#clojure – 2011-05-22

2011-05-22

00:57	dsantiago	Is there any way to use deftest to define a test, and then alter the metadata on the test function so that when a fixture you specify is run, it can access that metadata from the function passed in?
00:58	dsantiago	I can't seem to make it work using alter-meta! on the value in the test's var, or vary-meta on the symbol passed to deftest.
00:58	dsantiago	Might be doing something stupid here.
01:05	desertman_	hi, i am trying to use the sql library , i have mysql running on port 3306 , however i get No suitable driver found error , https://gist.github.com/985192
01:08	symbole	desertman_: I've never used that library, but I suspect you need the actual driver in the classpath.
01:09	desertman_	ok
01:11	symbole	desertman_: http://clojars.org/mysql/mysql-connector-java
01:14	desertman_	symbole : cool
01:15	desertman_	thanks
01:15	symbole	Np.
02:08	seancorfield	desertman_: if you're using leiningen, add this to your project dependencies: [mysql/mysql-connector-java "5.1.6"]
02:08	seancorfield	yeah, what symbole said :)
02:09	seancorfield	(dangers of catching up on irc late at night)
02:23	zakwilson	Using ClojureQL, I want to do something like (select (table db :items) (apply sql-or (map (partial like :longdesc) ["foo" "bar"]))) and get sql like "select * from items where longdesc like 'foo' or longdesc like 'bar'", but I'm not getting anything of the sort.
02:26	zakwilson	Oh, I see. I should be using or, not sql-or.
06:48	robonobo	is slurp lazy?
06:48	robonobo	or do i have to use slurp* from duck-streams for that?
10:36	a_robbins	Trying to setup lein so that 'lein repl' will automatically load and then activate a given namespace. :repl-init will load all the code from my file, but it doesn't switch my active namespace to that file, so I still need to call '(in-ns namespace-name) once I start. Any ideas?
10:47	TimMc	a_robbins: Let me check one of my projects...
10:48	TimMc	a_robbins: Try having a :main
10:48	a_robbins	TimMc: What would I put in it?
10:49	a_robbins	(in-ns 'namespace) ?
10:49	TimMc	https://github.com/timmc/CS4300-HW3/blob/master/project.clj
10:49	TimMc	So, in project.clj, :main mynamespace
10:50	TimMc	I think it's intended for when you want a runnable JAR, but it definitely does what you want as well.
10:51	a_robbins	Yeah, that does do what I need. I also don't need :repl-init when I am using it
10:51	a_robbins	I guess :repl-init is for other stuff that you'd like to load, iff you are on the repl
10:52	a_robbins	TimMc: thanks!
10:54	TimMc	np
10:58	a_robbins	TimMc: So, after messing with it a little more, I guess I see a use case for :repl-init. I'm working on an appengine-magic project, so any time I start the repl I want 1)To load my core namespace, 2) to activate it and 3) to start the dev server. :main handles 1 and 2, but :repl-init can be pointed to a script that makes 3 happen. That way it'll only start if I'm at the repl, and not up on app engine
10:59	TimMc	Yeah, that sounds reasonable. I haven't used :repl-init for any projects so far.
11:18	thorwil	technomancy: hi! if it is normal that "lein plugin install swank-clojure 1.3.1" seems to hang for minutes until it finally prints something, then please consider to add a warning about that
11:21	thorwil	technomancy: btw, what's not clear to me is the interplay or lack thereof with an already installed slime and paredit
11:22	a_robbins	thorwil: I think maven is down right now. That seems to be hanging a lot of lein commands
11:24	thorwil	oh, i would have expected an all or nothing, but "lein plugin install swank-clojure 1.3.1" took like 10 minutes to complete here. well, glad it worked, after all :)
11:29	a_robbins	thorwil: Yeah, maybe the server is responding to requests very, very slowly? http://repo1.maven.org/maven2/
11:31	technomancy	thorwil: yeah, stuff in jack-in completely overrides anything that's already there right now
11:31	technomancy	there's room for some subtlety to be added in for sure
11:31	technomancy	plus it should tell you what it's bootstrapping; right now it's only slime and slime-repl
11:33	technomancy	a_robbins: actually that's a bug; repl-init is supposed to set the initial ns
11:33	technomancy	it's just that I never use the repl task, so I did't notice
11:33	thorwil	installing clojure-mode via elpa led to a complaint about a paredit reference
11:34	a_robbins	technomancy: oh, good to know. Also, is there any easy way to switch leiningen to use the uk maven mirror for now? I'm hoping for some kind of global maven-url setting.
