#clojure – 2008-09-02

2008-09-02

07:50	parth_m	Hello
07:52	parth_m	If I am to write a print-decorator http://groups.google.com/group/clojure/msg/cb7a45124bbf92f5 what would be a good way to get the name of the function being decorated at runtime?
07:53	parth_m	In the method suggested, having to switch namespaces seems a little weird.
07:53	parth_m	If I don't switch ns, there is stack overflow.
08:01	hoeck	parth_m: why not just taking the functions classname at runtime?
08:02	parth_m	hoeck: as (class f)?
08:03	parth_m	This works, actually just a print also works but it shows the compiled form .. e.g user.foo__2372@5388b5
08:03	parth_m	I was wondering if I can get "foo"
08:03	hoeck	of course, with some string and regex matching
08:04	hoeck	and it has the advantage of working with (named) anonymous functions (which i use very often) :)
08:05	parth_m	Yes .. I could do that.
08:05	parth_m	I am not too clear on using meta data. I know the info exists ... just not sure how to get it.
08:05	parth_m	user=> (meta (var foo))
08:05	parth_m	{:arglists ([]), :file "NO_SOURCE_FILE", :line 9, :ns #<Namespace: user>, :name foo}
08:06	parth_m	So, "foo" is definitely there somewhere ... but in the decorator scenario it doesn't seem to work. Throws an exception: http://groups.google.com/group/clojure/msg/91b028c63ec440d6
08:10	parth_m	Its not a big thing ... I was just wondering in case there is a idiomatic way of doing this.
08:11	hoeck	mhh, aren't vars resolved at compile-time?
08:12	parth_m	I suppose so.
08:14	parth_m	But if we pass "foo" to "print-decorate" isn't the meta-data attached to "foo"? This may be a silly question but I still don't understand clojure meta-data fully.
08:15	hoeck	no, metadata is only attached to vars and a few clojure data-structures
08:16	parth_m	Ah. I think I get it now. So what gets passed is a function ... so there is no metadata attached. Right?
08:17	hoeck	yes, the metadata you create with defn gets only attached to the var holding the function object
08:18	hoeck	but the AFn Class actually has a withMeta method, but it throws an unsupported operation exception, so in theory, you could attach metadata to functions too
08:19	parth_m	Having metadata with functions would be nice ... I suppose that needs to fit into the overall introspection picture.
08:20	parth_m	Thanks hoeck. I understand this much better now.
08:20	parth_m	So when we do #'foo its a var. and just 'foo' is a function being passed.
08:25	hoeck	yeah, #'foo is a shortcut for (var foo), and foo evaluates to the value of foo (in this case a function)
08:26	parth_m	Common Lisp had me confused ... I thought #'foo was a function as with CL :)
08:26	parth_m	Thanks hoeck. Will use the class for now.
08:27	hoeck	me too, but clojure has only one namespace for functions and values, which I find pretty handy btw
08:28	parth_m	I agree. Its much nicer to say (map foo ..) rather than (map #'foo ..)
09:23	cemerick	rhickey: it turns out that the NB profiler chokes on clojure in general (though your genclass patch stops it from tossing a hard error); the process being profiled "hangs" (for lack of a better term) as soon as clojure.lang.RT is statically referenced.
09:24	rhickey	cemerick: that's bad, last time I tried it it ran no problem but only profiled the Java bits of Clojure
09:24	rhickey	cemerick: I see you got the 18-arg patch
09:25	cemerick	yeah I did; so, you set up the profiler to instrument only clojure.lang.*?
09:26	rhickey	I don't remember too well, but I think I asked for everything but standard Java libs, got only Java calls
09:27	cemerick	FWIW, dumping profiling data via -hprof options works just fine (which I load up in hpjmeter) -- crude, but effective.
09:31	rhickey	soneone suggested JiP at one point: http://jiprof.sourceforge.net/
09:31	rhickey	someone
10:11	cemerick	rhickey: thanks for the link; I think I'll try yourkit next, just to see if NB is the problem, or if clojure/asm/whatever is somehow at odds with JVMPI itself.
