#clojure – 2010-09-12

2010-09-12

04:20	LauJensen	Morning all
04:55	kjeldahl	Anybody using slime-connect in emacs who can comment on how or why delimiter matching isn't working in the repl environment?
05:19	tomoj	kjeldahl: what do you mean by "delimeter matching"?
05:19	tomoj	paredit?
05:19	clojurebot	paredit screencast is http://p.hagelb.org/paredit-screencast.html
05:46	kjeldahl	tomoj: When I write things like (let [[a b][1 2]][a b]) I need help matching the ] and )s. Differently from most other places in emacs (including clojure-mode), the slime REPL buffer in emacs doesn't seem to help.
05:46	LauJensen	kjeldahl: SLIME doesn't run Clojure-mode
05:47	kjeldahl	LauJensen: Yes, I get that. I still need help though. Which is why I asked.
05:47	LauJensen	try M-x clojure-mode
05:47	tomoj	that screws it up, doesn't it?
05:48	tomoj	kjeldahl: what kind of help are you looking for, though?
05:48	tomoj	paren highlighting?
05:48	kjeldahl	Yes, seems like that screws it up.
05:48	LauJensen	I tried it here a while back because I needed that highlighting for something, and it worked, and there yes I think there was some kind of bug but I forgot which
05:48	kjeldahl	tomoj: Yes, inside the repl in emacs.
05:48	tomoj	kjeldahl: M-x show-paren-mode
05:48	tomoj	I don't know how to get paredit to play nice with the repl
05:49	tomoj	if I M-x clojure-mode my repl, it's totally borked
05:49	tomoj	it's now just an R
05:49	tomoj	hell it doesn't even R, it's just totally gone
05:49	kjeldahl	Thanks, I know the basics outside of slime-connect repl mode. repl inside emacs matches (, but not [ and probably not {.
05:58	LauJensen	Guess it wouldn't be too hard to rip the font-locking stuff out of cloure-mode and make clojure-repl-mode
06:05	mrBliss	I use clojure-mode in my repl without problems. Here's how: http://github.com/mrBliss/dotfiles/blob/master/.emacs.d/clojure.el#L50
06:06	LauJensen	cool
06:07	tomoj	mrBliss: thanks!
06:07	tomoj	also paredit, wow
06:07	tomoj	you are a savior
06:07	mrBliss	I'm not using paredit at the moment, but it is there for when I intend to learn it
06:10	tomoj	aw, it makes you lose the colored repl prompt
06:10	mrBliss	look at slime-repl-prompt-face on line 24
06:11	mrBliss	it's not perfect
06:11	tomoj	ah, I skipped the syntax tweak
06:11	tomoj	paredit seems busted somehow too
06:11	LauJensen	true
06:11	tomoj	e.g. if you type (()), then point at ((\|)), DEL DEL leaves you with ))
06:12	mrBliss	sorry I'm not using it the moment, so I can't help
06:12	tomoj	the binding to paredit-backward-delete is gone for some reason.. hmm
06:12	tomoj	no problem
06:12	tomoj	it looks like the binding for DEL is coming from slime-repl-map-mode
06:13	mrBliss	add the bindings again in (eval-after-load "slime-repl" ...
06:17	tomoj	I think that's the only binding that gets clobberd
06:18	kjeldahl	mrBliss: Excellent, thank you.
06:20	tomoj	damn, I can't get that binding for some reason
06:20	tomoj	oh well, I'll look at it again later
06:20	mrBliss	which binding exactly?
06:22	tomoj	paredit-backward-delete
06:22	tomoj	to DEL
06:22	mrBliss	I'll see what I can do
06:22	tomoj	tried putting it where the bindings for paredit-open-curly and the other are, no luck. maybe the hook isn't being reloaded or something. don't worry about it though, I'm sure I'll figure it out eventually
06:24	mrBliss	alright
06:59	nlogax	(:lol {:foo "bar", :lol "bbq"}) i was surprised that worked, can someone explain why/how to a noob? :)
07:00	nlogax	nevermind, i just found it in the docs
07:00	LauJensen	nlogax: maps are functions of their keys
07:01	nlogax	LauJensen: i had seen that one before, but not "callable" keywords
07:01	jjido	I tried converting my program to trampoline but I quickly get a stack overflow. How do I prevent stack from growing? http://pastebin.ca/1938762
07:03	jjido	Note: my solution with (loop [next start] (recur (next))) works fine
07:03	tomoj	I think you have far too many trampolines
07:04	tomoj	I don't understand your code, but my guess would be to try only having the one trampoline in start, and get rid of all the rest
07:08	jjido	tomoj: I think I don't understand trampoline, hence my code
07:09	jjido	I want to throw away the current function stack then call a function
07:09	jjido	can trampoline do that?
07:10	tomoj	yes, just return the function
07:10	Chousuke	jjido: you return a thunk from the function and the trampoline calls it
07:12	LauJensen	,(letfn [(dec-even [x] (if (zero? x) x (dec-odd (dec x))))
07:12	LauJensen	(dec-odd [x] (if (zero? x) x (dec-even (dec x))))]
07:12	LauJensen	(trampoline dec-even 6))
07:12	clojurebot	EOF while reading
07:12	LauJensen	well, that would return zero, think its the simplest example of a trampoline I can think of anyway
07:12	Chousuke	LauJensen: that's not right.
07:12	Chousuke	LauJensen: you need to return a function from dec even, not call dec-odd directly
07:13	Chousuke	something like. (letfn [(x [] (print "x") #(y)) (y [] (print "y") #(x))] (trampoline x))
07:14	LauJensen	,(letfn [(dec-even [x] (if (zero? x) "even" #(dec-odd (dec x)))) (dec-odd [x] (if (zero? x) "odd" #(dec-even (dec x))))] (trampoline dec-even 5))
07:14	clojurebot	"odd"
07:14	LauJensen	,(letfn [(dec-even [x] (if (zero? x) "even" #(dec-odd (dec x)))) (dec-odd [x] (if (zero? x) "odd" #(dec-even (dec x))))] (trampoline dec-even 6))
07:14	clojurebot	"even"
07:20	jjido	tomoj: Chousuke: ok I just replace my loop with trampoline, that works
07:25	jjido	Updated program here (WARNING prints 700000 lines) http://pastebin.ca/1938773
07:30	Chousuke	jjido: you should use two spaces as the standard indent, it makes the code look less nested.
