#clojure – 2008-10-11

2008-10-11

06:28	Lau_of_DK	In emacs, the default binding for Clojure-eval-defun is (C-M-x) but this does not work for some reason, simply no reaction. How do I bind this function (that I dont even know whats called) to something like C-c c ?
06:30	tWip	Does C-h k C-M-x describe the command?
06:31	tWip	I think it should be lisp-eval-defun
06:31	Lau_of_DK	tWip, it does not, no reaction
06:32	Lau_of_DK	but yes, the command is lisp-eval-defun
06:32	tWip	you could try M-x local-set-key
06:32	tWip	to bind it
06:33	Lau_of_DK	What is the shortcut for ending the key-sequence, if I press enter it does includes that in the mapping
06:35	tWip	It should work without enter
06:35	tWip	I'm not really an emacs master myself.
06:35	Lau_of_DK	Ok, I'll fiddle with it. Thanks alot tWip
06:35	Hun	are you sure the major-mode is proper? it might just eval it as a emacs-lisp-defun
06:36	Hun	here C-M-x is bound to slime-eval-defun which sends stuff through swank
06:37	Lau_of_DK	If you mean wether or not I'm on Clojure-mode, then yes I am
06:37	Hun	oh, clojure-mode. don't know that, i use slime with clojure here
06:39	Lau_of_DK	Same here, Clojure-mode only handles formatting I think
06:40	Lau_of_DK	Anyway, we can drop the subject, because when I bound it to C-x C-x it actually works, so I'm up and running
06:40	Lau_of_DK	Thanks alot for your input, both of you
07:04	leafw	is there any reason why (map println (range 0 10)) prints numbers mixed up with the sequence full of nils ?
07:05	leafw	I would expect the sequence to print at the end, not at every iteration
07:25	fyuryu	leafw: you should avoid side effects in map
07:25	fyuryu	leafw: (doseq i (range 0 10) (println i))
07:26	leafw	it was just a test
07:32	leafw	I can't find how to say: do this N times.
07:33	leafw	without (doseq i (range 10) (....)) , where I don't need the i at all
07:33	leafw	same for looping. And for map, it creates and returns a seq that I don't need
07:34	kotarak	leafw: then you use side-effects. I would try to eliminate the side-effects if possible.
07:35	kotarak	side-effects are not the way clojure encourages..
07:35	leafw	I need the side effects.
07:35	leafw	I know. Thanks anyway. this is an exisiting library, can't override its behaviour, just script it nicely.
07:35	kotarak	then what changes between the loops?
07:35	kotarak	Iterate over that instead of "i"
07:36	leafw	I am processing lines of an image with multiple threads. Each thread grabs the next available line for processing.
07:36	leafw	the side effect is the editing of that image. And no I can't afford to duplicate it, not enough RAM.
07:40	fyuryu	for i in range(N): do_something() is a a common idiom in python
07:40	fyuryu	it translates nicely to Clojure with doseq or dotimes
07:41	leafw	dotimes, that's it
07:42	leafw	got erased from my mind for some reason
07:46	leafw	still, dotimes also uses an iterator ... never mind
08:17	leafw	I am puzzled by an error message: java.lang.IllegalArgumentException: Unable to resolve classname: int (macro_multithread.clj:72)
08:17	leafw	the code: (let [#^int offset (* width row)]
08:17	leafw	...)
08:18	leafw	where width and row are also declared as #^int
08:18	kotarak	Hmmm... int is no class. Try #^Integer maybe.
08:19	kotarak	I don't whether one can declare basic types like this.
08:19	kotarak	I don't know ..
08:19	leafw	(let [#^int i 0] (println i))
08:19	leafw	this works.
08:20	leafw	but I am not sure if it does what I intend
08:21	leafw	debugging clojure remains ... hard. Very hard.
08:23	leafw	and with macros, java stack traces are wrong.
08:23	leafw	i.e. they don't point to the right line on the code
08:27	leafw	and it would be great if macroexpand would print the statements with indentation and in separate lines ...
10:14	Chouser	leafw: I think primitive locals are declared thus: (let [offset (int (* width row))] ... )
10:15	leafw	that is casting, which sets the value, but does not add type declaration to the offset (I think)
10:15	Chouser	yeah, I know one woudl think that, but I'm pretty sure that's how you get a primitive local.
