomoj: good == clearest or fastest?
07:59	tomoj	in this case the difference in speed is not really significant
07:59	tomoj	100-200ms on a 100000 element seq
07:59	tomoj	so, clearest :)
08:00	rhickey	something that is clearer and slower today might be faster tomorrow, but will still be clearer
08:26	spuz	rhickey: thanks
09:00	solussd	is wrapping a function that calls a function that calls alter on a ref in a dosync sufficient to call it in a transaction? I have f2 that needs to run in a transaction, it is called by f1. can i (dosync (f1)) ?
09:01	solussd	nevermind- laziness was getting me
09:09	chouser	folding defclass into deftype sounds very pleasant
09:25	gerry`	will there be no defclass only deftype in future?
09:27	rhickey	chouser: ah, good, someone is reading that :)
09:27	rhickey	yes, I think very doable
09:27	rhickey	and desirable
09:27	rhickey	need cemerick to chime in
09:28	cemerick	rhickey: on?
09:28	rhickey	I think the ony gotcha will be people expecting the static aspects to update during dynamic development
09:28	rhickey	cemerick: http://www.assembla.com/wiki/show/clojure/Datatypes
09:28	rhickey	folding defclass into deftype, i.e. you get named class when AOT compiling deftype
09:28	rhickey	under: New ideas/scratchpad
09:29	gerry`	it seems cool
09:29	rhickey	for instance if you change the deftype and call new, you'll still get the AOT-compiled version
09:30	rhickey	and (.field calls) will fail on non-AOT based instances
09:31	gerry`	but if i really want a changed AOT class?
09:31	rhickey	OTOH, if (:field x) is as fast as (.field x) (at least for non-polymorphic sites), then why use (.field x)
09:31	rhickey	gerry`: compile again
09:31	rhickey	and restart :(
09:32	djpowell	what is :field using now? is it not using case any more?
09:32	rhickey	djpowell: it is backed by case, but there is not per-call-site caching of (:field x) calls
09:33	rhickey	in my tests, when the type of x doesn't change at a callsite, the perf is identical to (.field x)
09:33	rhickey	and of course, in real code using (.field x) the type of x isn't changing
09:34	djpowell	is the call site caching stuff described anywhere - i saw some checkins, but I didn't understand it
09:34	rhickey	cemerick: did you change all of your defstructs to defclasses or deftypes? and if the latter, to (.field x). If so maybe you could see if there is any perf disadvantage for you using (;field x)
09:35	rhickey	djpowell: I just tried to describe it to some people the other day, in person, with diagrams, took over an hour
09:36	gerry`	rhickey: your new ideas/scatchpad should be put at top of wiki page
09:37	rhickey	gerry`: I don't want people to get confused by speculation, the top is now working documentation for working code
09:38	cemerick	rhickey: they all got replaced by defclass; they're implementing public named interfaces
09:38	rhickey	cemerick: oh, that's right
09:38	rhickey	so you are not as good a test case then
09:38	rhickey	for deftype
09:39	cemerick	yeah, we're using it in only limited circumstances -- really, only where we'd otherwise be using regular maps with a stable set of slots
09:40	cemerick	I'm all for simplification though: right now, we have deftype, defclass, gen-class, proxy, and reify, which is quite a buffet to choose from if you're new.
09:42	rhickey	so, other than user confusion about the lack of dynamicity of named things (a recurring problem), the only real sticking point is the clash between the factory fn name and the class name
09:43	rhickey	seems a shame that people using Java can get (Foo. 1 2 3) where people using deftype dynamically will get (make-Foo 1 2 3) or something
09:43	rhickey	but my.ns.Foo can't name both the class and the facgory
09:43	rhickey	factory
09:44	rhickey	well, could but shouldn't
09:52	avital	Hello. I just started using Emacs/Slime with a remote Swank server and it keeps disconnecting. It may be something with my internet connection but I just wanted to check if anyone experiences similar issues...
10:00	cemerick	rhickey: w.r.t. "calls to (new Foo ...) will still use compiled class" -- perhaps the compiler should emit some hairy warning when loading a deftype is already defined in a compiled class?
10:02	rhickey	cemerick: If people aren't calling new or .field in Clojure code, i.e. using the factory fn and :field, then reloading a non-problem
10:03	rhickey	static name could just be for Java consumers
10:04	rhickey	or serialization, that was a use case of yours, any thoughts?
