#clojure – 2008-05-04

2008-05-04

08:45	leafw	hi. I'd appreciate an example on how to use the (bean obj)
09:15	leafw	hi all. I'd appreciate very much an example on how to use the (bean obj) -particularly on how to retrieve then the values/pointers
09:17	rhickey	user=> (bean (java.util.Date.))
09:17	rhickey	{:year 108, :class class java.util.Date, :seconds 52, :time 1209906832244, :day 0, :minutes 13, :timezoneOffset 240, :hours 9, :date 4, :month 4}
09:21	leafw	my problem is then how to access the map
09:22	leafw	(let [b (bean java.util.Date.))] (println (b :year))) ??
09:23	leafw	[that fails, of course)
09:34	rhickey	(:year b)
09:34	rhickey	or (get (bean (java.util.Date.)) :year)
09:50	rhickey	I made bean extend APersistentMap so implements IFn like other maps
09:51	rhickey	so ((bean (java.util.Date.)) :year) now works
10:14	meredydd	(moving from #enclojure for keeping-on-topic reasons)
10:14	meredydd	rhickey: What's your reasoning behind disallowing wildcard imports?
10:14	rhickey	meredydd: there is no programmatic way to enumerate packages. IDEs do it by parsing all the jar files, Clojure doesn't read the jar files
10:15	meredydd	Uh-huh - I've looked up how it's done. So, you just don't want a hack that nasty in the language core?
10:15	rhickey	no
10:15	rhickey	It would bring a tom of names into Clojure namespaces
10:15	meredydd	(uhhh...was that a 'no, that's not it', or a 'yes, I dont')
10:15	rhickey	tn
10:15	rhickey	ton
10:15	meredydd	uh-huh...
10:16	meredydd	(pretty much the point, isn't it?)
10:16	rhickey	making a mess is the point?
10:16	rhickey	Namespaces are reified things, having unused cruft in there is not productive
10:16	rhickey	it's not merely a lookup list for the compiler
10:17	meredydd	?
10:17	meredydd	(ahh...which it pretty much is for Java, as far as I can see)
10:17	meredydd	(or do you object to the same in Java?)
10:18	rhickey	In Java there's no way for the programmer to interact with the 'namespace' in use in a module, in Clojure there is
10:18	rhickey	(ns-imports ns)
10:18	rhickey	(ns-imports (find-ns 'clojure)) etc
10:19	meredydd	uh-huh
10:20	meredydd	I see. And you want that to be a useful tool for introspection, rather than a great big dumping-ground full of all of java.util, java.io...
10:20	rhickey	right, I don't want to see an entire package because someone was too lazy and used *
10:20	rhickey	so for now only java.lang and a couple of util things are auto-imported
10:20	rhickey	everything else must be explicit
10:21	meredydd	Okay.
10:21	meredydd	And people like me who want to start using Clojure to swing around big bits of our own applications are either going to write a lot of manual imports, or write hackity macros while you're not looking.
10:22	rhickey	that's okay, it's still important for Clojure to have a recommended approach
10:23	meredydd	Yep. And you have a coherent reason for wanting it that way.
10:24	meredydd	And, of course, the obligatory fanboyism - I am truly impressed with what you've done here, and I anxiously await more.
10:24	meredydd	(hmm. Although right now, 'more' is more a matter of a working Enclojure than anything else.)
11:27	Chouser	With my sparse Java experience, I very much prefer reading code that has no wildcard imports. That way I have a fighting chance of finding the classes that are being used.
11:28	Chouser	I wonder if "refer" (and or the stuff from lib.clj) would be better off also not doing wildcards.
11:29	rhickey	that stuff's about loading Clojure code - are you suggesting naming each imported function?
11:30	Chouser	yeah, I tend to use :only on refer for the same reason I don't use wildcard imports in Java.
11:30	rhickey	Granularity-wise a clojure lib is roughly equal to a java class
11:30	rhickey	but hey, more power to you!
11:36	Chouser	heh
11:37	Chouser	I just don't like referring to an unusual name with no suggestion of where it came from.
11:38	Chouser	(refer 'bing) (refer 'bang) (refer 'boom) (optimise {...}) ; go fish!
11:38	rhickey	(resolve 'optimise)
11:39	rhickey	not arguing your point, it's a good practice :)
11:42	Chouser	well, there is that. As long as you can get a REPL with the same context as the code you're reading. ...which is rather easier to do in Clojure than Java.
