#clojure – 2008-11-28

2008-11-28

00:13	dlonki	(dorun (for (for ...)))?
00:27	danlei	dlonki: compare (def x (for [i (range 5)] (do (print i) i))) to (def x (dorun (for [i (range 5)] (do (print i) i)))), and (def x (doall ...
01:00	dlonki	i see
01:13	dlonki	anyone good with matlab? is its code fast enough ti use for real apps or is matlab only for use in prototyping?
02:29	danlei	�
03:54	Lau_of_DK	Yyoo :)
05:19	AWizzArd	Moin
05:24	Lau_of_DK	Ola
07:20	Lau_of_DK	Hey heey =)
07:29	pdoubleya	Lau_of_DK: hey
07:30	pdoubleya	where is the . macro defined in the clojure clj files
07:31	lvijay	i think . is a built-in
07:31	lvijay	.. is the macro
07:32	lvijay	. is defined in java
07:32	pdoubleya	lvijay: ah, ok
07:32	pdoubleya	wanted to see what it looked like :)
07:34	lvijay	if you're interested in its java implementation you should look at clojure.lang.Compiler
07:35	pdoubleya	is Compiler used just for AOT, or for the interpreter as well? (no class Interpreter)
07:36	Lau_of_DK	(doc .)
07:36	clojurebot	excusez-moi
07:37	pdoubleya	Lau_of_DK: thx
07:38	lvijay	Compile has AOT
07:40	lvijay	i haven't looked into the AOT code yet
07:40	lvijay	I know that Compiler is used to parse the clojure forms because I was hacking on it yesterday
07:41	pdoubleya	lvijay: did it survive the hacking? :)
07:42	lvijay	that's up to Rich and the others that decide upon Clojure's syntax
07:42	lvijay	i made a suggestion and submitted a patch. Rich decides if it goes thru :-)
07:43	pdoubleya	nice to see people working on it...
07:53	lvijay	newbie question: how do I refer to a class that is not in the current namespace without importing it?
07:53	lvijay	user=> java.util/Collection
07:53	lvijay	java.lang.ClassNotFoundException: java.util (NO_SOURCE_FILE:0)
07:56	Lau_of_DK	like that
07:57	Lau_of_DK	(java.util/Collection. x y z)
07:58	Lau_of_DK	user> (javax.swing.JOptionPane/showMessageDialog nil "Its working")
07:58	Lau_of_DK	nil
07:58	Lau_of_DK
08:02	lvijay	here's my problem:
08:02	lvijay	user=> (try (java.net/URL. "http://www.google.com/") (catch java.net/MalformedURLException e (println e)))
08:02	lvijay	java.lang.IllegalArgumentException: Unable to resolve classname: java.net/MalformedURLException (NO_SOURCE_FILE:2)
08:04	hoeck	lvijay: "/" is for static member and method access, and for accessing stuff in namespaces
08:04	Lau_of_DK	java.net does not exist
08:05	lvijay	ok
08:05	hoeck	java.net is a package, not a class
08:06	hoeck	you probably want (java.net.URL. "http://...")
08:06	Lau_of_DK	exactly hoeck :)
08:06	Lau_of_DK	You literally took the words out of my ERC :)
08:06	lvijay	ah
08:07	hoeck	lvijay: and java.net.MalformedURLException
08:07	lvijay	I mixed up static references and package references
08:07	lvijay	the above worked
08:07	hoeck	Lau_of_DK: you need better auto-completion then :)
08:08	lvijay	thanks hoeck and Lau_of_DK
08:10	Lau_of_DK	nps
08:10	Lau_of_DK	hoeck: Ive got dabbrav-expand, what are you using? :)
08:11	hoeck	currently mibbit, but i love dabbrev-expand too
08:14	Lau_of_DK	k, never heard of mibbit
08:15	hoeck	http://www.mibbit.com/ ajax irc client, very useful at work :)
08:17	lvijay	hoeck: that's useful. i'm currently using chatzilla. i'm new to clojure and IRC
08:18	Lau_of_DK	hoeck: okay, but you realize that dabbrev-expand is not an irc client right? :)
08:18	hoeck	so was I'am about 3 months ago, i noticed mibbit in someones quit message
08:19	mibbit_test	uuuh, so pretty
08:19	mibbit_test	:)
08:19	hoeck	Lau_of_DK: yeah, its not capable of interpreting elisp, so no chance to dabbrev-expand something here :)
08:19	Lau_of_DK	lvijay: If you code in emacs, chat in emacs
08:20	lvijay	i code in emacs
08:20	lvijay	but is erc setup easy in emacsw32?
08:20	Lau_of_DK	:) then you know what to do
08:20	Lau_of_DK	dunno, probably like linux, emacs is emacs right?
08:20	pdoubleya	noobee question: learning clojure, is there a rule of thumb for when I don't need parens? e.g. (.substring "hello" 1 5) works, don't need parens around 1 5 altho i thought i would...
