#clojure – 2008-06-11

2008-06-11

09:23	rhickey_	A new Clojure talk, oriented towards those with no prior Lisp: http://clojure.blip.tv/file/982823
09:26	grosours	hi everybody
09:26	rhickey_	hi
09:38	cgrand	reduce retains a reference to the head of the seq :-(
09:41	cgrand	Is explicit looping (recur) the only way to process (very) large sequences?
09:42	rhickey_	reduce used to do that, now can leverage internal reduce of several collections
09:43	rhickey_	but I need to re-enable loop where collection can't do anything special, as internal reduce holds head as you saw
09:44	rhickey_	some sort of lazy? metric
09:44	rhickey_	for 'realized' collections, internal reduce is fastest
09:45	cgrand	because it may be inlined to a simple for
09:46	rhickey_	can leverage the internal structure of the collection, and eliminate reified seq objects
09:54	asbjxrn	Is there something like load-truename in clojure?
09:55	rhickey_	load-truename?
09:55	asbjxrn	I have a start.clj from which I want to load another clj file in the same directory.
09:57	asbjxrn	In CL you have, variables load-truename load-pathname that are set accordingly when a file is loaded
09:58	asbjxrn	so if I had a file in the same dir I could do (load (merge-pathnames load-pathname "foo.lisp"))
09:58	asbjxrn	(paraphrased.... :)
09:58	cgrand	rhickey_: just being curious: wouldn't a Reducer interface be an alternative to a lazy? metric (eg (.. s getReducer (reduce f val)) )?
09:59	rhickey_	asbjxrnL nothing like that yet
09:59	asbjxrn	I guess this would be outside the scope of a small core, though ...
09:59	rhickey_	may be something in contrib?
09:59	asbjxrn	Yeah, the library stuff in contrib may be what I want. Haven'
10:00	asbjxrn	haven't had a close look yet.
10:00	rhickey_	cgrand: yes, it's not really laziness, it's - does this support efficient internal reduce
10:01	rhickey_	part 2 of the talk: http://clojure.blip.tv/file/982957/
10:05	cgrand	Is it the talk you gave last week?
10:06	rhickey_	yes
10:06	rhickey_	all 2:48 of it
10:06	rhickey_	in 2 parts
14:07	Lau_of_DK	rhickey, everytime you write "Fixed -Thanks for the report" in the Googlegroup, is there an SVN or CVS I can checkout with those updates added?
14:07	rhickey	If I say fixed, it's fixed in SVN as of then
14:08	Lau_of_DK	Sweet
14:13	la_mer	rhickey: I was reading the page about the new primitive support, and noticed that you say that Clojure doesn't actual emit any bytecode for primitives at all, instead relying upon hotspot to optimize primitive operations (you say something like this again in the talk you posted most recently to blip). Are you just providing certain hints to hotspot that the numerics involved can be safely unboxed?
14:14	rhickey	I emit typed calls to static methods (of clojure.lang.Numbers) that wrap simple primitive arithmetic and HotSpot inlines them. So I emit method calls only.
14:15	rhickey	I do emit bytecodes for passing/returning primitives to methods
14:15	rhickey	but not arithmetic
14:16	Chouser_	while you're on the topic, what tool do you use to examine the code the hotspot ends up producing?
14:18	rhickey	I only see the effect, not the code at runtime. Since the speed is identical to that of Java using primitive arithmetic, the presumption is that is what HotSpot is yielding
14:18	Chouser_	ah.
14:18	rhickey	but there is some way to get that IIRC
14:25	Lau_of_DK	How much does the term "primitive support" cover ?
14:26	rhickey	int/float/long/double
14:26	rhickey	and arrays of same
14:28	Lau_of_DK	ok, thanks
14:29	Lau_of_DK	Chouser, one thing you said last night didnt make sense, but it worked. Why does (.contains x y) work? I get that (. method param) works because its the syntax, but what about your variant?
14:29	cgrand	Chouser_: I remember having used -XX:+PrintCompilation
14:31	Chouser_	Java: obj.method( arg1, arg2 ) Clojure: (. obj method arg1 arg2) or (.method obj arg1 arg2)
14:31	Lau_of_DK	oh I see
14:31	Chouser_	In your case the method was static, so obj was the classname. Which always confuses me a little.
14:34	Lau_of_DK	Ok, thanks for clearing it up and emphazing :)
14:34	Lau_of_DK	spell check ? :)
14:37	Chouser_	cgrand: that's cool!
14:37	Chouser_	It's not showing me the bytecode, but it's fun to see when stuff gets compiled.
16:47	Lau_of_DK	VIM Users: When you use VIM and Clojure - Do you have live interaction with the REPL? Like you evaluate directly into the REPL and such, or is that only in Emacs ?
16:48	Chouser_	I don't bother.
16:48	Lau_of_DK	why not?
16:49	Chouser_	Generally, I just re-run the repl on the file I'm working on.
16:49	Lau_of_DK	But then youre missing out on all the good stuff, like altering the logic while the program is running and all that
16:50	Chouser_	Well, I sometimes drop a new function into the running repl. That's two mouse strokes.
16:50	Lau_of_DK	ok - Maybe I should just give Vim a twirl
16:50	Lau_of_DK	Im just used to Emacs by now
16:50	Chouser_	I'm not claiming my setup it The Best, I'm just telling you what I currently do.
