#clojure – 2016-03-05

2016-03-05

00:51	will_sm	How should I make "structs" in clojure?
00:51	will_sm	should I just use a hashmap?
00:52	skelternet	will_sm: think so
01:01	skelternet	could use a record but it will include most funcs of a map.
01:02	skelternet	sorry not staying longer. good night
04:55	Confusionist	Hi, is there a way to get 'lein ancient' to also report what plugins and dependencies in my .lein/profiles.clj can be upgraded?
05:43	renl	Hi what libraries should I use for interprocess comma as well as distributed systems?
06:28	spuz_	Is there a better way to find the largest value in a sequence that is less than some value?
06:28	spuz_	, (apply max (filter #(< % 10) (range 1 19)))
06:28	clojurebot	9
06:53	Confusionist	spuz_, in general there isn't, but if you know the sequence is ordered you can exploit that. E.g. in the example case you can replace 'apply max' by 'last'
06:53	spuz_	Confusionist, yeah thanks
06:53	spuz_	or drop-while and first I guess
06:54	Confusionist	or reverse and find the first entry matching a predicate: that could also be significantly faster
08:04	OscarZ	i cant get lein repl to open.. i probably messed up something in my project.clj.. just getting message "Logging initialized..."
08:05	OscarZ	any ideas what are common causes for repl not to start ? after a timeout it fails with error "REPL server launch timeout"
08:07	OscarZ	hmm.. it loads the namespaces i suppose, maybe im doing something foolish somewhere in my .clj files
08:38	OscarZ	hmm i suppose i need to find out what lein repl actually does...
08:58	justin_smith	renl: manifold from ztellman ties those things together, and has nice things like flow control and back pressure too
08:59	justin_smith	OscarZ: it starts an nREPL server then loads your :main namespace
08:59	renl	thanks
09:00	justin_smith	OscarZ: I think your best bet is to run lein clean, then run 'lein run -m clojure.main' then that launches a vanilla clojure.main repl
09:00	justin_smith	OscarZ: in that repl (require 'my-main.ns) and watch for errors
09:00	justin_smith	I bet that will be informative
09:01	renl	is manifold like a message queue?
09:01	OscarZ	justin_smith, thanks ill try that.. forgot to mention that i have a dev profile with user.clj.. but it has nothing in it except requires
09:02	justin_smith	renl: no, it's a utility library with many facilities relating to message queues
09:03	justin_smith	OscarZ: a clojure.main repl should also end up loading your user.clj - but in my experience running clojure.main is more likely to expose errors that are silent in lein repl in some cases
09:05	OscarZ	ok.. i think this is an issue with some of my code that runs when the namespaces are loaded
09:10	renl	manifold doesnt handle the actual socket programming right? is aleph the goto library for all things socket?
09:10	justin_smith	renl: aleph is good (and it already pulls in manifold by default)
09:12	justin_smith	I think I misinterpreted your question because of the "as well as" - manifold can help do coordination inside one vm as well as coordination between vms, whether on the same host or different hosts, and can be used to tie socket comms together with distributed stuff
09:12	justin_smith	though in java IPC tends to fall back to the same stuff you would use for distributed, because there's not much for portable IPC and java aims to be portable
09:13	renl	nod thanks
09:13	justin_smith	I should say "on the jvm" and not "in java" but you probably get that's what I meant
09:15	renl	yup
12:02	arkh	is there a way to limit/truncate stacktrace length when using tools.namespace and (refresh)?
12:04	arkh	the interesting parts are usually the first 30 lines or so but some stack traces get in the ballpark of 120 lines
12:25	cortexman	what's a stateful transducer?
12:29	arkh	cortexman: http://stackoverflow.com/questions/26506689/what-is-a-stateful-transducer
12:55	cortexman	arkh, is it the same as a finite state tranducer?
12:55	cortexman	*transducer
13:04	arkh	cortexman: an FST is a bit more than a stateful transducer though to be honest I've never used one. Looks interesting though! I'm reading up on it now
13:04	arkh	e.g. https://github.com/structureddynamics/clj-fst
13:46	spuz_	, (-> (range 10) (partial map even?))
13:46	clojurebot	#object[clojure.core$partial$fn__4761 0x4e1b30c4 "clojure.core$partial$fn__4761@4e1b30c4"]
13:46	spuz_	why does that not return [0 2 4 6 8] ?
13:48	TMA	,(macroexpand '(-> (range 10) (partial map even?)))
13:48	clojurebot	(partial (range 10) map even?)
13:49	TMA	spuz_: that's why
13:49	spuz_	ah right
13:50	spuz_	if I want to use -> and a map, how can I do it?
13:50	TMA	spuz_: what do you want to accomplish?
13:50	spuz_	I want that first example to return a list of even numbers
13:51	spuz_	and to use the threading macro
13:51	TMA	why?
13:51	clojurebot	TMA: because you can't handle the truth!