10:15	Chouser	Let me see if I can find an example.
10:16	leafw	ok, let's see
10:16	leafw	indeed #^int is not accepted
10:17	rhickey_	leafw: this is pretty well documented at: http://clojure.org/java_interop, under Support for Java Primitives - did you read that?
10:18	leafw	I read indeed, rhickey_
10:19	leafw	basically it means it's automatic. i.e. (let [offset 512] would have offset as primitive directly
10:19	leafw	is that right?
10:20	rhickey_	No, 512 is an Integer without the (int ..) coercion
10:20	rhickey_	else math would be bad by default
10:20	leafw	by the way I created a macro to multithread the processing, in place, of lines in an image ... if there's something grating about it that I should know, I would appreciate very much. It's named "multithreader" and it's here: http://pacific.mpi-cbg.de/cgi-bin/gitweb.cgi?p=fiji.git;a=blob;f=plugins/Examples/Multithreaded_Image_Processing.clj;hb=HEAD
10:21	leafw	rhickey_: ok, then I need to add a couple of casts. Someday ...
10:21	leafw	thanks for your infinite patience -- if anything reasures me of the outcome of a project, is the patience of its developer(s)
10:28	Chouser	println will print the number and then return nil
10:29	Chouser	gah, sorry, I was scrolled way back.
10:41	alec	Is there a clean way to create a map with keys as strings and do case-insensitive lookups, like a Common Lisp equalp hash? I can always hack up an indirect lookup.
10:44	Chouser	I don't think so. I'd just use a transformed string as the key, and keep the original key and value in the map value.
10:45	Chouser	{"foobar" ["FooBar" "value"]}
10:47	Lau_of_DK	Is there someone in this group, who has superior RegEx skills?
10:48	Chouser	Lau_of_DK: Try asking your question, maybe someone will know something.
10:50	Lau_of_DK	Okay, I just figured that it wasn't too polite to have the actual RegEx discussion in a Clojure group. But since you ask :) I need a Regex that can identify the longest recurring cycle of digits in a string. For instance "1111111" is seen as a 1-digit cycle, and "123456123456" is seen as a 6-digit cycle
10:50	Chouser	hm, that's a good point -- wouldn't want to be OT
10:50	Lau_of_DK	Okay - Feel free to MSG me if anybody has a take on this
10:55	alec	Lau_of_DK: regular expressions are probably inappropriate, but I bet you could write some cool Clojure code taking a dynamic programming approach, and then it'd be on topic
11:02	Chouser	(second (re-find #"^(.?)(?:\1)$" "123123123123"))
11:03	Chouser	hm, I think that's the shortest recurring cycle.
11:04	Chouser	oh, and that requires my regex patch to clojure
11:05	rhickey_	Chouser: sorry I haven't pulled the trigger on that - not for lack of support for it - just working on extensible print/read
11:06	Lau_of_DK	Chouser, how to I apply the patch, and how does this patch extend Clojures way of doing it ?
11:06	Chouser	rhickey_: np -- I don't see it as urgent, as long as it's inevitable. ;-)
11:06	rhickey_	Chouser: yes, inevitable
11:06	Chouser	Lau_of_DK: skip it. Without my patch, use #"^(.?)(?:\\1)$"
11:06	Chouser	rhickey_: you're changing how read/print work?
11:07	Lau_of_DK	k
11:08	rhickey_	Chouser: extending - #=(java.util.HashMap. {:a 1 :b 2 :c 3}) will read a literal HashMap
11:08	rhickey_	#=(java.util.Date. "Sat Oct 11 11:05:23 EDT 2008") reads a Date
11:08	Chouser	rhickey_: ah, right. forgot you were working on that. Does the syntax keep chaning?
11:09	rhickey_	as does #=(java.util.Date. 2008 10 11)
11:09	rhickey_	#<...> doesn't work because > is not a terminating macro character, i.e. it is a constituent character - can be part of a symbol
11:10	rhickey_	I don't want to repeat the C++ space before > travesty
11:10	Chouser	indeed!
