#clojure – 2008-06-05

2008-06-05

00:00	Chouser	btw, I don't think I'd like suffix chars for primitive literal numbers.
00:01	JamesIry	Chouser: They borrowed some syntactical structures from Java where they didn't have a strong reason to do otherwise
00:01	rhickey	Still no substitute for a truly immutable data structure, just has much better memory and concurrency characteristics in the end
00:02	rhickey	Chouser: meaning you're opposed, or just wouldn't use them?
00:03	Chouser	rhickey: well, that's a good question. I guess my current opinion is that I'd rather not read them. :-)
00:04	rhickey	I ripped out all of my effectively-but-not-really-immutable data structures once I got the hash tries working. They're plenty fast.
00:04	Chouser	hm, I dunno. That's a gut feeling -- I don't know if I can back it up with anything. You should probably ignore me. ;-)
00:05	rhickey	gotta run, thanks all for a nice conversation
00:05	JamesIry	rhickey: thanks for the pointers on STM
00:05	JamesIry	Hopefully you and Martin Odersky can talk some time
00:05	rhickey	yes
00:06	JamesIry	Chouser: on my wishlist for Scala would be some equivilant of reader macros so I could create my own literal forms for things like regexs or BigInts
00:08	Chouser	JamesIry: Yeah, I asked about regular (non-reader) macros. Nobody seemed opposed...
00:08	JamesIry	I'm all for them. The natural model wouldn't be Lisp style macros though - it would be something more like Template Haskell or Nemerle templates.
00:09	JamesIry	Or the Ocaml one whose name I can never remember
00:09	JamesIry	caml4p
00:10	Chouser	but in most of those syntax-ical languages that have "macros", you can't call host language functions from within an macro.
00:10	Chouser	...which gets m4 or CPP-level functionality. Not impressive.
00:13	JamesIry	Chouser: CPP is a poor comparison. And I'm not sure what you mean. A template can't call host language at expansion time, but it certainly can at runtime. Isn't that roughly similar to many lisps?
00:14	Chouser	no, lisp macros can call any function they want at expansion time.
00:14	JamesIry	Not talking about CL. Thinking more like Scheme
00:14	Chouser	oh. well.
00:15	Chouser	It makes a huge difference in how powerful the macros can be.
00:16	JamesIry	Of course!
00:17	Chouser	Have you read On Lisp by Paul Graham?
00:17	JamesIry	Yup
00:17	JamesIry	Good book
00:17	JamesIry	I also read his "Ansi Common Lisp" which was as dry as a 3 week old tortilla
00:17	JamesIry	:)
00:17	Chouser	I didn't "get" what the big deal was with macros until I read it. Now I'm a believer. ;-)
00:22	JamesIry	Practical CL is also a good book which conveys the power of macros. It's not quite as tight as On Lisp, but does give a better feel for the rest of the language. When people ask me about lisp I usually recommend SICP, Practical CL, and On Lisp in that order. Unfortunately, I also now have to recommend them to Clojure but there aren't any books on it just yet.
00:28	JamesIry	Well, I gotta run... thanks for the chat
00:48	Leafw	is there any way to create a string in a macro, and make it become a keyword, not a string, in the expanded code?
00:48	Leafw	for example: (defmacro pra [T] `(println ~(str "#^" T "s")))
00:49	Leafw	that generates a string with str, but, is there anyway to make it become cleanly #^doubles , for example, with (pra "double") ?
00:50	Chouser	Leafw: yeah, just a sec...
00:50	Leafw	ok!
00:52	Leafw	the idea being, I want to write generic functions, that can be automatically type-decoreated for int, float , etc.
00:52	Leafw	with macros, of course
00:52	Chouser	try (symbol (str ... ))
00:52	Chouser	but I think you have other problems with that macro
00:52	Leafw	thank you
00:53	Leafw	that is just an example
00:53	Chouser	ok
00:54	Leafw	wow this is nice.
00:54	Leafw	thank you Chouse
00:56	Chouser	:-) np
00:56	Leafw	this is awsome
00:57	Leafw	:)
00:59	Ycros	mmm, macro enlightenment
01:00	Leafw	yes.
01:00	Leafw	good night all.
02:19	Leafw	clojure's pastebin ?