11:42	cemerick	yourkit profiles the same NB project without a problem; however, a super-small project I put together that contains only clojure.jar and a main class that references clojure.lang.RT is successfully profiled by NB....so, now I'm pretty confused.
15:13	lisppaste8	jamii pasted "qt-repl" at http://paste.lisp.org/display/66213
16:19	jgracin	rhickey, hi! how come there are no tests in Clojure's implementation?
16:19	jgracin	I'm obviously asking about your opinion on automatic testing. :-)
16:32	rhickey	jgracin: no one's written any yet
16:32	abrooks_	Heh.
16:33	rhickey	a test suite would be a welcome contribution
16:35	Chouser	people have talked some about how a test suite would be structured. It'll happen eventually.
16:36	rhickey	until then I'll just keep trying to get it right the first time :)
16:40	jgracin	rhickey, nice strategy. :-)
17:36	lisppaste8	jamii pasted "qt repl and slots in action" at http://paste.lisp.org/display/66224
17:44	jamii	How do I create instances of generic classes?
17:44	jamii	eg Signal1<Object>
17:44	Chouser	ignore the generic part
17:44	Chouser	so, just Signal1
17:44	jamii	Hmmm. Qt might not like that. Ill give it a try
17:51	jamii	How do I use a nested class? I would have thought (import '(com.trolltech.qt.QSignalEmitter Signal0)) would work
17:52	kotarak	Try QSignalEmitter$Signal0
17:53	jamii	Yep, that worked.
17:53	jamii	Is the $ specific to imports?
17:53	kotarak	No, it's for nested classes.
17:53	jamii	Ok. Cheers
18:11	jamii	Damn, I wish new wasnt a macro.
18:14	kotarak	It's not. It's a special form, AFAIK. What do you want to do?
18:18	jamii	kotorak: I need to create one of Signal0 to Signal10 depending on the argument number
18:19	jamii	something like: (defn signal [n] (new (sym "Signal" (str n))))
18:20	jamii	I dont think its possible with new though. Is there another primitive for constructing objects?
18:20	kotarak	Not that I am aware of...
18:21	jamii	Oh well. cond it is then
18:21	kotarak	You could resolve to ugly anti-features:
18:21	kotarak	(let [c TheClassYouNeed] (eval `(new ~c)))
18:23	jamii	That'll do. It doesnt have to be pretty
18:23	kotarak	cond is probably the better solution. Also not pretty, but one has a good conscience.
19:42	Chouser	is it any prettier to do the evals up front?
19:43	jamii	Is there a way to add java fields to a class using proxy? Signals can only appear as a field of a subclass of QSignalEmitter. Which is a little annoying. I've been trying to do this using gen-and-load-class but the :state option is causing problems
19:43	Chouser	(def sigs (vec (for [i (range 10)] (eval `(fn [] (new ~(symbol (str "Signal" i))))))))
19:44	jamii	Chouser: Im using almost exactly that code :-)
19:44	Chouser	jamii: no, you'll have to use gen-class to add a field.
19:44	jamii	So i need to use :state and :init
19:45	jamii	How does the scoping work in :init - it keeps complaining that my init function isnt defined
19:45	jamii	This is what I have at the moment:
19:45	jamii	(defn- make-signal-holder [n]
19:45	jamii	(gen-and-load-class
19:45	jamii	(symbol (str "slot.SignalHolder" n))
19:45	jamii	:extends QSignalEmitter
19:45	jamii	:constructors {[(eval (symbol (str "QSignalEmitter$Signal" n)))] []}
19:45	jamii	:init 'signal-holder-init
19:45	jamii	:state 'signal))
19:46	Chouser	you're running the last release, or latest SVN?