13:53	TMA	spuz_: if you want the even numbers, you might be better of with (filter even? (range 10)) or some such
13:53	spuz_	TMA, ok maybe it would be more accurate to say, I would like to learn how the -> macro works
13:54	TMA	now you are talking :)
13:54	TMA	,(macroexpand '(-> a (b) (c)))
13:54	clojurebot	(c (b a))
13:55	TMA	spuz_: it is quite easy: (a) (-> form) is just form
13:56	TMA	spuz_: (-> form (head rest...)) is (head form rest...)
13:56	spuz_	TMA is it possible to use -> with (map f) ?
13:56	TMA	spuz_: and finally (-> form (head rest...) others...) is (-> (-> form (head rest...)) others...)
13:57	TMA	spuz_: indeed it is. but the result might be very different from what you might expect
13:58	spuz_	is it possible to use it in a way that does what I expect?
13:58	spuz_	or do I have to use ->> ?
13:58	TMA	spuz_: (-> X (map f)) is the same as (map X f)
14:00	burhanloey	(->> (range 10) (filter even?)) I guess?
14:02	TMA	spuz_: also, map yields a sequence of the same length as its second argument, which is very unwieldy if you like to filter out some elements
14:03	TMA	spuz_: however, with proper obfuscation it can be done
14:03	spuz_	I meant to use filter, not map
14:03	spuz_	poor exampe
14:03	spuz_	example*
14:04	bacon198`	I found it hard to understand threading at first
14:04	bacon198`	you need to think in terms of (-> <context> <expressions...>)
14:04	bacon198`	<context> gets placed as the first argument of each expression
14:05	bacon198`	errr
14:05	bacon198`	the result of that previous expresssion gets passed on to the next one
14:05	bacon198`	as the first argument of the expression
14:06	will_sm	So I can't put a docstring in a defonce?
14:06	TMA	,(apply concat (-> (range 10) (((fn [f] (fn [a b] (f b a))) map) (fn [x] (if (even? x) [x] [])))))
14:07	clojurebot	(0 2 4 6 8)
14:07	TMA	spuz_: see? it can be done with -> and map
14:07	TMA	spuz_: with a bit of magic
14:08	spuz_	um
14:08	spuz_	that is going a bit too far for me
14:12	TMA	spuz_: please do not do that ever in production code
14:13	TMA	spuz_: from the inside ((fn [f] (fn [a b] (f b a))) map) is a function that is exactly like map, except when you call (map A B) you need to call (abomination B A) for the same result
14:14	spuz_	hah ok i see
14:14	TMA	spuz_: (fn [x] (if (even? x) [x] [])) is a function that returns [x] for even x and [] otherwise
14:14	spuz_	isn't there a function that does that for you in clojure?
14:14	spuz_	i.e reverses the order of arguments
14:15	TMA	it might be there
14:17	TMA	spuz_: and finally the (apply concat ...) merges the [[0] [] [2] [] [4] [] [6] [] [8] []] into (0 2 4 6 8)
14:17	justin_smith	TMA: that could be mapcat btw
14:17	spuz_	in haskell there is flip
14:18	justin_smith	in clojure I would do (fn flippy [f] (fn [& args] (apply f (reverse args))))
14:19	justin_smith	but that isn't a thing defined in clojure.core
14:19	TMA	justin_smith: I have already said that I do not know clojure ;) therefore I was ignorant of mapcat
14:19	justin_smith	aha
14:20	TMA	I am using it now and then, but I do not know it. It is so much better than java, I can be more productive even without knowing it
14:23	TMA	spuz_: personally I do not use -> or ->> or any of the ilk. they make code too cumbersome to figure out for me. However, that means there is a lot more deply nested parentheses in my code, which I personally do not abhor as much as the average programmer
14:23	spuz_	heh
14:23	spuz_	I have not used them so much so far
14:24	spuz_	but for this particular case they make a lot of sense
14:24	Somelauw	I see a lot of clojure programmers use unicode for variable names. What is your favourite method of doing unicode input?
14:25	Somelauw	I mean, how do you enter weird chars like → or ǽ or Greek λ or is that still a bad idea?
14:26	justin_smith	TMA: wait, I just realized your silly thing above was just (filter even? (range 10))
14:26	justin_smith	Somelauw: probably mostly people are using emacs
14:27	justin_smith	Somelauw: either something that automatically translates certain names, or gives shortcuts for inserting favorite chars (though in emacs you can insert any char by name with M-x insert-char)
14:27	TMA	justin_smith: yes. the goal was to implement it using -> and map; in particular -> had to be used
14:27	justin_smith	oh
14:28	justin_smith	,(->> (range 10) (mapcat #(when (even %) %)))
14:28	clojurebot	#error {\n :cause "Unable to resolve symbol: even in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: even in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6688]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol: even in this co...
