#clojure – 2010-12-19

2010-12-19

00:41	GOSUB	Clinteger: it will seem right.
01:20	TakeV	Does anyone here use Penumbra?
06:46	bartj	what would be the best way to remove nil, empty values from a hash-map
06:49	bartj	my attempt is this: (map (fn [[k v]] (if (and v (> (count v) 0)) [k v] nil)) x)
06:51	mduerksen_	bartj: (apply conj {} (filter (comp not nil? val) x))
06:52	mduerksen_	map wouldn't give you a sequence, not a hash-map
06:52	mduerksen_	would
06:53	bartj	mduerksen_, oops, I forgot to give a (into {}...) here
06:53	mduerksen_	ah, you want to remove empty collections as well?
06:54	mduerksen_	then my solution won't be complete
06:54	bartj	I'll just use a pos? as well :)
06:54	_ato	(zipmap (keys m) (filter seq (vals m)))
06:54	_ato	assuming all the values are collections
06:55	bartj	I sometimes tend to avoid zipmaps, I don't know why
06:57	_ato	(into (empty m) (filter #(seq (val %)) m))
06:57	mduerksen_	_ato: seq is a great idea - but the zipmap code won't work because it interleaves the wrong keys with the values that are left
06:58	_ato	mduerksen_: ah of course. Silly me.
07:00	mduerksen_	_ato: hmm, you're empty is nice, by the way. i should start using it since it does work for all kinds of collections
07:02	mduerksen_	_ato, bartj: the most elegant way IMHO would be: (into (empty m) (filter (comp seq val) m)) (i try to avoid the #-notation whenever possible)
07:03	bartj	ok guys, lots of thanks
07:05	mduerksen_	_ato: :D really? why?
07:09	_ato	A knee jerk reaction to overuse of pointfree style, I guess. I dunno. ;-)
07:12	Chousuke	avoiding #() is silly.
07:13	Chousuke	pointfree style in clojure becomes unreadable beyond the simplest cases :P
07:19	mduerksen_	hmm, i have heard the term "pointfree" here and then, but i don't actually know what it means. i find (comp seq val) very readable. just to be clear: i'm not forbidding myself to use #(), but i do think that often enough it's a sign that i haven't written my code very idiomatically
07:24	_ato	the terminology was probably made popular by Haskell where it's used much more often than Clojure: http://www.haskell.org/haskellwiki/Pointfree
07:26	_ato	essentialy just means combining functions with things like comp and partial and juxt so as to avoid local bindings
07:29	mduerksen_	i see, thanks. i for my part like partial, comp, complement etc., but i agree that this can be overdone (as almost everything)
07:47	LauJensen	mduerksen_: Did you see the slides from cgrands talk at Clojure Conj? If not, you should check them out
07:51	mduerksen_	LauJensen: no, i haven't. are they on slideshare?
07:51	LauJensen	mduerksen_: http://lmgtfy.com/?q=cgrand+slides+clojure+conj&l=1
07:54	mduerksen	LauJensen: sorry, my connection broke. did you write something while i was gone?
07:55	LauJensen	mduerksen_: http://lmgtfy.com/?q=cgrand+slides+clojure+conj&l=1
07:55	LauJensen	just the link
07:55	mduerksen	thanks
07:55	LauJensen	np
08:21	FireSnake	my Clojure app works perfectly on Jetty at localhost:8080 but I get 500 errors on Google App Engine. Anyone guess why?
08:34	Lajla	the stupid part about point free is that it doesn't exist.
08:34	Lajla	f x y = whatever in haskell is just sugar for f = \x -> (\y -> whatever)
08:34	Lajla	Also point free tada.
08:35	Lajla	Alternatively, f . g is just sugar for \fuckThisShit -> (f (g FuckThisShit))
08:51	pyrtsa	...With the difference that when you write "\x", you are expressing the "point" you are operating on.
09:27	mduerksen	LauJensen: those slides are really insightful. i assume you were referring to my question yesterday?
09:34	leif-p	Hi, where do I report bugs/request enhancements for clojure?