07:30	jjido	ok
07:30	Chousuke	the underscore names are curious too but other than that the code looks fine to me.
07:32	jjido	just to avoid clobbering throw (don't know if there is a return in Clojure)
07:33	Chousuke	there isn't.
07:34	Chousuke	and it's acceptable to shadow names in functions, as long as the function is short enough :)
07:34	jjido	I will use "return" and "error" instead
07:35	Chousuke	my first thought when I saw _return was that it's just a named unused parameter
07:35	Chousuke	as _ is the idiomatic "unused parameter" name
07:38	jjido	how about "loop"? I don't want to clobber that at the top level
07:38	Chousuke	yeah, you shouldn't.
07:38	jjido	would f-loop look more lispy?
07:38	Chousuke	what does the f mean?
07:38	jjido	function
07:39	Chousuke	hmm.
07:40	Chousuke	both names are pretty uninformative in my opinion
07:41	jjido	could be, I did have a "loop" function in my original program (in a different language)
07:41	Chousuke	even if you called it "loop" it raises the question "what loop?"
07:41	jjido	it is a loop that prints "Hello World!" seven times
07:42	Chousuke	so maybe you can call it print-loop or something?
07:42	jjido	is that better style: http://pastebin.ca/1938786
07:44	Chousuke	yeah, looks better. You can use more spaces to align parameters though if that makes the code look better.
07:45	Chousuke	fn_loop should be fn-loop though. (or print-loop as I suggested :P)
07:46	tomoj	Chousuke: yes, I also had to go test whether those would be named but unused
07:46	tomoj	and I was thinking, wow, someone wrote all this code without ever testing it?
07:46	tomoj	now I'm trying to remember where I've seen named unused parameters before
07:47	Chousuke	jjido: Maybe you should come up with a naming convention for the continuations to differentiate them from the other parameters
07:49	Chousuke	like yes-c or returnc. I think it would make the code easier to understand. (though more typing for you)
07:49	jjido	Chousuke: the code will be generated
07:49	Chousuke	ah, okay
07:50	tomoj	naming stuff is hard
07:51	Chousuke	yeah, it is.
07:52	LauJensen	was easier in CL
08:03	cwb	I'm reading Programming Clojure and don't understand the difference between next and rest: if rest always returns a sequence then why do we need next equivalent to (seq (rest aseq))?
08:04	LauJensen	,(next [])
08:04	clojurebot	nil
08:04	LauJensen	,(rest [])
08:04	clojurebot	()
08:04	cwb	Aha -- thanks!
08:04	LauJensen	np
08:42	Bahman	Hi all!
10:04	alpheus	What's good style for formal function parameter names that clash with well-known functions? Something scheme-like, spelling list as lst?
10:14	AWizzArd	alpheus: often people want to name parameters like the datatype they are holding. Another way is to type-hint them: (defn foo [^clojure.lang.PersistentList l] ...)
10:19	scottj	How do you disable congomongo's auto converting of strings to keywords? When I insert {"foo bar" 1} it will then always return it printing as {:foo bar 1} even though looking "foo bar" up in it still works
10:20	Raynes	There is an argument you can pass somewhere.
10:21	Raynes	Hrm, maybe not.
11:28	boredomist	Is there a better way of doing (str (char 65)) to change 65 to "A"?
11:28	boredomist	(for example)
11:38	AWizzArd	boredomist: that's fine.
11:57	LauJensen	If its not paypal, do you guys have some really good experiences with other cart/payment providers?
11:59	kotarak	Can someone explain me, how equiv works?
11:59	kotarak	Obviously I'm too stupid to implement it.
12:02	LauJensen	kotarak: http://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/APersistentMap.java#L72
12:02	LauJensen	That what we're talking about?
12:02	kotarak	Yeah. Roughly. More for list.
12:03	kotarak	A translated things into Clojure, but it doesn't like me.
12:03	kotarak	Argh.
12:03	LauJensen	Looks simple, if its not the same type return false, if its not the same size return false, otherwise, check all element
12:03	LauJensen	s
12:03	kotarak	LauJensen: Never mind. I'm stupid.
12:03	LauJensen	Ok - Now back to my Payment provider question, any recommendations?
12:16	chouser	LauJensen: I've used google checkout a bit. No particular recommendation one way or the other.
12:17	LauJensen	k
12:36	maravillas	from a buyer's or seller's perspective, LauJensen?
12:36	maravillas	I've bought through google checkout as well, and it's been straightforward enough
12:38	chouser	I guess google checkout provides a bit more management of the sales "workflow", with the payment authorization showing up in a list before the buyer has actually been charged.
12:38	chouser	...so that you can prepare and ship your item, then click the "ship" button to actually charge the buyer.
12:39	chouser	but neither google nor paypal strike me as being very good about customer service. I would be nervous if 100% of my income depended on either of them paying out promptly.
12:39	LauJensen	maravillas: seller
14:04	Bahman	My project.clj is (http://pastebin.ca/1938963)
14:05	ivey	Idiomatic clojure question: I'm building a library that wraps a remote API. Is it more appropriat to set username and password vars and use those everywhere, or create a client data structure and pass that around?
14:06	Bahman	When I run 'lein deps' Leiningen looks for clojure-1.1.0-alpha-SNAPSHOT and fails. Any ideas?
14:10	pomyk	Bahman: maybe incanter or org.clojars.ato/compojure tries to bring it in?
14:10	LauJensen	ivey: Passing arguments around is definitely more function and thus idiomatic. However some libraries take the approach that you save your credentials in a struct, then make all calls (with-credentials struct ....)
14:10	Raynes	ivey: You'll find fans of both styles. Personally, I prefer the latter style in this specific case. I do something similar in my clj-github library. I believe I have an authentication var that contains a map with credentials.
14:11	Raynes	I've seen some similar libraries do similar things. When you have doubts about whether doing stuff like that is a good idea, it's better go err towards passing arguments around.
14:13	ivey	Taking a look at clj-github now.
14:13	Bahman	pomyk: Checking...
