#clojure – 2009-09-24

2009-09-24

00:10	mabes	can anyone explain to me why I'm getting this error?
00:10	mabes	,(def l '(1 2 3)) (defn look_at_first (first l))
00:10	clojurebot	DENIED
00:10	mabes	hrm.. well the error is: java.lang.RuntimeException: java.lang.IllegalArgumentException: Don't know how to create ISeq from: Symbol (NO_SOURCE_FILE:22)
00:11	mabes	I can say (first l) but I can't say than in a function
00:11	mabes	it seems like l doesn't resolve to a sequence in the function for some reason
00:12	hiredman	ok
00:12	hiredman	,(doc defn)
00:12	clojurebot	"([name doc-string? attr-map? [params] body] [name doc-string? attr-map? ([params] body) + attr-map?]); Same as (def name (fn [params* ] exprs)) or (def name (fn ([params ] exprs*)+)) with any doc-string or attrs added to the var metadata"
00:13	hiredman	defn is for defining functions
00:13	mabes	right, which is what I want to do.. I see what I am doing wrong though.. I need to have an empty vector
00:13	mabes	even if I don't have any args
00:13	hiredman	yes
00:15	hiredman	I recommend looking at example code, of which there is some on clojure.org, some on core.clj, and some in the pastebin
00:16	hiredman	http://delicious.com/clojurebot/pastbin <-- not all of the code here is good, but there is some good code there
00:17	mabes	ok thanks, I actually have the book by Stuart Holloway I was just playing around in the REPL and ran into that.. I forgot about needing to always pass a vector
00:18	hiredman	http://delicious.com/clojurebot/pastbin+chouser should all be good
08:29	chouser	http://n01se.net/paste/4CK -- Currying
08:57	hamza	hey guys, i have a question regarding memoize call i have a function that reads a directory and returs a list of files in it. can memonize be used in this situation to cache directory listing?
08:57	Fossi	if you don't want to find new files or directoriess
08:58	hamza	that would be my second question files will only be updated by the application is there a way to tell memoize to reset when i edit the files?
09:02	Chouser	you'd have to re-run memoize itself and start over with a completely empty cache.
09:03	hamza	kk thx.
09:04	Chouser	or write your own memoize so that you can delete subsets of the cache as needed
09:06	hamza	is there a restriction for memoize or can i use it on any funtion i want?
09:10	Chouser	nothing will stop you from using it on any clojure function, but of course it may behave weirdly if used on non-pure functions.
09:11	hamza	kk thx. all the functions i am planning to use on disk io functions.
09:11	Chouser	I would generally consider those non-pure, so use with care.
09:12	Chouser	,(let [p (memoize println)] (doseq [i [1 2 3 2 1 0 1 2]] (p i)))
09:12	clojurebot	1 2 3 0
09:13	hamza	files wont change i only don't want to hit the disks on every read. i'll know when files change do still think it will cause trouble?
09:14	Chouser	I guess if you know when the files change and clear caches as appropriate, that would count as using with care.
09:14	hamza	kk thx.
09:50	vy	Hi! I've downloaded the shcloj-code.tgz of Programming Clojure and extracted the archive to /tmp/code. Despite I (add-classpath "file:///tmp/code"), (require 'examples.snake) complains that "Could not locate examples/snake__init.class or examples/snake.clj on classpath:". What might I be missing?
09:51	triyo	Was thinking, is there a way to interface clojurebot with a web front-end? I was thing to build a 'try clojure' page that allows user to try clojure online.
09:52	triyo	Any suggestions welcome pls.
09:54	crios	hello vy
09:54	crios	I also donwloaded those examples, but never used (add-classpath
09:55	triyo	vy: Where you running the example from? Was you command?
09:56	triyo	*what's your command you use to run example
09:57	vy	crios: triyo: I don't use the REPL supplied by shcloj-code.tgz, I've my own emacs+SLIME setup for Clojure. I just want to introduce the related classpath on the fly.
09:57	vy	triyo: Here is the related ps afx line: "/home/vy/usr/java/jdk/1.6.0_16/bin/java -server -classpath /home/vy/projects/clojure/clojure.jar:/home/vy/elisp/swank-clojure/:/home/vy/.clojure/clojure-contrib.jar clojure.main"
09:59	crios	exist file:///tmp/code/examples/snake ?
10:00	Chouser	in general, add-classpath is unreliable, though I don't know if that is the problem in this specific case.
10:01	vy	crios: `ls -l /tmp/code/examples/snake.clj' returns right stuff.
10:04	dnolen	vy: you need to add paths to your swank-clojure-extra-classpaths in your .emacs file.
10:04	triyo	That should work, perhaps try load-file
10:05	dnolen	vy: unfortunately this is not dynamic you'll have to edit your .emacs file and restart Emacs.
