#clojure – 2008-07-26

2008-07-26

01:55	jykrd	hi
01:56	jykrd	I'm trying to figure out how to convert java into clojure. As an exercise, I'm trying to convert this: http://www.devdaily.com/java/edu/pj/pj010016/pj010016.shtml
01:56	jykrd	(runs system commands)
01:57	jykrd	And to go off of, I'm trying to glean the method from the gui example on the wiki
01:58	jykrd	so the first thing I did was converted this: Process p = Runtime.getRuntime().exec("ps -ef");
01:58	jykrd	to this: #^Process p (. (. (Runtime getRuntime) exec (str "ps -ef")))
01:59	jykrd	(inside a let)
01:59	jykrd	But I get the feeling that's not the correct way
02:00	jykrd	I'm not worried about the str so much.. more so the #^Process at the beginning
02:05	mebaran151	I think you can drop that
02:05	mebaran151	clojure does a little bit of type inference
02:06	jykrd	so does Runtime.getRuntime() always return a Process? I was figuring that line was doing type casting, or casting to the super, or something
02:06	jykrd	Would have expected to see Runtime p = Runtime.getRuntime()
02:07	mebaran151	I'm not super familiar with that call
02:07	jykrd	ok
02:07	mebaran151	but yeah, I suppose if the javadocs say so it must be true
02:07	jykrd	well, from the repl, that compiles, so I guess I'll keep trucking
02:08	mebaran151	I think it just takes those comments as hints though
02:08	mebaran151	so even if you were wrong, it would valiantly try
02:08	jykrd	now, to do this in a let : BufferedReader stdInput = new BufferedReader(new
02:08	jykrd	InputStreamReader(p.getInputStream()));
02:08	mebaran151	I hate how long java names are
02:09	jykrd	would is there a more graceful way than: stdinput (new BufferedReader (new InputStreamReader (. p getInputStream)))
02:10	mebaran151	not in java land
02:10	jykrd	ok.. Well that might work then
02:10	mebaran151	but I don't think it would be much more graceful in java anway
02:10	jykrd	well, I mean, in clojure, is there a better way than calling a new withing a new
02:13	mebaran151	you can use doto for a lot of this
02:13	mebaran151	oh yeah
02:13	mebaran151	ClassName.. make work
02:13	mebaran151	I think I saw that in the docs
02:13	mebaran151	it's a macro that automagically instantiates that class
02:14	jykrd	huh
02:14	jykrd	it works
02:18	jykrd	You know what they need in the docs, under the "clojure for java people" section.. is a "converting a 'while' structure into clojure" and the like
02:22	mebaran151	yeah I'm using it for a cool webstartup that's partially written in scala
02:22	mebaran151	it would be really nice if the docs weren't so non-existent
02:23	mebaran151	or at least if they could wiki the doc section so we could add comments
02:23	mebaran151	you wouldn't use a while loop in clojure thouhg: it's not very functional
02:23	mebaran151	what are you trying to do
02:23	mebaran151	usually map or reduce will get you 90 percent there....
02:24	jykrd	trying to do:
02:24	jykrd	while ((s = stdInput.readLine()) != null) {
02:24	jykrd	System.out.println(s);
02:24	jykrd	}
02:25	mebaran151	reading a file eh
02:26	mebaran151	I've never really understood how do that functionally but we could write a monster hybrid for kicks
02:26	jykrd	And I'm actually thinking: (loop [s (. stdInput readLine)]
02:26	jykrd	(when-not (= s nill)
02:26	jykrd	(.. System out (println (str s)))))
02:26	jykrd	std input
02:26	mebaran151	I think loop is only for recur
02:27	jykrd	oh yea, and I'd have to add a recur at the end I guess
02:27	mebaran151	you could do something using
02:27	jykrd	with the same condition as when-not or something
02:27	mebaran151	(repeatedly (. stdInput (readline))
02:27	jykrd	hmm
02:27	mebaran151	that builds a lazy list of readlines
02:27	jykrd	really?
02:27	mebaran151	yeah
02:27	mebaran151	cloisng the file might be problematic though
02:28	mebaran151	if you close the file and try to run that
02:28	jykrd	its std input, not a file
02:28	mebaran151	some sort of exception has to be thrown
02:28	mebaran151	stdinput my bad
02:28	jykrd	you remember which doc page the repeatedly was on?
