#clojure – 2011-07-02

2011-07-02

01:11	hiredman	amalloy: `(quote ~x)
01:21	amalloy	hiredman: good point. the compromise is more readable than either extreme
02:00	replaca	technomancy: are you hanging around late on a friday night?
03:09	replaca	are re-split and re-partition gone in the new contrib layout?
03:09	replaca	I could really use a function index of this new stuff
03:09	replaca	oh wait, I'm writing that code now... :)
05:27	fliebel	I remember seeing some talk about simplicity by someone of clojure/core. Anyone knows what that was?
05:32	terom	Perhaps this one? http://blip.tv/clojure/stuart-halloway-simplicity-ain-t-easy-4842694
05:33	fliebel	terom: Probably, I only remember it being long.
05:35	fliebel	terom: No, it wasn't that.
06:12	stamp	hi
06:12	stamp	what framework do you recomend for simple blog?
06:13	stamp	I now little of clojure and didn't play with any frameworks
06:14	fliebel	stamp: Why do you want a framework for a blog?
06:18	stamp	simplest project to learn
06:19	fliebel	stamp: What I mean is, what do you want to get out of it? Get a blog? Use Wordpress or Jekyll. Learn X? use Y.
06:19	stamp	learn clojure and make blog with more than one contributor
06:27	fliebel	stamp: I'd go for the module bits on top of ring. I have the feeling that using things like Sandbar and Compojure teach you Clojure like Rails does ;)
06:27	fliebel	*modular
06:32	stamp	fliebel: so i should build my own microframework on top of ring?
06:34	fliebel	stamp: Well, I'd say you have different options. If you write directly on top of Ring, you'll probably learn more clojure than using the RoR of Clojure. If you want to get going quickly with a simple CRUD app, Sandbar is probably faster.
06:35	stamp	ok, i'll check both options
06:36	fliebel	stamp: Another nice options is writing a static site generator, and use git for the multiple author aspect.
07:26	Dranik	I'm trying to insert an entity to DB using SQL. How to get the id of the inserted entity?
09:00	schasi	Can I see the stepwise execution of something like reduce?
09:04	fliebel	schasi: reductions does that
09:04	fliebel	&(reductions + [1 2 3 4 5])
09:04	sexpbot	⟹ (1 3 6 10 15)
09:09	schasi	fliebel: I meant one step in the execution of reduce :) like (reduce + [1 2 4]) -> (reduce + (+ 1 2) [3]). Or something. Don't really get the sourcecode of reduce :D
09:10	fliebel	$source reduce
09:10	sexpbot	reduce is http://is.gd/SRobxr
09:11	schasi	With "don't get" i meant "don't understand on reading". But I might just have gotten it. But thank you :)
09:12	fliebel	schasi: You could copy the code and replace calls to reduce/recur with println to see one step of the execution.
09:14	schasi	Thanks
09:26	mneedham	Hey all - beginner question for ya. I'm trying to use one of the functions listed on clojure.java.io - http://richhickey.github.com/clojure/clojure.java.io-api.html#clojure.java.io/output-stream - but I'm not sure how to do that. I have the REPL running with 1.3.0 but when I try to require the namespace I end up with an error
09:26	mneedham	user=> (:require clojure.java.io)
09:26	mneedham	CompilerException java.lang.RuntimeException: java.lang.ClassNotFoundException: clojure.java.io, compiling:(NO_SOURCE_PATH:1)
09:27	mneedham	any ideas?
09:42	fliebel	mneedham: If you use a standalone require, don;t use the keyword ;)
09:42	fliebel	&[:require require]
09:42	sexpbot	⟹ [:require #<core$require clojure.core$require@10dbc37>]
09:43	mneedham	not sure I understand, sorry. What should I be doing instead?
09:44	Chousuke	mneedham: :require is part of ns's syntax, "require" is what you want
09:44	Chousuke	(doc require)
09:44	clojurebot	"([& args]); Loads libs, skipping any that are already loaded. Each argument is either a libspec that identifies a lib, a prefix list that identifies multiple libs whose names share a common prefix, or a flag that modifies how all the identified libs are loaded. Use :require in the ns macro in preference to calling this directly. Libs A 'lib' is a named set of resources in classpath whose contents define a library of Cloju
09:46	mneedham	ok. So should I expect (require clojure.java.io) to be ok if I'm just running a 1.3.0 based repl?