11:34	thorwil	clojure-jack-in briefly tells me that it exited with abnormal status
11:35	thorwil	"exited abnormally with code 1"
11:37	a_robbins	technomancy: or, instead of giving maven a new url, dropping it from the lookup list for a little while. Many of my lein commands just hang at '[INFO] artifact org.clojure:clojure: checking for updates from central'
11:39	robonobo	is there a way to pass all :keys from a function to another function?
11:42	thorwil	robonobo: what do you mean with :keys from a function?
11:43	robonobo	when you have a general function (defn foo [x & {:keys [y z]}] ...)
11:43	robonobo	and a helper-function that sets x to some value
11:44	robonobo	(defn foo-handy [& {:keys [y z]}] (foo x :y y :z z))
11:44	robonobo	is there a way to do that shorter?
11:45	technomancy	thorwil: there's also a bug where it'll get confused if there are multiple versions of swank in ~/.lein/plugins
11:45	technomancy	possibly fixed in clojure-mode 1.9.1, but it's something to look for
11:46	thorwil	technomancy: swank-clojure-1.3.1.jar is the only content of ~/.lein/plugins here
11:47	technomancy	a_robbins: you can try :omit-default-repositories true and then add in :repositories {"mvn-uk" "http:[...]"} I think
11:47	technomancy	haven't tried it myself
11:47	thorwil	robonobo: i'm not sure what you are trying to do, but have you considered using partial?
11:47	robonobo	thorwil: i'll look into that
11:47	robonobo	thanks
11:48	technomancy	thorwil: hm; hard to say what's going on. you might get more detailed output from regular lein swank
11:48	a_robbins	robonobo: maybe you should do the destructuring inside the helper function instead of in the outer function?
11:49	a_robbins	robonobo: If you are pulling it apart to get the keys, and then wanting to put the keys back together to pass them, maybe they don't need to be pulled apart?
11:50	robonobo	wait, can i just do (defn foo-hany [& opts] (apply foo x-default opts))?
11:50	technomancy	huh; the CLU language introduced iterators. that must be why they named the villain in Tron Legacy after it.
11:52	a_robbins	robonobo: I think this would do what you want: (defn foo-hany [& opts] (apply foo (merge x-default opts)))
11:52	a_robbins	robonobo: actually, I think you could drop the apply
11:53	robonobo	why not just (apply foo x-default opts) ?
11:55	Vinzent	(apply foo x-default opts) is ok, you can also (def foo-helper (partial foo x-default))
11:55	a_robbins	robonobo: It depends on how foo works I guess. My version used a hashmap to track all the different options, which would be destructured inside foo.
11:57	robonobo	ok, it works now
11:57	robonobo	thanks guys
12:00	thorwil	technomancy: indeed: http://paste.pocoo.org/show/393172/
12:01	thorwil	technomancy: the referenced file: http://paste.pocoo.org/show/393173/
12:05	technomancy	thorwil: yeah, gotta make that more exposed from emacs.
12:06	Vinzent	in enlive, I had some troubles when i tried to deftemplate\defsnippet with filename from the fn (e.g. (deftemplate foo (path "file.html") ...)): snippets was always returning empty seq (like no metched segments found), but no NullPointerException was thrown (like when file not found on cp)
12:07	Vinzent	Have anyone encountered similar problems?
12:07	thorwil	technomancy: any idea what the problem at hand is? could it be an appengine-magic swank 1.3.1 incompatibility?
