#clojure – 2009-02-27

2009-02-27

00:13	erohtar	chouser: you there?
02:24	hiredman	my sentiments exactly
02:24	hiredman	clojurebot: translate from jp #?4?????????,?????????????????????????
02:26	hiredman	clojurebot: translate from ja #?4?????????,?????????????????????????
02:26	clojurebot	# 4 I'd like to get one, and it would be prudent to think out collection
02:27	hiredman	clojurebot: translate from ja ?????
02:27	clojurebot	Now
03:50	Lau_of_DK	Hey guys
03:53	cmvkk	i have these two concurrent functions, one is hand rolled and the other uses pmap. they both run at almost exactly the same speed (one's 4% slower), but only the pmap version pegs both cores.
03:53	cmvkk	why wouldn't (doseq [cur-agent list-of-agents] (send-off cur-agent a-long-function)) run concurrently?
04:16	Lau_of_DK	(doc send-off)
04:16	clojurebot	Dispatch a potentially blocking action to an agent. Returns the agent immediately. Subsequently, in a separate thread, the state of the agent will be set to the value of: (apply action-fn state-of-agent args); arglists ([a f & args])
04:50	kotarak	The docstring discussion will also never die.......
04:51	cmvkk	it appears that i'm send-offing 4 agents at once, but three of them always wait for the first one to finish.
04:59	cmvkk	aha! i was using an incrementing atom (swap! counter inc) to make sure they didn't step on each other's toes, but apparently you can't do that from simultaneous dispatches.
05:03	Lau_of_DK	Try commute instead
05:03	Lau_of_DK	For a counter it'll work just fine
05:07	cmvkk	actually i really only needed to assign each agent a number then increment by (+ cur-num num-agents).
05:07	cmvkk	one of those 'should have used a pencil' scenarios...
05:12	Lau_of_DK	k
06:12	djpowell	Hmm, strings are seqable, but stringbuffers aren't. It might make more sense to define StringSeq to work over any CharSequence
06:13	leafw	djpowell: time to submit an enhancement proposal.
06:25	leafw	these tweets are out of place here, IMO.
06:27	Holcxjo	I agree -- maybe we need a #clojure-social channel for these bulk messages?
06:31	leafw	Holcxjo: do you know who is in charge of the clojurebot? Just suggest it to him if you do.
06:32	Holcxjo	Nope.
06:32	Holcxjo	clojurebot: who is your master?
06:32	clojurebot	Gabh mo leithsc�al?
06:32	Holcxjo	:-)
06:37	Hun	clojurebot: take me to your leader
06:37	clojurebot	Huh?
06:40	leafw	clojurebot: bdfl
06:40	clojurebot	I don't understand.
06:52	leafw	,(doc find-doc)
06:52	clojurebot	"([re-string-or-pattern]); Prints documentation for any var whose documentation or name contains a match for re-string-or-pattern"
07:30	AWizzArd	clojurebot: max people
07:30	clojurebot	max people is 149
07:35	kotarak_	leafw: isn't it hiredman?
07:40	leafw	kotarak_: sounds familiar; perhaps yes
08:05	clojurebot	svn rev 1311; fix print-method for objects with :type meta but no print-method, patch from Konrad Hinsen
08:39	MarkVolkmann	Is it correct to say that each loaded function is represented by an AFn object in memory?
08:55	kotarak_	MarkVolkmann: I think macros are simply functions with :macro true in their metadata.
08:55	kotarak_	Correction: Vars
08:56	kotarak_	You can even do (defmulti bla ....) and then a (.setMacro #'bla).
08:56	kotarak_	And you get a multimacro.
10:30	Holcxjo	Is there a form of let where the value can already make use of the name to be defined? I.e. something so that (let [a (cons 1 (map inc a))] (take 4 a)) works?
10:31	Holcxjo	Or do I have to model this with a loop or something?
10:41	Chouser	Holcxjo: interesting. the most common need for that is a fn referring to itself from inside its body. that's supported.
10:41	Chouser	otherwise you'll need some kind of reference type, a global var being the most common.
10:42	Chouser	If you don't like the global, you can use with-local-vars to get a local var, or use an atom or ref stored in a local.
10:44	Holcxjo	Chouser: I don't like the idea of an atom or ref or anything -- this is a fully functional algorithm...
10:44	Holcxjo	I'll need to learn about with-local-vars
10:45	Chouser	or use a different construct for the body of the expression. 'iterate' would work in your (I assume simplified) example.
10:46	Chouser	,(let [a (atom nil)] (reset! a (lazy-seq (cons 1 (map inc @a)))) (take 4 @a))
10:46	clojurebot	(1 2 3 4)
10:48	rhickey	looks like someone wants letrec again
10:49	Holcxjo	:-) Pretty please?
10:50	rhickey	Chouser: looked at :let, wondering if there might be some subtleties about order now :when guard :let [x something-expensive]
10:50	Chouser	rhickey: yes
10:50	Chouser	:-)
10:50	rhickey	:when and :while order themselves
10:50	rhickey	looks like :let always first in your patch?
10:51	Chouser	Is it really impossible for someone to want to use :when to guard and expensive :while?
10:51	Chouser	yes, :let comes first in my patch.
10:51	Chouser	"an expensive"
10:52	Holcxjo	Chouse: Couldn't that possibly cause exceptions? for [x natural-number :when (pos? x) :let [inv (/ 1 x)]
10:52	Holcxjo	I.e. the let may rely on the guard to be true to be valid
10:53	Chouser	Holcxjo: I think that's what rhickey is noting, yes.
10:53	Holcxjo	Chouser: Well he said "expensive". I meant "failing"
10:54	Chouser	but I wasn't sure if that was unacceptible, since it seems possible that the existing :when and :while have a similar ordering issue.