09:47	Chousuke	mneedham: you might need to quote the symbol, I don't remember whether require is a macro or a function.
09:50	mneedham	ahhh cool - thanks for your help
09:50	mneedham	I was trying to understand what's happened with clojure contrib - I last played with clojure about 18 months ago
09:50	mneedham	has some of the contrib stuff been pushed into the main libraries?
10:11	pcavs	why is this room so empty? Usually at least 100+ people in here...
11:06	mneedham	is there anyway from the repl to see which methods are available to call on an object? google hath failed me so far
11:13	ahritaur	hello, is there any way to print something to web-page? I have clojure+compojure+hiccup and i want something like (dotimes [i 4] (printToWebPage someDynamicContent)
11:55	mudge	hello
11:56	mudge	I want to convert clojure source code files into java source code automatically, any recommendations on how to do that? if it is even possible?
11:56	pcavs	You could do something really awful like compile clojure, then use a decompiler to decompile it into ugly java...
11:57	pcavs	mudge: but I don't think that would be a good idea. What's the use case here?
11:57	mudge	pcavs: yes, i was thinking of trying to use a decompiler
11:58	mudge	pcavs: to be honest, my boss will absolutely not except any programming language except Java but I want to write in Clojure, so I thought if there was a way to generate exceptable Java from clojure source ...
11:59	pcavs	mudge: ouch, doesn't sound good. I don't really see that working...You'd lose out on the entire purpose of Clojure I think.
11:59	mudge	pcavs: why?
11:59	mudge	pcavs: if i could just write clojure in the normal way and if it could be converted to Java source and it was good enough, what's the downside?
12:00	pcavs	mudge: because the decompiled java bytecode will be impossible to understand and extremely ugly java code. It would be unmaintainable as java code, so in order to change it you'd really be changing your clojure code and then compiling it and decompiling it again.
12:00	pcavs	So the decompiled java source code isn't really the source code
12:00	pcavs	it's some sort of fake intermediary
12:01	mudge	pcavs: i see, so perhaps it isn't really possible then
12:01	pcavs	at least that's my 2 cents
12:01	mudge	pcavs: have you played with a decompiler and seen its output?
12:02	mudge	it would be cool if Clojure had a function that converted clojure source to java source
12:02	pcavs	mudge: I have not, but I've decompiled straight java code before, and it's quite ugly from what I remember, but this was back in Java 1.3-4 days so maybe the decompilers have gotten ebtter.
12:02	clojurebot	hmm… sounds like your out of heap space
12:03	mudge	pcavs: okay, i'll check it
12:48	mudge	pcavs: i used a java decompiler, i think decompiling clojure bytecode into java source is too unreadable
12:48	pcavs	yeah, I kind of thought that would be the case
12:49	mudge	pcavs: I wonder if it is possible to write a clojure program that takes clojure source as input and outputs readable java code
12:50	mudge	pcavs: that sounds like an interesting project
12:50	mudge	the readable java source could depend on clojure libraries
13:13	roblally	What are people's thoughts on Matchure? It looks nice, but I'm nervous about building a dependency on it. With the imminent arrival of 1.3 and the lack of recent project activity....
13:34	fliebel	roblally: Dunno, I din;t like it very much, so I wrote this: http://pepijndevos.nl/clojure-micro-pattern-matcher/index.html
13:35	roblally	Interesting, fliebel, I'll take a look.
13:41	fliebel	Is there any sane way of implementing IFn? ... Without implementing all ±30 methods. I think dnolen had a huge macro for it somewhere.
13:42	fliebel	IMO, varargs is one point where Java interop fucked up.
13:46	cemerick	fliebel: extend AFn, and override the arities you want
13:46	fliebel	cemerick: I want varargs ;)
13:49	mids	what is the name again of that convenience wrapper around compojure / hiccup? it sounded like webiv
13:50	gfrlog	what do you get by wrapping compojure and hiccup?