11:12	rhickey_	but I've refined the semantics over the last couple of days - I had ##(expr) which evaluated the expr, but that ends up being too big a hammer for read, so #= constructs values with the unevaluated (i.e. as-read) args
11:13	rhickey_	ends up being very nice, essentially you can read it as - the value you would get from this expression, give literal args
11:14	rhickey_	it means people can extend print/read by just making prints that target #=
11:14	Chouser	Ah! nice
11:14	rhickey_	you can call ctors, static methods and instantiated vars
11:16	rhickey_	plus class literal: #=java.util.ArrayList, and vars: #=(var clojure/rest)
11:17	rhickey_	makes print/read a powerful and easy serialization tool
11:17	tWip	so you could embed java serialized objects in sexp
11:17	rhickey_	always on the todo list but I need it for AOT compilation
11:17	rhickey_	tWip: yup
11:18	tWip	very nice, clojure seems to be going forward in leaps and bounds
11:28	rhickey_	A Clojure-derived Lisp for the AVM2: http://github.com/aemoncannon/las3r/wikis
11:33	rhickey_	Chouser: you and he should talk
11:33	Chouser	yeah, looks like he's done more work than I
11:34	rhickey_	He's transliterated the compiler and dropped a bunch of stuff, I think the ClojureScript approach (just a different backed + support libs) has definite advantages
11:34	rhickey_	back-end
11:34	rhickey_	ClojureScript is still Clojure
11:36	Chouser	are you in touch with him? I see only one post that might be his on the group.
11:40	rhickey_	Chouser: not too much, he contacted me once or twice when starting out, then last night to let me know it was up
11:42	rhickey_	fun - this is the default print behavior:
11:42	rhickey_	user=> (java.util.Date.)
11:42	rhickey_	#=(java.util.Date. "Sat Oct 11 11:36:40 EDT 2008")
11:42	rhickey_	That's with no special print for Date!
11:43	Chouser	I'm way too lazy to solve the problem the he'd done. He's going to have work to do to keep his boot up to date.
11:43	rhickey_	Chouser: right, it's not Clojure anymore
11:43	Chouser	nice. And Date will probably even read that, right?
11:43	rhickey_	exactly
11:44	tWip	how do you know that Date does not have some secret state?
11:44	rhickey_	many types have ctors that can read their toString output
11:44	rhickey_	if they do, this works by default, if not define custom print
11:45	Chouser	but now that print is a multimethod, that's easy to provide without a Clojure patch.
11:45	rhickey_	tWip: if they have a public string ctor, it'd better produce a valid object
11:45	rhickey_	Chouser: right again
11:45	Chouser	And read is sufficiently generic already that new patches there shouldn't be necessary.
11:46	Chouser	...with the exception of things like my #"" which want to screw around with quoting rules.
11:46	tWip	yes, but If I have a class that has a public string ctor, but still has some other state that is not printed in toString)
11:46	rhickey_	It solves a fundamental problem, that the reconstitutor might not have the corresponding libs loaded yet, or ever
11:47	rhickey_	tWip: then you define a print-method for that class, this is just a useful default
11:47	tWip	ok, so it is optimistic in trying a public string ctor, if available
11:47	tWip	I agree, that it will be very useful in many cases
11:48	rhickey_	the only other possible default is error
11:56	Chouser	aemon's containers can't be called.
11:56	Chouser	I don't really like how that works in ClojureScript right now.
11:56	Chouser	But the other solutions I've thought of are all rather clumsy too.
11:57	rhickey_	Chouser: how so?
11:58	Chouser	AFAICT, the only thing that can be called directly in js is a Function.
11:59	Chouser	A Function can either be made using the constructor and passing in a string (ew!) or literally saying function(){}
12:00	Chouser	I could possibly make container instances using function(){}, but they'd essentially be closures (which I've now learned is slow) and they wouldn't participate in js inheritence.
12:01	Chouser	So for now, anytime I generate code to call something that might be a container, I emit foo.apply(this,[...])
12:02	Chouser	apply works on real functions, and is also a method I've written for AFn.
12:02	rhickey_	sounds ok to me
12:07	Chouser	It's a bit slower than a regular function call. I don't know if it's just the new array being made, or if the call itself has more overhead.
12:07	Chouser	plus it's ugly :-/
12:08	rhickey_	I missed the array, yeah.
12:10	Chouser	Another option is foo.call(this,arg1,arg2,...), but that's also slower than normal.
12:10	Chouser	I guess I need to do some more complete profiling and see how fast I can make either of those.