08:20	hoeck	Lau_of_DK: but (at least my) emacs hangs when erc looses the irc connection
08:21	Lau_of_DK	hoeck: Mine too, so the trick is not to loose the connection :)
08:21	Lau_of_DK	pdoubleya: () = evaluation
08:21	pdoubleya	Lau_of_DK: hmm ok, so it doesn't mean "a list of ..."
08:21	Lau_of_DK	user> (def f (fn [x] (+ x 2)))
08:21	Lau_of_DK	#'user/f
08:21	Lau_of_DK	user> f
08:21	Lau_of_DK	#<user$f__1305 user$f__1305@2b2cf8>
08:21	Lau_of_DK	user> (f 2)
08:22	Lau_of_DK	4
08:22	Lau_of_DK
08:22	lvijay	pdoubleya: do you know python?
08:22	pdoubleya	lvijay: no
08:23	lvijay	ok
08:23	Lau_of_DK	lvijay: Its not allowed to speak about Python in the presence of intelligent people, please respect the universal law
08:23	lvijay	:-)
08:24	pdoubleya	Lau_of_DK: thx
08:24	lvijay	Lau_of_DK: i guess that explains why i didn't get that memo. too busy py***ning
08:28	jdz	hello people!
08:30	hoeck	jdz: hello!
08:32	jdz	i assume the compilation stuff is supposed to be working?
08:32	jdz	i am having troubles with getting the example to work...
08:33	hoeck	jdz: do you mean :genclass?
08:34	Lau_of_DK	Catch all ya'll later
08:34	lisppaste8	jdz pasted "compilation problems" at http://paste.lisp.org/display/71165
08:46	hoeck	jdz: have you set your classpath to include "./classes" ?
08:47	hoeck	jdz: looks like foo.clj gets compiled successfully but then clojure can't load the generated .class file
08:48	hoeck	jdz: i get exactly the same error as you when ommitting the -cp ./classes at startup
08:50	jdz	hoeck: hmm, good point.
08:50	jdz	which means clojure is trying to load the class as well?
08:51	jdz	*classes
08:51	jdz	compiled files in short :)
08:51	hoeck	yes, it seems so, compile -> load .class
08:53	jdz	hmm, now i get java.lang.ExceptionInInitializerError
08:53	jdz	hoeck: compilation works for you?
08:53	jdz	if yes i'll bang at it until it works for me, too :)
08:54	hoeck	yes, it works here
08:59	jdz	yay, it works
08:59	jdz	i think the problem was with "classes" directory not existing before starting clojure
09:06	jdz	one question: what does it mean if the function name starts with a dash (like -main)?
09:07	hoeck	jdz: its for use with :genclass, specifies the method to implement in this function
09:08	hoeck	and "main" or "-main" is for a static public main method in the generated namespace class
09:08	jdz	oh, found documentation in gen-class
09:09	jdz	hoeck: "main" without the dash won't work, will it?
09:09	hoeck	compilation docs are pretty up to date now, you may want to read there too: http://clojure.org/compilation
09:10	jdz	yes, i think i will have to read it from start to end (i just now realized that the dash prefix is explained there, too)
09:10	hoeck	jdz: it has to be -main now
09:11	jdz	hoeck: thanks for help!
09:11	hoeck	jdz: np
11:29	freddy_d	hello
11:30	freddy_d	anyone here?
11:31	freddy_d	I'm trying to figure out how to generate a Java class stub from Clojure to do the bridge, and having some trouble
11:34	blackdog	freddy_d, the only trouble i had was not having the classes directory in the classpath
11:34	freddy_d	blackdog: any chance you could point me to some docs?
11:35	blackdog	rich did put new docs on the site a couple of days ago
11:35	blackdog	othre than that i worked from this http://paste.lisp.org/display/70665
11:35	freddy_d	basically I want to generate a.b.c.MyBean, with one method that returns MyClass
11:36	blackdog	so you want a a.b.c.MyBean namespace in clojure then
11:37	freddy_d	yes, I want to implement that one method in clojure
11:37	freddy_d	but I want the Java framework to "see" it from Java bytecode
11:38	freddy_d	(hopefully I'm making some sense)
11:38	blackdog	yes using (ns (:genclass///00 is the way to go then
11:38	blackdog	once you've defined your class in a clojure ns
11:39	blackdog	you compile it with (compile a.b.c.MyBean)
11:39	blackdog	http://clojure.org/compilation
11:40	freddy_d	blackdog: thanks for the pointers, I'll try it out
11:41	blackdog	k
11:47	freddy_d	blackdog: apologies, I'm a total newbie. why, in your pasted example, is it e.g. (defn- -mymax and not (defn mymax ?
11:48	blackdog	not sure, i think it's just convention so that clojure can find the methods
11:48	blackdog	as opposed to an internal function
11:48	blackdog	rich did mention something about it on the group if you do a search
13:49	danlei	b
14:16	sdfsf	is there no way to comment out a section in slime?
14:37	grkz	sdfsf: mark the region (go to start, C-space, go to end) and then M-;
14:39	peter_12	I'm curious how the Clojure folks approach the realm where OOP ORM's are commonly used for CRUD DB operations.