10:58	Chouser	(for [a (range -2 5) :when (not= a 0) :while (> (Math/abs (/ 1.0 a)) 1/3)] a)
10:58	Chouser	or something.
10:59	Chouser	I imagine allowing :when and :while to guard each other and :let would be possible, but would take a bit of work.
11:10	Holcxjo	So, back to my problem :-)
11:10	Holcxjo	How does one canonically and concicely represent a problem where I want to do something like (let [result (cons start-value (map some-function result other-seq1 ...))] result)
11:10	Holcxjo	Do I need to pollute the namespace with a global name to do that?
11:12	Chouser	did I fail to answer that? I think I listed the possible routes to solving that.
11:13	Holcxjo	Sorry, so the canonical way if via an atom? Yikes. :-(
11:15	Holcxjo	My apologies -- I assumes that was just a quick hack while thinking about a cleaner solution... I'll give that a try I guess
11:15	Chouser	well, your options are: global var, local reference type (var, atom, ref), or adjust your expression: somehow use a named fn or use something that can refer to itself but not by name
11:16	Chouser	for the example you posted, 'iterate' would work. It might not in your real world case, but perhaps something similar could be done.
11:17	Chouser	if nothing like that works, perhaps a self-recursive function would work, since they can have a private name for their own body:
11:17	Chouser	,(take 5 ((fn foo [] (lazy-seq (cons 1 (foo))))))
11:17	clojurebot	(1 1 1 1 1)
11:18	Chouser	failing that, and not wanting to touch a namespace global, 'atom' is probably the simplest reference type.
11:18	kotarak	Isn't that a candidate for a lazy-seq? (let [make-seq (fn make-seq [start-value other-seq] (lazy-seq (cons start-value (make-seq (compute-new start-value (first other-seq)) (rest other-seq))))) a (make-seq start-value other-seq)] (take 4 a)), not tested and kotarak is absolutely unclear about the new lazy-seq stuff.
11:18	Chouser	note it's mutated exactly once, so it's not as if the mutation is getting into your algorithm.
11:19	Holcxjo	Chouser: Thanks. That was a very elaborate an complete answer
11:19	Chouser	Holcxjo: I realize it's not letrec, but it's what we've got right now
11:19	Holcxjo	So, is there a reason for the absence of letrec?
11:20	Chouser	you'd have to take that up with rhickey. it's not something I've thought about, but I'm sure he has.
11:21	Chouser	kotarak: possibly something like that, yes, leveraging the private name feature of fn.
11:22	rhickey	http://code.google.com/p/clojure/issues/detail?id=89
11:24	Chouser	rhickey: would it not be called 'let'?
11:24	Holcxjo	rhickey: Thanks. I added my star to that
11:24	Chouser	I guess that would prevent using let to repeatedly replace the same local name.
11:25	kotarak	argh :(
11:25	rhickey	Chouser: no
11:33	rhickey	Where is Holcxjo's original problem? (came in late)
11:36	Chouser	(let [a (cons 1 (map inc a))] (take 4 a))
11:36	rhickey	Chouser: thanks
11:38	rhickey	would become: (letrec [a (lazy-seq (cons 1 (map inc a)))]
11:38	Chouser	and not 'let' because it would be a breaking change?
11:40	Holcxjo	rhickey: (let [result (cons start-value (map some-function result other-seq1 other-seq2 ...))] result)
11:40	Holcxjo	So basically a simple iterate doesn't work as I need other sequences as well in there
11:41	rhickey	mixing let and letrec is not normally done in non-lazy languages letrec/labels/let rec(ML)
11:43	rhickey	e.g. simply (letrec [a (cons 1 (map inc a))] (take 4 a)) wouldn't work because a is undefined when used in the initialization call to map
11:44	kotarak	,(let [make-seq (fn make-seq [start-value] (lazy-seq (cons start-value (make-seq (inc start-value))))) a (make-seq 1)] (take 4 a))
11:44	clojurebot	(1 2 3 4)
11:45	kotarak	Holcxjo: so lazy-seq may help you now, until letrec is available.
11:45	Holcxjo	kotarak: Thanks -- need to look into that to understand this solution
11:47	kotarak	Holcxjo: see also my previous example how to incorporate other-seq etc.
11:54	Holcxjo	kotarak: Thanks: I missed that example
11:55	kotarak	Holcxjo: it's kind of manual map
11:59	drewr	rhickey: Is (if (first s) s nil) an acceptable seq/nil implementation? That's essentially the patch I submitted.
12:03	Chouser	drewr: which patch is that, if I may ask?
12:04	drewr	Chouser: http://code.google.com/p/clojure/issues/detail?id=87
12:04	Chouser	ah, searching for "drew" was getting me nowhere.
12:04	Chouser	:-)
12:05	drewr	I'm surprised it doesn't put a name in there for gmail addresses.
12:07	Chouser	I think (if (seq s) s nil) or perhaps just (seq s) might be more generally correct, but I'm not sure if there's a specific problem with what you've got.
12:08	drewr	Good call. (seq s) is probably better.
12:08	drewr	brb
12:14	cgrand	Holcxjo: you can hide the atom trick into a macro, that's what seq-utils/rec-seq does: (let [a (seq-utils/rec-seq a (cons 1 (map inc a)))] (take 4 a))
12:19	Mec	how come let uses a vector to represent bindings instead of a map? is it just the aesthetic of the square vs curley or is there a reason?
12:21	kotarak	Mec: locals are serial: (let [a (initial-step) b (next-step a) c (another-step a b)] (use a b c here)). You loose this with a map.