10:42	LauJensen	mduerksen: yes
11:12	ohpauleez	Raynes: Can you play with the new clj-github changes and then when you feel solid, push a new drop to clojars?
11:14	dsop	hmm is there a nice way to validate email addresses in clojure? I only find some Java EE stuff to do it
11:19	fliebel	dsop: You mean just a nice regex?
11:40	leif-p	Is it just me, or is clojure's 'gensym' a little too liberal about its input?
11:41	fliebel	leif-p: How do you mean liberal?
11:42	leif-p	Unlike CL's, which essentially only takes strings, clojure's seems to take any old thing that can be 'str'ed.
11:42	fliebel	&(gensym :test)
11:42	sexpbot	⟹ :test27260
11:43	stuartsierra	symbol-generating fns are generally liberal in Clojure
11:43	fliebel	&(type (gensym :test))
11:43	sexpbot	⟹ clojure.lang.Symbol
11:43	stuartsierra	whether or not this is a good thing is a much-debated but never-resolved topic
11:43	fliebel	A symbol that starts with a colon is weird though.
11:45	leif-p	Is there a way to print this in a way that could be re-read? Like CL's \|:weird + symbol\|.
11:45	stuartsierra	leif-p: not right now, but also debated in the past
11:45	stuartsierra	There's ambivalence about whether Clojure symbols should be allowed to contain arbitrary characters.
11:46	stuartsierra	In CL it's a leftover from before Lisps had a String type.
11:46	fliebel	stuartsierra: Any idea what came of the escaping discussion? It was related to the \|syntax\| I think.
11:46	stuartsierra	There was no resolution as fas as I know.
11:48	fliebel	I liked the idea of r"raw strings" like in Python, or unicode quotes, and in case of emergency(huh?) even arbitrary delimiters.
11:49	leif-p	fliebel: Maybe this is the wrong room to say you liked a perl feature :)
11:52	fliebel	leif-p: I ultimately think that if you want wrid shit in your strings, you should read them from a file. And Perl is for emergencies. Like the way Haskell uses Perl to bootstrap Haskell to new platforms by fumbling with the generated assambly.
12:34	TakeV	Is there a way to save work done in a REPL to the namespace you are working in? The REPL makes it easy to test things, but changes don't stick unless I go back and add the changes to the file manually.
12:44	bortreb	Can you call an object created by defrecord in clojure using non-java-legal characters with java in some way?
12:44	chouser	bortreb: probably via reflection
12:44	chouser	TakeV: when you define a function at a standard repl, the source code isn't saved anywhere, so no.
12:45	chouser	TakeV: one could make a repl that saved things out to a file as you go along or something, but I think most people end up writing their code in a file and then either sending it from there to the repl,
12:45	chouser	or saving the file to disk and then reloading it from the repl.
12:46	TakeV	Ah, is there a way to automatically reload a file?
12:46	chouser	hm, not sure about automatically. Some of the IDEs may have that, and such a thing could be written.
12:47	chouser	lazytest has a "watch" mode that reruns appropriate unit tests when it sees a file has been written to disk.
12:47	chouser	I usually just push the up arrow in my repl to recall the (use foo :reload-all) line, and then hit enter.
12:47	TakeV	I think I'll write an auto-reload thing.
12:51	bartj	If a clojure file has a "main" method defined, can't I use the functions defined in it?
12:51	KirinDave	bartj: Defined inside the main method?
12:51	KirinDave	bartj: Or just the module containing the -main defn?
12:52	bartj	KirinDave, the latter
12:52	KirinDave	bartj: THen the answer is yes, absolutely
12:53	bartj	I did a ( :use, :only ) with no luck
12:53	KirinDave	Perhaps a gist.github.com demonstration of you problem is in order, bartj
12:56	bartj	KirinDave, unfortunately I can't :(
12:57	KirinDave	bartj: So one of two things is happening here. I'll list them on a probability gradient, high to low:
12:57	bartj	but, I think I am doing a recursive "use"
12:57	KirinDave	recursive use?
12:57	KirinDave	So two modules sharing required code?