02:21	lisppaste8	leafw pasted "macro primitives" at http://paste.lisp.org/display/61746
02:21	Leafw	I'd appreciate help with that macro
02:22	Leafw	it macroexpand-1 ok, and the code alone urns ok, but when called from a macro it fails with ArrayIndexOutOfBoundsException, which puzzles me
02:23	Leafw	if it makes you scream, this is just a test ......
05:22	cgrand	Leafw: did you make your sum<T> macro work?
08:32	Lau_of_DK	Is (lambda () (...)) directed swapped with (fn [_] (...)) in Clojure?
08:34	jteo	yup.
08:34	Lau_of_DK	k, thx
08:38	Lau_of_DK	user=> (def white (. (new Color 255 255 255 255) (getRGB)))
08:38	Lau_of_DK	#'user/white
08:38	Lau_of_DK	user=> white
08:38	Lau_of_DK	-1
08:39	Lau_of_DK	Should this return an object ?
09:00	Lau_of_DK	Noone knows? :)
09:00	rhickey	knows what?
09:00	Lau_of_DK	why white is -1 instead of a Color object
09:06	tomhickey	i believe it's because that's the result from calling getRGB (which returns an int)
09:07	Lau_of_DK	okay, thanks tom
09:07	Lau_of_DK	Not having worked with Java can trigger some dumb questions and Netbeans seems to have some flaws in its "intellisense"
09:36	Leafw	cgrand : no, I didn't
09:36	Leafw	new day, will try again
09:37	Leafw	should be using gensym instead of a __ in front of a var name, will fix that too ...
09:37	cgrand	leafw: you problem is with #^
09:37	Leafw	it's still here http://paste.lisp.org/display/61746
09:38	Leafw	the #^doubles type declaration?
09:39	Leafw	if I use it separately no problem
09:39	rhickey_	there are simple function casts for int/long/double/float and ints/longs/doubles/floats/ so you don't need to emit metadata
09:39	Leafw	will get to it in an hour or so
09:40	rhickey_	(let [arr (doubles a)] ...
09:40	Leafw	function casts? That's new to me
09:40	rhickey_	cast functions
09:40	Leafw	ok
09:40	rhickey_	they were always there for int/long etc, ints/longs are new
09:41	Leafw	yes, I know
09:41	Leafw	I'm Albert by the way.
09:41	Leafw	brb
10:20	lisppaste8	Lau_of_DK pasted "Ants-modified" at http://paste.lisp.org/display/61761
10:21	Lau_of_DK	Gents - Im trying to modified Rich's Ants example to simulate Langdons ant. So the first step was pretty simple, just modify the world to a checkerboard with alternating black/white squares. setup does this correctly, but I've hit a problem: Now it doesnt render anything at all. It wont render the checkers, and I tried just setting a random color to see if it would paint anything, but nothing happends - Am I overlooking something?
10:39	Lau_of_DK	no takers? :)
10:49	Chouser	Is there way to create a proxy with a method that returns "this"?
10:50	Chouser	Lau_of_DK: what you pasted doesn't run because of missing earlier bits (import, etc.) I'm too lazy to figure out what needs to be added. ;-)
10:50	Lau_of_DK	No that was on purpose, so you guys knew where the problem was :)
10:50	Lau_of_DK	But I can paste the whole thing
10:50	rhickey_	Chouser: is the this-returning method a method of one of the superclasses?
10:51	lisppaste8	Lau_of_DK pasted "Ants-modded" at http://paste.lisp.org/display/61762
10:51	Chouser	(let [myobj (proxy ... (mymethod [] myobj))]) ... doesn't work because myobj isn't bound correctly yet, right?
10:51	Chouser	rhickey_: yes. has to be for proxy, right?
10:52	rhickey_	yes, 'this is bound to this in all proxy fns
10:52	rhickey_	(mymethod [] this) should work
10:52	Chouser	rhickey_: oh! great.
10:52	Chouser	Lau_of_DK: are you not getting java.lang.ClassCastException: java.lang.Integer cannot be cast to java.awt.Color
10:53	Lau_of_DK	(getRGB) always returns an int, even in Rich's example
10:56	Lau_of_DK	Chouser, if I compile the whole thing, I get "IllegalArgument xception ISeq from: Symbol) but its pretty unclear whats firing it
10:57	Chouser	Lau_of_DK: I think I'm seeing the same exception
10:59	Chouser	anyone know how to get java to print the full stack trace instead of ending with "... 18 more" ?