10:05	vy	dnolen: Restarting current clojure session is what I was trying to avoid...
10:05	triyo	,(doc load-file)
10:05	clojurebot	"([name]); Sequentially read and evaluate the set of forms contained in the file."
10:06	dnolen	vy: add-classpath probably needs to absolute, did you try that?
10:07	vy	absolute?
10:08	triyo	You dont have to restart emacs after changing .emacs, you can eval the changes in emacs buffer
10:08	dnolen	vy: on my machine when I've add-classpath it always "/full/path/to/my/project/folder"
10:08	dnolen	triyo: no for that particular var, it's a design problem.
10:08	triyo	vy: try without file:// protocol
10:09	vy	dnolen: (add-classpath "/tmp/code") => no protocol: /tmp/code
10:09	triyo	Hehe
10:10	vy	dnolen: You sure add-classpath works with strings without a protocol?
10:10	rsynnott	ah, classpaths
10:10	dnolen	vy: pretty sure at one point I worked on a halfbaked Clojure project management tool and use it that way.
10:11	triyo	,(doc add-classpath)
10:11	clojurebot	"([url]); Adds the url (String or URL object) to the classpath per URLClassLoader.addURL"
10:11	Chouser	rsynnott: yes
10:11	dnolen	vy: OOPS. just check my code, you do need the protocol.
10:12	dnolen	when in doubt check the code :)
10:13	ngoc	hi, does clojure have light-weight thread? or does it use normal java's thread? I heard that agent uses some kind of thread pool
10:14	Chouser	ngoc: Clojure uses Java threads which are usually full OS threads.
10:14	triyo	rsynnott: Totally agree. I've worked on java ee and app specs never defined the way classloaders should load classes. So all app servers picked their own way of dealing with classloadig concerns.
10:15	Chouser	ngoc: but an agent is not a thread -- agents are assigned to threads from a pool as needed to get work done. So having a very large number of agents is cheap.
10:17	ngoc	I come to clojure from erlang. it seems that clojure focuses on data, while erlang focuses on processes
10:18	Chouser	ngoc: that's an interesting summary.
10:19	ngoc	in erlang I can wrap a variable inside a process (like state in gen_server), then when I want to create an instance of the variable, I will create an instance of the process
10:19	Chouser	one might also argue that Clojure focuses on functions.
10:19	ngoc	is there any way to create instance of agent in clojure? in the feeling of erlang's gen_server?
10:20	Chouser	an agent is a "variable". That is, an agent has a state, and you can change that state by sending it an action or task.
10:21	Chouser	but especially since you're coming from Erlang, beware or over-using agents. Clojure has several other concurrency mechanisms that may work better in certain cases.
10:24	dnolen	vy: for what it's worth I just tried a quick test myself of add-classpath and it just worked.
10:24	ngoc	For example, I want to create a tictactoe game. A game has many rooms. In Erlang I would model the game room into a gen_server which has state. When I want to create a new room I would spawn a gen_server instance. This way each room's state is wrapped inside a gen_server.
10:24	ngoc	How can I do this in Clojure?
10:26	ngoc	I think I will have to create a thread and wrap an agent inside that thread. Is this the right way to do?
10:26	stuartsierra	I would just use a function that returns a new agent each time it's called.
10:27	Chouser	ngoc: each room is an identifiable thing regardless of its state, right? So those would be some kind of reference object, probably a ref or agent. The state of a room at any moment would be the current board, whose turn it is, etc. all stored in a collection object, probably a map
10:29	Fossi	having done my share of erlang and clojure, i don't see where gen-server or agents come into play
10:29	ngoc	Ah, then all room should be put to a map of :room-id => agent, right?
10:30	Fossi	then, i don't really understand what a 'room' is, so that might be the problem
10:30	Chouser	ngoc: sure, and if you want that map to be global and change over time, that whole map could also be in a reference type
10:31	Chouser	(def all-rooms (ref {:the-first-room (ref {:turn :player-1 :board '[x o o, o x - ...] ...
10:31	ngoc	That's what I mean "data". How about code? When a player make a move, how to make the room "react"?
10:33	ngoc	Fossi: a room is a thing that has a state and some code attached to it
10:34	Chouser	(alter (:the-first-room @all-rooms) apply-players-move the-move)
10:34	Fossi	i'd argue that that's a bad (unpure) construct in most cases
10:34	Chouser	where the-move would be the user's input, and apply-players-move a function that takes an old room-state and the player's input and returns a new room-state
10:34	Fossi	i understand it from a message passing point of view, but i rarely find myself modelling things like that in clojure.
10:35	Fossi	might be related to my clojure problem-domain though
10:35	Chouser	that function could also do end-of-game checking and such. That's where most of your logic will live and should be a pure function.