02:28	mebaran151	the api is all doc'ed alpabetically
02:28	mebaran151	do a search text in firefox for lazy
02:29	mebaran151	and you'll find a lot of cool macros rick wrote
02:30	jykrd	gah, it's all so terse
02:33	jykrd	so, (repeatedly (.. System out (println (. stdInput (readline))))
02:33	jykrd	or something?
02:39	jykrd	gah.. looping control structures.. I'm having such a hard time wrapping my head around them in a functional way
02:40	mebaran151	yeah
02:40	mebaran151	io is not the best place to learn about fp
02:42	mebaran151	it would more like be something like
02:44	mebaran151	repeatedly (fn [] (.. System (println (.stdInput (readline))
02:50	jykrd	eeeoooh
02:56	mebaran151	you might put some more conditional logic in there
02:56	mebaran151	to represent each iteration
02:57	jykrd	yea, it's flooding the screen with nills
02:57	mebaran151	oh yeah
02:57	mebaran151	don't directly type in repeatedly
02:57	mebaran151	it will try to evaluate it fully
02:57	mebaran151	you have set it equal to something
02:57	mebaran151	like (def lines (repeatedly what .....))
02:57	mebaran151	then do first and rest stuff on it
02:57	jykrd	huh
02:58	jykrd	hmm
02:58	mebaran151	to print something it has to evaulate it
02:58	mebaran151	prn recursive tries to print everything, which fails for an infinie list
03:00	mebaran151	just keep a little pointer around and iterate until nil
03:01	jykrd	oh my gosh, it almost works :)
03:01	hoeck	or use (take n (repeatedly ..))
03:04	jykrd	wow.. I've got output
03:05	jykrd	I'm running the my linux' ps command from clojure ! :)
03:06	jykrd	now I just need to round this out into a tool of some sort and I might be able to start doing shell scripting with clojure
03:06	jykrd	you guys kick ass.. thanks.. I need to sleep now, but I'm glad I stayed up :) night
03:07	mebaran151	np
03:07	mebaran151	just looking at line-seq
03:08	mebaran151	I think that clojure should have some more clojurey file openers
03:09	hoeck	mebaran151: what about "slurp"?
03:10	mebaran151	isn't that only for valid clojure files though
03:10	mebaran151	you know
03:10	mebaran151	better reading and writer
03:11	mebaran151	and maybe some more in depth control structures
03:11	mebaran151	*deserializing structures
03:11	mebaran151	boy am I tired
03:12	mebaran151	also I was workng with a colleague in clojure (which we've snuck in our project via the all knowing JVM)
03:12	mebaran151	we think that it would be relaly nice if you guys could open the clojure api to wiki comments
03:12	mebaran151	sort of like php
03:13	hoeck	aha, i don't know much about php
03:14	mebaran151	I don't either
03:14	mebaran151	but when I had to fix one script
03:14	mebaran151	it was really nice that the php docs had a comment section
03:14	mebaran151	and other users had recorded their thoughts
03:14	mebaran151	spruced with a little ajax, people could note whether or not to look at the comments
03:14	mebaran151	sometimes the function is sort of unclear how it works, esp with things like refs and agents
03:16	mebaran151	the massive alphabetized list of functions is also rather unappealing: maybe some sort of tagging system to relate what their good for that people could use to sort them
03:18	mebaran151	also it's almost idiotic that we don't have a siimple way just to eval code and I have go through hell just to turn a string into a BufferedReader for eval like semantics
03:18	hoeck	yeah, the api docs are really huge and hard to search, especially if you don't know which function to search for
03:20	mebaran151	exactly
03:20	mebaran151	I'm currently writing a little object store in clojure sort of rucksack
03:20	hoeck	if you're on the repl, you can use (find-doc "file") to search for all functions containing "file" in their docstring
03:21	mebaran151	you have any suggestions, especially with regards to efficiently serializing a b* tree
03:22	hoeck	no, not really
03:22	mebaran151	it's hard to find good byte reading stuff on clojure
03:23	mebaran151	and I don't know much about training the interpreter to be more efficient at slurping in objects
03:24	hoeck	what kind of objects?
03:25	mebaran151	arbitrary hashes really
03:26	mebaran151	I do all the db management stuff using metadata which is really rather convenient
03:28	hoeck	i'm still wondering for what and when to use metadata, except for docstrings and test-related stuff
03:59	hoeck	mebaran151: i guess rhickey is going to think about your suggestions when he is up again.