14:14	Raynes	Calls are like (with-auth {:user "Username" :pass "password"} ...calls to various API stuff)
14:15	ivey	Raynes: but if you were doing a lot of calls, you'd do a (def authentication {...})
14:15	ivey	?
14:15	Raynes	I've never done that.
14:15	Raynes	But, I imagine yes, you could.
14:16	ivey	Interesting.
14:21	pomyk	ivey: why not make a "class" to hold the username/pass and provide api methods?
14:22	ivey	so you get an object that knows how to auth, and has all the calls on it?
14:23	Raynes	ivey: If you're thinking about what I think you're thinking about, that wouldn't work. You'd have to use binding.
14:24	Raynes	Doing (def authentication ..) from a client library shouldn't override the var in the library itself.
14:24	ivey	right
14:24	ivey	I have a conceptual map of this territory that's a mashup of Ruby and elisp.
14:25	ivey	I think I'll try it with a (with-creds) macro and see how that feels
14:32	Bahman	Is there a simple way to use REPL when working Compojure and Lein?
14:33	KirinDave	?
14:33	KirinDave	Bahman: What problem are you running into?
14:35	Bahman	KirinDave: Nothing. I just don't have any idea how/where to start. New to clojure.
14:35	KirinDave	Bahman: The answer is "yes, you just do."
14:35	KirinDave	Lein repl works.
14:35	Raynes	You can start a repl with 'lein repl'
14:36	Bahman	Nice. Any chance to use Emacs instead of command line repl?
14:36	KirinDave	yes
14:36	KirinDave	Works fine.
14:36	KirinDave	But!
14:37	Bahman	Just please give me a pointer and I figure it out.
14:37	Raynes	If you have SLIME set up, you can run a swank server with 'lein swank' and connect to it with M-x slime-connect
14:37	KirinDave	Please note that the launch directory for your java instance will be set to the file location of the curent buffer wehn you call slime.
14:37	LauJensen	KirinDave: Congrats on the book :)
14:37	Raynes	What he said.
14:38	KirinDave	LauJensen: Thanks!
14:38	Bahman	"lein swank
14:38	Bahman	That's not a task. Use "lein help" to list all tasks." I guess I'm missing something.
14:38	KirinDave	Bahman: Newer version required.
14:39	KirinDave	Bahman: I start swank-clojure-project from a dired buffer on the top of the file
14:39	KirinDave	Bahman: So that $ROOT/resources/templates will resolve
14:39	Bahman	KirinDave: Using 1.3.1 ... should I upgrade to 1.4?
14:40	KirinDave	Enlive's template generator, when I last tried it, was less than helpful on errors, especially FileNotFound.
14:40	Bahman	That's too advanced for me now :-) .but will keep it in mind.
14:40	Raynes	Bahman: Add swank-clojure "1.2.1" to your dev-dependencies in project.clj
14:40	Raynes	I forgot to mention that.
14:40	KirinDave	I don't actually know how to use lein with slime-connect
14:41	Raynes	swank-clojure has the lein plugin in it now.
14:41	Raynes	So, that'll do the trick.
14:42	KirinDave	Which version has that, is it in the packages, Raynes?
14:42	danlarkin	yes, put swank-clojure as a dev-dependency in your project descriptor and then lein deps, and then you can lein swank
14:42	Raynes	KirinDave: The jar, I mean.
14:42	Raynes	swank-clojure is on clojars. You just have to add it as a dev dependency.
14:42	KirinDave	Ah
14:43	Raynes	You don't need any Emacs-side swank stuff anymore. Just slime.
14:44	KirinDave	Ah
14:44	KirinDave	Death to swank-clojure-project then
14:44	KirinDave	bane of my existence.
14:44	anonymouse89	I'm confused by: "No matching ctor found for foo"
14:44	KirinDave	anonymouse89: So are we, without context. :)
14:44	danlarkin	there's a lein-swank elsip function floating around out there, maybe technomancy can point you to its canonical location
14:45	anonymouse89	where foo is a fn passed as an arg to another function
14:46	anonymouse89	I guess my question would be, is there any documentation that I'm missing that would help with this error? Or for those who have seen this is it more on the specific or general side of things?
14:46	KirinDave	anonymouse89: Could you make a gist of the context, please?
14:46	KirinDave	anonymouse89: gist.github.com has a clojure highlighting mode that is good. :)
14:47	anonymouse89	it's a little obscure, but sure
14:48	KirinDave	LauJensen: I'm looking forward to getting to writing, I just hope I've got the chops to write a whole book.
14:48	LauJensen	KirinDave: Im sure you do, but if not you're in good company I see :)
14:49	KirinDave	LauJensen: The other tough sell is that we want to talk to rubyists and pythonistas.
14:49	KirinDave	LauJensen: And maybe even JS people, in addition to the straightlaced java developer.
14:49	LauJensen	Yea I cant really help you with that, they've never liked my blogposts :)
14:52	Bahman	KirinDave and Raynes: Thanks for the assisst.
14:52	KirinDave	LauJensen: One thing we're not doing
14:52	LauJensen	Whats that?
14:52	KirinDave	LauJensen: is doing a chapter on macros. No macro chapter.
14:52	LauJensen	hehe - Why not?
14:52	Raynes	Anytime.
14:52	KirinDave	We're only going to mention them in context.
14:53	LauJensen	Good call
14:53	Raynes	Clever.
14:53	KirinDave	LauJensen: Well, because it's one of those things that most people won't understand. Syntax-oriented programming is a very alien concept.
14:53	anonymouse89	KirinDave: here's a pared down version: http://gist.github.com/576320 ... I completely understand if this is too involved of a problem (AKA my ignorance is too great :))
14:53	LauJensen	One guy at Conj Labs Brussels was horribly disappointed with macros and especially their frailty and uglyness, so I told him, that Macros were mostly important in discussions with other languages. Like if you're talking to some Scala guy you can always say "Have you got macros? because if not.." :)
14:54	LauJensen	(it was a joke, and funny at the time)
14:54	KirinDave	anonymouse89: Um, so
14:54	KirinDave	anonymouse89: Where is the error occuring?
14:55	anonymouse89	from what I can tell, it occurs when map-qubit-combinations is nested with itself
14:55	KirinDave	LauJensen: I'm researching to try and write an MBE lib. I think most complaints about macros are addressed by plt scheme's macro system
14:55	KirinDave	Which isn't always enough, but for most syntax it's WAY faster and less error prone to use MBE and a syntax transformer that has real eror handling, etc.
