#clojure – 2009-06-29

2009-06-29

00:22	fullets	Can someone give me a clue as to how I would create two (proxy [AbstractAction] ...) forms that refer to each other?
00:23	fullets	i.e., something like http://clojure.pastebin.com/d1be1fd79 that will actually work
00:29	replaca	fullets: I can think of a bunch of cheats that use specials or refs, but I'm having a hard time coming up with anything straightforward that feels right
00:30	replaca	fullets: But that may just be too much time in the sun this weekend
00:58	JAS415	is there a proxy and gen-class for common lisp dummies available anywhere?
02:08	fffej	in Clojure Contrib it says I can rebind the tracer function - embarassingly I don't know how to do that without wrapping my entires set of code in a (binding) construct
02:08	fffej	is there an easier way?
02:08	hoeck	fffej: you can use alter-var-root to change the root binding of a var
02:09	fffej	thanks!
02:10	fffej	so something like (alter-var-root tracer (constantly (constantly nil)))?
02:13	hoeck	fffej: yes, then your var-value will be (constantly nil)
02:14	fffej	thanks again!
02:15	hoeck	you may want to try set! too: http://clojure.org/vars#set
02:15	hoeck	you're welcome :)
02:15	fffej	I'd be looking at unalias in the namespaces - that didn't seem to help
02:24	fffej	hoeck: I got there in the end: (alter-var-root (var clojure.contrib.trace/tracer) (constantly (constantly nil))) seems to disable tracing, thanks for your help
02:30	hoeck	ah, yes, that disables the tracer function
02:31	hoeck	the clojure head has got :pre and :post conditions to functions; maybe those are suitable for inserting traces too
02:33	fffej	and any other AOP type applications too I guess
02:55	Lau_of_DK	Morning gents
03:31	cgrand	hi all
04:01	AWizzArd	Hi cgrand
04:05	cgrand	AWizzArd: good morning
08:10	AWizzArd	Hello dear regexperts. I would like to know how a regexp would look (if it exists) and what function I need to call that splits a text for me into several strings, depending on some "groups". For example I have the groups: whitespace, numbers, special-chars and non-whitespace. Into the first group I want to put all chars that I want to treat as whitespace. I would like to call (regexp-foo regexp "Greetings to/t /t/nall Clojure fans12345in the world.") ==
08:12	Chouser	that got cut off at ==
08:14	AWizzArd	(regexp-foo regexp "Greetings to/t /t/nall Clojure fans12345in the world.") ==> ["Greetings", " ", "to", "/t /t/n", "all", " ", "Clojure", " ", "fans", "12345", "in", " ", "the", " ", "world", "."]
08:14	AWizzArd	the ==> was your "=="
08:15	Chouser	(re-partition #"[\s\d]+" "Greetings to\t \t\nall Clojure fans12345in the world.")
08:15	AWizzArd	So, one whitespace group would contain space, \t, \r, \n but also for example the whitespace char that appears when one in Windows holds down the Alt key and types 255 on the number pad.
08:15	Chouser	re-partition is in clojure.contrib.str-utils
08:16	Chouser	oh, you want . classified as whitespace
08:16	Chouser	#"[\s\d.]+"
08:17	AWizzArd	Chouser: re-partition looks like what I want, or at least nearly as what I want. In your regexp [\s\d.] you list three of my groups: \s and \d and the .
08:18	AWizzArd	It is just that I would like to have some few more chars in \s. Can I do something like [[\s xß]\d[.-+*/']] ?
08:19	Chouser	I think you don't want the inner [], but yes that should work
08:19	Chouser	[-\s xß\d.-+*/']
08:19	Chouser	[-\s xß\d.+*/']
08:20	Chouser	or is it that you want each of those groups split differently
08:20	Chouser	"123 456" ==> ["123" " " "456"] ?
08:20	Chouser	cemerick: good morning!
08:20	AWizzArd	yes, if I have "hello x ßguys" I would like to get ["hello", " x ß", "guys"]
08:20	cemerick	Chouser: same to you :-)
08:21	cemerick	for a second, I thought someone had set up a greeting bot in #clojure ;-)
08:21	Chouser	AWizzArd: hm, yes that's a bit trickier.