14:39	peter_12	I don't like ORM's like Rails' ActiveRecord. All that imperative stuff is a real headache.
14:40	blackdog	rhickey, is mostly down on ORM i believe
14:41	peter_12	"down on" = ?
14:41	blackdog	he doesn't like it
14:41	peter_12	ahh
14:41	peter_12	the same for me
14:41	blackdog	so there would be nothing in core for it
14:41	peter_12	so what is the general approach to mutating a database?
14:41	blackdog	have a look at clojure.contrin.sql
14:42	blackdog	have a look at clojure.contrib.sql
14:42	peter_12	blackdog: ok. Thanks
14:42	blackdog	and you'll find resultset-seq in core.clj
14:42	peter_12	ahh that would be for SELECT
14:42	peter_12	That is the easy case
14:42	peter_12	DELETE is pretty easy too
14:43	peter_12	it is UPDATE and INSERT that are the tricky ones
14:43	peter_12	what should happen if failure etc
14:43	blackdog	the c.c.sql takes care of that
14:43	peter_12	ok
14:43	blackdog	it has a (transaction)
14:43	freddy_d	blackdog: it's all good now, I managed to compile .clj to java, scripted it with Ant, and Stripes web framework picks it up. Very nice. :)
14:43	blackdog	cool!
14:44	freddy_d	thanks for your help
14:44	freddy_d	would the Clojure community be interested in the Stripes/Clojure integration? or does Clojure already have its own web framework?
14:44	blackdog	yw, i usually defer to Chouser, rhickey and more knowedable folks but i think they're on holiday :P
14:45	freddy_d	hehe
14:45	blackdog	Pupeno, has someting called compojure
14:45	blackdog	and AWizzard is working on rife integration
14:50	peter_12	blackdog: looking at clojure.contrib.sql, it seems like that is dealing with one level of abstraction lower than I am interested in. I'm interested in how clojure folks might handle validation of data before attempting a db insert
14:51	peter_12	and then if there are errors how to get that back to the controller and view, in a web app, for example
14:52	blackdog	well i guess your app takes care of that, afaik there's no work on web stuff apart from compojure in terms of framework
14:53	peter_12	yeah, the app takes care of that, I was just wondering if there was a general attitude of how that should best be done. I don't like, and have never liked, how Rails does that.
14:54	peter_12	it isn't really a web-specific issue but that is my current application
14:54	blackdog	i'm not a lisper so I don't have a good idea of how they accomplish such stuff in CL etc
14:55	peter_12	I may ask the Common Lisp and Scheme folks what they do
15:03	Pupeno	blackdog: ?
15:03	blackdog	hello
15:09	freddy_d	blackdog: interesting. well, a Stripes/Clojure integration might still be useful.
15:11	blackdog	given the number of java web frameworks i'm sure we;ll see quite a few
15:11	blackdog	wrappers
15:12	ryrunfrnf	anyone good with common lisp? im translating pg ansi cl raytracer to clojure and wow clojure is so much cleaner and more elegant than cl.
15:12	ryrunfrnf	but what is the eq od do in cl?
15:16	gnuvince	ryrunfrnf: eq od do?
15:16	gnuvince	equivalent of do?
15:17	gnuvince	ryrunfrnf: look at loop/recur
15:55	kotarak	Say I have a gen-class: (ns foo.bar.Baz (:gen-class ...)). Can I refer to Baz directly in the source file?
16:26	sdfsf	who is albert cordona?
16:30	gnuvince	How do I get the absolute value of a number?
16:31	kotarak	Math/abs maybe?
16:32	gnuvince	Bingo
16:32	gnuvince	thanks
16:32	gnuvince	I was trying (.abs -3)
16:32	kotarak	gnuvince: that would be too easy. ;)
16:32	Chouser	(.abs -3M) works
17:01	AWizzArd	Chouser: how can it work? Is it because nM is treated specifically by the reader and is some kind of postfix reader macro which translates into (new BigDecimal "n") ?
17:10	sdfsf	anyone use the Fiji/ImageJ package?
17:10	sdfsf	i want to write apps in clojrue as normal with it
17:10	sdfsf	is that possible?
17:20	AWizzArd	sdfsf: yes, Clojure is good to write normal and not so normal apps with it.
17:21	AWizzArd	From todays perspective Clojure has the potential to make it easier to write non-normal apps (namely those that make use of multiple cores in CPUs).
17:45	Chouser	AWizzArd: yep. (class -3M) -> java.math.BigDecimal
17:45	Chouser	BigDecimal has an 'abs' method.
17:51	AWizzArd	yes, this I understand
18:14	ryrunfrnf	why doesnt errors report the linenumberwhere the error is ?