04:00	hoeck	just found out that find-doc doesn't print the function name :(
04:00	mebaran151	I keep the original hash of the reconstructed object and its id in metadata, and using those I can determine whether I should update the object in the db or do nothing
04:00	mebaran151	when a call to save is made that is
04:00	mebaran151	I hope he does
04:01	mebaran151	I think clojure is a pretty cool language
04:01	mebaran151	that could use just a little bit more love
04:06	hoeck	aha, nice
04:07	hoeck	what do you use for interfacing with the db?
04:22	mebaran151_	I'm gonna write that back end part later
04:22	mebaran151_	write now
04:22	mebaran151_	the filesystem is doing all the heavy lifting
04:24	mebaran151_	for this project, I was scared over overflowing int so I decided to make my primary keys vectors of integers which would map to file paths that would each contain buckets of say 128 tiny objects could be slurped up and sliced and diced
04:27	hoeck	so you're using the clojure reader to read those vectors?
04:27	Laurent_	nickname lpetit
04:38	mebaran151_	hoeck: currently yes
04:39	mebaran151_	I'm planning on supporting a sane way to query with simple key value semantics that can be joined together or orred
04:40	mebaran151_	I've never found SQL very easy to grok myself
04:43	hoeck	mebaran151_: i learned sql by reading the documentation and source at work and by the help of my colleagues
04:43	mebaran151_	I know SQL, just it seems so inefficient to produce massive query strings
04:43	hoeck	but got really enlightened by the relational algebra
04:44	mebaran151_	and much of this data is free form, so it doesn't fit in the table metaphor very well
04:45	mebaran151_	I know a bit of relation algebra actually. If SQL didn't seem so obsessed with covering up its relation roots
04:45	mebaran151_	it might be more sane to code gen it
04:46	mebaran151_	and I never thought it really stuck with lisp very well
04:50	mebaran151_	anyway I'm going to bed
04:50	hoeck	but the relational algebra fits good into the lisp world, imho
04:50	mebaran151_	it does
04:50	mebaran151_	I'll agree with that
04:50	mebaran151_	however, far too many problems get solved with SQL aren't really relational in nature
04:51	hoeck	a algebra->sql compiler is on my todo list :)
04:51	mebaran151_	and SQL doesn't do its roots justice I don't think
04:51	mebaran151_	it seems as though all the latest database tech is leaving the relational word
04:51	mebaran151_	with products like s3 and clouddb and the whole google appdb
04:52	hoeck	yeah, i've heard of that
04:52	mebaran151_	it seems as though relational logic should be done in the language itself
04:52	mebaran151_	with conj and disjuct operators on sets
04:52	hoeck	they are more like big berkeley-dbs
04:53	mebaran151_	we're planning on using S3 for some stuff in our app, so it seemed logical to role our own simple query engine
04:53	hoeck	i'm only working on a small-scale client-server insurance management application
04:54	mebaran151_	we're not so big yet ourselves
04:54	hoeck	(at work) so sql really fits that model
04:54	hoeck	aha
04:54	mebaran151_	sql is a good fit if all your data is going to look the same
04:54	hoeck	but i guess its hard to roll your own query engine efficiently
04:55	mebaran151_	reading up on redblack trees
04:55	mebaran151_	which I half way remember how to implement
04:55	mebaran151_	there isn't too much magic to SQL systems, esp for single transactions
04:56	mebaran151_	you can either loop over all the blocks of the rows in O(n) or hopefully leverage a query and do your work in O(log n)
04:57	mebaran151_	it's handling insertion and deletion properly that normally gets ya, but I think Clojure actually provides some pretty powerful primitives along those lines
04:57	mebaran151_	*leverage an index
04:59	mebaran151_	as none of the individual queries are going to be very complex, i really doubt that there will be too much room for a normal SQL engine to optimize their order, though I could be very ver wrong
05:00	hoeck	sometimes i'm really surprised how fast a crappy multiline sqlstatement on a long grown database schema can be
05:01	mebaran151_	yeah
05:01	mebaran151_	is there anything good in clojure world for sql mapping
05:01	hoeck	okay, for short queries, i guess its the index which is responsible for the speed
05:01	mebaran151_	cl lisp had rucksack and I looked at elephant, but didn't find much for clojure
05:02	hoeck	spring,hibernate :)
05:02	mebaran151_	most of the beneift of a big database comes from the fact the daemon can arbitrate queries and optimize the order in which they are received for locaity
05:03	mebaran151_	wouldn't hibernate fail though because clojure hashes aren't really classes?