08:21	Chouser	cemerick: :-)
08:22	AWizzArd	what is re-groups for?
08:22	AWizzArd	Does that allow me to define several chars that I want to treat as one group, and get all strings consisting out of those?
08:23	AWizzArd	And is there also such a splitting mechanism that keeps the positions (start, end) of the found groups?
08:23	Chouser	AWizzArd: no, it's just to help interact with the java regex api. You use it on a regex match object after the match has happened.
08:23	Chouser	kinda internal.
08:24	Chouser	There's an open question on what to do with things like that on non-JVM Clojures that implement regex's with a different api.
08:25	Chouser	AWizzArd: very interesting puzzle. You want (.split "\b" string) but with your own definition of word-boundary.
08:27	cemerick	yeah, I saw no one replied to D. Miller's post about making the re-* cross-platform.
08:27	achim	AWizzArd: how about re-seq?
08:28	achim	here's an example for 3 char classes: (re-seq #"[abc]+\|[def]+\|[jki]+" "adeadedfababacjki")
08:28	achim	,(re-seq #"[abc]+\|[def]+\|[jki]+" "adeadedfababacjki")
08:29	Chouser	cemerick: I nearly have a couple times, but with thoughts so vague I keep deciding it's not worth anybody's time.
08:29	Chouser	achim: ah! I think you nailed it.
08:29	cemerick	Yeah, I don't see myself using clojureCLR much if at all, so I'm keeping my poorly-informed opinions out of that one.
08:30	AWizzArd	achim: I will try that
08:31	AWizzArd	one sec
08:32	Chouser	I don't see how to avoid classifying "non-whitespace" using that method.
08:32	Chouser	but maybe that's not a problem.
08:32	AWizzArd	well, maybe there is something that matches everything
08:33	AWizzArd	re-seq looks at least very promising. It is basically doing 95% of what I want. It only does not report the positional info.
08:34	Chouser	oh, actually, maybe feed achim's regex into re-partition.
08:35	Chouser	(re-partition #"[abc]+\|[jki]+" "adeadedfababacjki") ==> ("" "a" "de" "a" "dedf" "ababac" "" "jki")
08:35	Chouser	AWizzArd: positional info can be re-created from the match seq
08:36	AWizzArd	Chouser: yes, re-partition would help. I would specify my whitespace, number and special-char group and leave the non-whitespace group unspecified. re-partition would then split as I wish.
08:37	AWizzArd	Yes, the result seq implicitly stores positional information. It looks as if nothing got thrown away.
08:37	AWizzArd	Very good, thank you Chouser and achim :-)
08:38	AWizzArd	btw, any one here knows the regexp for getting the numbers of the next lottery?
08:39	achim	hmm, i vaguely remember seeing a "reducing" fn somewhere, but don't remeber, where ...
08:39	Chouser	AWizzArd: I think so -- what's the format of the input?
08:39	Chouser	achim: clojure.contrib.seq-utils/reductions
08:39	achim	Chouser: thanks!
08:41	achim	(reductions + 0 (map count (re-partition #"[abc]+\|[def]+\|[jki]+" "adeadedfababacjki")))
08:41	AWizzArd	:-)
10:15	rhickey	Preferences? (partition n step pad coll) or (partition n step coll pad)
10:18	danlei`	I like the first one better
10:21	Chousuke	a keyword argument would be nicer IMO, but I also prefer the former of the two.
10:21	danlei`	keyword would be nice, indeed
10:22	rhickey	then step and pad would be keys
10:22	Chouser	the coll is important, and it most fns it appears either first or last (interesting when it's one vs. the other)
10:24	rhickey	rationale here: http://groups.google.com/group/clojure/msg/a8866d34b601ff43
10:25	Chouser	I've always been in favor of at least optionally named args in general.
10:25	rhickey	optionally named?
10:25	Chouser	rhickey: ah, nice link. That would argue for coll last.