12:58	bartj	Module A has func1, func2
12:58	bartj	Module B has func3, func4
12:58	KirinDave	Does it actually give you an error for this?
12:59	bartj	weird thing is it runs, but doesn't compile
12:59	bartj	am using "ant"
12:59	KirinDave	Yeah, so...
12:59	KirinDave	That may not work. :)
13:00	KirinDave	But without a clear example it's reeeeaallly hard to diagnose.
13:00	bartj	the function calls are like this: func1 -> func3 -> func2
13:00	bartj	with the appropriate use/require in place
13:01	KirinDave	Well, first.
13:01	bartj	so, I think there is something wrong with the code organization
13:01	bortreb	TakeV: I've already written an automatic reload function if you're interested
13:02	bortreb	also, with reagards to my earlier question, I've already taken all the necessary steps to AOT the clojure. i have a class called literally "clojure-object.class" -- note the hyphen. Is there any way to call that from java?
13:05	TakeV	bortreb: I would be very interested.
13:18	bortreb	TakeV: I'll put it on github... hold on
13:22	bortreb	TakeV: https://gist.github.com/747559
13:23	bortreb	the idea is you can just call rlm.rlm-commands/re to do a fast reload
13:23	TakeV	bortreb: Thank you.
13:23	bortreb	or (rlm.rlm-commands/reload) to do a very trough reload
13:23	bortreb	there's also an undef function which does about what you'd thing
13:23	bortreb	you're welcome!
13:25	bortreb	so, anyone know if you can call classes like "clojure-object.class" from java?
13:42	shortlord	How can I use partition to create vectors?
13:42	shortlord	I am using this line:
13:42	shortlord	(def fields (vec (partition 2 (interleave numbers resources))))
13:49	raek	shortlord: (def fields (map vector numbers resources))
13:49	fliebel	shortlord: (map vector (partition 2 seq))
13:49	fliebel	maybe
13:49	raek	no need to interleave them and then split them again
13:49	fliebel	oh right :)
13:49	raek	,(map vector [1 2 3] [:a :b :c])
13:49	clojurebot	([1 :a] [2 :b] [3 :c])
13:50	shortlord	raek: oh cool, thx :)
14:05	dsapala	anyone know anything about the clj-http project?
14:12	fliebel	the_shadow_of_dsapala: yes
14:14	dsapala	Are any of you folks familiar with clj-http?
14:14	fliebel	yes
14:15	fliebel	But that doesn't mean it's me, and it doesn't means anyone knows the answer to your question, therefore I suggest you just ask your question.
14:17	dsapala	How can I set a timeout for connections or reads using clj-http?
14:33	fliebel	LauJensen: How are plans for the Reddit clone based on "new" stuff?
14:33	LauJensen	fliebel: Plans are: As soon as I have an hour or two, I'll write it up :)
14:34	fliebel	LauJensen: I'm curious :) I have some plans for a project like this as well.
14:35	LauJensen	I'll make sure to announce it on Twitter :)
14:35	bhenry	how do i assoc into a vector but i want it to be an "insert before" rather than a "replace what's there".
14:36	fliebel	bhenry: I think you'll have to do split-at and concat.
14:37	fliebel	bhenry: Or do a zipper.
14:39	bhenry	thanks. i decided it was easier to pass what i want into the function that makes the vector.
15:03	currentB	what's the best way to assoc a new key in a hashmap stored within a vector in a dosync?
15:05	AWizzArd	currentB: what code do you currently use so far?
15:09	fliebel	currentB: Cant you just do (update-in vec [index :key] some-fn)?
15:09	fliebel	&(update-in [1 2 3] [1] inc)
15:09	sexpbot	⟹ [1 3 3]
15:10	currentB	alright cool thanks, checking that out
15:16	fliebel	Why can't I do this? (dissoc [1 2 3] 1)
15:18	ducki2p	fliebel: dissoc requires a map
15:18	fliebel	In most other ways, vectors seem to be like maps with integer keys.