18:14	ryrunfrnf	really annoying
18:38	AWizzArd	because in Lisp programming is not string editing
18:39	blackdog	AWizzArd, did you have any luck with the interation
18:39	AWizzArd	you are doing tree editing
18:39	blackdog	AWizzArd, did you have any luck with the integration
18:39	AWizzArd	blackdog: did not continue with it yet, but I will have a try tomorrow
18:39	AWizzArd	I will use your example and see how far I get with it
18:40	blackdog	i didnt try compiling it or anything, but it's close :P
18:43	AWizzArd	If I use purely java code from within Clojure the resulting .class file should be more or less exactly the same as if I had compiled it from a .java source. The clojure.jar would not be needed in that case.
18:43	ryrunfrnf	java.lang.RuntimeException: java.lang.RuntimeException: java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol (NO_SOURCE_FILE:1)
18:43	ryrunfrnf	is it now allowed to do: let [x blah c x]?
18:44	ryrunfrnf	what exactly does clojure check when compiling?
18:44	blackdog	well you;ll get lot's of class files not just one,
18:44	AWizzArd	But if I use any Clojure functionality I will have to use the clojure.jar and find a way how to start Jetty so that it will know about that as well.
18:44	blackdog	you get a class for each function and namespace
18:45	blackdog	and I'll be impressed if you can get away without clojure.jar
18:45	blackdog	don't know
18:46	hiredman	ryrunfrnf: sounds like somewhere (seq ...) is getting called on something that seq doesn't know what to do with
18:46	hiredman	do you do an destructering?
18:51	ryrunfrnf	meh, do youi guys have constant problems with getting stuck forever on dumb details?
18:52	ryrunfrnf	like so often it is some really small stupid detail that is right ther ein your face and yous till miss it
18:52	ryrunfrnf	i was using (defn f (params) instead of [params]...
18:53	Aisling	I used to work as a tutor in the lab at my university and I saw lots of people doing things like that.
18:53	Aisling	It's not just you. Attention to detail helps but still you'll run into these errors.
18:54	hiredman	well
18:54	Aisling	Syntax support in your editor can help with this.
18:55	hiredman	besides starting to write my lisp in ruby, and watching the mit sicp videos, I don't have previous lisp experience, so I don't automatically put parens everywhere :P
19:14	ryrunfrnf	java.lang.ClassCastException: clojure.lang.Symbol cannot be cast to java.lang.Number (NO_SOURCE_FILE:2)
19:14	ryrunfrnf	(let [n (minroot (+ (sq xr) (sq yr) (sq zr)))]
19:19	hiredman	clojurebot: cheesecake is delicious.
19:19	clojurebot	Roger.
19:33	ryrunfrnf	why os destructuring slower than first/rest?
19:38	gnuvince_	ryrunfrnf: destructuring has more bells and whistles
19:38	gnuvince_	> (let [[x y & z :as all] [1 2 3 4]] [x y z all])
19:38	gnuvince_	[1 2 (3 4) [1 2 3 4]]
19:44	ryrunfrnf	hmm when doign a raytracer
19:44	ryrunfrnf	that must be perfect for multimethods right?
19:44	ryrunfrnf	now i seee their advantage
19:44	ryrunfrnf	have amethod intersect
19:44	ryrunfrnf	and specialize on the thing its calle don
19:51	ryrunfrnf	god clojure is sooooo much cleaner than common lisp
19:53	gnuvince_	:)
20:29	ryrunfrnf	is it impossible to set swank/slime-intendation to 4 chars always?
20:39	ryrunfrnf	java.lang.IllegalArgumentException: Wrong number of args passed to keyword: :shape (NO_SOURCE_FILE:0)
20:42	ryrunfrnf	(intersect sph [10 20 30] 30 40 50)
20:42	ryrunfrnf	(defmethod intersect :Sphere [sphere point xr yr zr]
20:42	ryrunfrnf	(defn sphere-intersect [sphere point xr yr zr]
20:42	ryrunfrnf	wtf?
20:43	hiredman	ryrunfrnf: all the args to a multimethod get passed to the dispatch function
20:43	hiredman	so what happens there is (:Sphere sphere poit xr yr xr)
20:43	hiredman	which, uh, no?
20:44	hiredman	wait
20:44	hiredman	the is defmethod
20:44	hiredman	not defmulti
20:45	ryrunfrnf	so i want to refer to the sphere itself, how do i?
20:46	ryrunfrnf	(defmethod area :Rect [r]
20:46	ryrunfrnf	(* (:wd r) (:ht r)))
20:46	ryrunfrnf	hes assing the rect itself
20:46	hiredman	what does your defmulti look like?
20:47	ryrunfrnf	(defmulti intersect :shape)
20:48	lisppaste8	andjnsd pasted "defmulti" at http://paste.lisp.org/display/71202
20:51	ryrunfrnf	(defmethod intersect :Sphere [sphere a]
20:51	ryrunfrnf	(+ (:x sphere) a))
20:51	ryrunfrnf	works
20:52	hiredman	so
20:52	hiredman	yeah
20:53	hiredman	you are using a keyword as a dispatch function
20:53	hiredman	but that only works if you have one arg
20:53	ryrunfrnf	isnt ricks example?
20:53	hiredman	yeah it is
20:53	hiredman	but he only dispatches on one param
20:53	ryrunfrnf	ok
20:54	ryrunfrnf	so how should i change it?