10:27	rhickey	Chouser: yes, that's what I originally argued, now just double checking this doesn't feel more like a 2 seq fn, a la concat, since it really is the partitioning of the concatenation
10:27	Chouser	yeah, allowing the caller to name some (or all) the args, but also providing a way to not name them in simple cases.
10:28	Chouser	python has a solution for this (though it's not quite ideal).
10:28	rhickey	Chouser: sounds complicated and potentially slow
10:28	Chouser	if you "def foo(a, b, c)" you can call foo(1, 2, 3), foo(1, c=3), or whatever.
10:29	rhickey	early clojure had CL-style keyword and optional args
10:29	Chouser	you know how I feel about slow :-) but could something built on :inline help alleviate that in many cases?
10:29	danlei`	why did you drop the keyword args?
10:30	rhickey	danlei`: becasue they are not needed often enough, nor primitive
10:30	Chouser	actually, it was thoughts along these lines that prompted me to work on {:keys [...]} destructuring early on.
10:31	Chouser	rhickey: and by you accepting that patch, I fear you've sealed your fate -- you'll never be rid of me now.
10:31	danlei`	rhickey: hm, but hand-rolled keyword args are not seldom ... wouldn't something like defnk from c.c. be nice in core?
10:32	rhickey	I have nothing against keyword args, there's just no need for primitive syntax in fn for them
10:32	Chouser	the fact that java is so much faster when dealing with positional args over keyword args does modulate my opinion.
10:33	stuartsierra	Can keyword args be handled at compile time?
10:34	rhickey	In a large codebase of CL (where it is very idiomatic), keyword usage was < 10% of functions
10:34	rhickey	stuartsierra: some cases, sure
10:34	rhickey	&optional less still
10:35	Chouser	3 args is about the limit of what strikes me as comfortable without keywords. Putting keywords only on the end somewhat frustrates partial application. I could contradict myself all day...
10:35	rhickey	and both are somewhat covered by true variable arity
10:35	danlei`	hm ... to me something around 10% is not really sparse, but ok
10:35	stuartsierra	compile-time keyword args would certainly be more efficient than (apply hash-map args)
10:36	rhickey	danlei`: I bet you could nuke a ton of them just for :test, :start etc, which aren't really needed when you don't have so much variability in equality semantics and you have things like rseq
10:36	rhickey	:from-end
10:36	rhickey	etc
10:37	rhickey	Clojure's own code is a testament to the fact that keyword args aren't needed often
10:37	rhickey	So in the good fight against complexity, they lost
10:38	Chouser	I don't suppose 'partition' could be split up in such a way that no one function needs all 4 args?
10:38	stuartsierra	That's true for core fns, but they're more heavily used in contrib libs, where you need to configure some external object.
10:38	danlei`	I see, I'll think about it
10:39	rhickey	Chouser: I'm thinking now that overloading partition is wrong, as soon as I wrote "partitioning of the concatenation above"
10:39	Chouser	if partition always acted like it had a nil pad, then you could either filter on subseq length (original behavior) or pad to a given length (new behavior)
10:39	rhickey	really should have a different fn for partition with variable length trailing, rather than key it off of a pad
10:40	rhickey	Chouser: not changing original behavior
10:41	rhickey	just need a name for (partition+ n step coll) where it can yield partial partitions at end
10:42	Chouser	rhickey: clojure.contrib.seq-utils/partition-all
10:42	rhickey	right, but -all doesn't say much
10:42	rhickey	to me
10:43	Chouser	there was a discussion...
10:43	stuartsierra	partition-remainder
10:45	Chousuke	or simply partition-with-pad, but it's a bit long
10:46	rhickey	Chousuke: but it's not with-pad, you don't need pads since you have concat
10:46	Chousuke	hmm.
10:47	rhickey	partition*
10:48	Chouser	http://groups.google.com/group/clojure/msg/e34f62e95d9de1c9
10:48	Chouser	So I guess I'm to blame for -all
10:49	Chouser	originally proposed as "chunk" -- guess that's out. :-)
10:49	stuartsierra	Maybe "partition" includes the ending and "strict-partition" doesn't.
