#clojure – 2008-09-15

2008-09-15

00:14	abrooks	Chouser: That's really nifty! Congrats!
02:11	homercycles	Does anybody know if a book is currently being written about clojure? I've read the first 8 chapters of Practical Common Lisp to starting "thinking lisp" but want to start doing something with clojure, but am not sure where to get started really
02:12	homercycles	online reference is nice but probably not covered to the level I'll need in order to understand
02:13	homercycles	clojure.org/reader - especially the stuff on dispatch - needs more explaining for people like me :-)
11:55	Chouser	rhickey_: is there any easy way to determine if a FnMethod is going to be used as a target for a recur?
12:22	rhickey_	Chouser: doesn't appear so
12:24	Chouser	ok. I'm putting a do{}while in every function just in case. Not the end of the world, but I was hoping to skip that if not needed.
12:24	rhickey_	yuck
12:25	Chouser	Doesn't seem worth walking the tree differentiating between enclosed fns and loops vs. everything else.
12:29	rhickey_	you walk the tree when you emit anyway, just track the nesting level. If you look at the compiler, you'll see it tracks loop targets during emit, not analyze. Look for the use of LOOP_LABEL. You could track the (potential) loop target similarly with a dynamic var
12:30	rhickey_	each fn and loop pushes on the stack, when you hit a recur, top of stack is target. If you don't recur, stack is not used but at least the generated code isn't polluted
12:32	Chouser	hm. so far I've ignored subtrees when emitting the current level.
12:32	Chouser	I've passed context down, but not tried to return anything except the code to be emitted.
12:33	rhickey_	I see, yeah in bytecode I just drop labels as I go...
12:34	rhickey_	still, possible to do cleanly with mutable dynamic vars
12:35	Chouser	oh, yeah I hadn't considered that approach. not exactly immaculate, but if you're will to call it clean I guess I'll give it a shot.
12:36	rhickey_	it's thread safe, and stack based. The compiler does similar things...
12:37	Chouser	biab
13:07	Chouser	That's the first time I've explicitly used the stack built into a dynamic var. Not too shabby.
13:07	rhickey_	not too
13:08	rhickey_	it's sort of made for this problem
13:08	rhickey_	communicating across nested scopes
13:14	Chouser	Well it tightens up the .js pretty well. The only bit of cruft I've still got is a local var declared for functions even when nothing internal ever refers to it.
13:20	lisppaste8	Chouser pasted "JavaScript emitted by tojs" at http://paste.lisp.org/display/66866
13:22	rhickey_	cool
13:30	Chouser	I sometimes get a NPE from getAndIncLocalNum when the outermost form I'm analyzing isn't a def or a fn.
13:31	Chouser	Like this, for example: (doseq src (script-src) (prn src))
13:31	Chouser	Is there something better I can do than wrapping it in ((fn [] ...)) like I am now?
13:33	rhickey_	no, that's the right thing, else you will be writing an interpreter too. (see all the evals in addition to the emits in the Expr classes?)
13:41	rhickey_	added lazy parallel pmap (in rev 1026)
13:57	Chouser	I did see those evals, but I didn't pretend to understand them.
14:18	Chouser	more features less code! (re: pmap)
14:51	arohner	rhickey_: did you see my compiler error patch?
14:52	Chouser	arohner: I know very little about Java exceptions. Does your patch end up converting exceptions of all types to Exception instances?
14:53	arohner	oh, that's a good point
14:53	arohner	it doesn't convert the thrown exception, but it does wrap it in an Exception
14:53	arohner	but that shouldn't change the semantics of trying to catch exceptions
14:54	Chouser	oh, you can still catch the more specific exception type inside?
14:54	arohner	no, but compiler.java isn't picky about the types of exceptions it throws
14:54	arohner	so, I think I'm not making the situation any worse, but I'm not making it better
14:55	arohner	wrt to catching exceptions
14:55	arohner	I guess I need to clarify that. because java's checked exceptions, you have to declare what type of exceptions you throw
14:56	arohner	right now, compiler.java does very little of that, and just declares it throws Exception
14:57	arohner	we could change things so that for example Compiler.load() throws a clojure.lang.loadFile exception, etc
14:57	arohner	but that doesn't really buy you much
14:58	arohner	It looks like rhickey is writing C in java. I don't blame him, that's probably what I would do.
14:58	Chouser	I'm not really qualified to have an opinion. Just sniping. :-)
14:58	arohner	I'm not entirely sure I am either :-)
15:01	rhickey_	arohner: C in Java? in what way?