12:24	Holcxjo	cgrand: Thanks -- that looks neater; I'll try that
12:24	Mec	kotarak: makes sense i guess, thanks
12:36	drewr	Looks like seq is slightly faster than first too.
13:15	clojurebot	svn rev 1312; updated add-watch doc
13:26	erohtar	chouser: u there?
13:26	Chouser	yep
13:26	erohtar	chouser: so i was thinking about our conversation yesterday about vars
13:27	erohtar	chouser: so vars in clojure arent the same as dynamically scoped variables in common lisp?
13:27	Chouser	I don't know CL well enough to say for sure, but my understanding is that they're pretty much equivalent.
13:28	Chouser	a possible difference being how threads interact with them -- not sure what CL does there.
13:28	erohtar	chouser: the thing is... in common lisp, if i bing var-a to x, any thing down the call stack will see x...
13:30	erohtar	chouser: in clojure, it doesnt seem to behave like a closure... (laziness, during realization) is that correct? if var-a was bound to y elsewhere, realization of the old lazy stuff would now see y
13:30	erohtar	chouser: is that right?
13:31	Chouser	CL doesn't do lazy seqs, right? so lets ignore that for now
13:31	erohtar	chouser: ok...
13:31	Chouser	let's just look at how a closure works.
13:32	gnuvince	Is there a better tutorial about Swing than the Trail on on Sun's site?
13:32	erohtar	chouser: i think i understand how a closure works, but when a closure is going to be evaluated lazily... what happens to a var that has since been rebound?
13:33	Chouser	(def var-a 2), (let [add (binding [var-a 5] (fn [n] (+ var-a n)))] (add 3))
13:33	Chouser	ok, here's a little example that I would expect to work the same if translated to CL
13:34	Chouser	var-a has a root binding of 2.
13:34	erohtar	chouser: that should eval to 8, yes?
13:34	Chouser	no
13:34	erohtar	chouser: hmmm
13:34	Chouser	within the dynamic scope of the binding, a closure is created that refers to var-a
13:35	erohtar	chouser: ok... and that is 5?
13:35	Chousuke	nah, it's var-a
13:35	erohtar	oh
13:35	Chouser	at the moment the closure is created, var-a has a thread-local binding of 5, but that doesn't really matter because nothing is asking for var-a's value, just grabbing var-a itself.
13:36	erohtar	i see... ok...
13:36	Chouser	so that closure is returned to outside the binding, and named 'add'
13:37	Chousuke	I guess it's a bit surprising though.
13:37	Chouser	and what does the closure have bundled inside? it knows it wants one arg n, and it has references to the vars var-a and +
13:37	erohtar	and it dynamically uses the value 2, for var-a when it needs it?
13:37	Chouser	right
13:37	erohtar	arent closures supposed to capture their environment?
13:38	Chouser	their lexical environment, yes.
13:38	erohtar	not the values?
13:39	Chouser	which is why this works: (def var-a 2), (let [m 7, add (binding [var-a 5] (fn [] (+ var-a m)))] (add))
13:39	Chouser	hm, not that's not quite right, since m is still available when 'add' is called. But anyway, it wouldn't have to be.
13:40	erohtar	thinking about this
13:40	Chouser	if you think about how dynamic vars are used in clojure.core, you'll see it must be this way.
13:40	Chouser	let's look at in
13:40	Chouser	er, out
13:40	Chousuke	,(let [x 1 add (fn [] (+ 4 x))] [(binding [x 2] (add)) (binding [+ -] (add))])
13:40	clojurebot	java.lang.Exception: Unable to resolve var: x in this context
13:40	Chousuke	hmm
13:41	erohtar	ok - talking about out - is that the std-out ?
13:41	Chouser	somewhere there's something like (def out System/out)
13:41	Chouser	right
13:41	Chousuke	,(let [x 1] (let [add (fn [] (+ 4 x))] [(binding [x 2] (add)) (binding [+ -] (add))]))
13:41	erohtar	right
13:41	clojurebot	java.lang.Exception: Unable to resolve var: x in this context
13:41	Chouser	that's the root binding of out
13:42	erohtar	ok, with u so far
13:42	Chousuke	hmm, I guess binding let-bound variables does not work
13:42	Chouser	then you've got functions like prn that use out
13:42	erohtar	yes... i think they need to be vars
13:42	erohtar	right
13:42	kotarak	let-bound locals are not Vars
13:43	Chousuke	hmm
13:43	Chousuke	,(let [x 1] #'x)
13:43	clojurebot	java.lang.Exception: Unable to resolve var: x in this context
13:43	Chouser	we can pretend prn is defined something like (defn prn [& args] (.write out args))
13:43	erohtar	when u create a lazy something, that uses prn, what happens?
13:43	Chousuke	indeed.
13:44	Chouser	now, if prn took the value of the out when it was defined, there would be no way to get prn to write to any other stream -- it would always use the root binding, since that's what was in play when prn was defined.
13:44	Chouser	but that's not how it works.
13:44	Chouser	prn has a reference to the Var out, not its value.
13:44	erohtar	so something like - (map #(prn %) [1 2 3])
13:44	erohtar	chouser: i completely agree
13:45	Chouser	so instead, prn will use the dynamic value of out when you call it.
13:45	erohtar	chouser: hmmm
13:45	Chouser	,(with-out-str (prn 5 10))
13:45	clojurebot	"5 10\n"
13:45	Chouser	got it?
13:45	erohtar	i do
13:45	erohtar	im thinking about my confusion - and trying to figure out the question to ask next
13:46	erohtar	so lets take my example -
13:47	erohtar	(map #(prn %) [1 2 3])
13:47	erohtar	now, somewhere else, i rebind out to str... and in there, if i use the above object, will it also use the new binding?
13:47	erohtar	it will...