16:51	Lau_of_DK	But Im not sure that the clojure-mode and clojure-swank stuff is fully complete
16:51	Lau_of_DK	I think its acting a bit weird sometimes
16:51	Lau_of_DK	Compared to something like SBCL, which is just rock solid in this regard
16:58	Lau_of_DK	Anybody else got that impression?
17:00	Lau_of_DK	Alright, you guys arent editor reviewers, I got that, lets talk shop
17:00	Lau_of_DK	Lets say I want to generate a stream of all possible combinations of "ABCDEF" in sets of 4, ie ABCD or AAAB or ABAB and so on - Any ideas on how to attack that?
17:10	Lau_of_DK	No its not for Euler
17:11	Chouser_	:-) ok, ok.
17:11	Lau_of_DK	But there was a lexical permutation problem that I never managed to solve, which posed a similar problem
17:11	Lau_of_DK	But I'm really interested in how you do these kind of combinations
17:11	Lau_of_DK	This is for a Mastermind solver
17:13	Chouser_	(def s [:A :B :C :D :E :F]) (for [x1 s x2 s x3 s ...] (prn x1 x2 x3 ...))
17:18	Lau_of_DK	I think thats a little weird..
17:18	Lau_of_DK	Why didnt I think of that?
17:19	Chouser_	non-repeating combinations are a little more interesting.
17:19	Lau_of_DK	how so ?
17:20	Chouser_	well, the choice for x1 reduces the selection for x2, so it's a little trickier.
17:20	Lau_of_DK	Yea, fortunately, I dont need that now
17:20	Lau_of_DK	:)
17:20	Lau_of_DK	But thanks alot Chouser, you opened my mind a little bit there
17:20	Chouser_	So what's weird about the "for"?
17:21	Lau_of_DK	I just imagined that they would all execute in sequence
17:21	Lau_of_DK	a a a
17:21	Lau_of_DK	b b b
17:21	Lau_of_DK	c c c
17:21	Lau_of_DK	d d d
17:21	Lau_of_DK	...
17:22	Chouser_	yeah, the way that "for" sorta nests the sequences surprised me too the first time. But it sure is handy.
17:22	Lau_of_DK	yea - I remember one time though, where I got the opposite result - dont remember what I did
17:22	Lau_of_DK	but thats why I didnt try it
17:22	Lau_of_DK	I think that was mapping 2 sequences
17:24	Chouser_	(for [x1 s x2 s x3 s] [x1 x2 x3]) vs. (for [[x1 x2 x3] (map list s s s)] [x1 x2 x3])
17:25	Lau_of_DK	user> (map (fn [a b] (list a b)) (range 5) (range 5))
17:25	Lau_of_DK	((0 0) (1 1) (2 2) (3 3) (4 4))
17:25	Lau_of_DK	yea, or that type of thing
17:26	Chouser_	right.
17:26	Chouser_	(map list (range 5) (range 5))
17:26	Lau_of_DK	Showing off, will be punished :)
17:26	Chouser_	;-)
17:28	Lau_of_DK	Ok Chouser, you might recent me for this
17:29	Lau_of_DK	But if I want to change def s [:a ...] to an "inifinite" (its not its 1296) stream of lazy-cons...
17:29	Lau_of_DK	Can you hint me to how I go about it?
17:32	Chouser_	a stream of what? where are you getting your 1296 data items?
17:32	Lau_of_DK	if you count all the combinations, its 1296
17:33	Lau_of_DK	I just need to have a stream I can walk through
17:33	Lau_of_DK	So I wanted to do something like when we do fibs
17:34	Chouser_	This is a lazy seq: (for [x1 s x2 s x3 s] [x1 x2 x3])
17:35	Lau_of_DK	Oh thats right - Unless I force it with doall
17:35	Lau_of_DK	Thanks... :)
17:09	Chouser_	(defn comb [r m p] (if (> m 0) (mapcat #(comb (disj r %) (dec m) (conj p %)) r) [p]))
17:09	Chouser_	(comb #{1 2 3 4 5} 3 [])
17:21	Lau_of_DK	wow
17:21	Lau_of_DK	thats REALLY nasty Chouser
17:25	Lau_of_DK	Thats going in my toolbox
17:25	Lau_of_DK	When does your tutorial site launch Chouser ?
17:25	Chouser_	It's here, live, right now. ;-)
17:26	Lau_of_DK	Hehe, cheap skank
17:26	Chouser_	Lau_of_DK: are you in Europe?
17:26	Lau_of_DK	Denmark to be exact
17:28	Chouser_	hm, that won't work if any of the items are duplicated.
17:28	Chouser_	...since a set can't hold dups.
17:29	Lau_of_DK	right, then it just discards it
17:30	Lau_of_DK	Why did you ask my location Chouser ? Because if you're thinking of coming over to teach me some tricks personally, I'll buy you a whole cup of coffee
17:31	Chouser_	There's a little thing in Chicago next Friday -- just wondered how close you are.
17:32	Chouser_	To which the answer is "not very".
17:32	Lau_of_DK	true
17:58	Lau_of_DK	I gotta hit the sack - Again Chouser, you've been a great help, thanks! :)