10:49	Chouser	-all was meant to suggest that none of the original seq was left out.
10:50	rhickey	yeah, a completely different name, e.g. subseqs, wouldn't help people who first try partition and then want trailing partials
10:51	Chousuke	partition* might be good enough.
10:51	rhickey	chould also be considered a variant on take
10:51	rhickey	or take-nth
10:52	rhickey	take-seqs
10:53	rhickey	(take n step coll)
10:55	rhickey	for me, non-regular partition sizes isn't really partition
10:56	Chouser	a comment in the docstring would be sufficient to get from partition to something named differently
10:56	rhickey	I'm not arguing against the utility of taking subseqs every nth
10:57	rhickey	would (take n step coll) be misleading>
10:57	rhickey	?
10:58	stuartsierra	what does the step mean there?
10:58	rhickey	the nice thing about it is that it doesn't promise exactly n, as take doesn't
10:59	Chouser	seems more surprising to me for take to return something starting past the beginning, than for partiton to return short seqs
10:59	rhickey	stuartsierra: step is the offset (take n n coll) == (partition-all n coll)
10:59	stuartsierra	hmm
10:59	Chouser	(map #(take n %) (nth-nexts step coll)) ?
11:00	Chouser	except with a better name for nth-nexts
11:01	rhickey	(take-subs n coll) (take-subs n step coll)
11:02	Chouser	yes
11:04	rhickey	take-subs or take-seqs?
11:05	stuartsierra	"take-groups" ?
11:06	rhickey	stuartsierra: probably best not to consume another concept for this :)
11:06	Chousuke	take-subs makes me hungry :P
11:06	Chouser	I think "subs" because that more clearly indicates they're shortened
11:07	rhickey	Chouser: good point
11:07	rhickey	,(doc subs)
11:07	Chousuke	no clojurebot apparently :/
11:07	Chouser	clojurebot and hiredman are both MIA
11:07	rhickey	-------------------------
11:07	rhickey	clojure.core/subs
11:07	rhickey	([s start] [s start end])
11:07	rhickey	Returns the substring of s beginning at start inclusive, and ending
11:07	rhickey	at end (defaults to length of string), exclusive.
11:08	Chousuke	I wonder if it's too abbreviated. I wouldn't mind take-subseqs
11:08	Chouser	why is that even in core?
11:08	Chousuke	subs definitely is too abbreviated :P
11:09	Chouser	I guess it lets you avoid hinting the String shrug
11:10	rhickey	Spot the difference:
11:10	rhickey	http://java.sun.com/j2se/1.5.0/docs/api/java/lang/String.html#substring(int,%20int)
11:11	rhickey	http://msdn.microsoft.com/en-us/library/system.string.substring.aspx
11:11	Chouser	bleh
11:11	stuartsierra	one off
11:11	Chouser	end vs len
11:11	rhickey	right
11:11	Chouser	I think javascript has both. :-)
11:12	rhickey	so we don't want .substring calls everywhere
11:12	stuartsierra	But I've been bugged that (subs "hi" 0 10) throws an exception.
11:13	stuartsierra	This is why I wrote c.c.str-utils2.
11:13	Chouser	JS substr is like .net, JS substring is like Java
11:13	rhickey	subs was added when I was trying to get Norvig's spell corrector out the door
11:14	rhickey	vs Python which has something more concise for this
11:17	Chouser	ah, yeah -- array range syntax that works also on strings
11:18	rhickey	anyway, is take-subs confusing due to subs, hunger issues aside?
11:20	Chouser	any chance of renaming "subs" to "substring"?
11:20	Chouser	but either way, I'd say "no".
11:21	rhickey	Chouser: possible, but the comparison vs Python will remain. For people doing a lot of that, typing out substring will seem quite tiresome
11:22	Chousuke	I think it's better to be a bit more verbose and have take-subseqs
11:22	Chouser	I'd be fine with take-subseqs
11:24	Chouser	rhickey: but python can be concise there because it's leveraging the "namespace" of the object, just like any other OOP. Pushing object-specific methods up to the core namespace is a bit like cheating.