13:51	mids	I could tell you if I remembered the name/site :)
13:52	gfrlog	well you must know what it does if you know that you want to use it :P
13:52	cemerick	fliebel: then extend RestFn :-)
13:52	fliebel	cemerick: RestFN? awesome, going to look it up :)
13:53	cemerick	fliebel: https://gist.github.com/1061456
13:53	mids	gfrlog: iirc it wrapped a couple rest/compojure/hiccup/sandbar things in a single dsl
13:54	gfrlog	ah ha
13:55	fliebel	whoa. that is a lot of java code...
13:58	fliebel	$mail dnolen cemerick showed me RestFn, which could solve your IFn implementation problem as well, I think.
13:58	sexpbot	Message saved.
13:58	cemerick	fliebel: exactly; best to make use of it if it solves the problem.
13:59	cemerick	It being a concrete base class is likely a difficulty in certain circumstances, tho.
13:59	fliebel	cemerick: yea, I guess. maybe dnolen just avoided it for performance reasons :D
14:00	cemerick	There is no penalty for calls to subclasses of concrete bases. The problem is e.g. you can't make a deftype a RestFn.
14:05	hiredman	cemerick: does it need to be? can't you just provide doInvoke from IFn?
14:07	cemerick	hiredman: doInvoke isn't anything special; it's the massive pile of boring args -> args + rest conversions in RestFn's invoke impls that you need
14:07	hiredman	roblally: matchure and a few other libraries I looked at struck me as digusting, so I also wrote my own too
14:07	cemerick	That could get macro'ed in easy enough, but that's a lot of class-size overhead in every single variadic fn for not a lot of benefit.
14:08	hiredman	cemerick: are you sure about that?
14:08	cemerick	(again, the concrete base class limitations still being relevant)
14:08	cemerick	what, the class-size overhead?
14:08	fliebel	hiredman: Where does yours live? Which other?
14:09	hiredman	https://github.com/hiredman/match
14:09	hiredman	fliebel: I forget exactly, I looked at two at least, and one of them was matchure
14:10	hiredman	hah
14:10	hiredman	and I have my own cond-let too
14:10	fliebel	hiredman: Hah, you use core.logic :)
14:11	hiredman	yeah, but it's not like I know how it works or anything
14:12	fliebel	hiredman: So how is yours different from Matchure? It too is 90% macro and has the silly a? syntax.
14:13	hiredman	matchure may have been the one that wasn't updated since pre clojure 1
14:13	hiredman	one of them did eval'ing + fn creation which broke recur
14:16	hiredman	needed it for https://github.com/hiredman/moravec/blob/master/src/moravec/four.clj
14:21	fliebel	hiredman: What's that?
14:22	hiredman	it may some day be a compiler
14:22	hiredman	well, I guess it is already, it can generate byte code for the λ calculus
14:22	hiredman	(I got closures working last night)
14:22	dnolen	fliebel: yeah I looked at RestFn, don't think I need it since I can sit in front of IFn w/ a macro.
14:25	fliebel	dnolen: Can I see your macro?
14:25	dnolen	fliebel: I could be wrong look at prelude.clj in core.logic.
14:38	admiralbumblebe3	Im new to clojure and I'm having a bit of an issue.. when I try: (byte-array (map byte [0xF0 0x41 0x32 0x00 0x05 0x00 0xF7])), I get the error "java.lang.IllegalArgumentException: Value out of range for byte: 240"
14:38	admiralbumblebe3	what am I misunderstanding here?
14:39	hiredman	on the jvm bytes are signed values, crazy
14:39	morphling	admiralbumblebe3: java bytes are signed, -128 to 127
14:39	admiralbumblebe3	oh.. damn
14:40	admiralbumblebe3	thats what I get for not knowing java
15:46	fliebel	Does Daniel Renfer com in here sometimes? He's working on OStatus in Clojure it seems.