15:20	fliebel	&(vals (dissoc (into (sorted-map) (map-indexed vector [:a :b :c])) 1)) ; evil
15:20	sexpbot	⟹ (:a :c)
15:21	ducki2p	&(vec (filter #(not= 1 %) [1 2 3]))
15:21	sexpbot	⟹ [2 3]
15:21	fliebel	ducki2p: You remove a value, not an index.
15:46	tomoj	huh, #(not= 1 %) is shorter than (complement #{1})
15:47	tomoj	#\ is available
15:47	tomoj	#\{1} ? :)
15:48	tomoj	nah
15:48	tomoj	just (remove #{1} ..)
15:54	amalloy	tomoj: #(not= 1 %) can't be nested inside another #() function
15:54	amalloy	plus, i know it makes me a sinner, but i (def ! complement) in most of my code
17:23	amalloy	is there any particular guarantee about order of evaluation in a form like [(foo) (bar)]? i'm doing some interop and foo affects some state that bar depends on; is the above sufficient, or do i have to make bar a function of foo in order to make sure foo has been computed?
17:23	chouser	they'll go in order
17:23	chouser	maps are not guaranteed, I think.
17:24	amalloy	thanks chouser
17:24	amalloy	a point in favor of clojure that i didn't have to ask this question until i'd written clojure for about five months
17:24	Raynes	(inc clojure)
17:24	sexpbot	⟹ 1
17:29	chouser	heh
17:29	nickik	why did you do that raynes? it had no effect on clojure :)
17:29	chouser	scheme doesn't even promise function arguments will be evaluated in order
17:30	Raynes	It does in my little world.
17:30	Raynes	(inc clojure)
17:30	sexpbot	⟹ 2
17:30	amalloy	chouser: neither does C
17:30	chouser	!!!
17:30	amalloy	or any of its children (java, etc) as far as i know
17:31	chouser	wow, I had no idea
17:31	brehaut	nickik: presumably because (send clojure inc) or (swap! clojure inc) is long winded ;)
17:32	amalloy	chouser: if you do much imperative programming, http://en.wikipedia.org/wiki/Sequence_point is good reading for the fiddly details
17:32	amalloy	(4) under <Sequence points in C and C++> in particular
17:33	chouser	I've written a lot of C code in my life, and am surprised this hasn't ever bitten me.
17:33	amalloy	chouser: it rarely does. your functions probably don't affect a lot of global state
17:33	amalloy	and i think gcc does evaluate them in order, to be nice
17:35	_mst	java does go left to right, just for what it's worth (http://java.sun.com/docs/books/jls/second_edition/html/expressions.doc.html)
17:35	_mst	although it recommends you don't rely on it, which is a bit funny...
17:37	amalloy	_mst: ah, so it does. thanks (15.7.4 for anyone else who's looking)
17:49	amalloy	can someone load https://gist.github.com/747785 into an editor with paredit mode on? all the parens in my docstring are balanced, and indeed paredit-mode is happy to be enabled, but if i try to do anything interesting (backspace, M-(, etc) in the body of my function, it complains of unbalanced parentheses
17:49	amalloy	and i'd like to verify it's not something wrong with my config before i file a bug
17:50	amalloy	(and if i delete the docstring, the problem fixes itself)
17:54	_mst	amalloy: same deal for me here, yep. I notice if I put a space before your {'s in the docstring it's OK...
17:55	amalloy	_mst: aha! well spotted. in fact, any character at all before them is fine; it doesn't like them at the start of a line, apparently
17:56	_mst	it might not be paredit specific... if I do a C-M-a (to go back to the start of the defun) it jumps me to one of those braces
17:56	_mst	so maybe clojure-mode is mistaking where the defn actually begins...
17:57	_mst	ah! (setq open-paren-in-column-0-is-defun-start nil) seems to fix it for me
17:57	_mst	dunno what else it breaks though ;)
17:58	amalloy	_mst: fascinating. thanks
17:59	_mst	heheh no worries
18:02	lpetit	amalloy: works ok with paredit.clj :-p
18:02	amalloy	lpetit: is that for ccw?