11:33	albino	and cheating is the right way to do it :)
11:39	cemerick	There has to be a fool in every room, so I'll take that on today: why not a reader macro for subsequencing in general? #[seq-or-string 0 10]?
11:40	stuartsierra	Or first class ranges, like Ruby (#[0 10] seq-or-string)
11:40	cemerick	I'm not sure I'd ever use it myself, but if some group of users is doing a lot of string-mangling, it might make sense.
11:41	cemerick	stuartsierra: that's even better
11:42	Chouser	that would do substring, subvec, or drop/take as appropriate?
11:43	cemerick	yeah, that's the thought
11:44	cemerick	having all of these siloed fns for strings, vectors, seqs, etc., doesn't make sense to me
11:44	rhickey_	IBM's X10 was doing some neat thing with first-class regions, encompassing ranges and multidimensional indexing
11:45	Chousuke	shouldn't be too difficult. The crappy thing is that IFn seems to be a painful interface to implement :P
11:45	Chouser	reader support for ranges is independent of a general sub-part fns though
11:45	rhickey_	ranges for non-indexed data structures are bad
11:45	rhickey_	so not for take/drop
11:45	Chouser	Chousuke: AFn and RestFn aren't bad though, are they?
11:45	Chousuke	is AFn enough?
11:46	cemerick	or, I should say, having all those siloed fns makes a lot of sense, but they shouldn't be the primary interface for 98% of all users. That other 2% might have some really good reason to explicitly choose one of them in a hot loop if something's known to be a particular type.
11:46	Chouser	select-keys for maps?
11:46	Chouser	eh. hm.
11:46	Chouser	nm.
11:46	Chousuke	Chouser: hm, but AFn is a class. Range already extends ASeq
11:47	Chouser	ah
11:47	Chousuke	most of implementing IFn is just cut & paste.
11:47	Chouser	Chousuke: why not write it in clojure, for goodness' sake!?
11:48	Chousuke	Range is in Java. :/
11:48	rhickey_	Chousuke: not in chunks branch
11:49	Chousuke	oh? neat.
11:49	rhickey_	but something that only did ranges and not multidimensional indexing is a waste, IMO
11:51	rhickey_	in X10 it's something like #[0:10] for a range and #[0:10 20:100] for a first-class md region
11:56	Chousuke	hm, that will be trickier
12:17	achim	how do languages with native range support handle range-minus, e.g. [0, 3] \ [1, 2] ?
12:18	stuartsierra	Hm, Ruby doesn't define minus on ranges.
12:20	achim	that's the easy way ;) - i tried implementing some range arithmetics stuff a while ago and ended up with by basic type being a set of vectors (ranges). that's probably not the way to go in terms of code readibility
12:25	cheddar	what's a good way of making a queue? If it's n-elements long, should I just do (let [new-queue (cons new-element (take n-1 queue))])?
12:26	cheddar	performance-wise, would that be a reasonable approach?
12:26	achim	cheddar: (clojure.lang.PersistentQueue/EMPTY) - conj'es from the right, pops and peeks from the left
12:42	Chousuke	hm
12:42	Chousuke	well, implementing a simple splice was easy, but I'm not convinced it's good enough.
12:43	Chousuke	stepping and such will be the real problem anyway
12:46	Lau_of_DK	Good evening gentlemen
12:52	jackdempsey	evenin
12:52	jackdempsey	anyone have video recommendations for clojure? been through the blip.tv vids a bit, looking for other stuff easy to ingest while workin out
12:53	Lau_of_DK	technomancy had some screencasts going that looked awesome
12:53	jackdempsey	oh nice
12:55	technomancy	yups: http://peepcode.com/products/functional-programming-with-clojure
12:55	technomancy	not free though; sorry
12:56	jackdempsey	hehe
12:56	jackdempsey	i love open source, however, the day you produce something amazing and have to say "its not free, sorry"
12:56	jackdempsey	dunno :-)
12:56	jackdempsey	happy to fork over the huge sum of $9 for some great content
12:57	jackdempsey	was actually in the process of buying that when you linked to it
12:57	technomancy	cool. =)
12:57	jackdempsey	did you used to do some merb stuff as well? i recognize your nick from somewhere
12:57	technomancy	I used to write a lot of Ruby and have done a number of Elisp tools.