13:48	erohtar	i think im getting it now
13:49	erohtar	ok - final thought -
13:49	Chouser	(def q (map #(prn %) [1 2 3])), (with-out-str (doall q))
13:50	Chouser	so yes, even though you created the lazy seq and closure outside the with-out-str, since its not computed or realized until the doall which is within the with-out-str, all those prn's will use the binding provided by with-out-str
13:50	erohtar	got it...
13:50	erohtar	so my final thought - what if instead of out we're talking about a connection to a database... bad use of vars, right?
13:51	Chouser	now lazy seqs can be a bit tricky because they cache their results and can effectively contain multiple closures.
13:51	Chouser	hmm....
13:51	erohtar	if i read from a db a list of objects using a var that holds database config.... and then i rebind the config to write into another database
13:51	Chouser	if you're going to open a connection to a database, do a batch of work in a single thread on it, and then close the connection -- then that would be a fine use.
13:52	erohtar	since the initial read may be lazy... when it realizes... it will 'read from the wrong place'"?
13:52	Chouser	right
13:53	Chouser	basically you want to be very careful about passing closures (and therefore lazy seqs) past 'binding' boundaries.
13:53	erohtar	chouser: on that thought - what i did was, i read from a db, and to write into the other, i created agents, binding the new db config in each
13:53	erohtar	chouser: it didnt work...
13:54	erohtar	chouser: ok... im beginning to understand ...
13:54	erohtar	i need to rethink what im doing
13:54	erohtar	and avoid using vars for some of this stuff, since im doing a lot of agent related stuff
13:55	Chouser	yes, I'd recommend trying to have the behavior of as much of your code as possible depend only on the args passed directly in.
13:55	erohtar	chouser: this whole mess started when i wanted to avoid passing db-config around everywhere
13:55	Chouser	this is better for testing, reasoning about behavior, easier to work with threads, closures, laziness, etc.
13:55	Chouser	heh, yeah.
13:56	erohtar	yup - i hear you
13:56	Chouser	well, another thing that may be helpful -- just guessing since I haven't seen your code...
13:56	erohtar	thanks a ton for your time - ur incredibly helpful
13:56	erohtar	ok?
13:56	Chouser	would be to try to keep as much of your code purely functional as possible.
13:56	erohtar	yes - i understand
13:57	Chouser	so avoid writing a function that takes some args, does some computation, and then writes to a db. Instead, have a fn that takes args, does computation, returns result.
13:57	Chouser	then perhaps you don't have to pass in db config at all -- whoever calls this fn can to the db write itself.
13:57	erohtar	i think it mostly is... except for this stuff... where i ended up inadvertently depending on "global" db-config
13:57	erohtar	well, this is a persistence layer
13:58	erohtar	i take an object in, break it up etc., and put it into hbase
13:58	erohtar	the code is open-sourece... would u like to see?
13:58	Chouser	hm, sure. I may need to ramp up on hbase soon.
13:58	erohtar	http://github.com/amitrathore/capjure/blob/b939a7038ebb4aed0d068d6e86291cc881ecf72b/src/org/rathore/amit/capjure.clj
13:59	erohtar	its kind a messy - learning clojure and hbase while doing this...
13:59	Chouser	:-)
14:00	Chousuke	erohtar: first thought: use some newlines.
14:00	danlarkin	Noooooooooooo -jure
14:00	erohtar	danlarkin: haha - u've told me that already
14:00	Chouser	danlarkin: hey, at least he's got a name
14:00	Chousuke	erohtar: one newline after each def/defn would make it a lot nicer :)
14:00	danlarkin	erohtar, Chouser: :)
14:01	erohtar	ok - more newlines, check
14:01	Chousuke	well, the def group is fine I guess.
14:02	Chousuke	but (defn foo) (defn bar) without an empty line in the middle is a bit weird
14:02	erohtar	ok - those were sort of just quick utility functions... but i'll put newlines
14:03	Chousuke	newlines never hurt anyone
14:03	Chouser	erohtar: this is what you get for posting code. unsolicited advice. :-)
14:03	erohtar	haha
14:03	erohtar	its fine - maybe i'll learn something too :)
14:03	Chouser	but while we're at it -- I much prefer to have the code arranged so that 'declare' is only needed in mutually-recusive situations.
14:04	Chouser	though others may disagree with me
14:04	erohtar	right - i struggled with that one - cause i dont like to have to order the functions in "reverse"
14:05	erohtar	see - capjure-insert is the only one that most people will call
14:05	Chousuke	erohtar: you could add more newlines and some kind of "headlines" for sections of code
14:05	erohtar	u bind the config stuff - hbase-master and primary-keys-config - and then u call capjure-insert with the params
14:05	Chousuke	so people can easily skip the helper function blocks
14:05	erohtar	most of the remaining functions are functional
14:06	erohtar	only the ones dealing with hbase have (obvious) side-effects
14:06	erohtar	and it works fine... and its in production too... ran into issues trying to use TWO hbase configs (to move data between them)
14:06	Chousuke	that's a lot of functions for one namespace too, though :)
14:07	Chouser	I really don't think more namespaces would be better.
14:07	Chousuke	if possible maybe it'd make sense to put the "side-effecting" functions (that deal with hbase) in a separate file or namespace?
14:07	erohtar	cause lazy lists of data from one hbase, seem to be getting messed up when i rebind the config to start writing into the other hbase
14:08	erohtar	do u know what i mean? (trying to get discussion back to lazy closures and bindings :) )
14:08	Chousuke	ah
14:08	Chousuke	right, I can see why that happens :)
14:08	Chousuke	the laziness gets evaluated in the context of the new hbase.
14:08	erohtar	well, im only starting to see it :) thanks to u guys...