05:03	hoeck	iirc, there was a simple jdbc->clojure thing on the mailinglist
05:03	mebaran151_	seems like hibernate would have to be very Java or at least class oo centric
05:04	hoeck	i just know hibernate as a buzzword
05:05	mebaran151_	I've used it a little bit
05:05	mebaran151_	it's pretty pretty fancy
05:07	hoeck	i never used java before, clojure was my first encounter with java
05:08	hoeck	but i really like the java libs, though their use seems often over-complicated, once i have something working in clojure, i can abstract the uneccesary java-gluecode stuff away
05:08	hoeck	so clojure +1!
05:10	mebaran151_	I moved from Scala to Clojure
05:10	mebaran151_	sometimes I mis the static types
05:11	hoeck	do you miss them for the speed you gain from static typing?
05:12	msingh	are places first class in clojure?
05:13	mebaran151_	hoeck: not for the speed, but for the way it guided my modeling
05:13	mebaran151_	I have to be much more disciplined as I write lisp
05:13	kotarak	msingh: ehem... What is a place?
05:13	mebaran151_	I think clojure does a halfway decent job of coercing types
05:14	msingh	kotarak: not sure :)
05:14	mebaran151_	it's sort of like the difference between installation on a mac and on a PC: it took me forever to get used to the fact that you could just drag files to the Applications folders and everything could just work
05:15	mebaran151_	something about static typing makes me feel warm and fuzzy
05:16	msingh	yes, that's how a straight jacket feels like
05:16	mebaran151_	well it does catch some quick bugs and makes sure that your functions interop properly
05:17	msingh	not an issue
05:17	kotarak	there is a nice example, where static type checking (with inferencing) caught a infinite loop.
05:17	msingh	in lisp programming you test your functions as you work on them so those bugs tend to get caught by the programmer as a matter of course
05:18	mebaran151_	but for a current project, I want to be able to easily turn some of my functions into xml
05:18	mebaran151_	lisp is really really really good for that
05:18	kotarak	type are another layer to transport information.
05:18	hoeck	i like the way common-lisp provides types, for having speed where its necessary
05:18	mebaran151_	the JVM mostly discards your type info
05:19	mebaran151_	most of what I read doesn't really put too much emphasis on types
05:19	hoeck	yeah, on java, speed isn't such a big issue
05:19	hoeck	aha
05:19	mebaran151_	most of them can be inferred by a smart compiler (aka Hotspot) and fairly efficiently statically inlined
05:23	hoeck	i wrote a little physics simulation in clojure, and it was as slow as hell :(
05:23	hoeck	compared to the c++ demo in ran in wine
05:23	mebaran151_	hotspot does take awhile to warm up though
05:24	mebaran151_	and I don't know much about how well it vectorizes code
05:24	hoeck	but it was fully dynamic, like adding objects at any time
05:25	hoeck	well, it used the boxing number types in clojure, and vector-tuples, so it wasn't trimmed on speed either
05:25	hoeck	and it was way more fun than writing a c++ app :)
05:26	mebaran151_	can you tell clojure to downcast if to unboxed primitives if you know best?
05:27	hoeck	there are some tweaks on unboxed array access, and on using unboxed numbers
05:29	hoeck	it was discussed in a group-thread about imagej
05:54	mebaran151_	I need to get myself on the list...
05:56	hoeck	clojure moves pretty fast, personally, i read the list and the clojure-log
06:05	mebaran151_	because otherwise, I don't see any reason why clojure objects should technically have any slower dispatch once compiled
06:05	mebaran151_	but I'm gonna take a na
06:05	mebaran151_	p
06:06	mebaran151_	good night all
11:47	jykrd1	yerrp
11:56	jykrd1	I've got clojure to run the ps command, so the output is like: ("UID PID PPID C STIME TTY TIME CMD" "root 1 0 0 Jul25 ? 00:00:02 /sbin/init" "root 2 0 0 Jul25 etc.
11:56	jykrd1	but there's no /newlines in the output
11:57	jykrd1	it's just one long string.
11:57	jykrd1	doesn't ps print a string formated with new lines?
11:57	kotarak	What you just pasted is a list of strings, each string representing one line.
11:57	jykrd1	and tabs
11:57	rhickey	that looks like a list of strings
11:57	jykrd1	oh
11:58	jykrd1	so, lines (repeatedly (fn [] (. stdInput readLine))) is creating a list of words, rather than lines, really
11:59	jykrd1	er, (let [lines (repeatedly.... etc
11:59	rhickey	no, it's creating a list of lines, each of which is a string
11:59	kotarak	I would expect it to produce, what you pasted: a list of lines
12:01	rhickey	readLine doesn't return the line terminators
12:01	jykrd1	right... so should I concatenate a /nl onto lines each line after it returns?