15:02	arohner	indentation :-) I know you're using inheritance, OO in some places. I don't know, just a feeling I got
15:03	arohner	it didn't look like "standard" java
15:03	arohner	not that there's anything wrong with that
15:05	rhickey_	It's certainly not C-like
15:07	Chouser	heh
15:07	Chouser	arohner: that may not have been the fastest path to getting your patch accepted. ;-)
15:07	arohner	hah
15:07	rhickey_	http://n01se.net/paste/HTx
15:08	arohner	pretty
15:09	arohner	rhickey_: I'm really not trying to insult you. The code is nice. It didn't look like standard java, and when I tried to figure out what it looked like, the first thing that popped into my head was "C". I know that's not entirely correct.
15:10	rhickey_	but I think it's an interesting question - in what ways does it differ from 'standard Java'? (and I agree it is different) It's not C-like, so you need a better answer
15:10	rhickey_	answer/snipe :)
15:11	arohner	you're not constructing hammer factories, for one
15:11	arohner	http://discuss.joelonsoftware.com/default.asp?joel.3.219431.12
15:12	ozzilee	The indentation's all fucked up, for another :-)
15:12	ozzilee	I spent about half an hour trying to get Eclipse to match the indentation... no dice.
15:13	arohner	maybe it's the fact that 90% of the compiler code is pure code. Most java I've seen is just gluing one library to another
15:15	arohner	several of the important classes are arranged as OO for organization rather than functionality
15:15	rhickey_	The compiler code is especially different in that it uses the Clojure persistent data structures, not as pretty in Java, and uses Clojure's dynamic vars too.
15:15	rhickey_	arohner: like what?
15:15	arohner	i.e. Compiler.java. lots of static functions, rather than classes with lots of internal state
15:16	arohner	which of course fits clojure's style
15:18	rhickey_	ozzilee: switch to IntelliJ
15:19	ozzilee	rhickey_: Ok, I'll try that next time I load it up.
15:21	Chouser	arohner: nice link. Definitely the feeling I get from Java.
15:31	Chouser	rhickey_: In this code I'm writing, having an :interpose for "for" would be awfully handy. Thoughts?
15:32	rhickey_	I think you need to explain that to me
15:34	Chouser	(interpose 0 (for [i (range 3)] i))
15:34	Chouser	(for [i (range 3) :interpose 0] i))
15:34	rhickey_	they seem to be the same length
15:34	Chouser	Hm, it's not terribly compelling when written like that is it.
15:36	Chouser	When the "for" is multi-line, having interpose at the front forces "for" to be much more deeply nested than in the latter case.
15:37	ozzilee	Chouser: You mean there's a lot of blank space to the left of every line in the body of the for?
15:37	parth_m	rhickey: I have been toying with the idea of creating a user friendly clojure shell for the past few days (with jline integration, history, and stuff). Hopefully something like what ipython does for core python. Wanted your opinion on the same. Initial proto is here: http://code.google.com/p/iclj/source/browse/trunk/iclj.clj
15:37	ozzilee	Chouser: Hmm nm.
15:37	lisppaste8	Chouser pasted "proposed :interpose" at http://paste.lisp.org/display/66878
15:38	parth_m	Being in clj its easy to enhance and modify.
15:38	lisppaste8	parth_m pasted "interaction" at http://paste.lisp.org/display/66879
15:38	Chouser	ozzilee: yeah, you're right.
15:38	Chouser	anyway, not a big deal.
15:39	ozzilee	Chouser: Lisp indentation kind of sucks sometimes. I usually just plunk a newline in after the (interpose 0
15:39	parth_m	rhickey: do you say its best to keep something like iclj as a separate project or do you see value in rolling something like this into clojure? Both approaches seem fine to me.
15:40	lisppaste8	rhickey annotated #66878 with "press enter" at http://paste.lisp.org/display/66878#1
15:42	rhickey_	parth_m: we've been moving along on this line: http://groups.google.com/group/clojure/msg/78ebea4b2719bc7e
15:43	arohner	rhickey_: do you like my patch? is this a good approach? is there anything I should do differently?
15:45	parth_m	Yes. Thats actually nice. But I was thinking that doing the repl in clojure itself may make it easy to maintain and enhance. + there is builtin jline integration (tab-completion and stuff ... i suppose jline works on windows also though I havent tried it).
15:47	rhickey_	parth_m: yes, repls are trivial to write. jline is a dep I don't want to get into
15:50	rhickey_	arohner: It seems more like a band-aid than substantive. Given the abbreviated stack trace (see above), the real target should be at the exception generation points themselves, where I have enough info to talk about the nature of the problem
15:50	arohner	where is the abbreviated stack trace?