14:08	erohtar	yea
14:08	erohtar	drove me crazy
14:09	erohtar	and i did all this only so i wouldnt need to pass the db config around all the functions
14:09	erohtar	like u said, there are a lot of them...
14:09	Chousuke	which means you will have to move away from using global vars for config and instead create something you explicitly pass around to the functions.
14:09	erohtar	so now what... ? pass the config around everywhere?
14:10	Chousuke	maybe only to a few core functions.
14:10	erohtar	yea
14:10	Chousuke	which then would bind the dynamic vars.
14:11	erohtar	well, if i pass it in, i dont need dynamic vars, rite
14:11	Chouser	or don't use lazy seqs
14:11	Chouser	use doall or stuff them in a vector first
14:11	erohtar	hmmm
14:11	cemerick	uk, the ILC registration site doesn't allow one to register more than one person at a time
14:11	erohtar	that might be one solution
14:11	Chousuke	right, if they are side-effecting that might be better.
14:12	Chouser	cemerick: how many people are you?
14:12	Chousuke	though maybe not memory-efficient :/
14:12	erohtar	yea
14:12	cemerick	Chouser: oddly enough, 2 ;-)
14:12	Chouser	:-)
14:12	erohtar	i think i will get rid of the dynamic vars
14:12	Chousuke	it's a shame though
14:12	erohtar	what is the pattern for this kind of 'static' config being passed around?
14:12	Chousuke	they make the code much easier to write :P
14:13	cemerick	I may end up sticking around through Tuesday -- Sussman's talk on Tuesday sounds fantastic
14:13	Chousuke	I wonder if there's a better solution
14:13	Chousuke	some way to "bind" the current config to when the lazy-seq is first created
14:13	erohtar	in typical OO, u can create an instance variable to hold the config - i wonder if in clojure u can create something like that... and since its immutable, it should be fine, rite?
14:14	Chouser	yes
14:14	Chousuke	maybe do (let [config global] (return-some-lazy-seq-qith config))?
14:14	erohtar	but there is no way to do that, rite?
14:14	Chousuke	would that fix the value?
14:14	erohtar	yea
14:14	Chouser	stuff all your config into a map, and pass that single thing into functions that need to use it
14:14	erohtar	i thought of doing something like that... but other functions couldnt access those values...
14:15	erohtar	i thought of simulating an 'immutable object oriented system' -
14:15	erohtar	like how u do in javascript... but immutable
14:15	Chousuke	I did in clojurebot so that I pass a map of config stuff around with every function
14:15	erohtar	return a closure with the vars bound with a let... and then closures for all the other functions also
14:16	Chousuke	it's a bit tedious though :/
14:16	erohtar	i dunno if im being clear
14:16	erohtar	very tedious
14:16	erohtar	macros can help
14:16	erohtar	essentially what id be doing is creating an immutable OO system
14:16	erohtar	something like that
14:16	erohtar	does that make sense?
14:16	Chousuke	erohtar: but your problem is only with lazy seqs right?
14:16	erohtar	lazy seqs and dynamic vars
14:17	Chousuke	erohtar: don't you only need to fixate the config when returning a seq
14:17	erohtar	the interplay
14:17	erohtar	yes
14:17	Chouser	erohtar: clojure.zip does something like that
14:17	erohtar	chouser: like what?
14:18	Chouser	each node is a object with a several functions attached as metadata
14:18	erohtar	chouser: ah, i see
14:18	erohtar	got it
14:18	Chouser	most of the api fns are like (children my-node), where children calls fns from my-node's metadata, passing in my-node
14:19	erohtar	i see -
14:19	erohtar	thats rather cool - so u can basically have my-node equivalent contain the config data
14:20	Chouser	sure
14:20	erohtar	alright folks, thanks a lot for this conversation - im going to experiment and see how to get this done with the least amount of work :D
14:20	Chouser	the only reason zip nodes have fns in metadata is so it can be polymorphic.
14:20	erohtar	yes- makes sense
14:21	erohtar	(then everyone can tell me how my code sucks :) )
14:21	Chouser	if you're going to only have one kind of db config (seems likely) then you don't need the metadata piece.
14:21	erohtar	yes - just need to take care of the fact that the config will be rebound... so just closures that capture the config, and the functions that use it
14:21	erohtar	something like that
14:41	durka42	oh dear
14:41	durka42	that post on ACP must be before lazy
14:41	durka42	it's confusing me because it calls rest and has parameters named next
14:42	Chousuke	heh
14:42	Chousuke	I wonder what the point of the runnable function is
14:43	Chousuke	did the author forget that clojure fns implement runnable
14:43	Chousuke	the use of cons seems weird too :)
14:44	Chousuke	maybe it makes more sense to someone with a CL background, but I'd just use a literal vector :P
14:45	kotarak	literals have their gotchas, too. ;)
14:45	Chousuke	I guess
14:46	Chousuke	but (apply foo (cons bar zonk)) just looks unclojurey :)
14:49	kotarak	oerk
14:50	Chousuke	yeah, it's pretty rare
14:51	rhickey	(apply foo (cons bar zonk)) ==> (apply foo bar zonk)
14:52	Chousuke	oh, right.
14:52	Chousuke	no need for a vector either.
14:53	kotarak	well, cons will be revived with lazy-seq, I fancy.
14:56	kotarak	the author probably doesn't know that between the sequence and the function in apply, there might be other arguments. I came across this misunderstanding several times now.
14:58	tashafa	,(. "test" (replaceAll #"e" "a"))
14:58	clojurebot	java.lang.ClassCastException: java.util.regex.Pattern cannot be cast to java.lang.String
14:58	tashafa	hmm.. what im i doing wrong?