10:04	cemerick	rhickey: true, but if you're not calling new or using .field, then there's no reason to be AOT compiling, either.
10:04	cemerick	or, AOT compiling with any potential of reloading, I should say
10:05	rhickey	cemerick: not sure I get that, if I AOT for consumption by JAva, no harm/no foul if I reload during dev
10:06	rhickey	I just don't see it as a clear error
10:07	cemerick	OK, I'm reading "will still use compiled class" as meaning reloading will be a no-op for sites using new. Not an error, perhaps, but pretty darn surprising, I'd say.
10:08	rhickey	cemerick: why use (.field x) or new from Clojure code?
10:09	rhickey	note calls to new inside methods will work properly, as will naked local field refs: field
10:10	cemerick	hrm, OK. In that case, I withdraw. :-)
10:10	rhickey	the point of factory fns and fast (:field x) is to get people away from marrying AOT-static things
10:11	rhickey	note that I don't disagree - the behavior of new and .field may be both surprising and disappointing upon reload
10:12	rhickey	I get tired of explaining the static nature of Java classes and the problems with having/eating cake
10:13	rhickey	deftypes + protocols should provide a high-performance dynamic alternative, with good bridges
10:13	cemerick	Right. Well, that's largely why I suggested the warning, but the need for it depends a lot on how closely people will hew to idiomatic usage of the classes generated by deftype/class.
10:14	cemerick	i.e. :field rather than .field
10:14	rhickey	cemerick: I think the story has to be that new and .field are for interop consumption on the Java side
10:16	djpowell	if you are using new and .field for interop on the Java side, then having to recompile probably isn't too surprising
10:16	rhickey	djpowell: exactly
10:19	djpowell	so... what code do you have to write in clojure for the call site caching stuff to kick in? is it keyword based access?
10:21	rhickey	keyword callsites design diagram: http://www.assembla.com/spaces/clojure/documents/download/keywordcallsites.pdf
10:21	djpowell	ok cool i'll take a look
10:21	rhickey	djpowell: just (:k x) where x is a deftype/class instance
10:22	rhickey	that diagram is not meant to be self-explanatory :), just what I had at hand
10:26	Chousuke	Hopefully the JVM will be smart enough to optimise away most of the (identical? ret ...) checks, too.
10:28	Chousuke	though I suppose it'll have to have a check somewhere.
10:28	rhickey	Chousuke: yes, the fastpath presumes false, pipelining makes it 'free'
10:29	rhickey	the truly amazing thing is that hotspot can dynamically lift the thunk 'get' body inline into the host method
10:29	Chousuke	That's kind of counterintuitive, but nice nonetherless.
10:29	Chousuke	-r
10:30	Chousuke	Just goes to show that common sense assumptions about fast code hold less and less as processors and virtual machines advance :/
10:37	Chousuke	"Is the chart readable? no? Redesign."
13:03	chouser	We just need alternate punctuation for the factory fn, vs the trailing . for 'new'.
13:08	chouser	So (new Foo x) or (Foo. x) for java interop, (new-Foo x) or (Foo< x) for deftype
13:14	Chousuke	I suppose Foo: would be too easy to typo :P
13:14	chouser	but much prettier than Foo<
13:15	Chousuke	if Foo weren't capitalised I'd just suggest make-* but make-Foo is kind of icky.
13:18	mikehinchey	I don't think make-Foo is that bad, and more clear than a special char
13:20	chouser	google search is now apparently crawling the clojure-log every few hours now
13:22	hiredman	special
13:28	solussd	it's been doing that for awhile. :)
13:29	hiredman	clojurebot: fun with vars is <reply>http://www.slideshare.net/mudphone/fun-with-vars
13:29	clojurebot	Roger.
14:43	djork	would it be possible to build a lazy seq using StringTokenizer?
14:43	djork	I can do it all in one shot
14:44	djork	with loop
14:44	chouser	sure could
14:44	chouser	using lazy-seq directly is probably the most straightforward
14:44	djork	lazy-seq doesn't use any stack space?
14:45	djork	when evaluated?
14:45	chouser	a function that uses lazy-seq correclty and idiomatically will not consume stack space.
14:45	djork	ok
14:47	chouser	"StringTokenizer is a legacy class that is retained for compatibility reasons although its use is discouraged in new code."
14:48	djork	oh, that too I guess :)
14:48	chouser	you could produce a lazy seq from StreamTokenizer as well, though you'd have to be careful about getting the InputStream or Reader closed correctly.