18:03	lpetit	amalloy: yeah, pasted your gist into ccw. But don't worry, there are still some corner cases with paredit.clj, your example is just not one of those :-D
18:05	lpetit	amalloy: I'm currently doing the necessary (albeit boring) port of paredit.clj commands into the new repl client of ccw. Just ported join & split before going to bed
18:08	brehaut	does anyone know if there is an atom-pub lib built on top of ring?
18:29	qbg	How do you get a namespace qualified symbol from a var?
18:31	amalloy	&(apply symbol ((juxt (comp str ns-name :ns) (comp str :name)) (meta #'first)))
18:31	sexpbot	⟹ clojure.core/first
18:32	amalloy	is kinda disgusting but works
18:32	qbg	&(symbol (subs (str #'first) 2))
18:32	sexpbot	⟹ clojure.core/first
18:32	qbg	That is worse
18:32	amalloy	lol
18:38	shortlord	given a nested collection that contains a few values, that have to be mutable. Should I place the whole collection in a single ref or rather use separate refs for each value that has to be altered?
18:39	Chousuke	the fewer mutable things you have, the easier they will be to handle.
18:39	Chousuke	so prefer a single ref, unless it becomes a bottleneck
18:41	shortlord	Chousuke: the only problem I have is how to change that single ref with alter. Using assoc-in results in ugly code, because I have to alter the value using assoc-in, which means that I need to dereference the ref directly as the first argument of assoc-in
18:41	shortlord	which destroys the point of using alter instead of ref-set, right?
18:44	qbg	I'm proud of this: https://gist.github.com/747841
18:46	qbg	Something like syntax-rules in Clojure!
18:50	Chousuke	shortlord: hm, no you don't?
18:50	amalloy	shortlord: i don't understand what you're saying
18:51	Chousuke	shortlord: (alter somerefref assoc-in [keys here] val)
18:51	Chousuke	-ref
18:51	Chousuke	shortlord: update-in is useful too
18:54	shortlord	Chousuke: ah ok! I thought that alter provided the ref as the last argument, not the first one
19:00	shortlord	what would be the best way to increment that value?
19:00	shortlord	Right now I am using:
19:01	shortlord	(dosync (alter players (fn [players] (assoc-in players [player resource] (inc ((players player) resource))))))
19:01	shortlord	but that does not look very elegant
19:03	qbg	(dosync (alter players update-in [player resource] inc))
19:06	amalloy	(inc qbg)
19:06	sexpbot	⟹ 1
19:06	shortlord	thx a lot :)
19:39	currentB	let's say I have a vector of hash-maps. i will periodically conj a new hash-map to the vector which will just be the "peek" of the vector (ie the first current hash). Occasionally values pairs from this first hash will be chagned or new ones will be added. The lazyness of clojure makes this efficient right? as in a new hash isn't created when each new peek value is conjed to the vector right? or when a new value is assoced in the first
19:40	currentB	(i need to implement a simple compiler for a class and I'm wondering if I can just create a new hash-map to represent each scope with the values of all "lower" scopes included, or if it's best to just create a new hash map for each scope and search them sequentially
19:47	amalloy	currentB: i don't understand what you're talking about with "peek". the peek of a vector is the last element in it; if you conj something to a vector it is the peek by definition
19:48	currentB	but if i want to create a new scope, i might want to copy everything in the previous scope to that new scope
19:48	currentB	so i can alter those old values
19:48	currentB	and just remove it when the scope is exited
19:49	amalloy	oh, you mean if you have like a 10KB hash table, and want to create another one just like it but with one additional item?
19:49	currentB	yes
19:49	currentB	i think
19:49	amalloy	you're correct that clojure doesn't copy all 10KB worth of keys, but that's not really related to laziness
19:50	currentB	ok, so that's just the persistence + tricks with pointers?
19:50	amalloy	right
19:50	amalloy	neither vectors nor hashes are lazy
19:50	mister_roboto1	what is the right way to expose a function that you always want call via memoize? that is, if you are writing a library function and the set of return values is always small so rather than cache it yourself you want to leverage memoize?