14:58	tashafa	,(. "test" (replace "e" "a"))
14:58	clojurebot	"tast"
14:59	tashafa	,(. "test" (replaceAll "e" "a"))
14:59	clojurebot	"tast"
14:59	tashafa	,(. "test" (replaceAll #"e\|s" "a"))
14:59	clojurebot	java.lang.ClassCastException: java.util.regex.Pattern cannot be cast to java.lang.String
15:00	Mec	anyone know the etymology of clojure
15:00	tashafa	doesn't "replaceAll " take a regexp pattern as its first argument?
15:00	Chouser	tashafa: no, it takes a string
15:01	kotarak	,(replaceAll "test" "e\|s" "a")
15:01	clojurebot	java.lang.Exception: Unable to resolve symbol: replaceAll in this context
15:01	kotarak	,(.replaceAll "test" "e\|s" "a")
15:01	clojurebot	"taat"
15:01	Chouser	so sad
15:01	Chouser	,(.replaceAll "test" (str #"e\|s") "a")
15:01	kotarak	sad?
15:01	clojurebot	"taat"
15:02	MarkVolkmann	What's the best/most idiomatic way to return a non-lazy map from a function when that function obtains a lazy map by calling some other function?
15:02	MarkVolkmann	This is related to some database code.
15:02	Chouser	so sad that .replaceAll takes a regex as a string instead of as a regex.
15:02	kotarak	Chouser: the glories of interface design....
15:02	tashafa	ah ...thanks guys
15:03	MarkVolkmann	The result set is a lazy map. I want to return it, but when this function exits, the ResultSet will be closed and I won't be able to get to the ResultSet anymore.
15:03	kotarak	MarkVolkmann: I suppose you mean (map ....) by "map". I would thing doall.
15:03	Chouser	"lazy map" isn't the right term. map returns a lazy seq
15:03	tashafa	,(. "test" (replaceAll "e\|s" "a"))
15:03	clojurebot	"taat"
15:03	MarkVolkmann	Oh right ... a lazy seq of MapEntry object.
15:03	kotarak	There is a lazy-map though. commercialonair
15:04	Chouser	a seq of mapentry objects? you want to put them in a hash-map perhaps?
15:05	Chouser	in general you can use doall to realize a lazy seq so it's no longer lazy, or use vec to create a non-lazy vector.
15:05	MarkVolkmann	Got it! Returning (doall rs) did the trick.
15:06	Chouser	Mec: http://groups.google.com/group/clojure/msg/766b75baa7987850
15:11	Mec	ah hah, thanks. i'd guess that clojure has closures then?
15:11	Chouser	indeed it does
15:26	MarkVolkmann	I think you have to get to the point that you're convinced about the benefit of code and data having the same syntax.
15:26	MarkVolkmann	Someone posted the URL of an article that addresses this. Just read it last night.
15:27	MarkVolkmann	http://www.defmacro.org/ramblings/lisp.html
15:27	pjstadig	http://paul.stadig.name/2009/02/clojure-terracotta-yeah-baby.html
15:28	MarkVolkmann	It supports the use of parens in Lisp by stressing the advantages of being able to easily write code that generates code.
15:28	pjstadig	i wrote up my experiment with integrating Clojure and Terracotta
15:28	rhickey	pjstadig: just read it - fun!
15:30	pjstadig	yeah it was fun
15:30	pjstadig	thanks for a great language
15:33	rhickey	pjstadig: you're welcome!
15:35	Mec	is a trailing . a special form or a macro?
15:39	kotarak	Mec: A trailing to dot is a synonym for new: (some.Class.) <=> (new some.Class)
15:39	kotarak	Mec: leading dot is for methods: (.method some-object) <=> (. some-object method)
15:39	kotarak	Mec: and / is for static members: some.Class/STATIC_CONSTANT
15:40	kotarak	,(macroexpand-1 '(String. "Hello"))
15:40	clojurebot	(new String "Hello")
15:40	WizardofWestmarc	and don't forget the ever fun $ for internal classes
15:40	WizardofWestmarc	had fun w/that last night before Chouser reminded me to use it
15:41	WizardofWestmarc	"why the hell can't I access this enum?" "oh just do blahblah full qualified path.classname$subclassname/enumval
15:41	WizardofWestmarc	lights go on and everything just works
15:44	kotarak	Also Class. and .method are treated specially in syntax-quote.
15:44	kotarak	,`(String.)
15:44	clojurebot	(java.lang.String.)
15:44	kotarak	,`(.method obj)
15:44	clojurebot	(.method sandbox/obj)
15:44	cp2	i have a string that i want to coerce into a map. its formatted as "key\value\key\value....". obviously, i split by \ to get each component. whats a quick/decent way to use the evenly indexed elements in the resulting array as the keys parameter for zipmap, and likewise with the oddly indexed values?
15:45	kotarak	cp2: why not simply (apply hash-map splitted-things)?