12:01	rhickey	depends on your goal - what is your goal?
12:02	jykrd1	to make a function that can take any shell command and return it like it would in the shell, i guess
12:03	rhickey	return a single string or print it?
12:03	rhickey	print directly: (dorun (map println ["a" "b" "c"]))
12:04	rhickey	print into a string: (with-out-str (dorun (map println ["a" "b" "c"])))
12:04	rhickey	replace ["a" "b" "c"] with your list of lines
12:44	albino	jykrd: fyi, I think the java sigar libs have ps in them if you wanted to call an api instead of forking a process
13:03	jykrd	albino: thanks. Actually it was just an example. Was wondering if I could use Clojure for shell scripting. some kind of run-command function might help with that.
13:03	jykrd	seems to work
13:04	kotarak	Heretic, I know, but: there is also scsh which is kind of specialised on shell scripting, in case you just want something lispish.
13:05	albino	jykrd: It's a good use case, a lot of what I do is fork processes with my code so I would want some sort of abstraction for that
13:17	shoover	albino: Just curious, what's the nature of your forking? Is it aimed at fault tolerance or just not sharing state across threads or something else?
13:20	albino	shoover: getting stuff done on unix requires calling all sorts of command line utilities
13:20	albino	shoover: for work I write a lot of code that automates the use of our products via command line
13:20	albino	shoover: In my case it ends up being calls to subprocess.Popen in python
13:24	shoover	albino: ah, ok, you're talking about good ol' shell scripting. I was getting ahead of myself thinking you were wanting the process abstraction for full-blown Clojure apps.
13:27	albino	shoover: yep, no api like the command line :)
13:42	mebaran151	I'm gonna reiterate my proposal for wiki'izing the docs
13:42	rhickey	there is a wiki, the docs are a reference
13:43	mebaran151	it would be nice if they weren't just a long alphabetical list
13:43	rhickey	there are many pages of docs in addition to the API list
13:44	mebaran151	and I think certain functions could stand nice little docs
13:44	mebaran151	*comments
13:45	mebaran151	kind of the way php lets users add optional annotations and tips
13:45	rhickey	link?
13:51	rhickey	mebaran151: hello? do you have a link for the php wiki you are recommending I emulate?
13:51	mebaran151	oh sorry
13:52	mebaran151	I have to refind it: I haven't done php in quite awhile but I remember the comment system being superb
13:54	mebaran151	http://www.php.net/manual/en/install.macosx.bundled.php
13:54	mebaran151	look at the user contributed notes section
13:54	arohner	postgres has something similar
13:54	arohner	http://www.postgresql.org/docs/
13:54	mebaran151	postgres I think took the idea from the PHP people
13:55	arohner	the API section on the website is generated from the docstrings in the code, right?
13:55	arohner	so it's simple enough to patch that
13:56	mebaran151	we could add a more human feel if we did it this way: esp when it comes to little examples for the fancy concurrency goodness that's baked in
13:56	rhickey	the wikispaces I am using currently has no membership granularity - i.e. all members can edit pages and submit comments. I really don't want people editing pages. I would prefer people use the wiki and build any supplementary material they want. I've asked for examples many times - people will get out of it what they put into it
13:57	rhickey	I understand the docs are not much of a tutorial
13:58	mebaran151	I was pretty new to LISP, but luckily alot of the scheme stuff on the internet helps out
13:58	rhickey	but there needs to be an accurate reference somewhere
13:59	rhickey	I've also put up many hours of talks on blip.tv
14:01	mebaran151	I've watched them, and they were very informative and what alerted me to clojure in the first place. However, talks are very inefficient when it comes to trying to find specific information.
14:01	mebaran151	you can't just search text or skim a talk
14:56	jykrd	I'd find it useful if someone put examples in the java section of the wiki that described conversion practices, like converting a while loop int clojure
15:30	jgrant	is clojure a lisp-1 dialect ?
15:31	kotarak	I think so.
15:31	kotarak	jgrant: http://clojure.org/lisps has more info on this.