11:43	Chouser	Hm, any reason someone couldn't create a Java REPL, compiling Java source on the fly just like you do with Clojure?
11:43	Chouser	I guess if I ever wanted to write Java code, I might care.
11:44	rhickey	see: http://www.janino.net/
11:46	jteo	the verboseness of java code makes that an effort.
11:56	leafw	Chouser: bean shell is essentially that. Java on the fly and without the static type verbosity
11:57	leafw	(but a very poor scripting language compared to clojure)
12:09	rhickey	I've added docs for gen-class - feedback welcome!
12:29	leafw	another one about beans: can one not just get but also set?
12:29	rhickey	leafw: no set yet
12:29	leafw	oks
12:30	leafw	is it planned?
12:31	rhickey	the semantics are muddy - maps are immutable and logically the altering operations produce new values
12:31	rhickey	whereas I think people may expect changes to flow through to the underlying object
12:32	rhickey	bean is not meant for that
12:32	leafw	ok
12:32	leafw	I am just used to jython
12:33	leafw	where beans are direct for both get/set
12:33	leafw	and change the underlying object.
12:34	rhickey	it would be, IMO, be desirable to have the map alter ops produce new maps, but no flow-through alteration
12:35	lisppaste8	aking pasted "recursive shootyout" at http://paste.lisp.org/display/60211
12:35	aking	rhickey: to practice Clojure, I thought I'd convert some of the shootout benchmark progs. Here's the recursive one
12:35	aking	It seems to run about 16x slower then the java server one
12:36	leafw	I hope I haven't said anything silly: http://pacific.mpi-cbg.de/wiki/index.php/Clojure_Scripting
12:36	leafw	the wiki is just starting, more to come soon.
12:36	aking	That includes removing the startup time
12:36	aking	ANything (other than changing the algorithm) I missed?
12:37	rhickey	That's the arithmetic, not the recursion. Not sure the declarations are useful - you should avoid them unless proven to be so
12:37	aking	rhickey: yeah.. I noticed there was almost no difference in speed with or without them
12:38	rhickey	aking: clojure looks much better without in that case
12:38	aking	also - the println seems to put an extra space before and after a number?
12:39	rhickey	The algorithms seem fine
12:39	rhickey	aking: yes, pr functions put spaces between multiple args, use str first if you want to avoid that
12:40	aking	ok - thanks
12:43	aking	rhickey: Is there an example of getting command line arguments into clojure?
12:43	rhickey	aking: command-line-args
12:45	rhickey	leafw: looks fine
12:47	aking	rhickey: thanks - found a reference to it in the Feb 25th news :)
12:48	rhickey	aking: yeah, there are a few non-fn vars like that undocumented, sorry
12:49	aking	rhickey: no prob - I should generally look in the clojure source first before asking
12:50	jteo	rhickey: on a scale of 1 to 10, where you are with regards to stability of the clojure "core" language?
12:51	rhickey	jteo: I'm probably the wrong one to ask :) - anyone else want to chime in?
12:51	rhickey	or are you talking about feature stability?
12:52	jteo	feature?
12:52	jteo	technically, anything doable in the jvm or java libs is already a feature. ;)
12:55	rhickey	I haven't run out of ideas, but I don't have anything significant about what I've already done that I'm looking to change. Clojure is pretty small and that is also a feature IMO.
12:57	rhickey	For instance, I just added gen-class, which doesn't alter anything that already exists in Clojure, but is a pretty big enhancement
12:59	jteo	true.
12:59	aking	rhickey: where's the docs for gen-class? I've checked website "Java Interop", "news" and "API" - and svn
12:59	Chouser	are you going to rename "for" "doseq" and friends?
13:00	rhickey	aking: (doc clojure/gen-class)
13:00	rhickey	aking: when I get some feedback I'll do a news item. The rest of the site documents the release, so it won't appear there until the next release.
13:00	aking	heh - didn't think of that :)
13:02	rhickey	Chouser: I thought only "for" to "from" was on the table, doseq stays the same and doseqs would be new
13:03	rhickey	Chouser: I realize that's not an answer :)
13:04	aking	rhickey: hmm.. not in boot.clj - had do (load-file "src/genclass.clj") first
13:04	rhickey	aking: right, it's in incubation right now
13:05	rhickey	bleeding edge svn stuff :)
13:06	aking	heh - I'll go play with gen-class for a bit. I see it will reduce the amount of enclojure java source required.