11:00	Lau_of_DK	In SBCL you can set break-on-signals t
11:00	Lau_of_DK	If you want to break on signals that is
11:01	Lau_of_DK	Chouser, the exception comes when (go) tries to map the send-off, so setup might not be returning something that you can Iseq
11:01	Lau_of_DK	but this should affect the painting at this stage?
11:08	Chouser	Lau_of_DK: you need a [] after (defn go
11:11	Chouser	Lau_of_DK: I don't think you need (getRGB) at all -- just create the color object and pass that.
11:12	Lau_of_DK	And can test it, but can you see why it doesnt update the panel at all ?
11:12	Chouser	...and did you change setup? It looks like it used to return a seq of agents (as created by spawn-ant), but is now returning a seq of StructMaps (as returned by alter)
11:13	Lau_of_DK	yea, that was my mistake. I had to modify some of it. Now Ive simply moved the for loop to the bottom, which should return the ants, but instead it throws an error ala "No transaction running"
11:14	Lau_of_DK	And thats an illegal state exception
11:16	Chouser	I'm not seeing that.
11:17	lisppaste8	Lau_of_DK annotated #61762 with "setup-modded" at http://paste.lisp.org/display/61762#1
11:17	Lau_of_DK	Are you running it like that annotation ?
11:18	Chouser	nope. You had two separate loops before, and now have them nested?
11:18	Lau_of_DK	yea
11:19	Lau_of_DK	(doall is a nest, and (dosync is another
11:20	Lau_of_DK	But was does "no transaction running" mean? I was under the impression that dosync started a transaction
11:20	Chouser	to fit with the rest of the code, setup need to return a seq of agents.
11:21	Lau_of_DK	Yes - And I suppose it will do that, if I get past that exception, right?
11:21	Chouser	with your annotation, you've got an "alter coordiante" outside any sync
11:21	Chouser	and I think setup is returning a seq of alternating structmaps and agent-seqs.
11:22	Lau_of_DK	ok, well I guess thats just a matter of applying a sequences structure to them, but I really dont get that exception, where does it come from? Even if I wrap the top-nest in a dosync, it still fires
11:24	Lau_of_DK	ok, merged the loops, now it looks like its working
11:24	Chouser	great
11:25	Lau_of_DK	Yea - btw, thanks alot for helping out - I really hate these first few days with a new language, can feel abit like slamming your head against a wall :)
11:33	lisppaste8	Lau_of_DK annotated #61762 with "setup-working" at http://paste.lisp.org/display/61762#2
11:34	Lau_of_DK	That works. It alternates all the colors in a transaction and creates a sequence of ants on locked start-positions. But it does not motivate the program to render anything on the panel
12:04	lisppaste8	Lau_of_DK pasted "Ants-mod" at http://paste.lisp.org/display/61767
12:04	Lau_of_DK	Could somebody please have a look at this. It somewhat works. Setup initializes the board and creates ants. The frame is setup the way it should be, the only thing thats wrong is that I cannot get it to paint the panel
12:05	Lau_of_DK	Also, it doesnt throw any color exceptions
12:22	Lau_of_DK	Any ideas are welcome, Ive got nothing to go on
12:22	cgrand	Lau_of_DK: move (. g (drawImage img 0 0 nil)) in render after (dorun ...)
12:23	cgrand	(you have to first draw on the image, then draw the image)
12:23	Lau_of_DK	haah
12:23	Lau_of_DK	okay cgrand , thanks alot :(
12:34	Lau_of_DK	man this STM approach is awesome
12:36	Chouser	cgrand: is your js* up anywhere I can peek at it?
12:38	cgrand	chouser: http://code.google.com/p/clj-stuff/source/browse/trunk/clj-stuff/template/js.clj#85
12:42	Chouser	cgrand: thanks
12:42	cgrand	chouser: "process-form" is where the action tooks place
12:43	cgrand	(some examples: http://code.google.com/p/clj-stuff/wiki/TemplatingExamples#Javascript_HTML_templating_examples)
12:48	Chouser	cgrand: cool.
12:48	Chouser	the destructering is fantastic. ;-)
12:49	cgrand	thanks to macroexpand-1 :-)
12:50	Chouser	keywords in function position are automatically evaluted instead of translated?