20:54	ryrunfrnf	how do irefer to the sphere inside its defmethod? :Sphere?
20:55	hiredman	is the first argument always going to be hash with a :Sphere keyword?
20:55	ryrunfrnf	it is going to be a :shape
20:55	ryrunfrnf	hash-map
20:55	ryrunfrnf	sphere, cube etc
20:55	ryrunfrnf	it is for a raytracer
20:56	hiredman	(doc defstruct)
20:56	clojurebot	Same as (def name (create-struct keys...)); arglists ([name & keys])
20:56	hiredman	btw
20:56	ryrunfrnf	yes
20:56	ryrunfrnf	but isnt this pretty much was multimethods are for?
20:56	ryrunfrnf	hvaing an intersect functiona nd dispathicng on the type
20:56	ryrunfrnf	of :shape?
20:57	ryrunfrnf	(defmethod intersect :Sphere [a]
20:57	ryrunfrnf	(+ (:x :Sphere) a))
20:57	hiredman	so replace :shape in the defmulti with (fn [& x] (:shape (first x)))
20:57	ryrunfrnf	doesnt work
20:57	ryrunfrnf	i dont get how to use them then
20:57	hiredman	ryrunfrnf: you don't seem to understand how dispatch functions work
20:57	ryrunfrnf	correct
20:58	hiredman	that is what multimethods are for, you just are passing more then one arg, but using a dispatch function that only takes one arg
20:58	hiredman	keywords in clojure are functions of maps
20:58	ryrunfrnf	which is the dispathc function? defmulti?
20:58	hiredman	ryrunfrnf: you are using :shape as a dispatch function
20:58	hiredman	the keyword :shape
20:59	ryrunfrnf	yes
20:59	ryrunfrnf	what should i use?
20:59	AWizzArd	ryrunfrnf: have a look at this examplefor the generality of multimethods: http://paste.lisp.org/display/68846
20:59	hiredman	a function that can take as many args as you pass
21:00	hiredman	the dispatch function needs to have the same arity as the method it dispatches to
21:00	hiredman	or something like that
21:01	hiredman	a keyword has an arity of 1
21:01	hiredman	your method as an arity of more then 1
21:01	hiredman	boom
21:06	ryrunfrnf	then i dont get what defmulti is for
21:06	hiredman	then don't use it
21:08	hiredman	clojurebot: where are you?
21:08	clojurebot	http://gist.github.com/27733
21:08	hiredman	I use multimethods there
21:09	AWizzArd	ryrunfrnf: defmulti takes a function
21:10	AWizzArd	when you say (defmulti foo my-fun) then my-fun gets called with the arguments that you gave to the call of foo
21:10	AWizzArd	if you say (foo 1 2 3) then Clojure will do (my-fun 1 2 3) for you
21:10	AWizzArd	my-fun yields a result
21:11	AWizzArd	then Clojure goes through all (defmethod foo)'s to see if one of them was done for this result
21:11	AWizzArd	look at http://paste.lisp.org/display/68846
21:11	AWizzArd	there is the call (foo 2 4)
21:11	AWizzArd	Clojure secretly calls my fn from above
21:12	AWizzArd	This fn takes either 1 arg or 2. As I gave two we need to look into that branch. It simply adds both numbers. So, (foo 2 4) will yield 6.
21:12	AWizzArd	There exists a method foo for 6
21:13	AWizzArd	it gets both original arguments that were given, which were 2 and 4, and then passes them to the respective defmethod foo, which will multiply it's args
21:14	AWizzArd	Clear now?
21:17	ryrunfrnf	no
21:18	ryrunfrnf	(classes-of int int) would be clear
21:18	hiredman	...
21:18	ryrunfrnf	i want to write a method intersect that takes an abstract shape and then dispatches to the correect shape-method
21:19	AWizzArd	what exactly is unclear in this example?
21:19	hiredman	ryrunfrnf: you are not going to be able to use a keyword as a dispatch, because your methods take more then one arg
21:20	hiredman	your best bet is to write a dispatch function that takes a variable number of args
21:20	ryrunfrnf	ok i see
21:20	AWizzArd	you can pass keywords to defmulti btw, because they are treated asfunctions
21:20	hiredman	and uses the keyword to determine the :shape of the first argument
21:20	AWizzArd	(:my-key my-hashtable) ==> value for key
21:21	jeremy___	ok here's a newbie question: Here's a function my-sum that take a list of numbers and adds them together: (defn my-sum [x]
21:21	jeremy___	(+ ~@x))
21:22	hiredman	no
21:22	jeremy___	I get a ClassCastException when I run (my-sum `(1 2 3))
21:22	hiredman	yeah
21:22	hiredman	you do
21:22	hiredman	ok
21:22	jeremy___	what am I doing wrong?