10:35	Chouser	As such, apply-players-move will be easy to test at the repl or in unit tests, etc.
10:36	Chouser	...and completely thread safe, so you can spawn as many threads as needed to process incoming player moves.
10:39	ngoc	Can the pattern be generalized like this: (1) create a central variable, (2) when some event happens, call a central code to modify the central variable?
10:41	ngoc	Does the central variable become the bottle neck: all threads must do some kind of locking on this variable?
10:41	ngoc	If there are tens of thousands of players, the variable will become the bottle neck?
10:42	Chouser	(1) design a structure of data to hold the kind of data your app needs (2) write pure functions to manipulate that type of data in useful ways (3) decide what kinds of identity or reference objects will be holding that kind of state
10:43	Chouser	ngoc: each room in my example was a ref, which can only be changed in a transaction. If a thread has a transaction that only touches one ref (one room) it will not have to wait on threads touching other refs.
10:44	Chouser	ngoc: an alternative would be for each room to be an agent. when you send the agent a task, it'll get a thread assigned to do that work which will then also be able to proceed without waiting on any other threads that may or may not be working on other rooms.
10:45	Chouser	so in short: no bottleneck.
10:45	Chouser	the top level map of rooms is a single thing so if lots of threads try to add or remove rooms at the same time, they would have to line up, so there could be a bottleneck there.
10:46	Chouser	if that's a actual problem, you'd split that up so you don't have a single map of rooms -- partition it across multiple mutable reference objects somehow.
10:48	ngoc	Is there a way to map a room name like "room1" (for example a string) to a ref that floats somewhere in the JVM? This way when I have a name, I will be able to get back the ref?
10:49	stuartsierra	Sure, just define a var.
10:49	ngoc	I mean when all the refs are not put inside a single collection to avoid bottle neck...
10:49	Chouser	I don't think so. Things floating around tend to get garbage collected. Something needs to act as the root and provide the mapping from name to ref.
10:50	triyo	A map of refs perhaps then you can lookup re by :key
10:50	rhickey	j.u.c.ConcurrentHashMap is a fine place to put a top-level registry of refs, if all you'll ever do is add/remove/lookup by single key
10:52	ngoc	Is map in Clojure the same as ConcurrentHashMap? Or do I have to use ConcurrentHashMap explicitly?
10:52	stuartsierra	rhickey: is a namespace basically a ConcurrentHashMap of vars?
10:52	Chouser	ngoc: the latter
10:53	hiredman	rhickey: what do you think about lifting Agent.Action out into AAction and IAction and providing some indirection in Agent so it is easy to proxy Agent with a custom Action
10:53	Chouser	stuartsierra: the list of namespaces is a ConcurrentHashMap
10:53	rhickey	one way to think about j.u.c. maps is: they are to refs-to-persistent-strucutres as atoms are to refs, only supporting atomic non-coordinated access, but more concurrency than putting a persistent structure in an atom
10:54	Chouser	stuartsierra: each namespace is basically (atom {})
10:54	rhickey	namespaces use both strrategies
10:54	stuartsierra	ok
10:55	rhickey	the biggest difference being you can get a snapshot of a pds in an atom easily, can never get one from the j.u.c. stuff
10:55	rhickey	j.u.c. collections make good caches/registries
10:56	rhickey	i.e. single lookup vs really treating the collection as a value
10:57	ngoc	I have another question. How to have a timeout callback? For example the callback function will be called after 30s of room inactivity?
10:57	rhickey	hiredman: custom action that does what?
11:05	ngoc	I feel that Java thread must be used to create this timeout effect. But the problem is not too many threads can be created in JVM. Is there a solution?
11:05	stuartsierra	ngoc: java has a Timer class that does this
11:06	mccraig	is there a destructuring way of defaulting an optional parameters value ?
11:09	dnolen	mccraig: have you looked at clojure.contrib.def defnk, it's pretty handy.
11:11	drewr	+1
11:12	mccraig	that should do the trick. thx
11:16	Chouser	ngoc: java.util.Timer allows you to schedule multiple events in a single thread
11:33	Chouser	is there a way to do an unsigned-bit-shift-right?
11:36	ngoc	The doc of java.util.Timer says "Timer tasks should complete quickly. If a timer task takes excessive time to complete, it "hogs" the timer's task execution thread. This can, in turn, delay the execution of subsequent tasks, which may "bunch up" and execute in rapid succession when (and if) the offending task finally completes." I think this single thread implementation is not good.
11:37	Chouser	ngoc: that's your call of course. I think if your timer tasks simply send off agents you'll probably be fine.
11:37	ngoc	Ah, what a trick!
11:40	cgrand	Chouser: no
11:40	ngoc	In the API (http://clojure.org/api) I see there are some "shift" functions
11:41	ngoc	Can't (bit-shift-right x n) be used?