12:10	thorwil	Vinzent: where does the (path) from come from? use just the path in quotes, with the templates in resources
12:15	Vinzent	thorwil, (defn path [filename] (str "long/path/to/templates/dir" filename)) just for shorteness
12:16	thorwil	Vinzent: deftemplate is a macro and you would have to use eval, or something
12:18	thorwil	or wrap it in your own macro, just for assembling that path
12:19	thorwil	then again, I would expect a NullPointerException if that is the problem, so maybe i'm talking bs
12:22	Vinzent	thorwil, lol, it's much easier: by distraction, I forget to add filename to the str form
12:23	thorwil	heh
12:25	no_mind	anyone used clojure.contrib.find-namepspaces ? I cannot figure out the input params for find-namespaces-in-dir ? If I pass a string as dir name, it says it needs java.io.File
12:26	Vinzent	so i've passed path to directory to the deftemplate; funny that it was working and returns something like "<html><body>layout.html\npost.html\n etc :)
12:29	Vinzent	no_mind, then you should pass java.io.File
12:30	Vinzent	(find-namespaces-in-dir (java.io.File. "src")) works fine for me
12:31	no_mind	I get an error ava.lang.ClassCastException: java.lang.Class cannot be cast to clojure.lang.IFn
12:31	raek	no_mind: sounds you are missing the last dot... :)
12:31	Vinzent	no_mind, note dot in the end of the class name
12:31	no_mind	k
12:57	Vinzent	With appengine-magic I have to recompile whole program after changes made; why? I'm passing var to the def-appengine-app
14:34	thorwil	awesome. so i had a working setup, but wanted to try http://technomancy.us/149 to have something repeatable, a way to recommend to others. somehow doesn't work with my appengine-magic project.
14:34	thorwil	i got rid of the lein swank plugin and rolled back my entire .emacs and .emacs.d
14:35	thorwil	and still get the same error
14:36	thorwil	java.lang.NullPointerException (init_repl.clj:0)
14:36	thorwil	http://paste.pocoo.org/show/393173/
14:51	thorwil	if i remove the init-script from project.clj to do things manually, (ae/serve tlog-app) leads to "java.lang.NullPointerException (NO_SOURCE_FILE:0)"
15:04	raek	thorwil: can you post the complete stacktrace?
15:04	thorwil	raek: java.lang.NullPointerException (NO_SOURCE_FILE:0) is all it says now
15:05	raek	in the repl?
15:05	thorwil	yes
15:05	raek	try (.printStackTrace *e)
15:07	thorwil	http://paste.pocoo.org/show/393270/
15:08	zakwilson	So I dove head first in to ClojureQL last night, and my first impression is that it is amazing and wonderful. All query languages should be like that.
15:11	raek	thorwil: no old files in classes/ lying around or something?
15:11	raek	the NPE from the java.io.File constructor seems suspicious
15:12	thorwil	raek: removing everything in classes is the solution. thank you!
15:13	thorwil	now ofcourse i have to wonder if the new setup would have worked after clearing classes, too :/
16:17	polypus	~ping
16:17	clojurebot	PONG!
16:27	duncanm	technomancy: how did you install emacs24 on your ubuntu laptop?
16:41	amalloy	duncanm: sudo apt-get install emacs-snapshot probably works, and building it from source isn't that hard either
16:42	amalloy	do a little research, though; i'm not 100% sure snapshot is 24
16:46	technomancy	duncanm: I built from the github mirror. pretty easy to do.
16:47	technomancy	I dimly recall the -snapshot package having lost its maintainer and being stuck in the past
16:47	technomancy	you can use it for its build-deps though
16:48	duncanm	amalloy: yeah, it's no longer up to date
16:48	duncanm	technomancy: thanks
17:02	Cozey	Hello. I'm not sure if i got it right: is it possible to make a class hierarchy with defrecord? Or otherwise how do I provide just one implementation for a protocol P, implemented by Parent class and its Descendants?
17:03	Cozey	should I use a multimethod for this? It seemed to me that defrecord is not to be used with multimethods... is it?
17:13	technomancy	how many clojure libraries are there with native components?
17:13	technomancy	I only know of three: penumbra, serial-port, and the arduino one
17:25	dnolen	technomancy: overtone.
17:28	amalloy	Cozey: building a class hierarchy feels like the wrong way to approach the problem. if you only want one implementation, just define it as a plain function that takes a Parent object as its first arg
17:30	Cozey	ok. on the other hand - is it a good practice to use protocols with multimethods?