21:22	hiredman	a lot
21:22	hiredman	~ is unquote
21:22	hiredman	mostly only used in macros
21:23	AWizzArd	you can use ~ or ~@ only inside a backquote expression. Your (+ ~@x) is just a plain list
21:24	AWizzArd	try instead (defn my-sum [x] `(+ ~@x))
21:24	AWizzArd	when you then (my-sum `(1 2 3)) ==> (+ 1 2 3)
21:24	hiredman	(doc apply)
21:24	clojurebot	Applies fn f to the argument list formed by prepending args to argseq.; arglists ([f args* argseq])
21:25	jeremy___	ah thanks it's starting to make sense
21:26	AWizzArd	This is used to contstruct lists. Lists are data. Data is code. So the backquote and ~ as well as ~@ are very often used to create code.
21:26	ryrunfrnf	int he examples oyu posted both defmulti and defmethod contains information on implementation
21:26	ryrunfrnf	they seem intertwined, thats what is confusing me
21:27	AWizzArd	Note however that you can write all programs without `, ~ and ~@. They are just shortcuts to plain function calls.
21:27	AWizzArd	ryrunfrnf: You could have a (defn my-count [obj] (count obj)). And then you do (defmulti foo my-count).
21:28	AWizzArd	this means that now all calls in the form of (foo ...) will in secretly be (my-count ...)
21:28	ryrunfrnf	so whats the point then?
21:28	AWizzArd	example: (foo [1 2 3]) === (my-count [1 2 3]) ==> 3
21:28	AWizzArd	but without defmethods it would be pointless
21:29	AWizzArd	now we put in a method: (defmethod foo 3 [arg] (println "Hello"))
21:29	ryrunfrnf	I thought it worked like: declare a function name and what it takes. then declare a bunch of methods to call depending on the type
21:29	AWizzArd	We said the call (foo [1 2 3]) ==> 3. There exists a (defmethod foo 3 ...)
21:30	AWizzArd	the 3 in the (defmethod ..) is the one that was the result of the call to (foo [1 2 3]) which under the hood was really a call to my-count.
21:30	AWizzArd	What now happens is: put the original argument to foo (it was [1 2 3]) to this method
21:30	arohner	what is the value of clojure.core.test?
21:30	AWizzArd	in this method it is called arg. We could have called it peter. The body of the method is (println "Hello")
21:31	AWizzArd	So, (foo [1 2 3]) will print Hello
21:31	arohner	it's slightly annoying that the test function expects failures to throw exceptions, yet it does nothing to catch & report them
21:31	ryrunfrnf	Like I thought it worked kind of liek inherited methods so i could do Obj.method and dont do inthe function If obj == type then blah else blahaba
21:31	AWizzArd	that was the old school dispatching, as most languages do
21:31	AWizzArd	this is the plain old type dispatch
21:31	hiredman	you can do that sort of thing
21:31	AWizzArd	but in Clojure you are not bound to that
21:32	AWizzArd	This is just a subset of what Clojures methods can do
21:32	hiredman	yeah
21:32	AWizzArd	you can dispatch for example on the number of elements in your argument, as we just did in the my-count example
21:32	AWizzArd	so no longer the type of the argument is important
21:32	AWizzArd	but only how many elements it contains
21:33	hiredman	you can dispatch on just about anything
21:33	hiredman	because the dispatcher is just another function
21:33	AWizzArd	add a (defmethod foo 5 [ryrun] (reverse ryrun))
21:33	AWizzArd	now you can say: (foo "Hello")
21:33	AWizzArd	and see what happens
21:34	ryrunfrnf	but i want a funiton intersect so i should have one defmulti and sveral defmethods?
21:34	hiredman	yes
21:34	AWizzArd	ryrunfrnf: first you should understand in detail how it works. I think these examples were pretty obvious. If not, what exactly puzzles you?
21:34	hiredman	but you will need slightly more complicated dispatch function because you are using more then one argument
21:41	AWizzArd	ryrunfrnf: in other languages a defmulti always looks basically the same. It is always something like: (defmulti name class)
21:42	AWizzArd	where (class obj) returns the type of that object
21:42	AWizzArd	you can not simply replace class with your own function
21:43	ryrunfrnf	but i dont get the 6 and the \H
21:43	ryrunfrnf	wtf are those names of the methods?
21:43	ryrunfrnf	if it is a 6 then do this?
21:44	hiredman	those are return values of the dispatch function
21:44	hiredman	if the dispatch function returns 6 then do this method
21:45	hiredman	which method is run is the result of what the dispatch function outputs
21:45	AWizzArd	ryrunfrnf: okay, so your problem lies in the (fn) which is passed to defmulti
21:45	AWizzArd	in Clojure a function can have many parameter lists and bodies
21:46	AWizzArd	The anon function that I passed to defmulti is such an example. It has the parameter collection and the body (first collection)
21:46	AWizzArd	If this function is called with just one arg then this branch of the fn is used
21:47	AWizzArd	Now the fn has a second branch. One that has two parameters. If we pass in two args they will be added.
21:47	ryrunfrnf	but why are they instances of a somehting instead foa type?