19:46	jamii	Somewhere in between... svn 1-2 weeks old
19:47	Chouser	ok, your defn probably needs to use the name SignalHolder-signal-holder-init
19:49	rhickey	jamii: for no-arg dynamic new - (.newInstance (Class/forName str))
19:49	jamii	rhickey: Thanks
19:52	jamii	Hang on, that needs to be (.. (Class/forName str) (getConstructor types) (newInstance))
19:53	rhickey	jamii: are there args? your examples didn't have any
19:54	jamii	Sorry. The examples didnt have any because the jambi docs are wrong. There is in fact a single mystery arg
19:55	rhickey	(clojure.lang.Reflector/invokeConstructor (Class/forName str) (to-array args))
19:56	jamii	cool
19:57	rhickey	better still, use RT.classForName which will leverage Clojure's classpath stuff
19:59	rhickey	(resolve (symbol "java.util.ArrayList")) is another way to look at it
20:06	jamii	It seems that jambi is not fooled by gen-and-load-class: "java.lang.RuntimeException: Signals must be declared as members of QSignalEmitter subclasses"
20:06	rhickey	jamii: are you extending that class?
20:07	jamii	Yes
20:07	jamii	And putting the signal in the :state slot
20:09	jamii	google has nothing. Does :state produce a real field. Maybe I should try a property instead
20:10	rhickey	http://doc.troll.no/qtjambi-4.3.4_01/doc/html/com/trolltech/qt/qtjambi-signalsandslots.html says: All normal member methods can be used as slots, so there are no specific requirements for a method to function as a slot.
20:11	jamii	Signals and slots are not the same. I've managed to wrap clojure functions as slots quite easily. The trouble is that new signals have to be created as members of a QSignalEmitter
20:18	rhickey	jamii: :state does produce a public final field of type Object.
20:19	rhickey	but it seems like you can define accessor methods for signals, rather than use fields, as implied by "It is customary to declare signals as public rather than to provide access methods for them."
20:20	jamii	I'll try using :exposes
20:21	rhickey	jamii: that's just for exposing an existing protected field of a superclass
20:21	jamii	Damn
20:31	Chouser	does final mean everything inside that object will be immutable, or is it just that the top-level value of that field cannot change?
20:36	rhickey	Chouser: the latter
21:09	jamii	To import a java file in clojure do I have to do anything beyond compile it and set the classpath?
21:18	shoover	jamii: That should do it. If the file is compiled to a .class, put the directory on the classpath. If the .class is part of a jar, put the jar on the classpath.
21:20	jamii	Ok, i probably have a typo buried deep in the folder hierarchy
21:34	jamii	rhickey: Turns out signals have to be declared inside the scope of the QSignalEmitter subclass. Dropping into java seems to be the way forward
21:34	jamii	s/declared/instantiated
21:35	jamii	public Signal0 signal = new Signal0(); is the single only way it will be accepted
22:05	Chouser	no way to get to "this" from the init function?
22:27	Chouser	wouldn't matter anyway -- Qt's using getDeclaredFields to poke through the Emitter's parentage looking for a matching Signal member.
22:43	jamii	Chouser: I have it sort of working. It gives me an exception the first time I use a signal and works fine thereafter. I'm tempted to just have the wrapper force and catch that first exception before returning the signal. A little hacky though
22:43	Chouser	hm...
22:47	Chouser	that's with Java code for the signals?
22:48	jamii	I hava a java class that looks like:
22:48	jamii	public static class QField extends QObject {
22:48	jamii	public QField() {
22:48	jamii	super();
22:48	jamii	}
22:48	jamii
22:48	jamii	public Object field;
22:48	jamii	}
22:49	jamii	Because I couldnt figure out how to do fields properly from withing clojure
22:49	jamii	Then I set! field with a new signal. The mystery arg in the signal turned out to be because they're non-static inner classes - they need an instance of their container class which in this case is QField
23:03	jamii	svn ~2 weeks out of date
23:04	jamii	oops
23:12	jamii	java.lang.RuntimeException: Signal initialization failed
23:12	jamii	Thats a new on
23:12	jamii	*one
23:15	jamii	Chouser: All signals are failing on the first emit with "Signals must be declared as members of QSignalEmitter subclasses". Zero arity signals work fine afterwards but others fail with "Signal initialization failed". I have no idea whats going on
23:17	Chouser	I'm looking at the source for resolveSignal() in QSignalEmitterInternal -- but I'm don't really understand it.
23:38	jamii	fetchSignal is native. im getting the qt source now
23:59	jamii	I think I have it