16:40	mattmitchell	i'd like to create a macro that "captures" the & body arg in a hash, and returns the hash. I can't seem to figure out how to capture the syntax quoted & body arg. Would someone mind giving me a clue on to how to do something like: https://gist.github.com/1061620
16:44	gfrlog	mattmitchell: I'm a bit confused about the backquote there
16:45	gfrlog	(defmacro def-field [a b] {:fields a, :builder `(quote ~b)})
16:46	gfrlog	can you try that and say what's wrong with it?
16:46	mattmitchell	gfrlog: well, I'll tell you what I'm trying to do. I want to "capture" the body, so I can call it later. So I assumed I'd need the syntax quoted value?
16:46	mattmitchell	gfrlog: oh sure, let me try
16:47	gfrlog	apparently it returns {:fields [:data], :builder (str "hello!")}
16:47	gfrlog	mattmitchell: creating a function to call later would be insufficient? you need the actual form?
16:48	mattmitchell	gfrlog: I guess I didn't want to have to call fn everytime I setup one of these "fields"
16:48	gfrlog	mattmitchell: you can do it in the macro
16:48	gfrlog	I'd bet half of all macros exist mostly for doing that
16:48	gfrlog	so let's change the macro definition to...
16:48	mattmitchell	gfrlog: oh, you mean create a function that wraps the body, the returns the function?
16:49	mattmitchell	ok :)
16:49	gfrlog	(defmacro def-field [a & b] {:fields a, :builder `(fn [] ~@b)})
16:49	gfrlog	works for me
16:50	gfrlog	I changed the args so that you can give several forms for the function, for side effects
16:50	mattmitchell	wow, that's awsome
16:51	mattmitchell	gfrlog: thank you for that. Very helpful. I'm going to pull that apart and see if I can get my tiny brain to understand :)
16:51	gfrlog	most of the macros I write assemble a fn for some reason or another
16:51	mattmitchell	gfrlog: ok, so that's a typical way to "capture" the body and eval later?
16:51	gfrlog	any macro called (with-<something>) usually doest hat
16:51	gfrlog	mattmitchell: yep
16:51	mattmitchell	i see
16:57	mattmitchell	gfrlog: if I wanted to pass an arg to that function, how would I do that? I get a "Can't use qualified name as parameter"
16:58	gfrlog	mattmitchell: um
16:58	gfrlog	is that gonna be like a magic thing? like you'll call (def-field [:a] (+ x 12))
16:58	gfrlog	and the macro will set it up to have an arg called x?
16:58	mattmitchell	gfrlog: exactly, although... is that a bad thing?
16:59	gfrlog	I think it makes the code confusing. I've done such a thing only once, and tried to avoid it otherwise. If you explain the use case a little more I might be able to recommend something else. But yes, this is possible.
16:59	gfrlog	The reason what you tried didn't work is because the symbol is being processed by backquote; so rather than:
17:00	gfrlog	%`(fn [x] (+ x 12))
17:00	Chousuke	mattmitchell: in general, it's best to just let the user decide what to bind things to, even if there's just one that's almost always bound to the same name.
17:00	gfrlog	&`(fn [x] (+ x 12))
17:00	sexpbot	⟹ (clojure.core/fn [clojure.core/x] (clojure.core/+ clojure.core/x 12))
17:00	gfrlog	you'd want &`(fn [~'x] (+ x 12))
17:00	mattmitchell	i see ok
17:00	gfrlog	damn I'm bad at triggering sexpbot today
17:00	gfrlog	&`(fn [~'x] (+ x 12))
17:00	sexpbot	⟹ (clojure.core/fn [x] (clojure.core/+ clojure.core/x 12))
17:01	gfrlog	ignoring the body of the fn there, since that wouldn't be given explicitely in your macro
17:01	gfrlog	but anyhow I was asking what you're trying to do with all this
17:04	mattmitchell	gfrlog: well, i have a hash-map, where each key is an output key for a new document. The value defines a list of db fields to use when performing a select. I then want to use the function (builder) to transform data from the row, for the field. Does that make sense?
17:04	mattmitchell	gfrlog: there are about 10-20 fields per table, and about 10 different tables. So my goal was to create a macro, that would eliminate a lot of (fn [x]) code
17:05	gfrlog	mattmitchell: is it all within one namespace? I think magic names like that is a lot more acceptable if you keep it all in one file
17:05	mattmitchell	gfrlog: it is yes, all in one file.