17:30	Cozey	or should one use (extend.. )
17:31	Cozey	but then - this only extends one type, and not the whole hierarchy
17:31	Cozey	say I'd like to have a method (save-to-db ) for a hierarchy of records like Person, Order, etc.
17:31	technomancy	dnolen: thanks
17:31	Cozey	what would be the Clojure approach to this?
17:32	Cozey	I'm a little lost in the 'function only multimethod' and protocols/record/types new speedy paradigms
17:38	dnolen	Cozey: you can compose default implementations w/ function maps and extend-type.
17:38	Cozey	extend-type applies to records, not just types
17:38	dnolen	Cozey: however for I/O bound stuff like saving to a db, multimethods are fast enough.
17:39	dnolen	Cozey: yes.
17:42	Cozey	thanks; so this means a class generated by defrecord will always get an implementation from a protocol it implements or from it's definition; inheritance between records is not used to implement polymorphism? And the way to write an implementation of a protocol is to extend on a specific type (how to extend many types implementing one protocol?)
17:43	dnolen	Cozey: Clojure adopts the stance "inheritance considered harmful"
17:46	Cozey	ok. so I use multimethods - and this way can give a different implementation for different part of some hierarchy - is there a way to achieve the same using the 'optimized' methods defined with defrecord/deftype?
17:48	dnolen	Cozey: extend-type can take a map filled /w fns, these are composable - they are just maps.
17:48	Cozey	what's the semantics of (extend nil Proto ... ) - with nil instead of type ?
17:49	Cozey	I'd love to see an example
17:49	dnolen	Cozey: allows adding custom dispatch for nil value.
17:49	dnolen	quite useful.
17:50	Cozey	but how do I extend a set of records this way?
17:52	Cozey	Say I have a (defprotocol Sleep (sleep [this] ... )) and then I have (defrecord Animal) (defrecord Person), (defrecord Vampire) - how do I specify an implementation of sleep, which would work with animals, persons and vampires?
17:52	Cozey	or should I just use a normal method hinted with ^Sleep (I could do that?)
18:25	dnolen	Cozey: 2 ways to accomplish the same thing, https://gist.github.com/985965, https://gist.github.com/985967. I recommend getting comfortable w/ the later first.
18:28	Cozey	Ah! Thank You so much
18:28	Cozey	just one more question - how about a defmulti on a protocol ?
18:36	dnolen	Cozey: I think initially it's wise to consider multimethods and deftype/record/protocols as two completely distinct systems. It may seem like they overlap in functionality, but certain types of performant programs are simply not possible w/ multimethods.
18:36	Cozey	ok - in which case the 'sleep-shared' pattern is to be used
18:37	Cozey	enough of dissecting this problem! Thank You for the examples on gist :-)
18:40	dnolen	Cozey: No in the highest perf situation sleep-shared is also a not an insignificant perf hit. You simply just have to reimplement the function for each type (or macro it away). This is a good thing, inheritance just causes too many bigger problems compared to this inconvenience.
18:42	Cozey	ok, btw: is there a predicate to test if a record implements a protocol?
18:42	dnolen	Cozey: I do have some hope that invokeDynamic can allow for objects to be cleanly composed via delegation, but this a ways off.
18:43	dnolen	,(doc satisfies?)
18:43	clojurebot	"([protocol x]); Returns true if x satisfies the protocol"
18:43	Cozey	It says that defprotocol creates an interface as well - but the Foo protocol is actually some structure
18:43	Cozey	cool
21:16	no_mind	is there a library for parsing config files in clojure ?
21:18	amalloy	no_mind: well, clojure is such a library, if you store your config files as clojure data structures
21:18	amalloy	if you have a specific config format in mind, now's the time to say so :)
21:19	no_mind	yes, ini files
21:19	no_mind	storing config in clojure files is not an option when your app is going tobe installed and maintained by sys admins,
21:34	no_mind	using find-namespaces/find-namespaces-in-dir I can find out which namespaces exists in a given dir. But how do I load selective namespaces from the result of find-namespaces-in-dir ?