11:41	Chouser	,(bit-shift-right -12345 8)
11:41	clojurebot	-49
11:42	Chouser	anyway, I think I have a sufficient work-around here.
11:42	tmountain	Chouser: is this helpful? http://www.mail-archive.com/clojure@googlegroups.com/msg13789.html
11:43	Chouser	tmountain: ah, that's what I was doing. But that post gives me confidence I'm doing the right thing, thanks!
11:43	tmountain	Chouser: happy to help
12:04	mtm	is there any work in progress to to enhance 'memoize'? I've got a few ideas but didn't want to reinvent the wheel
12:04	ambient	how can it be enhanced?
12:05	mtm	right now, the cache can grow without bound
12:05	mtm	also, it holds a strong reference to the return value
12:05	ambient	news for me, i thought it had a bound
12:05	mtm	nope
12:06	hiredman	mtm: it's been discussed here in the paste
12:06	hiredman	past
12:06	ambient	clojure has weak refs?
12:06	hiredman	~logs
12:06	clojurebot	logs is http://clojure-log.n01se.net/
12:06	mtm	thanks, I'll dig into it
12:06	hiredman	hmm
12:06	mtm	but, yes, I'd like to use weak refs in the cache
12:07	Chouser	ambient: java has weak references, so yes
12:07	mtm	or, at least, be able to pass in a user defined cache
12:07	Chouser	I don't know that weak references would always be appropriate for a memoize fn
12:07	hiredman	for example around 2009:Aug:30:08:55:07 PDT
12:07	hiredman	you'll to translate to the timezone the logs are from
12:07	mtm	if not weak refs then at least an LRU cache
12:08	cgrand	it doesn't fit every case but I like (binding [foo (memoize foo)] (some code))
12:08	Chouser	cgrand: oh, that's interesting.
12:09	mtm	cgrand: I like it
12:09	Chouser	but some takes 2 args
12:10	hiredman	http://clojure-log.n01se.net/date/2009-08-30.html#11:51
12:11	mtm	it just seems you have to be really careful with memoize: it's pretty easy to have it retain the head of sequence
12:13	mtm	hiredman: thanks, reading it now
12:14	Chouser	anyone know how to get the pid of the current process?
12:16	mtm	I wasn't thinking of using a WeakHashMap; that only uses weak refs for the keys
12:16	stuartsierra	Chouser: there are ways to do it in Sun Java
12:16	Chouser	hm. or with jna I suppose.
12:17	stuartsierra	yeah, nothing in the standard JDK
12:17	Chouser	ok, thanks.
12:20	Chouser	(.invoke (com.sun.jna.Function/getFunction "c" "getpid") Integer nil)
12:33	hiredman	clojurebot: git 64323d8c6ad4962ac780d4d904b69a891ab312f8
12:34	clojurebot	added ->>
12:50	ngoc	Just a curious question: Java uses camelCase, why Clojure is designed to use hyphen-case?
12:51	eevar	because clojure is a lisp
12:51	stuartsierra	tradition, no other reason
12:51	mabes	ngoc: not a clojure expert by any means, but that is more of clojure's lisp inheritance
12:51	djpowell	Chouser: this works in practice on Sun's JDK, but it is a hack, and not guaranteed: (-> (java.lang.management.ManagementFactory/getRuntimeMXBean) (.getName) (.replaceAll "@.*" ""))
12:55	ngoc	Is there any Clojure book to be published in the near future? I don't know Lisp, the current Clojure book looks like only an introduction.
12:57	ngoc	I read the first chapter: well, this is introduction. Next chapter: oh, still introduction. Next... still introduction... Last chapter... God, still introduction :D
12:58	crios	+1 ngoc. "Programming Clojure" does not give you the right "mental shift" into Clojure
12:58	crios	this is my experience
12:58	lisppaste8	mtm pasted "pid " at http://paste.lisp.org/display/87654
12:59	mtm	it's a bit more portable (though I haven't tried it on windows)
12:59	djpowell	mtm: I just pasted something similar just above. I can confirm that it works on windows
13:00	mtm	djpowell: argh1 you beat me to it1 ;)
13:00	mtm	oops, those 1's were supposed to be !'a (playing with a remapping of my top row on this keyboard)
13:02	mtm	I can confirm that it also works on OS X
13:03	mtm	so the only thing left: does it work on Android?
13:03	rsynnott	does clojure work on android?
13:04	mtm	I vaguely remember hearing that it did but I can't confirm that
13:04	stuartsierra	rsynnott: it has been demonstrated to work
13:05	dnolen	rsynnott: some work has been done on that. check the mailing list. I also think that is the point of clojure-slim.jar
13:06	hiredman	eh?