15:32	jgrant	Really then why is this a problem ? -->
15:32	jgrant	Clojure
15:32	jgrant	user=> (defn fact[n]
15:32	jgrant	(if (= n 0)
15:32	jgrant	1
15:32	jgrant	(* n (fact (- n 1)))))
15:32	jgrant	#'user/fact
15:32	jgrant	user=> (fact 10000)
15:32	jgrant	java.lang.StackOverflowError
15:32	jgrant	java.lang.StackOverflowError
15:32	jgrant	at clojure.lang.Numbers$IntegerOps.equiv(Numbers.java:444)
15:33	kotarak	Because the jvm has no tail call optimisation
15:33	kotarak	use loop and recur for such things
15:33	jgrant	that function does not use tail-recursion
15:34	jgrant	just simple recursion
15:34	kotarak	jgrant: then it will even stack overflow on things like scheme
15:34	jgrant	no you are wrong about that
15:37	kotarak	jgrant: no I am not. The nice thing about tail recursion is that it runs in constant space (with TCO), recursion as in your example does not since the original context has to be saved.
15:38	jgrant	recursion in lisp or dialects is idiomatic and fundamental
15:38	jgrant	it's one of the things that make lisp well.... ...lisp
15:38	kotarak	yes and every decent text will tell you: use tail recursion.
15:39	jgrant	really ? which ones ?
15:39	jgrant	tail recursion is simply an optional compiler optimization
15:39	kotarak	eg. "teach yourself scheme in fixnum days", IIRC
15:39	jgrant	it's not required by any implementation
15:40	kotarak	in scheme it is part of the RxRS
15:41	jgrant	the code above runs perfectly on mzscheme, scheme48 and a couple others
15:41	mac__	kotarak is right, you can't get optimization unless you have the recursive call in a place that the compiler recognizes as tail position, even in other lisps. If you do a non tail recursion that is large enough you will blow the stack. Nothing strange about that, just has different limits (depth) in different languages and runtimes
15:41	jgrant	also with slight modification on sbcl, allegro, clozure(ccl) and lispworks
15:42	jgrant	kotarak has changed my initial question
15:42	jgrant	i'm not asking about tail call optimization
15:42	kotarak	I did?
15:42	jgrant	simply recursion
15:42	mac__	oh, then use loop/recur to get optimization, otherwise it will be nested calls
15:42	kotarak	You asked, why your code does not work. And it doesn't work because it uses recursion.
15:43	kotarak	Even with tail recursion it wouldn't work, because the JVM does not support TCO.
15:43	jgrant	is it 'my' code that does not 'work' ?
15:44	mac__	but loop/recur in clojure "supports TCO" :) so use that?
15:44	jgrant	that's merely and idiomatic factorial function
15:44	jgrant	for ANY lisp dialect
15:44	kotarak	jgrant: sorry. It works. But it has a problem.
15:44	jgrant	lets try this from another angle...
15:44	Chouser	jgrant: your example will use 10000 stack frames in very nearly any language. Whether that's enough to cause an exception or not has to do with how deep the stack can get.
15:45	mac__	^^
15:45	Chouser	I believe there is a command-line option for java to request a bigger stack.
15:45	jgrant	Chouser : no it will not
15:46	jgrant	this is one if the reasons why people choose to use Lisp(or dialects) over stack based languages/vms
15:48	Chouser	lisp uses a stack. What little CL I know I learned from "on lisp", and it devotes several sections on how to restructure your code so that recursion happens in the tail position.
15:48	kotarak	SICP (or how it is called) will probably say the same.
15:49	mac__	yes and SICP is about scheme, not CL, so that goes for scheme too, at least their version
15:50	kotarak	TCO is a requirement in the RxRS, the Scheme standard.
15:51	mac__	which means it has a stack ;)
15:51	jgrant	kotarak, Chouser : you are confused about the use of the word 'stack' in 'On Lisp' and 'SICP'
15:51	jgrant	In 'SICP' page 506 he's referring to the implementation of a stack for the register machine NOT a stack in the underlying implementation of Scheme
15:53	jgrant	All of CH.5 in 'SICP' covers the design/implentation of a register machine using scheme
15:53	mac__	Seems like this discussion has derailed because no matter who is right, it will still blow the stack in clojure since it uses java calls and the jvm does not do TCO so you have to use loop/recur to not blow the stack on deep recursion.
15:54	mac__	It's even kinda nice actually since the compiler will tell you when recur is not in tail position so it always get's optimized.