22:02	mefesto	no_mind: for parsing ini files you could use [commons-configuration/commons-configuration "1.6"] http://commons.apache.org/configuration/
22:39	desertmen	hi, i'm learning leiningen, if i created a project , whats the best way to run and test it. One tutorial has you compile it into a jar and run it from java everytime. Is that the best way, or can you run it from leiningen?
22:42	offby1	I'd do "lein --help" and see if it says anything about testing
22:45	amalloy	desertmen: it wouldn't be a bad idea to define actual tests, which you can run easily with "lein test" without requiring interaction
22:45	amalloy	but you can also define a :main namespace in project.clj, which i believe is what lein run calls
22:46	desertmen	ok thanks
22:56	no_mind	Ok someone needs to tell me how to do this. I have a directory with bunch of .clj files. I want to selectively load the namespaces from those files. How do I do this ?
23:24	desertmen	hi, i (noob) am having some problem getting this sql connector example going -> https://gist.github.com/986166
23:26	alandipert	desertmen: looks like you need to add clojure.contrib.sql to your dependencies in project.clj
23:26	wolfjb	how do I alter the value of a local variable?
23:26	amalloy	alandipert: just clojure.contrib
23:27	amalloy	wolfjb: don't
23:27	wolfjb	ok, then how do I read a file in a loop?
23:27	desertmen	ok, thanks
23:27	wolfjb	I want to read n bytes until there aren't any more
23:28	wolfjb	usually, I'd say while ((count = in.read(...)) != -1)
23:28	wolfjb	but I would need to modify count in that case each time through the loop
23:29	wolfjb	if I shouldn't modify a local variable, is there a better way to read a file?
23:29	amalloy	wolfjb: you don't need to modify it at all. a straightforward translation would be to create a new count variable at each iteration of your imperative loop
23:30	amalloy	eg, (loop [] (let [count (...)] (when-not (= count -1) ...)))
23:30	wolfjb	ah
23:30	wolfjb	wonderful
23:31	amalloy	wolfjb: a nicer solution would depend on what you're actually doing with the bytes you read
23:31	wolfjb	so, is loop like the common lisp loop then?
23:31	amalloy	no, not at all
23:31	wolfjb	I'm zipping a file
23:31	wolfjb	this is "library" code in a larger project
23:32	amalloy	loop is just a nicer syntax around defining an anonymous function that calls itself recursively and "looks" more imperative
23:32	wolfjb	I'm using java.util.zip.ZipOutputStream and calling write(bytes, 0, count)
23:34	wolfjb	I'm rewriting some old common lisp code I have as an exercise to learn clojure
23:34	amalloy	okay. if you just want side effects based on the current chunk of bytes, loop/recur is probably a fine solution
23:35	wolfjb	wish there was a book to read, the 'Clojure In Action' I guess is still forth-coming
23:35	amalloy	wolfjb: there are several clojure books
23:35	wolfjb	?
23:36	amalloy	the Joy of Clojure comes highly recommended and is also recent, which matters for a young language
23:36	wolfjb	must have missed them MEAP only had a couple and they look like they are still being written
23:36	amalloy	nah, JoC hit shelves a month or two ago
23:36	wolfjb	ah, cool!
23:37	wolfjb	missed it then, I'll have to go find it
23:37	wolfjb	wow, april 4! that is pretty recent
23:38	amalloy	(let [buf (byte-array 1024)] (loop [] (when-not (= -1 (.read in-stream buf 1024))) (.write out buf) (recur)))) ; a rough sketch
23:38	amalloy	i guess not a very good sketch, since it doesn't pass a size to .write
23:41	ataggart	,(doc clojure.java.io/copy)
23:41	clojurebot	"([input output & opts]); Copies input to output. Returns nil or throws IOException. Input may be an InputStream, Reader, File, byte[], or String. Output may be an OutputStream, Writer, or File. Options are key/value pairs and may be one of :buffer-size buffer size to use, default is 1024. :encoding encoding to use if converting between byte and char streams. Does not close any streams except thos...
23:42	amalloy	(inc ataggart)
23:42	sexpbot	⟹ 1
23:42	wolfjb	(loop [count (.read in buf 1024) (when-not (= -1 count) (.write out buf count)(recur) ?