14:56	anonymouse89	basically, map-qu-combos applies a function a bunch of times, but if that function also calls map-qu-op then there is the ctor problem
14:56	LauJensen	KirinDave: Sounds incredibly interesting, got a mock of it somewhere?
14:56	KirinDave	anonymouse89: Can you reproduce your problem with fewer than 138 lines of code?
14:56	KirinDave	LauJensen: You can look at the racket documentation if you wanna see how it looks
14:57	KirinDave	I haven't started coding yet. It's a pretty involved project.
14:57	KirinDave	LauJensen: Racket's guide is an excellent intro: http://docs.racket-lang.org/guide/pattern-macros.html
14:58	LauJensen	Great, thanks
14:58	KirinDave	LauJensen: The classic example of a "rotate" macro: http://gist.github.com/raw/576326/b85a4eaa1b47e4f7459eb05dc2fc13df8444f83d/ex.plt
14:58	KirinDave	LauJensen: But the ... expansions can get pretty tricky.
14:59	LauJensen	hehe
15:00	KirinDave	I am trying to go to the conj
15:00	KirinDave	but fuck flying to NC is a pain in the ass.
15:00	KirinDave	Expensive and painful.
15:01	LauJensen	yea, fly to Frankfurt instead
15:01	Raynes	Chas is making my airline reservations. :>
15:01	KirinDave	At least that'd be _easy_.
15:01	KirinDave	Lol
15:01	Raynes	No complication for me. :D
15:01	KirinDave	I should ask him to do that for me.
15:01	KirinDave	Because Delta is refusing my credit card. :\
15:01	KirinDave	And I am not the kind of guy with multiple cards to try.
15:09	KirinDave	anonymouse89: Here is a hint, btw
15:09	KirinDave	anonymouse89: You do not need eval. You never need eval. If you think you need eval, it's a sure sign that you don't.
15:10	LauJensen	Yea, thats the give-away sign :)
15:11	anonymouse89	KirinDave: do you see what I'm trying to do in those lines?
15:11	anonymouse89	KirinDave: I'd like something like (-> foo (fn-a 0) (fn-b) (fn-a 1) (fn-b) ...)
15:11	KirinDave	Yes, you're trying to make -> statements.
15:13	KirinDave	I'd recommend NOT doing it that way
15:13	KirinDave	What I'd do is use reduce.
15:14	KirinDave	anonymouse89: -> is just a fancy syntax for reduce. You don't need to use that error-prone eval method if you use reduce. Build a list of the functions you need, in order, then use reduce to perform your transform.
15:14	KirinDave	anonymouse89: -> is for syntactic convenience, only.
15:15	KirinDave	It will make debugging easier, too
15:16	anonymouse89	KirinDave: ok, that makes sense.
15:23	KirinDave	Twinql?
15:25	LauJensen	(find-twins :named "Jack")
15:25	LauJensen	returns all twins on facebook as a sql statement
15:25	KirinDave	dang
15:26	LauJensen	yea, powerful technology
15:26	LauJensen	Naah Im just kidding, dont know what that is :)
15:34	_ulises	evening
16:05	anonymouse89	((a) (b) (c)) into (a) (b) (c) ?
16:06	LauJensen	anonymouse89: one form which expands into 3 forms?
16:07	anonymouse89	LauJensen: yes, I guess more precisely, using (for [i (range 3)] i) gives (1 2 3) where I would like 1 2 3
16:08	anonymouse89	*0 1 2
16:08	LauJensen	All Clojure forms return the result of evaluating the final element. I don't know of anyway of returning multiple values that are all atoms
16:09	wwmorgan	anonymouse89: are you doing this in a macro? If so, you can use macro unsplice ~@
16:10	anonymouse89	wwmorgan: no. but thanks for the hint
16:10	LauJensen	wwmorgan: still, it cant be a return, only the argument to something else
16:10	LauJensen	(within the macro)
16:10	anonymouse89	LauJensen: right, that's my situation
16:10	anonymouse89	I think I might just use a macro
16:11	LauJensen	either a macro, or apply. Prefer apply
16:11	wwmorgan	anonymouse89: What is your use case? I can't think of one
16:12	anonymouse89	I want to assoc specific indices of a vector with 1 or 0 depending on a condition
16:13	LauJensen	,(map #(if (even? %) 1 0) [1 2 3 4 5 6])
16:13	clojurebot	(0 1 0 1 0 1)
16:13	anonymouse89	like (assoc index myvector (if (cond index) 1 0)) for indices in (1 3 7 9)
16:13	LauJensen	You could probably work that seq in a more functional style, like the map above
16:14	anonymouse89	LauJensen: that seems like exactly what I should be doing
16:15	LauJensen	anonymouse89: great. If you're coming from an imperative language. I suggest trying to ask your questions more broadly, because odds are you can pick up a few hints about functional design
16:16	anonymouse89	LauJensen: how did you guess? :p I'll try. Also, I think I need to do a lot more general reading on writing functionally
16:17	LauJensen	Either that, or attend conj-labs.eu :)
16:19	anonymouse89	LauJensen: sounds great but ... I'm a student :(
16:19	LauJensen	Well students are welcome as well. I wonder if we should make a special student discount.
16:20	morphling	hi guys, is there a common interface that all integer classes share?
16:20	morphling	like Number, but ratios also implement/extend that
16:22	morphling	by "all integer classes" I mean Integer, Long and BigInteger
16:24	wwmorgan	,(->> (ancestors (class 1)) (clojure.set/union (ancestors (class (bigint 1)))) (clojure.set/difference (ancestors (class (/ 5 2)))))
16:24	clojurebot	#{}
16:24	Bahman	morphling: java.lang.Number
16:25	LauJensen	wwmorgan: that was cool :)
16:25	wwmorgan	morphling: it looks like there are not. You could compute the information by doing (zero? (mod n 1)), I think
16:26	morphling	wwmorgan: thanks :)
16:27	morphling	I want to dispatch on type with multi methods, and I essentially have the same code for Integer, Long and BigInt
16:28	LauJensen	morphling: use meta data?