15:54	jgrant	mac__ : by that logic ANY lisp/scheme implementation should have the same problem because it's implemented in C/C++
15:54	jgrant	mac__ : but somehow it does not ;-)
15:56	jgrant	so it's hard to call clojure a dialect of lisp (even a lisp-1) if simple recursion is not supported
15:56	mac__	I was trying to answer you question which was why you couldnt do recursion that way safely in clojure right? The answer is that the jvm uses a stack and you are using too many stack frames with that function and therefore you need to use loop/recur instead or make the stack limit higher. There is no other way that I know of in clojure
15:57	jgrant	mac__ : this has less to do with the JVM but the actual implementation of clojure
15:58	mac__	well yes, but that's part of my point, since clojure uses javas call mechanism it is this way
15:59	jgrant	mac__ : right and if it does then you have hit it on the head as to why that's the problem
16:00	jgrant	mac__ : and why clojure is not a dialect of lisp at all (but does has some lisp features in syntax, macros)
16:00	mac__	Well, I'm not good enough at all this to answer why rich did it that way, you need to ask him. I think I've seen a discussion about this on the google group, start by searching there
16:00	jgrant	mac__ : I would love to hear Rich's response on this, could you point me to it somewhere ?
16:00	kotarak	I think it was something about Java interaction.
16:00	Chouser	it doesn't blow the JVM operator stack (which is used instead of registers), it blows the JVM's call stack, which all these languages use.
16:01	mac__	here is the group, don't recall the discussion topic though, use the search field
16:01	mac__	http://groups.google.com/group/clojure
16:02	jgrant	Thanks
16:03	jgrant	So according to Rich Clojure will never be a lisp dialect but simply some type of functional language
16:03	jgrant	Clojure could have been implemented with a heap-based stack, with a
16:03	jgrant	cost in performance and call-compatibility with Java. I chose not to
16:03	jgrant	do so, and am very happy with the results. It's not an aspect of
16:03	jgrant	Clojure that is going to change.
16:03	jgrant	Sorry the last 5 lines are a quote
16:05	jgrant	and
16:05	jgrant	RIch : As such, it has its own set of idioms.
16:05	mac__	there you go, it's for performance and java interop, good reasons IMO, you get used to loop/recur pretty fast
16:06	jgrant	and that's fine I agree completely that not all functional languages will follow all of Lisps features BUT it's these features of Lisp that make it
16:06	jgrant	and Clojure should not be referred to as a Lisp by any stretch
16:07	jgrant	It's definitely not a lisp-1
16:09	jgrant	The very first paper by McCarthy in 1960 was titled "Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I"
16:10	jgrant	which detailed Lisp's design
16:13	jgrant	The very first 2 implementations by Russell (in assembly language) supported recursion
16:13	arohner	what does lisp-1 vs. lisp-2 have to do with recursion?
16:14	mac__	well if you absolutely insist that recursion must be done using the original name of the function then you can avoid stack blowage by using a lazy sequence in clojure, look up lazy-cons. I don't see you point at all.
16:14	jgrant	It cannot even be done with (recur ...) in clojure , you are forced to implement it as tail-recursive
16:14	mac__	if you can write a function that looks like a recursive function but compiles to an iterative loop, why do you need to care?
16:14	jgrant	what about n-recursive functions ?
16:16	jgrant	So fine Clojure is a functional language
16:16	jgrant	but please do not keep calling it a Lisp (see the headline of this room above)
16:37	shoover	that's an interesting definition of lisp. McCarthy's paper just says functions can call themselves, with no stated depth requirement. Norvig and Pitman say not to use recursion for iteration (http://www.cs.umd.edu/~nau/cmsc421/norvig-lisp-style.pdf). And a simple emacs lisp function just blew up at a depth of 347.
16:38	kotarak	Since the state of the function has to be saved, it doesn't matter whether you have a stack or not. At some point in time you will run out of space. With a tail call and TCO the function runs in constants space. So this cannot happen.
16:38	shoover	Ah, that too
16:40	mac__	yeah, jgrant was weird. I always thought what made lisp lisp is the combination of read/eval and sexp/macros
16:40	mac__	that's pretty much the only thing still unique to lisp
16:41	kotarak	I actually don't care. Lisp is Lisp. Clojure is Clojure. Scheme is Scheme. And at least the latter two are fun. :)
16:42	mac__	yeah I don't understand why he made a big deal about it
16:44	shoover	This all speaks to the accuracy of Clojure's tagline. Please don't change it
17:19	albino	Is someone here writingcode.blogspot.com ?
17:47	Chouser	well it's a little unfair to challenge jgrant's statements while he's not here, but I don't want to leave them unchallenged.
17:48	Chouser	If I understood him correctly, the following Common Lisp function when called will run forever but not crash: (defun i () (+ 1 (i)))
17:48	kotarak	That was his claim.
17:48	Chouser	Executing that in Steel Bank Common Lisp, I get "Control stack exhausted (no more space for function call frames). This is probably due to heavily nested or infinitely recursive function calls."
17:49	kotarak	Surprise.