14:49	djork	yeah
14:54	djork	I'm looking at things like re-partition from clojure.contrib.str-utils
14:54	djork	it seems like it would consume stack space
14:56	djork	I see a pattern like (fn foo [] (lazy-seq (cons bar (foo))))
14:56	djork	where foo is most definitely not in tail position... but is that not an issue with lazy-seq?
14:59	chouser	lazy-seq is a macro -- the expression inside it is put into a closure and returned
15:00	chouser	do you know how trampolines work, either in Clojure or other languages?
15:01	porpoise	Can someone help me with getting clojure to work with swank and jswat? I have it working with swank/Emacs but can't get it to open a port of external debugging
15:02	porpoise	Bill Clementson's site describes how to do it, but it's completely different from the automatic set up that was recommended to me as the current way to install it
15:02	lisppaste8	froog pasted "with-open and out, is this the way to do it?" at http://paste.lisp.org/display/90001
15:03	djork	chouser: nope, not familiar with trampoline
15:03	djork	http://gist.github.com/229461
15:03	chouser	froog: looks good to me
15:04	djork	damn, trampoline means about 20 different things :) http://en.wikipedia.org/wiki/Trampoline_(computers)
15:05	porpoise	What's the recommended way to install clojure with swank, and enable Jswat?
15:05	chouser	djork: don't worry about trampolines -- if you already were familier I could use that to explain lazy-seq.
15:05	djork	oh ok
15:06	chouser	djork: your gist is close, but the body of the lazy-seq needs to always return a seq (or nil), not a string
15:06	djork	next-tok will be nil in the false case of that if
15:06	djork	bad style, probably
15:06	froog	chouser: I wish the extra binding wasn't necessary, but I guess there's great wisdom behind the different 'let' and 'binding'
15:06	chouser	djork: oh! sorry, let me read again.
15:07	djork	there has to be an idiomatic way to express (if foo bar nil)
15:07	chouser	djork: (when foo bar)
15:07	djork	excellent
15:07	djork	you know I was reading some article that said "Clojure doesn't have a faq, it has chouser"
15:08	chouser	heh
15:08	djork	you need a break man
15:08	djork	clojure.contrib.chouser-vacation-fund
15:09	chouser	Speaking of which, I'm off to read Narnia to the kids. Good luck, all.
15:09	djork	edited: http://gist.github.com/229461
15:10	chouser	djork: perfect, though I might recommend the name 'step' instead of 'next'
15:11	djork	yes, now go be an awesome dad
15:58	turbo24prg	morning
18:44	skybound_	i was wondering if i might suggest a small fix for repl_utils.clj; (source load-file) throws an NPE, as the symbol doesn't have a :file meta entry and .getResourceAsStream doesn't appreciate nil. i realize this isn't a critical kind of bug...
19:19	chouser	skybound_: fixed, thanks.
19:25	skybound_	chouser: you are welcome; and thanks for fixing, i wouldn't want to send in a contrib-agreement for such a small patch.
19:31	skybound_	i think this would be nice to have for java code as well, but for the moment i don't see an easy way to do it
19:32	chouser	you mean for Clojure's own .java files?
19:33	chouser	they're not usually in the .jar or on the classpath, so the files would be a bit tricky to find in the first place.
19:33	skybound_	no, i mean for any kind of java/class files where both are available to the classloader; like my own legacy java libs
19:34	chouser	oh, you have .java files in the classpath? I'm not a Java guy -- is that common?
19:34	chouser	you can use 'show' to do some examination of the Java classes themselves.
19:35	chouser	maybe not the best chosen names. :-/
19:38	skybound_	it depends i guess, during dev i usually package source into the jars. for the moment my main usage of clojure is poking around in a java app via the repl.
19:39	skybound_	the idea is probably not worth the effort
19:41	chouser	when tracking down a Clojure behavior I often start with 'source' at the repl, but as I walk down the function calls end up at a java interop form, at which point I have to load the .java in an editor which is an unfortunate transition.
19:45	skybound_	right
20:48	littleidea	Learning clojure, philosophical question, when do you choose (. class-or-instance method-name args) or
20:48	littleidea	(.method-name class-or-instance args)? Is it just style or is there ever a clear preference for one over the other?