12:11	rhickey_	Chouser: profiling JS is dangerous, as there is so much platform variance, plus there's a perf war going on (can only help in the long run)
12:11	Chouser	yeah
12:12	Chouser	"complete" includes each test on at least 4 browsers. bleh
12:12	rhickey_	No point in optimizing for anything other than the top-of-the-line engines - V8, WebKit, as they or similar tech will soon win
12:13	rhickey_	and likely be the most viable platforms for ClojureScript
12:13	Chouser	well there's Chrome, WebKit, and Firefox -- plus you still can't afford to ignore IE
12:14	rhickey_	you want to make sure it works there, sure
12:14	Chouser	Opera's not shabby either, and has a good chunk of the mobile market still
12:15	rhickey_	sorry I meant to say et al before, not to limit to V8/WebKit
12:15	rhickey_	just that _optimizing_ for older JS implementation tech is a waste of time, they'll all be doing what V8/WebKit do soon enough
12:17	Chouser	perhaps you have more confidence in IE than I :-)
12:19	rhickey_	people who use IE get what they deserve
12:20	rhickey_	Chrome exists for a reason
12:25	arohner	lisppaste8: url
12:25	lisppaste8	To use the lisppaste bot, visit http://paste.lisp.org/new/clojure and enter your paste.
12:26	lisppaste8	arohner pasted "repl no exception" at http://paste.lisp.org/display/68317
12:26	arohner	if you manage to throw an exception that is caught on that line, the repl does not print a stack trace
12:26	arohner	the paste fixes that
12:30	arohner	still trying to figure out what I did, but the original error was not helpful
12:30	arohner	java.lang.RuntimeException: java.lang.IllegalArgumentException: Too many arguments to struct constructor (NO_SOURCE_FILE:0)
12:32	rhickey_	new print/read support is up, rev 1061 - tire-kickers encouraged
12:35	kotarak	rhickey_: Exception in thread "main" java.lang.IllegalArgumentException: Multiple methods match dispatch value: class clojure.lang.APersistentVector$Seq -> interface java.util.Collection and interface clojure.lang.ISeq, and neither is preferred
12:40	kotarak	Also (doc var) works, but (print-doc var) says "unable to resolve symbol: var in this context".
12:43	kotarak	Ok. Forget the last one.
12:54	alec	kotarak: I get that one, too, but only when starting via slime
12:54	alec	(the first one, IllegalArgumentException)
12:55	kotarak	the second one is stupidity of mine. Just ignore...
12:56	kotarak	I get the first one by starting a new REPL and do a (doc doc).
13:00	arohner	found it. resultset-seq explodes if your query has duplicate column names
13:00	arohner	rhickey: what would you like resultset-seq to do in that case?
13:03	Chouser	kotarak: you got that exception by doing something like (seq [1 2 3]) ?
13:04	kotarak	Chouser: I did actually (doc doc), but (seq [1 2 3]) also throws the exception.
13:58	achim_p	mmh, there seems to be something wrong with the latest rev - sequences won't print
13:58	achim_p	(prefer-method print-method clojure.lang.ISeq java.util.Collection)
13:59	achim_p	that's probably missing in boot.clj
14:18	qawsx	anyone own a lisp-machine?
14:30	Lau_of_DK	Could somebody point me in the right direction of how I make an optimal Decimal expansion in clojure?
15:19	arohner	does anyone else get frustrated by slime's default behavior with exceptions?
15:20	arohner	I don't really understand how to use it, and it just gets in my way
15:33	alec	it's not so nice in Clojure because it only gives you the option to abort or move up the stack trace (which is also pretty useless)
15:33	arohner	is the moving up the stack trace supposed to show you the exception cause?
15:34	arohner	because that doesn't seem to work
15:34	alec	it does in other lisps; I don't know if there's enough machinery to support it in Clojure yet
15:36	arohner	I'd also like if there were an option to disable the exception thing popping up in emacs, so it would just print the exception in the repl
15:36	alec	that would be a useful improvement
15:36	rhickey_	acj, sorry about print in 1061 - I'd made half a change I didn't intend to check in
15:37	rhickey_	all should be well now, I've made an enhancement so that prefer-method handles entire trees - it was too tedious to make each specific preference
15:38	rhickey_	so, e.g. (prefer-method print-method clojure.lang.IPersistentCollection java.util.Collection) says prefer all IPersistentCollections to all java.util.Collections
15:48	pointerfun	can anyone see me or i need to register?