15:45	leafw	cp2: get even into one list, odd into another, then zipmap
15:45	cp2	leafw yes, i know, but i was wondering if there was a better way
15:45	cp2	kotarak ok, ill see
15:46	hiredman	,(apply hash-map (.split "foo\bar\bleep\bloop" "\"))
15:46	clojurebot	EOF while reading string
15:46	cp2	they need to be escaped
15:46	cp2	\\
15:46	hiredman	,(apply hash-map (.split "foo\bar\\bleep\\bloop" "\\"))
15:46	clojurebot	java.util.regex.PatternSyntaxException: Unexpected internal error near index 1 \ ^
15:46	cp2	yeah
15:46	cp2	i got the same thing
15:46	hiredman	,(apply hash-map (.split "foo\bar\\bleep\\bloop" "\\\\"))
15:46	clojurebot	java.lang.IllegalArgumentException: No value supplied for key: bloop
15:46	hiredman	anyway
15:47	kotarak	,(apply hash-map (.split "foo\\bar\\bleep\\bloop" "\\\\"))
15:47	clojurebot	{"foo" "bar", "bleep" "bloop"}
15:47	cp2	oh right
15:47	cp2	regexps are funky in java
15:47	cp2	double escaping, etc
15:47	cp2	thanks
15:47	leafw	cool -- learnt something :)
15:49	hiredman	nah, the funkiness is because those are not actaully regexs
15:49	hiredman	those are strings that get turned into regexs
15:49	cp2	hiredman, String.split actually does take a regexp
15:49	cp2	well, yes
15:49	cp2	you are right, i should have let you finish typing :)
15:56	cp2	ah, one more bit onto my previous question
15:57	cp2	actually, nevermind
15:59	cemerick	pjstadig: nice writeup
16:00	pjstadig	thanks
16:00	WizardofWestmarc	haven't had a chance to read it but I plan to later. Terracota looks interesting as hell, and mixed with Clojure? Mmmm
16:01	pjstadig	yeah i think its a really compelling combo
16:01	pjstadig	and of course the only production clojure app (that I know of) supposedly uses Terracotta
16:02	WizardofWestmarc	nods
16:02	WizardofWestmarc	It's stuff like Terracotta, and on my end Smack, which really make me appreciate the choice of putting Clojure on the JVM
16:02	pjstadig	it was definitely a brilliant move
16:03	gnuvince	WizardofWestmarc: Smack?
16:03	gnuvince	Clojure made me like the JVM
16:03	cemerick	is the appeal of Terracotta the semi-unlimited memory potential?
16:03	gnuvince	Now I just need to learn how to use Swing :-/
16:03	WizardofWestmarc	gnuvince: It's an xmpp client library
16:04	cemerick	vs. messaging-oriented architectures, I should say
16:04	WizardofWestmarc	setting up a web app w/processing backend written in clojure
16:04	WizardofWestmarc	going to use xmpp and a lightweight server (openfire) to inform the backend when it has work to do
16:05	WizardofWestmarc	took me a while to get it all figured out but finally got all the clojure code working last night
16:06	pjstadig	cemerick: i think one of the appeals is removing the ORM impedance mismatch
16:07	cemerick	pjstadig: so there's a whole-cluster-JVM persistence mechanism available?
16:08	pjstadig	not sure what you mean...terracotta is just that
16:09	pjstadig	it's not only pitched to replace your database
16:09	pjstadig	one use case (on their site) is to store temporary data in terracotta
16:09	pjstadig	like if you have a wizard interface with stages of completion
16:09	pjstadig	or there example is an exam that someone takes
16:10	pjstadig	only stuff it in your DB when it's complete
16:11	cemerick	they've clarified a lot of things on their site since the last time I was there. Just read http://terracotta.org/web/display/orgsite/Kill+Your+Database
16:11	cemerick	my last impression was that it was only in-memory clustering
16:12	pjstadig	there's in memory and a permanent store mode that commits to disk and maintains state between restarting Terracotta
16:12	pjstadig	i don't know the history...maybe it wasn't always that way
16:14	cemerick	jeez, if that actually works, that'd be outrageous on a number of fronts.
16:15	WizardofWestmarc	cemerick: exactly!
16:16	WizardofWestmarc	and the Terracotta guys are even interested in clojure, so they should be friendly in helping with any problems run into on tying it all together to boot.
16:16	pjstadig	when I signed up at the terracotta site i was contacted by a sales person
16:16	pjstadig	i responded and told him i was just investigating and sent a line to my blog article
16:17	pjstadig	he said he forwarded it to their dev team, and they like to hear about cool integrations like this
16:18	WizardofWestmarc	hm, didn't know there was a terracotta book
16:18	WizardofWestmarc	will have to remember that for when I am ready to start playing with it.
16:18	cemerick	we're using jms right now (openMQ), relatively happily, tho. I wonder how applicable that kind of approach is.
16:18	pjstadig	i think terracotta has its own niche
16:19	pjstadig	they're not necessarily trying to replace your database or messaging system
16:20	Chouser	pjstadig: I think it would be a relatively trivial use of gen-class to hold Var roots
16:20	Chouser	nice writeup, btw, thanks.
16:21	pjstadig	it would be interesting to have an example of that
16:21	cemerick	I'll definitely have to take a look at it.
16:21	pjstadig	maybe you could fork my github
16:21	pjstadig	or maybe i'll play with it
16:21	Chouser	pjstadig: ok, I may look at that tonight.
16:21	Chouser	apparently I need to get into this whole distributed server thing.
16:22	Chouser	terracotta, hbase, hadoop, mongodb, and such
16:23	pjstadig	haha!
16:23	hiredman	:(
16:23	pjstadig	information at the speed of twitter!
16:23	WizardofWestmarc	oh my new clojure book beta? goes
16:24	WizardofWestmarc	hm, looks like it isn't uploaded yet, as it hasn't switched to "regenerate pdf"
16:24	hiredman	is it too much? should I unhook the tweets?
16:25	WizardofWestmarc	hiredman: I'd say yes, anyone who cares can just rss the feed
16:25	WizardofWestmarc	that's what I have set up anyway
16:27	cemerick	hiredman: you could hook -clojurebot up to its own twitter account that we could follow :-P
16:28	hiredman	oh, hmmmm, for svn messages?
16:28	WizardofWestmarc	svn messages I like, personally
16:28	cemerick	oh, that'd be handy too, but I meant for the twitter feed as well
16:28	WizardofWestmarc	they don't tend to flood the room but are useful to see
16:29	cemerick	I need to figure out how to get all my rss feeds into something I can follow on twitter.