20:48	hiredman	.method-name is the prefered idiom
20:50	littleidea	ok, thanks, that seems closer to the CLOS idiom
20:51	hiredman	even before .method-name existed I think (. class-or-instance (method-name args)) was prefered over (. class-or-instance method-name args)
20:52	chouser	(. i m (a)) is the oldest -- we've gotten steadily better since then. :-)
20:52	chouser	er, (. i (m a))
20:52	hiredman	chouser: oh
20:52	chouser	I think. I could be remembering wrong. anyway, don't use either one.
20:52	littleidea	gotcha
20:53	chouser	unless you're generating them in a macro. Sometimes they're a bit more convenient there.
20:54	hiredman	because .foo is taken care of by the reader, and once you are in macro land you don't have the reader holding your hand
21:19	chouser	not quite
21:19	chouser	,(read-string "(.foo bar)")
21:19	clojurebot	(.foo bar)
21:19	chouser	,(first (read-string "(.foo bar)"))
21:19	clojurebot	.foo
21:19	hiredman	huh
21:19	chouser	it's actually expanded during macro-expand time, so you can use that form in a macro, it's just annoying.
21:20	chouser	,(macroexpand (list '.foo 'bar))
21:20	clojurebot	(. bar foo)
21:23	chouser	,(macroexpand (let [method 'foo] `(. bar ~method)))
21:23	clojurebot	(. sandbox/bar foo)
21:24	chouser	^^ simple
21:24	chouser	(macroexpand (let [method 'foo] `(~(symbol (str "." method)) bar)))
21:24	chouser	,(macroexpand (let [method 'foo] `(~(symbol (str "." method)) bar)))
21:24	clojurebot	(. sandbox/bar foo)
21:24	chouser	^^ annoying
21:59	chouser	hiredman: does your reader expand them? :-)
22:00	hiredman	nope
22:01	hiredman	I think I was misrembering the part where the reader turns symbols naming classes into Class objects
22:20	st3fan	i see parenthesis when i close my eyes
22:20	st3fan	too much code
22:20	st3fan	totally sarting to like clojure
22:28	st3fan	is there a shortcut for (filter #(not (nil? %)) c) ?
22:29	timothypratley2	I think (remove nil? c) from memory
22:30	timothypratley2	,(remove nil? [1 2 nil 3])
22:30	clojurebot	(1 2 3)
22:34	hiredman	,(filter identity [1 2 nil 3 4])
22:34	clojurebot	(1 2 3 4)
22:34	plunket	,(loop infinite)
22:34	clojurebot	java.lang.IllegalArgumentException: loop requires a vector for its binding
22:34	st3fan	cool
22:34	hiredman	,(filter (comp not nil?) [1 2 nil 3 4])
22:34	clojurebot	(1 2 3 4)
22:34	plunket	,(loop (print "hello))
22:34	clojurebot	EOF while reading string
22:34	plunket	,(loop (print "hello"))
22:34	clojurebot	java.lang.IllegalArgumentException: loop requires a vector for its binding
22:35	st3fan	even better would be a map function that would only return non-nil items
22:35	plunket	,(loop [print "hello"])
22:35	clojurebot	nil
22:35	hiredman	,(filter (complement nil?) [1 2 nil 3 4])
22:35	clojurebot	(1 2 3 4)
22:35	plunket	,(loop [5])
22:35	clojurebot	java.lang.IllegalArgumentException: loop requires an even number of forms in binding vector
22:35	plunket	,(loop [5 8])
22:35	clojurebot	java.lang.Exception: Unsupported binding form: 5
22:43	wtetzner\|nyx	,(loop [x 10] (if (zero? x) (println "done.") (do (println (str "x = " x)) (recur (dec x)))))
22:43	clojurebot	x = 10 x = 9 x = 8 x = 7 x = 6 x = 5 x = 4 x = 3 x = 2 x = 1 done.
22:45	st3fan	can anyone give me an example of if-let ?
22:45	timothypratley2	,(if-let [a true] 10)
22:45	clojurebot	10
22:45	wtetzner\|nyx	,(if-let [a false] 10)
22:45	clojurebot	nil
22:46	st3fan	oh so it is simply if the binding evaluates to a true value then the body is executed
22:46	timothypratley2	yup
22:46	wtetzner\|nyx	it only executes what's in the if-let if the binding is non-nil and non-false
22:46	st3fan	ok
23:03	st3fan	hm too bad if-let doesn't support multiple bindings .. would be nice if it would try all bindings and exec the body if they all returned a non-nil value