17:50	Chouser	Similarly in clojure, (defn i [] (+ 1 (i))) produces java.lang.StackOverflowError
17:50	kotarak	It doesn't matter whether there is a stack involved or not. The machine has only finite memory to save function contexts.
17:50	Chouser	(when I run (i))
17:50	kotarak	There was some explanation like this:
17:51	kotarak	(fac n)
17:51	kotarak	(* n (fac (- n 1)))
17:51	Chouser	If I put the lisp recursion in tail position, like this (defun i () (i)) then indeed SPCL seems to run indefinitely without crashing.
17:51	kotarak	(* n (* n-1 (fac (- n-1 1)))
17:51	kotarak	---> grows into that direction
17:51	Chouser	kotarak: yup
17:51	kotarak	(fac n 1)
17:52	kotarak	(fac n-1 n)
17:52	kotarak	(fac n-2 n*n-1)
17:52	Chouser	The equivalent clojure also runs indefinitely without crashing: (defn i [] (recur))
17:52	kotarak	stays constant
17:54	kotarak	I think he got something terribly wrong. And it shows that prove-by-experiment doesn't really work.
17:56	scgilardi	although disprove by experiment works fine. a "simple" recursive factorial in DrScheme with a memory limit of 128MB runs out of memory at some value under a million.
17:58	kotarak	"prove" by counter-example, yes. But he was some kind of advice-resistent.
17:59	arbscht	proof by experiment doesn't always work, then. it does really work sometimes, though
18:01	arbscht	and that was the most puzzling definition of lisp I've encountered
18:18	rhickey	sorry I missed jgrant, here are the facts:
18:19	rhickey	Lisp-1 has nothing to do with TCO, it has to do with whether functions have an independent namespace. Clojure is like Scheme in that they don't, so both are Lisp-1s.
18:19	rhickey	Supporting recursion has nothing to do with TCO. All Lisps support recursion (a function calling itself), and so does Clojure
18:20	rhickey	Scheme requires TCO, Common Lisp does not. Common Lisps are obviously Lisps, and so is Clojure
18:20	rhickey	Clojure is not a Scheme
18:24	Chouser	rhickey: we're all sorry you missed jgrant :-)
19:46	abrooks	jgrant: There was some reply to your Clojure as Lisp inquiry: http://clojure-log.n01se.net/date/2008-07-26.html
19:46	abrooks	jgrant: You'd probably be best scrolling down to the bottom.
22:27	jgrant	abrooks : thanks I see rich's response
22:28	jgrant	not sure why this became a discussion about TCO
22:28	jgrant	my initial question had to do with simple recursion
22:29	jgrant	and rich's response that i quoted earlier today already provided the answer -->
22:30	jgrant	http://groups.google.com/group/clojure/browse_thread/thread/72a7fa0fe5a56c9c/e3849c42b21551c0?lnk=gst&q=recursion#e3849c42b21551c0
22:30	jgrant	"Clojure could have been implemented with a heap-based stack, with a"
22:30	jgrant	cost in performance and call-compatibility with Java. I chose not to
22:30	jgrant	do so, and am very happy with the results. It's not an aspect of
22:30	jgrant	Clojure that is going to change. "
22:31	jgrant	it was a design choice to not allow recursion until until the heap allocated memory is exhausted
22:31	jgrant	and that's fine
22:32	jgrant	As I've stated here and elsewhere I think Clojure is great, it's probably my most favorite language on the JVM
22:32	jgrant	thanks again Rich
22:38	jgrant	As to my personal opinion about why it's not really a Lisp...
22:38	jgrant	...from McCarthy's original paper in 1960 :
22:39	jgrant	(in the introduction)
22:39	jgrant	http://www-formal.stanford.edu/jmc/recursive/node1.html
22:40	jgrant	It's clearly stated what Lisp was intended to be :
22:40	jgrant	"In this article, we first describe a formalism for defining functions recursively."
22:41	jgrant	only after that came s-expressions and s-functions and thirdly an example of the s-function 'apply'
22:42	jgrant	The paper itself is titled "Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I"
22:42	jgrant	This is just my opinion as calling Clojure a dialect of Lisp
22:45	jgrant	however it's definitely a functional language
23:27	dudleyf	jgrant: Are you claiming that Clojure doesn't support "defining functions recursively"?
23:27	Chouser	If you exclude TCO from the conversation, Clojure supports recursion just as well as Common Lisp does, as my SBCL exmples help demonstarte.
23:31	Chouser	dudleyf's question is better than my assertion. Let's go with that. :-)