13:08	rhickey	aking: the idea is to eliminate the need for Java stubs, as well as provide a general class extension mechanism. Looking for feedback as to the comprehensibility of the docs...
13:31	leafw	is there any way to list all vars in the current namespace?
13:32	leafw	that would help in finding things like out and command-line-args
13:32	leafw	ns-amp
13:32	leafw	looks like it
13:33	rhickey	yup
13:34	leafw	I still lack an intuitive knowledge on clojure ... (apply ns-map (all-ns)) doesn't work, and was the first thing that came to lind
13:34	leafw	s/lind/mind/
13:34	leafw	aha, so (map ns-map (all-ns)
13:34	leafw	that works.
13:45	aking	rhickey: after doing a 'gen-and-load-class' it looks like you have to then import it into namespace you were in?
13:46	aking	also, maybe a comment about it being a one time only operation in the docs?
13:48	leafw	thanks for help and hints. Out
13:50	rhickey	aking: good point, yes, one-time only is the tricky part
13:54	aking	Does clojure use a classloader per namespace?
13:54	aking	Or just a root classloader?
13:57	aking	If it was a classloader per namespace, couldn't you do a gen-class in that namespace's classloader - and if you wanted to recreate a gen-class, jsut delete the namespace, recreate it then call gen-class again?
13:58	aking	It's been a few years since I played with java classloaders, so my memory might be a bit fuzzy on it..
14:02	rhickey	I'm not going to take on same-named class reloading, there are all kinds of issues, esp. since you might want to use the class from multiple namespaces. Right now there is a root namespace and a bunch of tear-offs which are per compilation (load/eval), not per namespace
14:03	rhickey	the idea behind gen-class is that, since it is implementation-free, the gen-class declaration should be fairly stable
14:03	rhickey	the Clojure side of gen-class is completely dynamic and supports iterative development
14:04	aking	rhickey: ok - just thought I'd check - forgot about the cross namespace usage - that would be ugly to handle.
14:21	jtra	Hello
14:21	rhickey	hi
14:22	jtra	I'm new to clojure, I know both Java and Common Lisp well, and after reading documentation I think I like the clojure :-)
14:23	rhickey	great!
14:23	jtra	I have also bit of Haskell experience, so paradigm suits me well
14:31	baggles	the world is crying out for clojure.
14:31	baggles	or if it isn't, it should be.
14:31	baggles	please save us all
14:32	rhickey	:) blogging about Clojure is welcome...
14:32	baggles	yeah... if only i had enough energy for this stuff. i've been running around outside in the hazy sun today :)
14:33	baggles	getting a real job recently, i now have lot of admiration of wthose who manage to keep up on the FLOSS stuff and work aswell....
14:35	jtra	I played with repl and simple JPanel in JFrame, it works as expected but when I run it as script, it exits despite AWT thread is running (which would not exit when such code would be written in Java itself). What is proper way to prevent exiting main thread in Clojure when GUI is active?
14:38	rhickey	jtra, I'm going to take the System.exit call out of Script.java - seems to trip a lot of people up...
14:40	rhickey	jtra: that's up if you're on SVN
14:41	jtra	ok, I will remove it from Script.java and recompile - I have 20080329 release
14:44	jtra	it works as expected now
15:44	rhickey	Servlets in Clojure - no Java required:
15:44	rhickey	(clojure/gen-and-save-class "/Users/rich/dev/clojure/gen/"
15:44	rhickey	'org.clojure.ClojureServlet
15:44	rhickey	:extends javax.servlet.http.HttpServlet)
15:44	rhickey	ClojureServlet.clj:
15:44	rhickey	(in-ns 'org.clojure.ClojureServlet)
15:44	rhickey	(clojure/refer 'clojure)
15:44	rhickey	(defn doGet [this req resp]
15:44	rhickey	(let [out (. resp (getOutputStream))]
15:44	rhickey	(. out (println (str "Hello World at " (new java.util.Date))))))
15:45	rhickey	drop into Tomcat/Glassfish
22:53	Chouser	bpattison: welcome!
22:56	bpattison	thanks
22:58	bpattison	making a concerted effort to learn clojure
23:21	Chouser	anyone here have gen-and-load-class working?
23:22	bpattison	why does (println "hello world") produce "hello world"\n nil -- what's the extra nil for?
23:22	Chouser	bpattison: that's the return value from println
23:22	Chouser	the REPL prints return values for you.
23:23	bpattison	oh! thanks
23:38	Chouser	Ah! It helps to have rebuilt clojure instead of just updating the sources.