16:29	WizardofWestmarc	hah
17:04	brennanc	brand new to clojure here. I'm going through the programming clojure book and am trying to figure out how the "examples" folder is included. I created my own folder and put a .clj file in there but I can't load it using "use". What do I need to do so I can use "use"
17:05	Chouser	brennanc: the examples from the git project are loading, but not your own .clj files?
17:10	lenst	/quit
17:16	WizardofWestmarc	wonder how long it takes for a new book upload by the pragprog guys to hit the gerbils
17:19	scottj	Are contrib and slime up-to-date with the fully-lazy changes?
17:19	scottj	or clojure-swank rather
17:19	digash`	scottj: yes, i am using it.
17:25	hiredman	what
17:25	hiredman	I thought I disabled that
17:38	danlarkin	the tweets will never die!
17:39	hiredman	someone should tell them that those stars mean a var that it is intended to be rebound
17:40	Chouser	how ironic
18:04	brennanc	Chouser: I guess I don't really know how the include system works. How do I invoke Clojure and tell it where to look?
18:07	Chouser	brennanc: the simplest way to load a single file is (load-file "foo.clj")
18:07	Chouser	that'll load "foo.clj" from your current working directory
18:16	brennanc	not able to get that to work. doesn't seem to take a string
18:16	brennanc	user=> (load-file "my-test.clj")
18:16	brennanc	java.lang.RuntimeException: java.lang.RuntimeException: java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol (my-test.clj:1)
18:20	danlarkin	brennanc: that means my-test has an error
18:20	danlarkin	not the call to load-file
18:21	danlarkin	you probably have an error in your namespace definition, judging from the error
18:28	hiredman	danlarkin: I kind of get the feeling he may not have a namespace declaration
18:29	blbrown	is pircbot still the standard irc bot or has something better come along
18:30	hiredman	pircbot is nice and simple
18:45	twopoint718	I had a facepalm moment just now with using a quoted ns call when it shouldn't have been.
18:47	twopoint718	brennanc: check your ns or in-ns call, it could be the same thing.
19:16	brennanc	ok, thanks, guys. How do I add a directory of .clj files to the class path so I can use it with "use"?
19:19	brennanc	do I need to jar up the whole folder each time and put that jar in the class file or can I just have it look in a folder?
19:19	Chouser	no need to jar
19:20	Chouser	for a namespace foo.bar.baz, put the code in a file src/foo/bar/baz.clj, and put src in your classpath
19:21	Chouser	then you can say (use 'foor.bar.baz)
19:25	brennanc	by put src in my classpath you mean like "export CLASSPATH=$CLASSPATH:/full-path-to/src"?
19:25	Chouser	yes
19:26	Chouser	note that -cp on the java command line will cause the CLASSPATH env var to be ignored
19:30	brennanc	I modified the repl.sh to add the folder that has my .clj but it still is complaining that it can't find my file in the classpath
19:32	brennanc	do I need to add a ns at the beginning of my .clj file?
19:32	Chouser	yes
19:34	Chouser	if you're still having trouble, paste your classpath, .clj file, and the error you're getting
19:34	Chouser	lisppaste8: url
19:34	lisppaste8	To use the lisppaste bot, visit http://paste.lisp.org/new/clojure and enter your paste.
19:37	brennanc	got it. I had to add namespace like "folder.base-file-name". I was just doing "ns folder"
19:37	brennanc	the repl.sh includes the classpath with a simple "." for the CWD
19:42	Chouser	great
19:47	mrsolo	is there something in closure api so that (eq? 'a 'a) => true?
19:47	Chouser	,(= 'a 'a)
19:47	clojurebot	true
19:48	Chouser	is that what you mean?
19:48	mrsolo	duh
19:48	mrsolo	i typed = wrong..nm
19:48	mrsolo	yep
19:48	mrsolo	thanks :-)
19:48	Chouser	np
19:50	slashus2	,(contains? [1 2 3] 3)
19:50	clojurebot	false
19:51	Chouser	,(contains? '[a b c] 1)
19:51	clojurebot	true
19:55	slashus2	I guess it doesn't work the same as (.contains [1 2 5] 5)
19:56	slashus2	Works on maps :-\|
19:57	Chouser	vectors map from index to value
19:58	Chouser	'contains?' tells you if the index exists
19:58	slashus2	I get that now.
19:58	Chouser	if you're doing membership checks, a set is faster and more convenient
19:58	Chouser	,('#{a b c} 'b)
19:58	clojurebot	b
19:58	Chouser	,('#{a b c} 'd)
19:58	clojurebot	nil
20:01	slashus2	Okay, neat.
20:02	slashus2	,(some #{20} [1 2 20])
20:02	clojurebot	20
20:02	Chouser	did you read that somewhere?
20:03	slashus2	I was just playing around with some.
20:04	slashus2	Why?
23:16	danlarkin	so a var is like a thread-local variable, I want to update it with each call to a function
23:16	danlarkin	with atoms I would use swap!
23:16	danlarkin	but I don't want an atom, since that'll be cross-thread
23:17	Chouser	set!
23:18	danlarkin	it complained that it can't change/establish a root binding with set!
23:18	danlarkin	but I have (def blocks {}), am I missing something?
23:26	danlarkin	Chouser: ping
23:31	cmvkk	i think you have to use binding first?
23:31	danlarkin	ohh, you are probably right
23:31	Chouser	yep
23:38	Chouser	binding pushes a thread-local context, and 'set!' can change that.
23:39	Chouser	to change the root, use alter-var-root, but of course that's shared among threads.
23:41	danlarkin	I will have to find the proper place to establish a binding