12:55	cgrand	Hmm... a keyword in function position is handled by the default case of process-form: translating to a function call (and :kw becomes the identifier kw in js)
12:56	cgrand	so (:kw {:kw 1}) doesn't produce anything useful
13:33	lisppaste8	cgrand pasted "for chouser" at http://paste.lisp.org/display/61773
13:40	Chouser	hm. So what does (:id item) do in the wiki example?
13:47	cgrand	chouser: dynamically inserting the value of (:id item) (I was using an awkward special symbol named "jstr" but I changed that to support quote instead, I updated the wiki example)
13:55	Chouser	ah, I see. great.
13:55	cgrand	(jstr "#" (:id item) " a") meant at runtime evaluate (str "#" (:id item) " a") -- keep in mind that's a templating lib so some parts are static (and serialized once for all) and some are dynamic (and jstr (now quote) is delimiting dynamic parts)
13:56	Chouser	yup.
13:58	Chouser	it's very interesting. I'm not sure, but I think it's slightly different than what I was imagining.
13:58	Chouser	Or maybe you're just using it differently than I had in mind.
14:00	Chouser	of the 38k lines of JS I mentioned yesterday, none of it is generated dynamically. It's all static .js files.
14:01	rsynnott	yargh
14:06	cgrand	a simple use case is passing values computed by the server to the client-code eg generating something like: init({some: "js", data: structure}) (init being defined in an external js file)
14:09	Chouser	sure. we do that, but the json is converted from C++ data structures instead of clojure ones.
14:09	Chouser	What intruiges me would be the possibility of replacing the 38k lines of JS with some smaller amount of clojure.
14:10	cgrand	a complex use case is generating client-side templating functions from their server-side counterparts
14:10	rsynnott	common lisp has a very nice js generator thing; wonder has anyone done anything similar for clojure?
14:12	cgrand	chouser: by "some smaller amount of clojure", do you really mean Clojure or some notation for JS code?
14:13	Chouser	well... that's a good question. I mean something very very close to clojure.
14:14	Chouser	...as was discussed here yesterday.
14:14	Chouser	No sync or agents, but probably PersistentHashMaps and Vectors.
14:16	Chouser	I want to be able to use some (most?) of the Clojure idoims, instead of some new idioms required by a goofy offspring of JS and Clojure.
14:29	Lau_of_DK	Can somebody explain some of the syntax from Rich's ant simulator? In (behave) he sometimes has this action (-> loc drop-food (turn 4)) what is that?
14:34	Chouser	-> is a macro that pass each expression as the first argument of the next expression
14:34	Chouser	it turns it turns it inside-out, so that becomes: (turn (drop-food loc) 4)
14:38	Chouser	man, I can't type. sorry.
14:40	Lau_of_DK	man thats a weird macro, is that widely used in your programs?
14:42	Chouser	It's nice in limited context where it's easier to read the other way around.
14:42	Chouser	...and it saves parens, which is great in this economy with the high paren prices and all.
14:42	Lau_of_DK	ok, well thanks alot for the explanation, Im glad I didn't go with my intuition
14:51	rapido	rich, have you considered using treaps for set operations?
14:52	rapido	here's the paper: http://www.cs.cmu.edu/afs/cs.cmu.edu/project/scandal/public/papers/treaps-spaa98.pdf
14:52	rapido	a nice property of a treap is that they always turn into the same structure, independent of insertion order
14:53	rapido	i think clojure has the right default: immutability will save the world ;)
14:54	rapido	with persistents treaps the set operations, such as union, difference, etc can be made optimal
15:14	lisppaste8	Lau_of_DK pasted "Almost-Ants" at http://paste.lisp.org/display/61777
15:14	Lau_of_DK	Chouser, - or anybody really - Can somebody tell me why behave looks like its executing once, and then returns nil and the program "halts"
15:14	Lau_of_DK	?
15:35	Lau_of_DK	Good question huh? :)
15:38	Chouser	why does it "#'behave" instead of just "behave". Rich's original does too.
15:38	Lau_of_DK	Im not sure
15:43	Chouser	well, that code's still throwing an exception for me, regarding color.
15:44	Lau_of_DK	really?
15:44	Lau_of_DK	Thats "impossible", I've removed all those
15:44	Lau_of_DK	Sure you loaded a fresh file in a fresh repl ?