17:06	gfrlog	okay. you know about the #() syntax though right?
17:06	mattmitchell	The the map without magic looks like: {:address [:line1 :line2 :city :state :country] (fn [row] )
17:06	mattmitchell	gfrlog: yes that's true, i could just use that
17:07	gfrlog	mattmitchell: and a lot of simpler functions can be built up compositionally without #() at all
17:07	gfrlog	e.g., if you're just going to do (fn [row] (:country row)), that's just :country
17:07	gfrlog	(fn [row] [(:country row) (:state row)]) is (juxt :country :state)
17:08	mattmitchell	i see, so maybe are you suggesting stay away from macros for this?
17:08	gfrlog	that's good default advice :)
17:09	Chousuke	heh, yeah
17:09	Chousuke	first rule of macro writing: make sure you actually need a macro
17:09	Chousuke	then don't write it
17:10	gfrlog	:)
17:10	Chousuke	then if you get annoyed enough, start thinking about writing it :P
17:11	mattmitchell	ok good, makes sense. But one of these days I need to come to grips with macros. I get so confused with all the quotes :(
17:12	gfrlog	mattmitchell: that's pretty normal. but I think you get a lot more mileage out of learning to use HOFs well than macros.
17:12	mattmitchell	gfrlog: and much more simpler to understand yes. OK, I'll back out a bit and try this again :)
17:13	gfrlog	good luck
17:13	mattmitchell	gfrlog: thanks! and thanks for your help.
17:13	gfrlog	np
17:35	currentB	What's the best way to test if a value is a clojure boolean
17:36	gfrlog	(map boolean? [true false nil 8 "wut"])
17:36	currentB	(isa? true java.lang.Boolean) doesn't work, for example
17:36	currentB	oh
17:36	currentB	didn't see that in the docs
17:36	gfrlog	isa? is between two classes I think
17:36	gfrlog	so ##(instance? true java.lang.Boolean) should work
17:36	sexpbot	java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.Class
17:36	gfrlog	&(instance? java.lang.Boolean true)
17:36	sexpbot	⟹ true
17:36	gfrlog	there it is
17:36	currentB	awesome thanks
17:37	gfrlog	but of course ##(boolean? false) is nicer and shorter
17:37	sexpbot	java.lang.Exception: Unable to resolve symbol: boolean? in this context
17:37	gfrlog	but it doesn't exist
17:37	gfrlog	so I'm dumb
17:37	currentB	haha
17:37	gfrlog	but the other way works :)
17:38	gfrlog	&(isa? java.lang.Boolean java.lang.Object)
17:38	sexpbot	⟹ true
17:38	terom	,(map boolean [true false nil 8 "wut"])
17:38	clojurebot	(true false false true true)
17:38	gfrlog	terom: thanks :)
17:38	gfrlog	I'm forgetting all of my bot-triggers today
17:39	gfrlog	oh that's different anyhow
17:39	gfrlog	doubt it would have helped currentB
17:39	terom	True. (No pun intented...;)
17:40	gfrlog	(def boolean? (partial instance? java.lang.Boolean))
17:52	hiredman	gfrlog: not inlinable :/
17:52	gfrlog	hiredman: isn't it strange that boolean? doesn't exist?
17:53	hiredman	meh, booleans are just kind of odd anyway
17:53	gfrlog	yeah who needs them
17:53	hiredman	why not just call boolean on the value
17:53	gfrlog	could just use :true and nil
17:53	gfrlog	it's a good point
17:57	terom	,(Boolean. "true") ; something to watch for...
17:57	clojurebot	true
17:57	terom	,(true? (Boolean. "true"))
17:57	clojurebot	false
17:58	gfrlog	wut it does
17:59	pdk	,(identical? true (Boolean. true))
17:59	clojurebot	false
17:59	pdk	,(.class true)
17:59	clojurebot	java.lang.IllegalArgumentException: No matching field found: class for class java.lang.Boolean
17:59	pdk	,(map type [true (Boolean. true)])
17:59	clojurebot	(java.lang.Boolean java.lang.Boolean)
17:59	terom	Boxed boolean, I guess, but not boolean primitive.