13:07	hiredman	clojure-slim just omits compiled clojure code, certainly not suitable for the android
13:07	dnolen	hiredman: gotcha. I vaguely remember some patches for dalvik and I thought clojure-slim was related.
13:08	hiredman	I don't think there have been dalvik specific patches
13:08	hiredman	just patches to allow for leaving out the dynamic bits
13:08	hiredman	since code generation doesn't work on android
13:10	dnolen	hiredman: sounds like patches for dalvik to me ;) but whatever.
13:11	Chouser	clojurescript has also never supported generating code itself.
13:13	hiredman	dnolen: it's also useful in places where the security context does not allow for code generation
13:15	dnolen	hiredman: i see.
13:17	ngoc	Why "some" form does not have question mark ("some?")? Why there is "not-any?" but there is no "any?"?
13:17	ngoc	(Just a curious question about the API)
13:20	ngoc	And "some" returns true or nil, not true or false!?
13:20	stuartsierra	"some" returns the thing that made the predicate true
13:20	stuartsierra	,(some #(= 5 %) [1 2 3 4 5 6])
13:20	clojurebot	true
13:20	stuartsierra	no,
13:21	stuartsierra	It returns the result of the predicate function.
13:21	stuartsierra	,(some #(when (= 3 %) "yes") [1 2 3 4 5])
13:21	clojurebot	"yes"
13:27	dnolen	back did I miss anything?
13:27	dnolen	oops wrong channel :)
13:28	ngoc	In http://java.ociweb.com/mark/clojure/article.html, (some #(= % "Mark") stooges) should return nil, I have just reported this typo to the author
13:56	pixelman	Is it possible to make a lazy reverse range? like (range 9000000 1) somehow?
13:59	tmountain	pixelman: (range 10 1 -1)
14:00	pixelman	tmountain: thanks!!
14:00	tmountain	pixelman: np, you know about the doc function right?
14:01	tmountain	,(doc range)
14:01	clojurebot	"([end] [start end] [start end step]); Returns a lazy seq of nums from start (inclusive) to end (exclusive), by step, where start defaults to 0 and step to 1."
14:01	tmountain	pixelman: pretty handy... I use it constantly
14:01	pixelman	yep, I just assuemed range would not be able to do it, without looking it up :)
14:02	pixelman	btw, is there a way I could search and get a list of all functions that works with lists and arrays?
14:06	Chouser	Sure! But you probably want seq functions too, right?
14:06	Chouser	(find-doc #"seq\|list\|array")
14:06	pixelman	wow. that's great!
14:06	Chouser	That should keep you busy for a while. ;-)
14:06	pixelman	awesome.
14:53	LauJensen	I don't, see you there in a sec
14:58	LauJensen	Someone asked me on my blog to do a Haskell Vs Clojure piece, but which application space does Haskell cover?
15:06	ambient	academic study
15:06	ambient	:p
15:07	ambient	chouser, you're a better man than I clearly
15:08	LauJensen	prettier anyway :)
15:08	Chouser	er
15:08	LauJensen	This might be a very dumb question, but Haskell has no use in industry ?
15:08	stuartsierra	not necessarily
15:09	stuartsierra	I know companies that use OOCaml, for example.
15:09	Makoryu	LauJensen: Yep, it's only useful for processing li... er, parallel distributed... uhm.... Academia. Yeah, that's it. It's strictly a research language.
15:09	Makoryu	Haskell is general purpose.
15:10	Makoryu	There's some company that uses it to make tractors, and of course there are several that write financial apps.
15:10	LauJensen	haha
15:10	LauJensen	That was fun Makoryu :)
15:12	tmountain	LauJensen: there's a book called "Real World Haskell"
15:12	tmountain	LauJensen: it's an appeal to the world that haskell is useful for things besides quicksort
15:12	Makoryu	LauJensen: But seriously, the biggest Haskell apps (aside from the compiler, which serves as a back end to a bunch of logic/theorem languages these days) are probably darcs and xmonad
15:12	tmountain	Makoryu: and pugs...
15:13	LauJensen	All 3 of which are foreign to me
15:13	Chouser	I find Haskell to be quite impressive and I hope one day to be smart enough to use it.
15:13	Makoryu	tmountain: I... can't really vouch for pugs >_>
15:13	Makoryu	LauJensen: Darcs is a DVCS, and xmonad is a tiling window manager
15:13	LauJensen	Ok
15:13	LauJensen	Chouser: What impresses you about iT?
15:13	tmountain	LauJensen: Pugs is a Perl 6 interpreter
15:14	sfuentes	i like xmonad
15:14	ambient	i will be intriqued to use haskell the day someone uses it for actual commercial purposes successfully
15:14	tmountain	I used xmonad for a bit. It's pretty nice, but it's config file basically scared me away form haskell
15:15	Chouser	LauJensen: Haskell is succicnt, appears to have a powerful static type system with inference, has good immutable data structures, encourages pure functions...