21:47	ryrunfrnf	if u make a general speci it should be diosptache dona type
21:47	ryrunfrnf	not an isntanc eof the type
21:47	AWizzArd	try (defn blah [x] (first x) [x y] (+ y x)) and call blah
21:48	AWizzArd	try calling blah with one arg and with two
21:48	hiredman	AWizzArd: I think you may be missing some parens
21:48	AWizzArd	oki right
21:49	AWizzArd	parens around [x] (first x) and also around the second guy
21:49	hiredman	and the (first ...) is kind of pointless
21:49	AWizzArd	hiredman: why?
21:49	hiredman	AWizzArd: well I guess it depends
21:49	AWizzArd	(blah (range 8 24))
21:49	ryrunfrnf	i thin i see a little now
21:49	hiredman	I just assumed that since the [x y] form uses (+ )
21:49	AWizzArd	but also (blah 10 5)
21:50	hiredman	anyway
21:50	hiredman	whatev
21:50	AWizzArd	ryrunfrnf: when you understand blah just do in my example at http://paste.lisp.org/display/68846 a replacement of the defmulti. (defmulti foo blah)
21:51	AWizzArd	when we call (foo "Hello World") then foo gets only one arg. This means we go into the branch 1 of blah. This simply returns the first element of the collection.
21:52	AWizzArd	A string is a collecting. The first element of "Hello World" is the char \H
21:52	hiredman	clojurebot: multimethods?
21:52	clojurebot	multimethods seperate the 20% from the 80%
21:52	AWizzArd	How can one teach the clojurebot new things?
21:53	hiredman	clojurebot: a is b
21:53	clojurebot	c'est bon!
21:53	hiredman	clojurebot: a?
21:53	clojurebot	a is b
21:53	hiredman	clojurebot: a is also c
21:54	clojurebot	Ack. Ack.
21:54	hiredman	clojurebot: a?
21:54	clojurebot	a is c
21:54	hiredman	clojurebot: a?
21:54	clojurebot	a is b
21:55	AWizzArd	clojurebot: multimethods is also what separates the boy from the man.
21:55	clojurebot	c'est bon!
21:55	rottcodd	clojurebot: b?
21:55	clojurebot	excusez-moi
21:56	ryrunfrnf	if i want to pass 5 args and dispatch on the ttype oa the first?
21:56	ryrunfrnf	(defmulti intersect (fn [a b c d e]
21:56	ryrunfrnf	(class a))) ?
21:57	hiredman	uh
21:57	hiredman	you most likely don't want to use (class ...)
21:57	hiredman	but that is the general idea
21:57	AWizzArd	this fn looks like a function that takes 5 arguments and returns the class of the first (while it ignores the other 4)
21:58	jeremy___	Here's another newbie question: Is there a way to force floating points when I run (/ 1 2 3 4) besides making one of the args a decimal (e.g 2.0)?
21:58	hiredman	(doc float)
21:58	clojurebot	Coerce to float; arglists ([x])
21:58	AWizzArd	(float (/ 1 2 3 4))
21:58	hiredman	clojurebot: botsnack
21:58	clojurebot	thanks; that was delicious. (nom nom nom)
21:58	AWizzArd	(/ 1 2 3 4.0)
21:59	jeremy___	ah thanks I overlooked that on the API page.
21:59	ryrunfrnf	so if i want to dispatch on a type i should have a defstrcut not a function calle dpshere?
22:00	AWizzArd	a defstruct is done for optimization,it will not create types
22:00	AWizzArd	structs are simple hashtables
22:01	AWizzArd	but they don't use up RAM for (some) of their keys
22:02	ryrunfrnf	oh my
22:02	ryrunfrnf	god
22:02	ryrunfrnf	so i cant disptach on something called a sphere?
22:02	hiredman	YOU CAN DISPATCH ON WHATEVER YOU WANT
22:02	ryrunfrnf	becaus eif i d struct sphere it passes back a ahsh howthe f doi matcht hat?
22:02	AWizzArd	if you have a (defstruct person :name :street :age :telephone) and want to do it for New York, then you would have 18 million instances or something like that. If it were a hashtable then all 18 mio entries would consume space for the keys :name :street :age :telephone.
22:02	hiredman	JUST WRITE THE RIGHT FUNCTION
22:03	ryrunfrnf	yes but since all :shapes will use hashmaps how do i differ them?
22:03	hiredman	you could even dispatch on time of day
22:03	AWizzArd	in a structure map only one time the keys need to be stored.
22:03	AWizzArd	ryrunfrnf: you will manually have to put some key/value into the hashtable
22:03	hiredman	ryrunfrnf: you have a key {:shape :sphere}
22:03	AWizzArd	(defstruct person :name :age)
22:03	hiredman	and you have a function that returns the value of that key of the hash
22:04	AWizzArd	(defn make-person [n a] (assoc (struct person n a) :type :person)
22:04	AWizzArd	now each instance of your hashtable will also have the key/value pair {:type :person}
22:06	SimonAdameit	Good evening
22:07	AWizzArd	Moin Simon
22:13	lisppaste8	blarf pasted "im dying of frustration" at http://paste.lisp.org/display/71210
22:13	hiredman	man, I wonder who blarf is
22:13	hiredman	ok
22:14	hiredman	NO
22:14	hiredman	no no
22:14	hiredman	no
22:14	hiredman	no
22:14	albino	that's a lot of 'no's
22:14	hiredman	see, here you have one thing you are passing, the hash
22:14	hiredman	so your dispatch function should take one value
22:15	hiredman	I think you will be better off if you have your dispatch function take a variable number of args
22:16	ryrunfrnf	but it takes a sphere a point and 3 coordinates
22:17	hiredman	ryal all of which are in the hash
22:17	hiredman	the hash is one "thing"
22:17	gnuvince_	Does clojure have a divmod function?