16:28	morphling	I'll probably just put the actual code in an external function and call that three times, or do everything in the bigint case
16:28	tomoj	,(map integer? [(int 1) (long 1) (bigint 1)])
16:28	clojurebot	(true true true)
16:29	KirinDave	anonymouse89: Sorry man, but sadly clojure doesn't support multiple return values like common lisp's.
16:29	KirinDave	anonymouse89: The best way to do it is to assume 0->inf number of elements on all return values OR an error.
16:29	KirinDave	anonymouse89: error-kit should help you handle the error case more rigorously.
16:29	morphling	LauJensen: how can i use meta data for that?
16:29	LauJensen	morphling: multi-methods can dispatch on anything
16:30	LauJensen	So as long as your data supports its. If you want the pure numbers being passed, then you cant
16:30	KirinDave	LauJensen: The burden of history. :)
16:30	LauJensen	?
16:31	KirinDave	LauJensen: No meta on numbers.
16:31	KirinDave	An implementation detail :(
16:31	LauJensen	yea well... :)
16:31	wwmorgan	morphling: do you need to dispatch on type? If not, then you would just change your dispatch method from type to integer?, or something like that
16:31	morphling	LauJensen: I thought about using a more complicated dispatch function and dispatch on keywords, like :integer for those three, but I don't think it's worth it
16:32	morphling	wwmorgan: see above :)
16:32	morphling	thanks guys!
16:34	anonymouse89	LauJensen, KirinDave: ah, i think the big thing I was missing was map can take multiple collections, thanks again for your help and patience
16:34	KirinDave	anonymouse89: Don't worry, it's complex for everyone
16:34	LauJensen	thats what we're here for :)
16:55	Bahman	wwmorgan: What does ->> do in the statement above?
16:58	wwmorgan	bahman: ->> is thread-last. (->> a (b c) (d e)) becomes (d e (b c a)). Along with -> (thread-second), it's useful for showing the flow of data and avoiding deep nesting of s expressions
16:59	LauJensen	,(-> 5 (/ 10))
16:59	clojurebot	1/2
16:59	LauJensen	,(->> 5 (/ 10))
16:59	clojurebot	2
17:00	Bahman	Thanks wwmorgan and LauJensen.
17:01	LauJensen	np
17:01	wwmorgan	LauJensen: that's a great comparison
17:01	Bahman	By "deep nesting" you mean using "let" forms?
17:01	LauJensen	wwmorgan: yea I think its a lot easier to follow than a b c d examples
17:01	LauJensen	(no offense whatsoever)
17:02	wwmorgan	none taken :-p
17:03	Bahman	Right...now the above mystical statement is clear to me :-)
17:03	Bahman	I was wondering if it was sort of Assembley language :-)
17:04	Bahman	One last question: What is an "s" expression?
17:04	LauJensen	technically, everything in (println "hi" "there") is an s-exps which contains 3 s-exps, unless I misunderstood completely :)
17:06	Bahman	LauJensen: So every form in Clojure is an S expression?
17:06	LauJensen	yea
17:06	LauJensen	S expressions could be labeled, intelligent XML I guess
17:07	Bahman	Got that. Thanks.
17:11	LauJensen	Im off now - Those looking to secure a seat at Conj Labs Frankfurt with the EB discount, book tomorrow morning :) http://conj-labs.eu
17:14	ivey	If I have an XML doc in a string, how can I turn it into a structmap? xml/parse wants a file.
17:17	ivey	nevermind, I got it.
17:45	anonymouse89	is there any way to have a binding without already having that var root-bound?
17:46	wwmorgan	,(doc with-local-vars) ; <- anonymouse89
17:46	clojurebot	"([name-vals-vec & body]); varbinding=> symbol init-expr Executes the exprs in a context in which the symbols are bound to vars with per-thread bindings to the init-exprs. The symbols refer to the var objects themselves, and must be accessed with var-get and var-set"
17:47	anonymouse89	wwmorgan: thanks
17:47	wwmorgan	anonymouse89: actually, it doesn't appear to do what you want
17:47	wwmorgan	,(with-local-vars [a 1] (binding [a 3] @a))
17:47	clojurebot	java.lang.Exception: Unable to resolve var: a in this context
17:48	anonymouse89	I've never seen this before:
17:48	anonymouse89	,(with-local-vars [a 1] (println a))
17:48	clojurebot	#<Var: --unnamed-->
17:49	dakrone	,(with-local-vars [a 1] (println (var-get a)))
17:49	clojurebot	1
17:49	anonymouse89	dakrone: is that any different than deref-ing?
17:50	wwmorgan	,(with-local-vars [a 1] (println @a)) ; This works too. @ is a reader macro for getting the content of a reference type
17:50	clojurebot	1
17:50	dakrone	anonymouse89: using @ is better
17:50	anonymouse89	dakrone: right, I meant var-get vs. @
17:52	wwmorgan	anonymouse89: looking at the macroexpansion of binding suggests that, if you want to use binding, the vars need to root-bound
17:53	anonymouse89	hmm, it seems like I can't set! vars bound with with-local-vars
17:54	wwmorgan	anonymouse89: set! is for java interop. You want var-set
17:56	anonymouse89	i'm really failing today :( .. but now I know, thanks
18:23	amalloy	i used destructuring to peel apart a complex nested-map structure that one of my functions is receiving, and now it looks way harder for me to read than the naive (fn [obj] (let [thing1 (:child obj)...])) form
18:24	amalloy	is this usual, or something i'll get used to like all the parens, or a way i should be formatting it more legibly?
18:25	rhudson	What does your destructuring look like?
18:25	amalloy	(defn minimax
18:25	amalloy	[{{{{p :to-play} :state} :posn
18:25	amalloy	:as posn} :posn
18:25	amalloy	:as consq}]
18:26	rhudson	Seems like it would be better to unnest it
18:26	amalloy	by which you mean...?
18:28	rhudson	Something like your suggestion above. Like have one level of destructuring in your arg list, then 'let bindings to destructure successive levels.
18:28	rhudson	Destructuring is in the lang (I think) partly to make the code more readable, not less
18:29	rhudson	Generally if you have trouble reading your own code, that's a bad smell
18:29	amalloy	chuckle
19:18	Bahman	Couldn't sleep. NetBeans+Enclojure is really nice...maven-based build and nice repl.