19:51	mister_roboto1	just def it ahead of time and make the real function private?
19:51	amalloy	mister_roboto1: do you want to memoize recursive calls as well?
19:52	mister_roboto1	amalloy: this function is not recursive
19:52	amalloy	(def myfn (memoize (fn [args] (compute))))
19:52	amalloy	is a solution that works and doesn't seem too ugly to me
19:52	mister_roboto1	ahh, internally make it anonymous. i like it
19:53	amalloy	another useful trick is (def ^{:arglists '([args])} myfn (memoize...))
19:53	amalloy	so that (doc myfn) and eldoc will be useful
19:54	mister_roboto1	amalloy: that second thing is totally new to me. i'll have to read up on that one.
19:55	currentB	amalloy: ok so if I have a vector x [{:a 1 :b 2}] I can later alter it to (conj x (peek x)), or [{:a 1 :b 2}{:a 1 :b 2}], then later alter just the first hash so it is [{:a 1 :b 2 :c 3}{:a 1 :b 2}], this is better than just structuring things so I have [{:c 3}{:a 1 :b 2}], and then, if I need to find :a, first looking through the first map, then checking the second, etc?
19:55	amalloy	mister_roboto1: ^{key value} is how you attach metadata to a var (or to anything): ##(-> first var meta :arglists)
19:55	sexpbot	⟹ ([coll])
19:57	raek	with defn, you can also put a map after the docstring (or after name if there is no docstring). the metadata will be merged with that map
19:57	raek	,(doc defn)
19:57	clojurebot	"([name doc-string? attr-map? [params] body] [name doc-string? attr-map? ([params] body) + attr-map?]); Same as (def name (fn [params* ] exprs)) or (def name (fn ([params ] exprs*)+)) with any do...
19:57	amalloy	currentB: i think that depends on the performance characteristics of your application. how big the hashes will be, how often they'll change, and so on
19:58	amalloy	my inclination is to search maps sequentially because it feels like a better description of how nested scopes behave, and especially if the values in the hashes can change you don't want to have to ripple through to all parent scopes
19:59	currentB	ok sweet, that actually seems really obvious now that you put it that way, thanks a ton!
20:00	currentB	this room is the great, it solves all my clojure struggles :)
20:24	shortlord	is there any way to alter all the leafs in a nested ref structure? I have a hash-map in a ref vector and I need to change the hash map for every entry in the vector
20:25	amalloy	shortlord: like (ref [{:foo 1} {:bar 2}])?
20:26	shortlord	amalloy: no, rather like [[:key1 {:foo false}] [:key2 {:foo false}]
20:26	shortlord	and I want to set every :foo to true without changing the keys :key1 or :key2
20:27	shortlord	there is only one entry in the vector supposed to be {:foo true}, so it would also be ok to find this entry and then selectively switch that to false
20:28	amalloy	&(map #(assoc-in % [2 :foo] true) [[:key1 {:foo false}] [:key2 {:foo false}]])
20:28	sexpbot	⟹ ([:key1 {:foo false} {:foo true}] [:key2 {:foo false} {:foo true}])
20:28	amalloy	whoops
20:28	amalloy	&(map #(assoc-in % [1 :foo] true) [[:key1 {:foo false}] [:key2 {:foo false}]])
20:28	sexpbot	⟹ ([:key1 {:foo true}] [:key2 {:foo true}])
20:29	amalloy	shortlord: like so?
20:29	shortlord	amalloy: that could work, I'll try that
20:29	shortlord	thx
20:30	currentB	one more thing, using map on a seq will always process the seq in order right?
20:31	amalloy	currentB: yes. as long as the seq has some notion of order; for example, hash-maps don't
20:32	currentB	k
20:34	amalloy	even for non-ordered seqs, you're guaranteed (i think?) that if you iterate over an identical seq N times, it will always be in the same order. but if you, say, add a key or change a value, you may get a completely different order
20:39	shortlord	amalloy: it still does not work:
20:39	shortlord	(dosync
20:39	shortlord	(alter fields map #(assoc-in % [3 :bandit] false))
20:39	shortlord	(alter fields assoc-in [field 3 :bandit] true)))
20:39	shortlord	that's the error: clojure.lang.LazySeq cannot be cast to clojure.lang.Associative (repl-1:582)
20:40	amalloy	shortlord: well, one issue is that you're passing the arguments to map in the wrong order: it will look like (map @fields #(fn...))