15:15	Chouser	in short, it's not PHP
15:16	tmountain	it also allows oodles of user-defined operators, which makes any new source file completely alien until you determine what the programmer had in mind this time around
15:16	Chouser	and the people who use it seem to love it. Who loves C++?
15:18	LauJensen	Chouser, please explain the term 'powerful static type system'
15:18	ambient	i think C++ is in many cases, the pragmatic choice
15:18	Makoryu	LauJensen: Haskell has a really nice implementation of parametric polymorphism (generics)
15:18	tmountain	LauJensen: http://book.realworldhaskell.org/read/types-and-functions.html
15:18	LauJensen	ambient: pragmatic means "if it works, its good", meaning c++ could never be the pragmatic choise
15:18	Makoryu	LauJensen: It's statically typed, but it uses whole program type inference so you don't usually have to worry about type declarations
15:18	ambient	LauJensen most of Googles Code Jam top coders disagree
15:19	tmountain	haskell is soooo controversial ;-)
15:19	LauJensen	ambient: that tells you something about them doesn't it? :)
15:19	LauJensen	Makoryu: Alright
15:19	Chouser	ambient: yes, people use C++, and perhaps sometimes it's the best choice. But it's been a while since I heard someone who really understands C++ express joy at the idea of using it.
15:19	ambient	i think C++ is way too convoluted that it's even possible to fully understand it
15:19	LauJensen	Makoryu: By parametric polymorphism, do you mean overload of functions based on arity ?
15:20	ambient	personally, im just happy using a simple subset of it
15:20	Makoryu	LauJensen: No. I mean overloading of functions, data structures, and values based on parameterized types
15:20	ambient	LauJensen it tells me that they get things done
15:20	LauJensen	exaple?
15:21	LauJensen	+m
15:21	Makoryu	For example, you'll see type signatures like "[b] -> b" which means "A function that takes a parameter of type 'list of b' and returns a value of type 'b'"
15:21	Makoryu	(Where b can stand for any type)
15:22	Makoryu	So, this will work on [String], [Int], etc.
15:22	Makoryu	That's fairly basic
15:22	manic12	aren't you glad I'm keeping my mouth shut.
15:23	LauJensen	manic12: Yes
15:23	LauJensen	Makoryu: k
15:23	Makoryu	manic12: About the sinister dangers of static typing? ;)
15:23	manic12	no, just in general
15:24	manic12	i could go off on that though
15:24	Makoryu	LauJensen: Okay, something cooler: Numeric literals are overloaded. For example, the token 5 can represent an Int, Integer (ie. a bignum), Float, Double, or anything else that implements the typeclass Num
15:25	LauJensen	Makoryu: Similar to Clojures automatic Int -> Bigint ?
15:25	wooby	hi everybody i'm new, i tried to code a solution to a problem from the holloway book from scratch: http://gist.github.com/192966, thanks in advance for ripping it apart ;)
15:25	Makoryu	LauJensen: For literals alone, yes.
15:26	Makoryu	LauJensen: Of course, you have to explicitly convert a value of type Int if you want to use it as a value of type Integer :p
15:26	Makoryu	> [5 :: Int, 5 :: Integer]
15:26	Makoryu	Hmm, lambdabot's gone
15:26	Makoryu	Oh, duh, what channel am I in?
15:27	Makoryu	LauJensen: Anyway, the above line would cause a type error, since lists have to be homogeneous.
15:28	LauJensen	oh ok
15:29	Makoryu	I should probably send you to #haskell, by the way, to talk about this
15:29	Makoryu	I have to leave soon anyway :p
15:30	LauJensen	Thanks for taking the time
15:30	Makoryu	No sweat
15:31	Makoryu	You'll find other #haskell folks equally willing to help, of course...
15:31	LauJensen	Nice
15:34	LauJensen	wooby: I don't know the problem description, but are you aware that passing a sec like [:p :h :h :t :h :h] will cause the 2x :h not to be filtered?
15:35	wooby	LauJensen: yeah, the problem description is to return the number of sub-sequences of a specified type and length
15:35	wooby	so input like [:p :h :h :t :h :h] should return 2
15:35	wooby	given type :h and length 2
15:37	LauJensen	ok
15:37	LauJensen	Then you need to rework it :)
15:38	wooby	LauJensen: how do you suggest i improve it?
15:39	LauJensen	Its the partition that's tripping you up, so maybe parse it using take-while and filter those of the length you need
15:40	wooby	LauJensen: is that a better way to do it? it seems to work
15:41	LauJensen	That's how I would do it, but it's good that you ask in here, so hopefully other people can chime in as well if they have improvements
15:42	wooby	i see, thanks
15:45	miltonsilva	hi!