17:59	pdk	stay fresh clojure
18:00	gfrlog	,(map #(System/identityHashCode %) [true (Boolean. "true")])
18:00	clojurebot	(14929221 28937278)
18:00	gfrlog	,(map #(System/identityHashCode %) [true (Boolean. true) (Boolean. "true")])
18:00	clojurebot	(14929221 2760940 30908546)
18:01	terom	,(.booleanValue (Boolean. "true"))
18:01	clojurebot	true
18:20	hiredman	the clojure mailing list should make everyone who sends an email over X characters provide a useful clojure library to the community before allowing the email through
18:23	hiredman	"oh, it looks like you want to send 500 words that boil down to 'I think clojure is awsome and aren't we all so cool for using it!' to the mailing list, please take over one of the new contrib libraries and I will be happy to send it for you"
19:24	mjg123	Hello guys - how can I turn (:a 1 :b 2) into a map {:a 1 :b 2} :)
19:26	dnolen	,(apply hash-map '(:a 1 :b 2))
19:26	clojurebot	{:a 1, :b 2}
19:26	dnolen	mjg123: ^
19:26	mjg123	oh that's cool
19:26	mjg123	thanks dnolen
20:12	davekong	Is there a function like print that also takes a stream to print to as an argument?
20:32	amalloy	davekong: java interop. just call .write on the stream
20:32	davekong	amalloy: k, thanks
20:32	amalloy	(or, really, on the reader)
20:34	amalloy	&(let [out-str (java.io.StringWriter.) out (java.io.PrintWriter. out-str)] (.print out "test") (str out-str))
20:34	sexpbot	⟹ "test"
20:34	amalloy	davekong: 6
20:34	amalloy	er, ^
20:34	amalloy	still getting used to having my numbers and symbols swapped :P
20:35	davekong	for typing faster?
20:35	amalloy	but a lot of these cases can be solved with just ##(doc with-out-str)
20:35	sexpbot	⟹ "Macro ([& body]); Evaluates exprs in a context in which out is bound to a fresh StringWriter. Returns the string created by any nested printing calls."
20:35	amalloy	davekong: mostly just so i don't have to hold shift so often. i don't think it will improve speed that much, but it should help with comfort
20:36	amalloy	&(with-out-str (dotimes [n 10] (prn n)))
20:36	sexpbot	⟹ "0\n1\n2\n3\n4\n5\n6\n7\n8\n9\n"
22:28	hugod	swank-clj is now ritz, to try and avoid confusion with swank-clojure
22:38	tmciver	hugod: I spoke to you the other night about debugging clojure code and you informed me that you could open the .clj files from the jar in emacs, edit and then C-c C-k to compile. When I do this, I get a FileNotFoundException for the jar file. Any ideas?
22:45	tmciver	hugod: Even with this error it seemed to work just saving the file. But tonight I think I'm getting some strange behavior that may be classpath related. Do you know how the slime classpath is set up?
22:46	hiredman	tmciver: use C-c C-c
22:46	hiredman	(will re-evak the current top level form)
22:46	hugod	tmciver: not sure what the problem is compiling - works fine here - all the file's namespace dependencies have to be on the classpath
22:47	tmciver	hiredman: Ah yes, that seemed to work! Thanks.
22:47	tmciver	I'll have to add that one to my list of slime commands.
22:52	tmciver	hiredman: does 'top level form' mean that it compiles the whole file?
22:52	tmciver	hugod: how can I determine what my 'slime' classpath is?
22:53	hugod	(.getURLs (.getClassLoader clojure.lang.RT))
22:54	hugod	the slime classpath is determined by the project you started the swank server in
22:55	tmciver	hugod: so it will be lib/:lib/dev/ in that project?
23:02	hiredman	tmciver: the top level expression
23:07	hugod	tmciver: if you're using lein, then yes, plus source, classes and resource paths
23:07	tmciver	Great. Thanks again!