20:41	shortlord	amalloy: I tried partial and even a custom fn, but it didn't help
20:41	amalloy	the other is that assoc-ing will only work on maps and vectors; if fields contains lists or seqs, it won't do the right thing
20:43	shortlord	amalloy: that's strange, because I am operating on a vector
20:43	amalloy	shortlord: then it's probably the first problem
20:43	shortlord	amalloy: well, partial is supposed to curry a function, right?
20:44	shortlord	so I thought this should work: (alter fields (partial map #(assoc-in % [3 :bandit] false)))
20:45	amalloy	it does seems that way
20:47	shortlord	amalloy: do you know a good paste service that supports clojure syntax highlighting? I could paste the whole source then
20:47	amalloy	so fields is a (ref of a) vector of things you want to work with; each things is a vector whose fourth element is a map you want to add :bandit false to?
20:47	amalloy	shortlord: http://gist.github.com
20:48	amalloy	&(let [fields (atom [[0 1 2 {:player true}]])] (swap! fields (partial map #(assoc-in % [3 :bandit] false))) @fields)
20:48	sexpbot	⟹ ([0 1 2 {:bandit false, :player true}])
20:49	shortlord	amalloy: https://gist.github.com/747927
20:51	amalloy	shortlord: map is going to return a seq, not a vector
20:51	amalloy	&(map inc [1 2])
20:51	sexpbot	⟹ (2 3)
20:51	amalloy	&(vec (map inc [1 2]))
20:51	sexpbot	⟹ [2 3]
20:51	clojurebot	map is lazy
20:52	amalloy	so after you map over fields, it's turned into a lazy seq and the next assoc-in fails because it's not a vector
20:52	amalloy	the easiest fix is to make it back into a vector when you're done: (comp vec (partial map...))
20:53	amalloy	clojurebot: that was surprisingly on-topic. have a cookie, i guess
20:53	clojurebot	Titim gan éirí ort.
20:54	amalloy	shortlord: follow all that?
20:55	shortlord	amalloy: yeah, that works and makes sense :)
20:55	shortlord	thx a lot
20:55	shortlord	this channel is incredibly helpful :)
21:13	tomoj	if aleph clients are channels, you can only issue one request at a time without causing problems about figuring out which response was to which request, right?
21:55	hippiehunter	is there some relative of clojure.contrib.monads.maybe-m that throws an exception or logs on what step it failed?
21:56	brehaut	hippiehunter: why not just use exceptions or conditions?
21:57	hippiehunter	because the only failure condition is nil and i'm not good enough with macros to make that a palatable syntax
21:58	amalloy	hippiehunter: write a monad transformation on top of maybe-m?
22:01	hippiehunter	Im pretty noobish when it comes to doing anything other than basic consumption of monads. I was just asking to see if there was anything already in existance that my search missed.
22:02	brehaut	hippiehunter: while you could do it with a monad or monad transformer i think it would be overkill. great if you want to learn how they work more but probably not the right solution
22:03	brehaut	hippiehunter: that being said, maybe-m is trivial to write, so you could easily concoct your own version that throws an exception on nil
22:04	tomoj	was there somewhat recently a change in the way the metadata works?
22:04	tomoj	something to make :static easier, I think?