19:18	Bahman	Only if I could make its auto-completion work for project libs. Currently only works for Clojure and Clojure contrib.
19:22	rps_	If I have a vector of articles, how would I print the :title of each article?
19:27	cinim0d	rps_: Hint: map, :title, articles
19:28	rps_	cinim0d: thanks
20:28	sproust	Leiningen question: when I start my VM with "lein swank", I can then connect with slime-connect, but the "lein swank" target does not eval the code of my project. Is there a way to tell leiningen to evaluate some module and then start a swank server, so I don't have to do that every time I reconnect?
20:40	amalloy	i notice that (memoize fib) is no faster than (fib) the first time you call it, because fib does all its recursion internally where memoize can't intercept it. is there a macro somewhere like defmemo that rewrites the function definition to recur through the cache?
20:43	wtetzner	the problem is that (defn fib [n] ...) expands to something like (def fib (fn fib [n] ...))
20:44	wtetzner	so the recursive call doesn't reference the var
20:44	amalloy	wtetzner: sure, i understand why it doesn't work
20:44	wtetzner	there is defn-memo in contrib, but it doesn't solve the problem
20:45	wtetzner	you have to do (def fib (memoize (fn [n] ...)))
20:46	amalloy	you sure defn-memo doesn't solve the problem? it looks like it might, from the source
20:46	Bahman	Does (defn -main [&args] ...) mean that I have to pass some args to -main?
20:47	Bahman	I thought & means args is optional.
20:47	dakrone	Bahman: args is optional
20:47	Bahman	dakrone: #<CompilerException java.lang.IllegalArgumentException: Wrong number of args (0) passed to: core$-main (NO_SOURCE_FILE:3)>
20:48	Bahman	That's what I get when I call it like (guestbook.core/-main)
20:48	_ato	Bahman: you need a space between & and args
20:48	wtetzner	amalloy: defn-memo just calls defn and then alters the root var
20:48	dakrone	yea, should be [& args]
20:48	Bahman	Doh!
20:48	wtetzner	amalloy: so you still have the (fn fib [] ...) problem
20:48	Bahman	Thanks.
20:49	amalloy	hm. okay, i think i see
20:49	wtetzner	defn-memo really should have been implemented to expand to (def fib (fn [] ...)) without the name in the call to fn
20:50	_mst	if you want to force the recursive call back through the memoized version, you might want to do the recursive call with: (#'fib ...)
20:51	_ato	or just forget the macro and write your function using (def fib (memoize (fn [n] ...))) :-)
20:51	Raynes	_ato!
20:51	Raynes	I haven't seen you in forever.
20:52	amalloy	it can't be that hard to write a macro that walks the tree and converts (recur) and (fib) calls and converts them back into calls to the memoized version
20:52	_ato	yep, or do that :)
20:53	wtetzner	tree-walking macros like that are always a bit tricky
20:53	wtetzner	it's easy to forget some case where the replacements you're doing won't work
20:54	wtetzner	for example, what if recur is referencing loop instead of the enclosing function?
20:54	wtetzner	you can account for it, but things like that are easy to forget
20:54	amalloy	bah! who uses loops? :)
20:55	wtetzner	also, if someone is using recur, chances are it's because they want tail recursion
21:04	Bahman	Is it possible to deploy Compojure apps in an ordinary application server (not embedded)?
21:08	chouser	Bahman: pretty sure, yeah.
21:10	Bahman	chouser: So I should use jetty adapter only for development right?
21:13	scottj	What's the easiest logging solution to use w/ c.c.logging, and how to run in debug mode? The default sucks bc all messages look like "Sep 12, 2010 8:59:01 PM clojure.contrib.logging$eval7120$impl_write_BANG___7123 invoke INFO: message"
21:13	chouser	well, that's up to you I guess
21:13	chouser	Bahman: if it'll do, I'd use it until it won't do anymore. :-)
21:13	Bahman	chouser: Got your point...thanks.
21:16	amalloy	scottj: passing it through perl or awk or something sounds easier than reconfiguring c.c.logging. perl -p -e 's/^.*invoke/;' < my_log_file
21:16	scottj	amalloy: well c.c.logging supports several logging backends, I'm just wondering which is easiest
21:17	scottj	there are like a million tutorials on monads for clojure but none on setting up another backend for logging :)
21:23	dakrone	how do I type something like "^M" in Emacs?
21:23	Raynes	dakrone: C-q-C-character
21:23	dakrone	Raynes: thanks
21:24	Raynes	dakrone: I discovered that by accident about three hours ago.
21:25	scottj	C-q is very common in emacs, you'll use it in paredit too if you ever get unmatched parens
21:25	Raynes	scottj: That's how I discovered it.
21:26	scottj	Raynes: you were right, there's somnium.congomongo.coerce/keywordize but it kinda stinks
21:26	Raynes	I knew there was something. I couldn't find it though.
21:26	Raynes	I was looking in the wrong namespace.
21:27	scottj	it stops string keys from becoming keywords, but it also means you can't use keywords for keys
21:49	sproust	Wouldn't it make sense to throw an error when a struct-map is accessed with an invalid key?
21:49	sproust	Quite often the default behaviour of returning nil for a key not found hides errors in accessing the s/m's "members".
21:50	sproust	Makes typo errors harder to find.
21:50	sproust	I suppose I could just create my own failing-getter, but isn't that a really common use case?
21:52	Raynes	It'd be inconsistent, at the very least. Maps return nil if a key isn't found in them. The general idea is that, if you need something other than nil to mean "key not found" you can use get.
21:54	scottj	you don't even need get on either, (:foo {} (Exception. "key not found")) or ({} :foo ...)
21:57	sproust	scottj: that's nice, but it doesn't raise the exception.
21:57	sproust	Adding (raise) won't help either, it evals the not-found form before it checks, it seems.
21:57	chouser	people have written safe-get and I think even a safe-map
21:58	sproust	,(:foo {:foo 42} (throw (Exception. "Not found.")))
21:58	clojurebot	java.lang.Exception: Not found.
21:58	sproust	chouser: Funny I was going to call it just that. Should be core IMHO, so common.
21:59	sproust	Oh wait, it's in map-utils
21:59	sproust	Never mind, thx.