23:42	amalloy	nnnooooo, you've gotten the syntax there wrong in several ways
23:43	amalloy	should probably look up how to use loop/recur
23:43	wolfjb	:-)
23:43	wolfjb	thanks, I'll look
23:43	amalloy	the general structure is (loop [loop-var init-value] (recur next-value))
23:47	amalloy	ataggart: fwiw, sexpbot gists instead of truncating: ##(doc clojure.java.io.copy)
23:47	sexpbot	java.lang.Exception: Unable to resolve var: clojure.java.io.copy in this context
23:48	wolfjb	hmm... that copy thing looks cool
23:48	amalloy	&(doc clojure.java.io/copy)
23:48	sexpbot	⟹ "([input output & opts]); Copies input to output. Returns nil or throws IOException. Input may be an InputStream, Reader, File, byte[], or String. Output may be an OutputStream, Writer, or File. Options are key/value pairs and may be one of :buffer-size buffer size t... http://gist.github.com/986197
23:48	ataggart	##(doc clojure.java.io/copy)
23:48	ataggart	nice
23:48	sexpbot	⟹ "([input output & opts]); Copies input to output. Returns nil or throws IOException. Input may be an InputStream, Reader, File, byte[], or String. Output may be an OutputStream, Writer, or File. Options are key/value pairs and may be one of :buffer-size buffer size t... http://gist.github.com/986198
23:49	wolfjb	(let [in (new BufferedInputStream (new FileInputStream fileName) 1024)] (clojure.java.io/copy in out) (.close in))
23:49	wolfjb	much cleaner than what I was trying
23:50	wolfjb	-- assuming that would work and I didn't goof it up :-)
23:50	amalloy	wolfjb: (Foo. x) is a more usual way to write (new Foo x)
23:51	amalloy	and yeah, it looks like it should work
23:51	wolfjb	ah
23:51	wolfjb	you'd think I hadn't read a thing, but really I have! I promise!
23:51	wolfjb	:-D
23:51	ataggart	and you can drop all that and replace it with clojure.java.io/file
23:52	amalloy	&(doc clojure.java.io/file)
23:52	sexpbot	⟹ "([arg] [parent child] [parent child & more]); Returns a java.io.File, passing each arg to as-file. Multiple-arg versions treat the first argument as parent and subsequent args as children relative to the parent."
23:52	ataggart	gah, I mean input-stream
23:52	amalloy	&(doc clojure.java.io/input-stream)
23:52	sexpbot	⟹ "([x & opts]); Attempts to coerce its argument into an open java.io.InputStream. Default implementations always return a java.io.BufferedInputStream. Default implementations are defined for OutputStream, File, URI, URL, Socket, byte array, and String arguments. If th... http://gist.github.com/986202
23:53	ataggart	e.g., (with-open [in (input-stream "foo.txt")] ...)
23:53	amalloy	or (doto (input-stream filename) (copy out) (.close))
23:53	ataggart	except manually handling the close is dumb
23:53	amalloy	ataggart: i should get to know clojure.java.io better
23:53	ataggart	:)
23:54	ataggart	ya they did good work in there
23:55	amalloy	ataggart: yes, i like the with-open version better. but only a little, and i do like a chance to introduce doto
23:56	ataggart	the problem with the doto is what happens if an exception is thrown
23:56	amalloy	yes, all right. my version is horrible
23:56	ataggart	heh
23:56	amalloy	but it has doto!
23:56	ataggart	doto is mutation is bad
23:57	amalloy	eyeroll it's well-labeled and cleanly-written mutation
23:58	wolfjb	heh, I thought doto was a typo
23:58	ataggart	doto is lovely when having to deal with javaland, e.g., swing
23:59	amalloy	your with-open version does exactly as much mutating, but hides it. mind you, it does the mutating better than i did, but you can't really frown on mutation when recommending with-out
23:59	ataggart	though it's been about a decade since I wrote any swing
23:59	amalloy	wolfjb: ##(macroexpand '(doto (+ 1 3) println))
23:59	sexpbot	⟹ (let* [G__14616 (+ 1 3)] (println G__14616) G__14616)