15:51	rhickey_	http://groups.google.com/group/clojure/msg/78ebea4b2719bc7e
15:51	rhickey_	but I'm not putting any of this in until after I cut a release
15:52	ozzilee	parth_m: I think a separate project for that would be cool. I can think of some repl features that would be cool to see, but probably would get implemented very quickly in the main clojure repo.
15:52	ozzilee	*probably wouldn't
15:54	parth_m	rhickey: jline seems fairly common now (as its under BSD license). groovysh and jruby are using it. Is the intent to keep the distribution small? The problem with using jline from the command line is that we don't get tab-completion. And rlwrap is unix only.
15:54	arohner	rhickey_: it is superficial, but it does help. you have different information at the exception generation point. I wouldn't say it's more
15:55	arohner	for example, load a.clj, a.clj requires b.clj. b.clj generates an exception. print the sourcePath at that point, and it will say a.clj
15:55	rhickey_	jline is not pure Java on windows. I've seen bug reports on JRuby or Groovy related to jline
15:55	Chouser	There are going to be a bunch of repl projects: intergrated into various editors (emacs, netbeans, jedit, etc.), various terminal wrappers (rlwrap, jline), GUI toolkits (Qt, swing), etc.
15:55	Chouser	In fact, most of those exist already.
15:56	parth_m	ozzilee: yes. separate project could also work. probably features like color, logging, printing source lines with exception (like ipython) and such. Not sure how much it makes sense to have that in the core REPL.
15:56	arohner	maybe the correct solution is to fix the source path so it correctly points to the file you're actually loading. I can go down that route, but that is exactly the kind of thing I wanted to get buy-on for first.
15:57	parth_m	rhickey: Yes. Thats true.
15:58	parth_m	Chouser: Yes. That seems to be the standard practice. Especially for lisp :)
15:59	parth_m	And it has its advantages.
16:00	rhickey_	arohner: doesn't load already set the source path?
16:00	rhickey_	gotta run
16:02	cemerick	I have a genclass impl in a .clj file, which appears to load fine when the corresponding MyClass class is loaded. However, for some baffling reason, a couple of vars that I def using defn are unbound when I refer to them (java.lang.IllegalStateException: Var MyClass-removeAll is unbound, etc). Anyone have any ideas as to why that would be?
16:02	ozzilee	parth_m: I'd like to see a repl brought the up previously typed line with the cursor positioned at the error in the case of one. That would be slick.
16:04	parth_m	ozzilee: I am not sure I understand you.
16:05	Chouser	cemerick: the defn and the exception are in/from the same .clj file?
16:05	ozzilee	parth_m: Sorry, I should have proofread that :-)
16:05	parth_m	:-)
16:06	cemerick	Chouser: No. I bring up a repl with an appropriate classpath, and do (import '(foo.bar MyClass)). Then, foo.bar/MyClass-removeAll => exception.
16:06	ozzilee	parth_m: Say I type "(print foo)", and I get an error saying "Can't find symbol foo". Then instead of a blank line, I'd like to see "(print $foo)", with the $ being the cursor.
16:07	cemerick	Chouser: Oddly, only the functions that start with MyClass-r seem to be affected, although I have to think that that's coincidence.
16:07	Chouser	you're seeing other side-effects from inside the .clj? That's why you're sure it's loading?
16:08	parth_m	ozzilee: Ah. Yes. That would be nice. Getting the line is certainly possible. Don't know about the cursor with jline yet ... still learning jline.
16:08	cemerick	Chouser: Oh, yeah, the .add, .count, .seq, etc., methods all work, and those are implemented in the same .clj file
16:09	parth_m	I suppose I will maintain iclj as a separate project and see how it shapes up. I am hoping to take some inspiration from ipython. Thats a really neat interactive shell.
16:11	cemerick	Chouser: nevermind. An old version of the .clj file was being loaded from another netbeans project I have open. D'oh!
16:11	Chouser	cemerick: yeah, ok. Kinda had to be something like that. ;-)
16:11	cemerick	yeah, I thought I was in the twilight zone there.
16:12	ozzilee	parth_m: Cool, perhaps I'll make a fork and screw around with adding that feature myself.
16:12	parth_m	Sure.
17:40	drewr	Is there an example in the wild of when fnseq would be used? I cannot come up with a case for it by perusing the source.
17:42	rhickey	drewr: it used to be used in lazy-cons, now it's legacy
17:42	drewr	Ah, OK.