12:57	technomancy	only dabbled in merb a small amount
12:58	jackdempsey	ah ok cool
12:58	jackdempsey	maybe it was sequel, or dm, or who knows :-)
12:58	jackdempsey	nice, cardio here i come
13:09	Lau_of_DK	technomancy: When will your screencast on ClojureQL be up ? And how much should I expect to get from that in terms of royalities ?
13:11	technomancy	hehe
13:11	technomancy	Lau_of_DK: I'm actually thinking of doing a short intro to paredit
13:12	Lau_of_DK	Ok, thats actually not the same thing :)
13:12	technomancy	since it's easy to get confused by it, but it's super-helpful once you get the hang of it.
13:12	Lau_of_DK	I never use it - hitting shift+8 just didnt seem like a big investment
13:14	jackdempsey	clojureQL?
13:14	Lau_of_DK	Yep
13:15	Lau_of_DK	Its hot
13:15	jackdempsey	ah
13:15	jackdempsey	i see
13:15	Lau_of_DK	http://github.com/Lau-of-DK/clojureql/tree/master
13:15	jackdempsey	cool
13:15	jackdempsey	yeah looking
13:16	Lau_of_DK	I'll make a post on the group later, but its v0.9 now, coming up on 1.0, so people are very welcome to fire away with bug-reports/feature-requests/love-letters etc. (last one should go to meikel)
18:40	Chousuke	I finally figured out how c.c.monads
18:56	Chousuke	danlei: see http://gist.github.com/137862 for a monadic version of ansi2html
18:56	Chousuke	now I need some sleep.
19:20	danlei	Chousuke: mee too, 1:19am over here ;) thanks for the effort, I'll have a look at it tomorrow (and a little talk I guess ;)
20:26	durka42	did anyone enter icfp in clojure?
20:29	jackdempsey	durka42: dont' think so, seen that asked here a couple times
20:29	jackdempsey	actually one person did say they were doing something for it....but maybe that was you? :-)
20:29	durka42	did i?
20:29	durka42	i did, but i don't remember mentioning it
20:29	durka42	i didn't have time to really do it, but i solved the first challenge
20:30	durka42	~logs
20:30	jackdempsey	ah cool
20:30	jackdempsey	yeah i think it was someone else
20:30	jackdempsey	can't recall their nick tho
20:34	Chouser	http://clojure-log.n01se.net/date/2009-06-27.html#12:02b
20:35	blbrown_win2	I think I am having classloader issues NoClassDefFoundError, etc. I am trying to invoke a java library from clojure I get an error where Log4J Logger is not found. I believe it has to do with the DynamicClassLoader. Is there more than one DynamicClassLoader can I use the Clojure classloader?
20:37	durka42	hiredman: where's your protegé? :p
21:53	samwisem	hey I was just wondering, 'clojure.lang.Script' and 'clojure.lang.Repl' seem deprecated, and the preferred way is to launch everything through 'clojure.main' now?
21:54	durka42	correct
21:55	samwisem	thanks
22:24	eyeris	What is the syntax for a function that returns a constant, literal value?
22:25	fullets[w]	(constantly 42) might do what you want
22:25	eyeris	Nice. Thanks.
22:29	eyeris	Why is this false? (== ((constantly true)) true)
22:29	eyeris	,(== ((constantly true)) true)
22:29	eyeris	In fact, (== true true) is false
22:30	fullets[w]	I believe == is for comparing numbers
22:30	fullets[w]	(= ((constantly true)) true) is true
22:31	eyeris	Okay
22:31	eyeris	Thanks
22:37	eyeris	I read the documentation for each about 5 times.
22:37	eyeris	Knowing that my first understanding is wrong, it totally makes sense.
22:38	eyeris	But when I read it, the brevity of the definition of == made it seem as if it were just a modification of the definition of =, meaning that it returned a non-nil value, not garunteeing a boolean.