21:59	Raynes	Orly
21:59	Raynes	-> (:foo {} "not found"}
21:59	sexpbot	java.lang.Exception: Unmatched delimiter: }
21:59	Raynes	-> (:foo {} "not found")
21:59	sexpbot	=> "not found"
21:59	Raynes	When did that happen!!!
22:00	sproust	Raynes: not good enough for my use case; it just returns the value, that'll sweep th eproblem under the rug too many times.
22:00	sproust	Hmmm, also surprising we don't have PG's aif in core.
22:00	chouser	sproust: rhicky doesn't like anaphora
22:01	chouser	has called them "evil", I believe
22:01	sproust	Oh. He'd really hate Hoyte's entire book then.
22:01	Raynes	You could always write a safe-get like chouser alluded to.
22:01	sproust	Raynes: there's one in map-utils.
22:02	sproust	chouser: clojure.contrib.anaphoric?
22:02	Raynes	clojure.contrib.evil >:)
22:03	sproust	Hahaha
22:03	chouser	I don't like that they introduce new bindings without calling out their names
22:03	sproust	With great power comes great responsibility :-)
22:04	Raynes	I've been guilty of such acts before reading Joy.
22:04	chouser	introduce or change the value of.
22:05	chouser	sproust: we do have if-let and when-let
22:07	sproust	Haa, nice. That's cute. I didn't know if-let.
22:07	sproust	Lovely.
22:07	sproust	Clojure is full of surprises, really a wonderful language.
22:10	sproust	How do you switch between "edit expression" and "eval"? I have a bookmark and move my cursor to my "main" expression, then C-M-x, and then back to edit-modify-eval, and then repeat, but it's getting a bit annoying. I'm starting to think I should automate this a bit.
22:24	scottj	if anyone else was wondering how to use log4j w/ c.c.logging and set log level http://groups.google.com/group/clojure/msg/30738d8efc179ea3
22:31	laurus	Does anyone else find the Incanter graphics library horribly ugly?
22:31	chouser	the library or the graphics it produces?
22:31	laurus	chouser, sorry, the graphics it produces :)
22:32	scottj	I think the graphs look decent, definitely better than old excel or old incanter :)
22:32	laurus	I have a lot more experience in Python than Lisp, and I was considering using Clojure to try to do some data analysis, but those plots are a real turn-off for me, unfortunately...
22:32	laurus	Is there a way to swap graphics libraries or something?
22:32	scottj	you're definitely not the first to complain
22:33	scottj	you can use the dark theme
22:33	chouser	are there not config settings to improve the look? I'm afraid I haven't used Incater at all.
22:34	laurus	chouser, there are themes, but they still look kind of unprofessional, to me at least
22:34	laurus	I can't understand why they picked that library, other than sheer convenience
22:38	rhudson	There's quite a bit you can do with the underlying JFreeChart to change appearance
22:40	laurus	rhudson, really, okay!
22:41	laurus	That's good to know...
22:41	laurus	Perhaps I just need to poke around?
22:44	scottj	wonder why there's no ChartTheme repo for jfreechart
22:45	laurus	I'm new to Clojure, the only Lisp I've really used much is XLisp, where I could run (^ 2 3) and get 8. How do I do exponents in Clojure?
22:46	scottj	,(Math/pow 2 3)
22:46	clojurebot	8.0
22:46	scottj	lame, I know
22:46	laurus	scottj, haha, honestly that is kind of lame, but whatever :)
22:46	Zhivago	So, define a function name that you prefer ...
22:47	laurus	Zhivago, will do :P
22:47	laurus	Or I'll just get used to it, probably the better way.
22:53	laurus	Is _Practical Clojure_ a good introduction to the language?
22:53	scottj	Zhivago: then you have differnt names for a basic function in different people's code or stupid import statements for a basic function that should have been in core.
22:55	chouser	hm. what import statement?
22:56	scottj	say you didn't want to define pow all the time, (:use 'basic-math)
22:56	scottj	(sorry if import instead of use was the confusing part)
22:57	scottj	s/basic-math/clojure.contrib.math
22:59	chouser	oh, I see. yep.
22:59	laurus	scottj, I wonder why it's not in the core
22:59	chouser	laurus: I don't know, but here's a guess... clojure is pretty minimal and doesn't include much that doesn't add real value.
23:00	laurus	Heh
23:00	chouser	the other math functions are included because they work seamlessly across number types in a way that java interop methods don't.
23:00	laurus	chouser, that's interesting.
23:02	rhudson	As it is, core defines over 500 symbols -- not everything that everyone wants can go into core
23:03	laurus	rhudson, it's cool
23:03	chouser	I suppose one could make an exponent function that returned whole nubmers for whole inputs. But would people actually use it? I dunno...
23:03	rhudson	I use string join or split a hundred times for every time I need an exponent
23:03	laurus	I think I better read some more about Clojure before messing around any more
23:03	rhudson	Apparently that's what clojure.contrib.math/expt does
23:03	laurus	I just wanted to try entering a couple XLisp functions to see what happened :P
23:04	scottj	rhudson: but how many times have you defined a function named expt that wasn't an exponent function? :)
23:04	rhudson	I've never named a function 'expt :)
23:04	chouser	heh, yeah, clojuse is not scheme. there are a lot of differences considering they're both lists.
23:06	laurus	I find it somewhat hilarious that I've seen mentioned on at least three blogs how Clojure is supposedly difficult to get working. It took me about 3 minutes to find the download, download it, unzip the jar, and run it.
23:06	laurus	One blogger bragged about how it only took him 20 minutes to get the thing started as I recall, and others claimed to have given up in frustration.
23:07	rhudson	laurus, I think "Programming Clojure" is a great introduction to Clojure, despite it describing 1.0. Some folks here have said that "Practical Clojure" is a good intro, and describes 1.2. "Joy of Clojure" is an outstanding second book on Clojure
23:08	laurus	rhudson, thanks for your opinion. I'll go for one of those two then.
23:08	laurus	:)
23:08	rhudson	Laurus, it seems a lot of folks coming from the Lisp side of things find the Java world arcane
23:08	rhudson	(and vice versa)
23:08	laurus	Ahh... I've actually programmed more Java than Lisp
23:09	scottj	I really like programming clojure. and I think joy is good in theory, but I'd highly reccommend waiting till it's been edited
23:10	rhudson	That's soon now, right chouser?