22:06	tomoj	did "^:foo" no longer mean "{:tag :foo}"? post 1.2
22:09	amalloy	tomoj: i don't think that's the case, but i'm still on 1.2
22:11	tomoj	oh well, :tag is fine
22:13	shortlord	what is the best way to keep indices in "looping" bounds? for example: if the vector has the length 5, the indices 0 to 4 stay the same, 5 becomes 0, -1 becomes 4, etc. In python it's possible to use the modulo, but clojures (rem -1 5) returns -1 instead of 4
22:14	amalloy	&(mod -1 5)
22:14	sexpbot	⟹ 4
22:14	shortlord	oh, mod exists as a separate function? great! :D
22:14	amalloy	shortlord: yeah, read the doc for mod and rem. they behave differently for negative numbers
22:15	shortlord	amalloy: ok, thx
22:17	amalloy	btw shortlord, a fun mod trick: ##((juxt quot rem) 23 4)
22:17	sexpbot	⟹ [5 3]
22:17	cemerick	tomoj: ^:foo means {:foo true} in 1.3
22:17	cemerick	^String means {:tag String}
22:17	cemerick	since 1.2
22:20	bortreb	what's a good way to write and read objects created by clojure with defrecord to and from disk?
22:21	tomoj	cemerick: ah, ok
22:21	tomoj	cemerick: and then you can do "^:foo ^:bar" for "{:foo true :bar true}" ?
22:21	tomoj	that would be great
22:21	cemerick	exactly
22:22	tomoj	that will force me to generate a bunch of stub classes if I keep it this way... :(
22:25	joshua__	Question for you guys. I'm trying to help my uncle out by building a dll in C++. I want to talk in the C++ channel to ask questions, but it says that the message can't be sent. What am I missing here or is this a glitch?
22:25	amalloy	joshua__: you probably need to register your nick
22:25	bortreb	do something like /msg nickserv identify <your-password> ?
22:30	anthony__	(completely new at all things lisp/functional) I'm using doseq to iterate through the elements in a vector, and I need to append each one to a string, which will be the value of my function. What's the best way to do this? Should I be using map instead of doseq?
22:31	cemerick	anthony__: welcome :-)
22:31	cemerick	,(map #(str "foo" %) (range 10))
22:31	clojurebot	("foo0" "foo1" "foo2" "foo3" "foo4" "foo5" "foo6" "foo7" "foo8" "foo9")
22:31	amalloy	anthony__: you should be using reduce, probably
22:31	amalloy	&(reduce str ["foo1" "foo2" "foo3"])
22:31	sexpbot	⟹ "foo1foo2foo3"
22:32	anthony__	Ah man, that's so elegant.
22:32	amalloy	anthony__: welcome to lisp! :)
22:32	cemerick	of course, apply is far more efficient for string concatenation
22:32	amalloy	well yes
22:32	cemerick	&(apply str ["foo1" "a" "k"])
22:32	sexpbot	⟹ "foo1ak"
22:33	anthony__	Dang it. I used apply in another function. Tried to use it here and couldn't figure it out. Java has ruined me.
22:33	anthony__	Thanks for the help.
22:34	amalloy	anthony__: good thing you couldn't figure apply out - now you know about reduce, too!
22:35	anthony__	haha very true
23:03	Lajla	(thunk)
23:03	Lajla	I take that back.
23:03	Lajla	(thunk-cps Lajla)
23:03	Lajla	So, what have you got for me baby
23:04	currentB	eh, if I'm implementing a recursive descent parser, is it only necessary/ideal to put one dosync before the recursion entry to handle everything? is that bad form?
23:06	amalloy	currentB: why do you need mutable state for a parser?
23:06	amalloy	$google fnparse
23:06	sexpbot	First out of 104 results is: joshua-choi/fnparse - GitHub
23:06	sexpbot	https://github.com/joshua-choi/fnparse
23:08	currentB	yeah i found stuff like that but it's for an undergrad class where we could just use whatever language we want, and I figured it'd be cool to use clojure but it's probably best to just go with the method the rest of the class is supposed to use
23:08	currentB	definitely against the current in a few places..
23:09	amalloy	currentB: well, parsers are very recursive in nature; it's very convenient to be able to backtrack and have the right state already on the stack without having to restore it manually from a ref
23:12	currentB	k cool I'll meditate on that a bit :) thanks again
23:54	mister_roboto1	is there a library function to get the index of some value in a collection? e.g. if i have [:a :b :c] i want to pass :b and get 1 back
23:55	mister_roboto1	if there is something built in, i can't find it