15:48	Lau_of_DK	We see you :)
15:49	pointerfun	ok so must just be that the c-people are ignoring me
15:50	Lau_of_DK	:(
15:52	pointerfun	ANYONE KNOW C? if i have a function that takes a string should ibe of the type char or char[]?
15:54	arohner	pointerfun: you know this is a channel for a lisp on the jvm. Not really the place for C questions
15:57	danlarkin	char *
15:57	danlarkin	:-D
15:58	pointerfun	*? that menas pointer no?
15:59	danlarkin	pointerfun: you're in the wrong channel, try #c
17:53	H4nsX	lisppaste8: url
17:53	lisppaste8	To use the lisppaste bot, visit http://paste.lisp.org/new/clojure and enter your paste.
17:55	lisppaste8	H4nsX pasted "Proper? Slow?" at http://paste.lisp.org/display/68331
18:08	Chouser	looks fine to me. This is to allow replacing individual methods without replacing the whole object?
18:09	H4nsX	no, it is just some syntactic sugar. i'm still thinking of ways to make working with java apis more pleasant, and one of the things that disturbed me was the syntax for proxy, as it allows for object as well as interface instantiation, where i only need interfaces.
18:10	H4nsX	also, i do not like writing the handlers in-line, thus the apply/partial thing. that way, i'll have very short implements clauses when calling the java framework
18:11	H4nsX	i am not sure whether the apply will incur a (notable) performance penalty. i guess not, but as i am new to clojure, i rather ask :)
18:38	Chouser	you don't need the apply if there are not pre-applied-args
18:41	Chouser	actually, in neither case.
18:46	lisppaste8	Chouser annotated #68331 with "implement without apply" at http://paste.lisp.org/display/68331#1
18:46	Chouser	then you're always incurring a single extra function call, which is the sort of thing HotSpot is supposed to be able to inline away.
21:10	pjb3	So now that maps are Maps, we have another problem
21:10	pjb3	clojure maps typically are keyed by keywords
21:10	pjb3	java Maps are typically keyed by Strings
21:11	pjb3	so passing {:foo "bar"} into a Java method that calls whatever.get("foo") isn't going to work
21:12	pjb3	So we could write function to convert all the keyword objects in a map to string
21:12	pjb3	but I'm wondering if there is a way to avoid that
21:44	danlarkin	proxy is confusing me, anyone have an example to point me towards? there's only two uses in clojure-contrib
21:51	Chouser	danlarkin: there's one on the wiki as well
21:52	Chouser	Also: http://groups.google.com/group/clojure/browse_thread/thread/3c3a2ef16d2b0467/d9aed18eb65abdff?pli=1
21:55	danlarkin	Ah ha, I see what I was missing... proxy "Expands to code which creates a instance of a proxy class that implements the named class/interface(s)"
21:55	danlarkin	so it doesn't create a class, but an instance of a class
21:55	danlarkin	d'oh
21:56	Chouser	right. Actually, it creates a class behind the scenes the first time, and reuses it next time you call proxy on the same class/interace
21:56	Chouser	but it returns the instance, not the class.
21:56	Chouser	if you actually need a class, you have to use gen-class
21:58	danlarkin	mmhmm, so when the code in mmap.clj calls (proxy [InputStream] ...) as a function, that's because InputStream implements runnable, or callable?
21:59	Chouser	that seems unlikely.
22:00	Chouser	hey, I wrote this. hmm...
22:00	Chouser	ok, calling buffer-stream creates a new InputStream and returns it.
22:00	danlarkin	not knowing java definitely makes it harder to understand how to do some things in clojure :-[
22:01	Chouser	load-file passes that new InputStream to a new instance of InputStreamReader
22:01	Chouser	heh, someone was just complaining to me today how not knowing lisp makes Clojure docs hard to understand.
22:01	danlarkin	haha
22:01	danlarkin	can't win!
22:03	danlarkin	ok so InputStreamReader takes an instance of InputStream in its constructor. And that's what buffer-stream returns
22:03	danlarkin	(an instance of InputStream)
22:03	Chouser	there you go.
22:05	danlarkin	so (. (buffer-stream (mmap f)) available) would be valid, for instance?
22:23	Chouser	danlarkin: right
22:29	danlarkin	Chouser: great! thanks