23:10	rhudson	The most recent MEAP is really quite good -- a few typos here and there
23:11	phobbs	when is it scheduled to be printed?
23:11	phobbs	I find it so much harder to read ebooks
23:11	rhudson	That's why I want to get an iPad!
23:12	laurus	phobbs, I prefer paper books too...
23:12	scottj	rhudson: w/ "retina display"!
23:13	rhudson	Scottj: amen! I just got a 4G iPod touch, and the display just blows me away
23:13	rhudson	My MacBook looks grainy after that
23:13	sproust	laurus: if you're just running the main clojure jar and typing commands at the repl it's pretty straightforward. Slightly more complicated (but not much) issues come about when you need external jars if you're not familiar with Java, and it used to be a bit broken for a little while when clojure's swank support was in flux. That's probably why some people bitched about setup.
23:14	chouser	the MEAP update for "joy" that came out a couple weeks ago has tons of typo/spelling/grammar corrections from the original chapter MEAPs
23:14	laurus	sproust, right, that makes sense... jars are a pain.
23:14	laurus	Without ant, or something
23:14	rhudson	laurus, phobbs -- I go for paper too when there's a choice -- but there's too much early access stuff I can't wait to get my hands on
23:15	chouser	I don't think there will be another update until it's ready to be printed, but I haven't heard anything about the schedule of that. All I know is Amazon says December for shipping paper copies.
23:15	rhudson	The Manning site says November (est.)
23:15	sproust	My limited experience with Java Jars is fairly positive; once you provide your list of jars to the vm it pretty much always works. Problem is, startup time is just... very... slow.
23:15	chouser	that's good. Amazon used to and changed it. I hope it's Nov not Dec.
23:16	scottj	the last meap update sounded like there wouldn't be any more till release
23:16	rhudson	me too. You guys did an amazing job with that book
23:16	laurus	sproust, right, I guess it depends how one loads the app. My experience in Java was with web applications on Tomcat, and ant helped a lot there.
23:17	chouser	rhudson: thank you very much. fogus deserves the bulk of the credit, really. it was his project from the beginning and I was pleased to be included.
23:18	chouser	I glad it's done
23:18	chouser	turns out I prefer writing code to prose. shocker.
23:18	rhudson	:)
23:19	laurus	So what's with this whole Clojure on Clojure thing?
23:20	laurus	Er, sorry, Clojure in Clojure.
23:20	scottj	laurus: a goal, unless rhickey has been coding on it in private, there's nothing there but features have been added to clojure to make it easier to accomplish
23:20	laurus	scottj, but what is the purpose of that goal? To make it more independent of the JVM or the Java language?
23:21	rhudson	laurus, a lot of the Clojure runtime, including the persistent collections, are currently in Java.
23:21	rhudson	laurus, I think partly Rich Hickey wants to be writing in Clojure not Java :)
23:22	scottj	I always thought it was funny how fogus and chouser would tweet back and forth about each other and their book. fogus: @chouser's book is brilliant!. chouser: mark twain's got nothing on @fogus!
23:22	laurus	But it would still run on the JVM?
23:22	scottj	oh, I forgot the discount coupon links
23:22	chouser	there are places that the JVM (as it is and will be in the foreseeable future) doesn't fit well. I want to be able to use Clojure in those places anyway.
23:23	scottj	laurus: yeah, it makes porting clojure to .net and javascript etc much easier because clojure datastructures etc are written in clojure
23:23	chouser	such as: iOS, javascript, unix command-line, etc.
23:23	laurus	scottj, oh, got it. So it doesn't affect the end users that much, it's more for the developers of the core language.
23:23	laurus	And for portability.
23:23	chouser	laurus: right.
23:23	laurus	Sounds great! :)
23:23	laurus	I think it would be great to not have to run it on the JVM, actually
23:23	chouser	Users of Clojure on JVM should see either no difference, or boosts in features and performance.
23:23	laurus	Don't ask me why I think that, it's just a feeling
23:36	laurus	Is there a way to log a Clojure REPL session to a file?
23:48	sproust	laurus: do you mean to dump the image, or just the text?
23:49	sproust	e.g. like (sb-ext:save-lisp-and-die)
23:49	sproust	Actually I've wondered about this too: is there a way to dump the runtime and somehow restart it later, like you would with some CL's?
23:50	KirinDave	sproust: The JVM isn't image based
23:52	sproust	,(boolean (list))
23:53	clojurebot	true
23:53	sproust	I get bitten by this all the time.
23:53	sproust	KirinDave: I was wondering if the runtime LISP structures couldn't be dumped and then have a new process pick them up later.
23:54	wwmorgan	,(boolean (seq (list)))
23:54	clojurebot	false
23:54	sproust	I find the dual role of that seq function inelegant. On the one hand it returns a seq on the collection, on the other hand it's needed to check if the collection is empty.
23:54	sproust	wwmorgan: thx
23:55	sproust	I don't know how many times I've tripped up over this; a lot. I'm just too used to cons cells.
23:56	sproust	I should just get used to using empty?
23:56	sproust	,empty?
23:56	clojurebot	#<core$empty_QMARK_ clojure.core$empty_QMARK_@15c7277>
23:56	sproust	,(doc empty?)
23:56	clojurebot	"([coll]); Returns true if coll has no items - same as (not (seq coll)). Please use the idiom (seq x) rather than (not (empty? x))"
23:56	sproust	Hmmm, it says I shouldnt...
23:57	wwmorgan	sproust: the only reason that it works is that nil is logical false
23:57	wwmorgan	,(if nil 1 2)
23:57	clojurebot	2
23:57	sproust	So (seq x) is the recommended idiom. But it doesn't look like a predicate.
23:57	sproust	wwmorgan: _that's_ the only bit that makes sense to me.
23:58	wwmorgan	,(if (filter even? [1 3]) 0 1) ; sproust: don't let this trip you up either
23:58	clojurebot	0
23:58	sproust	,(filter even? [1, 3])
23:58	clojurebot	()
23:59	sproust	Right, empty list is true.
23:59	wwmorgan	sproust: not the behavior I was trying to highlight, actually. Not my best example