15:45	LauJensen	yo
15:45	miltonsilva	I need some help with a function
15:45	LauJensen	shoot
15:46	miltonsilva	(defn calc [nBlocks & inodes]
15:46	miltonsilva	(let [inodes (if (nil? inodes) (/ nBlocks 8) (first inodes))
15:46	miltonsilva	iUsageT (/ inodes 128)
15:46	miltonsilva	nBData (/ (+ (* 128 (- nBlocks (+ 1 inodes iUsageT))) 4) 129)
15:46	miltonsilva	freeCT (/ (- nBData 4) 128)]
15:46	miltonsilva	[inodes nBData freeCT]))
15:46	Chousuke	hm
15:46	miltonsilva	hmmm how can I past this in a more readeble maner
15:46	Chousuke	you should use a pastebin :/
15:46	Chousuke	lisppaste8: url
15:46	lisppaste8	To use the lisppaste bot, visit http://paste.lisp.org/new/clojure and enter your paste.
15:46	miltonsilva	thanks
15:46	Chousuke	put it there, it'll be easier for us to help
15:47	lisppaste8	miltonsilva pasted "untitled" at http://paste.lisp.org/display/87670
15:48	Chousuke	to start with, dividing the calculations to multiple lines might make them more readable
15:48	LauJensen	second, whats it supposed to do exactly?
15:49	Chousuke	or you might want to make them their own functions
15:49	miltonsilva	ok, I would like to make this as idiomatic as possible... second is there some func that takes a math expression (infix) and evaluates it?
15:49	Chousuke	also, mixedCase is not very lispy. you should use hyphenated-names instead :)
15:49	miltonsilva	it's just
15:49	miltonsilva	ok ;) good tip
15:51	Chousuke	what's the iUsageT supposed to mean anyway?
15:51	miltonsilva	this function is to make some calculations... I need to format a disk (write a formater) and some things depend on others... the inode usage table depends on the number of inodes etc
15:52	miltonsilva	(actually i'm going to write it in C but I would like to test this function with clojure)
15:52	Chousuke	but an integer is not an iusagetable? does it signify the count or something? :/
15:53	miltonsilva	iusagetable is the size in blocks of the inode usage table
15:54	Chousuke	and what does nBData signify?
15:54	miltonsilva	number of blocks for data
15:56	miltonsilva	you could as well this of it as x y z etc... but some things like the way I verify if inodes were passed, I think theres probably a better way of dealing with arity in this case...
15:58	Chousuke	hmm, right
15:58	Chousuke	you could actually override on arity
15:58	miltonsilva	how do I do that?
16:05	lisppaste8	Chousuke annotated #87670 "suggestion" at http://paste.lisp.org/display/87670#1
16:06	Chousuke	I didn't change the freeCT name for now though
16:06	Chousuke	also I forgot to change the name of the first function :P
16:09	Chousuke	actually it might also help to swap the (* 128 (- blocks (inc (+ inodes iut-blocksize)))) and 4 expressions :)
16:09	miltonsilva	ahah :) I like it
16:11	Chousuke	note though that / in Clojure is exact if you're dealing with integers. if you're relying on truncating behaviour I think you need to be explicit
16:11	Chousuke	,(/ 3 4)
16:11	clojurebot	3/4
16:13	miltonsilva	thanks for the tip but, this problem requieres a more complex ajustation system..
16:14	manic12	I know the answer is "it depends", but just to ask the question, what would I use in clojure to represent what I might have used a defvar for in common lisp? (accessible to all threads) an agent?
16:14	miltonsilva	(in order to maximize the number of free blocks of data)
16:14	stuartsierra	manic12: any reference type, stored in a var
16:19	manic12	use def to create it and def again to change it's state?
16:26	stuartsierra	no, do (def thing (ref initial-value))
16:26	stuartsierra	then change with (dosync (alter/ref-set thing ...)))
16:27	manic12	ok
16:27	Chousuke	if you want something that's not controlled, you can use an atom
17:41	mtm	any opinions of the book "Let over Lambda"? how much of the content would be relevant to clojure?
17:44	Chouser	mtm: I've never heard of it, but Common Lisp macros have many similarities with Clojure macros.
17:44	Chouser	I learned macros in CL with "On Lisp" and most of that knowledge came over pretty cleanly.
17:46	Chouser	none of the debugging, disassembling, or other CL internals are going to be relevant.
17:49	mtm	chouser: thanks, I figured most of the CL stuff wouldn't apply, but it's good o know about the macro simularities
17:50	Chouser	the main difference in the macros themselves are how clojure improves hygene
17:56	Chousuke	if you come from CL I suppose you'll need to understand the namespace qualifying thing and how to get around it and then you're all set :)
17:59	mtm	no real CL experience, but in the dim past I played around with a TI Explorer. I have to say clojure is the most fun I've had programming since my FORTH days (and that was 25 years ago)
18:51	lisppaste8	hamza pasted "mac to string" at http://paste.lisp.org/display/87683
18:52	hamza	hey guys, i am trying to convert a byte array in to mac id string but i get class cast exception?