22:17	hiredman	object, datastructure, thing
22:18	hiredman	(doc rem)
22:18	clojurebot	remainder of dividing numerator by denominator.; arglists ([num div])
22:18	ryrunfrnf	but which is thet dispatch function? defmethods?
22:18	hiredman	no
22:18	SimonAdameit	Using swank-clojure I get the following error: "Exception in thread "main" java.lang.NoClassDefFoundError: clojure/lang/Repl"
22:18	gnuvince_	hiredman: that's only the second part :)
22:18	hiredman	the dispatch function is the function you pass to defmulti
22:19	hiredman	gnuvince_: well I don't know what divmod is
22:19	hiredman	so I guessed
22:19	SimonAdameit	Alot of people seem to have gotten that, but the tip to fully qualify the clojure jar path that I found in the google group did not work
22:19	SimonAdameit	Any Idea how to fix this?
22:19	gnuvince_	hiredman: (divmod 3 2) => (1 1)
22:20	gnuvince_	hiredman: basically, it'd be: (defn divmod [m n] [(quot m n) (rem m n)])
22:20	hiredman	ok
22:20	AWizzArd	SimonAdameit: do you use the newest versions?
22:21	hiredman	clojurebot: emacs?
22:21	clojurebot	emacs is hard, lets go shopping!
22:21	SimonAdameit	AWizzArd: for slime, swank-clojure and clojure yes
22:21	SimonAdameit	and emacs 22
22:22	AWizzArd	I have the same, for me it works
22:22	SimonAdameit	could you paste the relevant .emacs parts, maybe I could try yours
22:22	AWizzArd	oki
22:23	ryrunfrnf	but isnt the defmethod that has a value of what the defmulti retuns called?
22:23	ryrunfrnf	defmulti intersect retuns :shape a whc should be :Sphere
22:23	ryrunfrnf	then defmethid intersect :Sphere is called?
22:24	lisppaste8	rte annotated #71210 with "multis" at http://paste.lisp.org/display/71210#1
22:24	hiredman	that should work
22:25	hiredman	and could you use your own nick when you paste stuff?
22:26	SimonAdameit	AWizzArd: Yay, got it working to
22:27	SimonAdameit	It actually was a "stupid" error in specifying the wrong path :)
22:27	ryrunfrnf	yes but it doesnt
22:28	hiredman	what is the error
22:28	lisppaste8	AWizzArd pasted "Example emacs config for Clojure+slime" at http://paste.lisp.org/display/71211
22:28	AWizzArd	oki
22:28	hiredman	ryrunfrnf: paste the whole thing again
22:28	hiredman	uh
22:28	hiredman	yeah
22:28	hiredman	you are missing parens
22:29	hiredman	inside the fn, you need (:shape a)
22:30	ryrunfrnf	wow so annoying
22:30	ryrunfrnf	now it works
22:30	ryrunfrnf	hehe sorry guys
22:30	AWizzArd	I think you don't need these 5 args for defmultis dispatch fn
22:31	AWizzArd	try (defmulti intersect :shape)
22:31	hiredman	AWizzArd: ssh it's working, back away slowlyr
22:31	AWizzArd	g
22:31	hiredman	AWizzArd: he passes more then one arg
22:31	hiredman	not just the hash
22:31	hiredman	keywords are functions of arity 1
22:31	hiredman	so they blow up
22:31	hiredman	which is how this whole thing started
22:32	AWizzArd	wow
22:32	AWizzArd	well, you could need a calm-down-tea for tonight hire ;-)
22:32	AWizzArd	it was a moving theme
22:32	hiredman	huh
22:33	Chouser	keywords can take 2 args (not found)
22:33	hiredman	Chouser: just noticed that
22:34	hiredman	the point is, he is passing to many args to dispatch via a keyword, so cargo culting the examples doesn't work
22:36	sdfsf	the intersect function takes 5 args
22:37	sdfsf	a sphere a point and 3 coordinates
22:37	sdfsf	so i need to pass everala rgs aight?
22:38	sdfsf	i should do porn instead
22:46	AWizzArd	sdfsf: if this data is already inside the hashtable then you would only have to pass this one arg, namely the hashtable
23:19	matzero	hello is this working?
23:19	matzero	microphone check 1 check 2
23:20	sdfsf	anyone seen matzero lately? i never se him around here
23:21	matzero	lol
23:21	matzero	cool thanks for the ping back