15:45	Chouser	yeah, it's the 0 on line 25
15:46	Lau_of_DK	argh, you've got sharp eyes
15:46	Lau_of_DK	Or do you have some type of debugging tool that told you ?
15:47	Chouser	no, I'm running the thing and it crashes.
15:47	Chouser	java gives me a stack trace.
15:48	Chouser	the reason you only get one cycle appears to be because of a crash in the agent function as well.
15:49	Chouser	java.lang.NullPointerException at clojure.fns.user.behave__1888.invoke(ant.clj:99)
15:49	Lau_of_DK	by "the agent function" you mean (behave) ?
15:51	Chouser	looks like it. I just meant that because the crash is from inside an agent, it doesn't get reported as conveniently.
15:52	Chouser	I don't really know this code at all, so I'm learning as I go here.
15:56	Lau_DK	Sorry Chouser , Gnome just crashed, last thing I got was you said some invoke error on line 99
15:57	Chouser	ok. Yes, I guess I meant (behave). But the reason I didn't say that is I wasn't sure which function the agent was running when the exception was thrown.
15:57	Chouser	I don't really know this code at all, so I'm learning as I go here.
15:58	Lau_DK	ah ok. Well I really appreciate you taking the time, just let me know if its too much. But before you say stop - What could cause that error in behave? Basically its just (move loc) loc) - thats it
15:59	Chouser	somehow the locs are getting set to nil.
16:02	Lau_DK	For some odd reason I'm not getting the debug information that you are
16:03	Lau_DK	To me it just runs, then stops
16:05	Chouser	oh, nevermind. it's still running, just the ants aren't going anywhere.
16:05	Lau_DK	Oh - So it just returns nil after having sent off every ant?
16:05	Chouser	no, I was wrong about nit
16:06	Chouser	nil
16:06	Chouser	(cond (not (:ant @ahead))
16:07	Chouser	(move loc))
16:08	Chouser	(:ant @ahead) seems to always return a hash, which is true, so (move loc) never gets called
16:09	Lau_DK	I just removed the whole cond, so its only (move loc) loc)
16:09	Chouser	...and I wasn't completely wrong about nil. (behave) used to return loc from inside the sync, but your version it's outside the sync. That seems to matter.
16:09	Lau_DK	still just stays in the middle... but move seems to work when I test it in repl
16:10	Chouser	Lau_DK: I think you've made more changes than you realize or something.
16:10	Chouser	we've found several of these functions are returning different types of objects than they used to.
16:10	Lau_DK	Ive made quite a few - But there's quite a gab in the purpose of the applications, they just share the name and the need for drawing a JPanel :)
16:10	Chouser	you might want to back out your changes and make them more incrementally, testing as you go.
16:10	Lau_DK	I'll right, I'll run through the whole thing
16:11	Chouser	oh. well, in that case you might try starting from scratch and writing just what you need.
16:11	Chouser	It's hard to change a program correctly without understanding what's already there.
16:11	Lau_DK	Yea, maybe I should. I just figured I'd be an easy way to learn som basic clojure
16:11	Lau_DK	Considering I've heard Rich explain most of it on a video
16:11	Chouser	I'm not sure that demo counts as "basic clojure" ;-)
16:11	Lau_DK	hehe - I would actually agree
16:12	Chouser	anyway, I'm done for now. good luck.
16:12	Lau_DK	Thank you so much for your help
16:13	Chouser	if you want to tell me why I can't get my jtable to use a monospace font, that'd be great.
16:13	Chouser	actually, I think I need to punt on that problem as well.
16:13	Lau_DK	Did you set the font in the cell renderer?
16:14	Lau_DK	perhaps you should check out the API doc for this table.setDefaultRenderer(Object.class, new TableCellRenderer());
16:16	Chouser	yeah, I've got all that. And I can create and set the font, but only the size and style seem to actually get applied. The font family is ignored.
16:48	Lau_DK	Since progn is removed from clojure, what do we use instead?
16:50	Chouser	do
16:51	Lau_DK	thanks, btw. Chouser , ants are moving now :)
16:51	Chouser	nice
16:51	Lau_DK	Yea, when you can change the code while the GUI is running, you really have an advantage
18:54	Lau_DK	Chouser, you still up ?