18:55	Chousuke	hamza: you're not using reduce correctly there.
18:56	stuartsierra	the first argument to your fn should be the accumulated return values of the function
18:56	Chousuke	you might want something like (apply str (map (fn [k v] ...) mac-bytes)))
18:59	stuartsierra	More likely (apply str (map (fn [v] ...) mac-bytes))
19:02	hamza	kk apply worked thx. for reduce i should use one more varible for the accumulation and return that?
19:39	drhodes	,(union #{1 2} #{3 4})
19:39	clojurebot	java.lang.Exception: Unable to resolve symbol: union in this context
19:40	mtm	,(clojure.set/union #{1 2} #{3 4})
19:40	clojurebot	#{1 2 3 4}
19:41	drhodes	thanks mtm
19:41	mtm	np
19:47	khora	not trolling, I'm trying to pick a language between Scala and Clojure. What are the advantages of using Clojure over Scala?
19:48	andrewaclt	khora: There are a lot of blog posts that outline the differences between the two.
19:49	khora	andrewaclt: the ones I've found had little substance to it
19:51	hiredman	khora: have you read rhickey's rationale?
19:51	hiredman	~why?
19:51	clojurebot	http://clojure.org/rationale
19:51	khora	hiredman: no, I didn't
19:53	hiredman	there are also the intro to clojure videos, in which rhickey mentions a few design decisions that went into the language
19:54	hiredman	~blip.tv
19:54	clojurebot	blip.tv is http://clojure.blip.tv/
19:55	khora	hiredman: may I confess you something?
19:55	hiredman	my standard pitch is "LOOK LOOK, SO AWESOME, CAN'T YOU SEE!?!?!" which doesn't work very well
19:56	khora	scala syntax makes me want to cry, and I'm sick of OOP. However, Clojure's lack of support for tools really put me off.
19:56	hiredman	which tools?
19:57	khora	hiredman: textmate
19:57	hiredman	oh, uh, well, uh...
19:58	hiredman	really? textmate?
19:58	dnolen	khora: why not netbeans+enclojure. can't get more user friendly than that.
19:58	slashus2	khora: Have you tried IDE plugins? enclojure?
19:58	andrewaclt	hiredman: pretty sure there is a clojure textmate bundle
19:58	hiredman	I know there is
19:58	khora	no I didn't try IDEs because I thought they would be overkill for single scripts
19:59	hiredman	I assumed he is saying the textmate bundle isn't very good
19:59	andrewaclt	hiredman: sorry that was to khora :)
19:59	hiredman	~google textmate clojure bundle
19:59	clojurebot	First, out of 638 results is:
19:59	clojurebot	nullstyle's clojure-tmbundle at master - GitHub
19:59	clojurebot	http://github.com/nullstyle/clojure-tmbundle/tree/master
19:59	khora	the textmate bundle I found didn't work for me
20:00	hiredman	clojurebot: vim?
20:00	clojurebot	Gesundheit!
20:00	hiredman	bah
20:00	hiredman	clojurebot: vimclojure
20:00	clojurebot	vimclojure is http://kotka.de/projects/clojure/vimclojure.html
20:00	khora	it said that I didn't have clojure installed, then proceeded to install it for me, but next time... same thing
20:00	hiredman	clojurebot: vim is <reply>http://kotka.de/projects/clojure/vimclojure.html
20:00	clojurebot	Ack. Ack.
20:01	ambient	there's also vim plugin for netbeans which is pretty nice :)
20:01	khora	netbeans+enclojure is the state of the art?
20:01	hiredman	I installed netbeans once :(
20:01	hiredman	khora: most here seem to use emacs
20:02	hiredman	I installed emacs once too :(
20:02	khora	hiredman: I tried to get imto emacs
20:02	khora	h
20:02	khora	hiredman: too much all at once
20:02	hiredman	anyway, I use vim, it works, and I don't have to think about it
20:03	khora	hiredman: I may have to use vim too
20:14	khora	trying to install vimclojure I get an error
20:14	khora	BUILD FAILED
20:16	dnolen	khora: netbeans+enclojure = no configuration. you can just start a project, make a script, be done wit it.
20:17	wavis	i use jedit, which has an edit mode for clojure that is pretty good. http://github.com/djspiewak/jedit-modes/blob/master/clojure.xml
23:24	hamza	how do i set a field in a class?
23:40	rboyd	hamza: I think you use set! http://clojure.org/java_interop