14:28	justin_smith	ergh
14:28	justin_smith	,(->> (range 10) (mapcat #(when (even? %) %)))
14:28	clojurebot	#<IllegalArgumentException java.lang.IllegalArgumentException: Don't know how to create ISeq from: java.lang.Long>
14:28	justin_smith	oh right
14:29	justin_smith	,(->> (range 10) (mapcat #(when (even? %) [%])))
14:29	clojurebot	(0 2 4 6 8)
14:29	TMA	justin_smith: ->> was expressly forbidden, hence the argument flipping abomination
14:30	justin_smith	oh, man, I should have just read the scrollback
14:30	Somelauw	justin_smith: ah, in vim there is ctrl-k. I just think I want this system-wide or something
14:30	TMA	it was fun to design it though. :)
14:31	Somelauw	If emacs also uses RFC 1345, vim and emacs might actually be using the same mappings
14:31	justin_smith	Somelauw: emacs uses the full written name of the char (with tab completion) for insert-char at least
14:31	spuz_	Is there a better way to write this function? https://www.refheap.com/a3fa8bcb058f49e845a7dc0e5
14:32	spuz_	I am not entirely sure why I have to use map, apply and str to convert the partitioned values back into a string
14:32	justin_smith	Somelauw: thanks for the info, I just switched to vim a week ago (I had been using evil mode for wrist reasons, and I figured I might as well try the real thing)
14:33	justin_smith	Somelauw: oh cool, C-kl*
14:50	OscarZ	how does clojure namespaces work.. say i have some core namespace that has some namespaces that are :required at the top of the file.. does it load and run them recursively in the order then ?
14:54	hiredman	because a string becaomes a seq of characters, and partition partitions that seq of characters in to a seq of seqs of characters, and join takes a collection of strings
14:55	justin_smith	spuz_: also, unlike in haskell, in the jvm a list of chars is not a string
14:59	OscarZ	im using the ns :require in dev/user.clj to require some namespaces, one of them is db.clj where im doing some db initialization work .. for some reason when running lein repl this init gets stuck
14:59	justin_smith	OscarZ: when you require a namespace, all top level code is run
15:00	justin_smith	so if there's something at the top level of the namespace that would block or error, require will make that blocking or error happen
15:00	OscarZ	but if i comment the particular namespace out from ns, lein repl starts.. and if i then run (require 'db) it works fine
15:00	justin_smith	hmm
15:00	OscarZ	seems like some kind of race condition or something..
15:01	justin_smith	require doesn't do anything concurrent, (but if you have async stuff at the top level of your namespace that has side effects I'd expect all kinds of problems)
15:04	OscarZ	no async stuff as far as i know :)
15:08	OscarZ	somehow related to repl and its loading .. it works when repl is loaded and then i require the namespace..
15:15	jumar	willharrison, you should be able to download it from http://www.infoq.com/presentations/Are-We-There-Yet-Rich-Hickey
15:16	jumar	just look at the source code - you should find the link like http://videoh.infoq.com/presentations/09-sep-clojure-keynote.flv
16:00	Somelauw	justin_smith: I admit that emacs insert-char is easier to use than vim digraphs. Maybe not faster, but definitely easier.
16:42	Somelauw	justin_smith: I ported the emacs insert-char function to Python: https://pastee.org/3pwmc
16:43	justin_smith	Somelauw: so is that a plugin for dmenu? I think that's what I use as a launcher with i3 on my linux box
16:43	justin_smith	honestly I forget what the program is called
16:44	Somelauw	yes, i3 uses dmenu in its standard config
16:45	Somelauw	not completely finished, because it only prints the character, I need to insert it as well
16:48	Somelauw	unfortunately, xdotool key "!" doesn't work for me
16:56	Somelauw	justin_smith: An ugly workaround, but it works if you call it like this: python insert-char.py \| xclip -i && xdotool key "shift+Insert"
16:57	rhg135	Beats learning vimlang
16:58	Somelauw	and instead of print, you need sys.stdout.write in the last line of my paste
17:11	Somelauw	blegh: it seems that in Python printing unicode works fine when printing to a console, but that an encoding is needed when piping to another process
17:12	Somelauw	so here is yet another version: https://pastee.org/t3w4c
17:14	Somelauw	rhg135: I could maybe rewrite it as a plugin for some fuzzy-completion plugin in vim, but now I have it system-wide
17:15	Somelauw	Unix says: DOTADIW but sometimes it's unclear which resposibility should be given to whom
17:15	rhg135	Somelauw: I think you can spawn subprocesses, they must be synchronous though
17:16	rhg135	r!stuff is useful
17:16	Somelauw	rhg135: i'm already doing that, I now have a small shell wrapper around python that can also be put in the code itself using subprocess
17:16	Somelauw	what is r!stuff?
17:17	rhg135	Insert the output of a command
17:18	Somelauw	in shell?
17:18	justin_smith	Somelauw: clearly what you need is to turn vim into a window manager
17:19	rhg135	Any executable
17:19	Somelauw	rhg135: can you give an example?
17:19	Somelauw	justin_smith: that's what Emacs said
17:19	rhg135	:r!echo 1 would insert 1 in vim
17:20	Somelauw	oh, in vim
17:20	Somelauw	and I thought that needed a space between r and !
17:20	rhg135	Maybe it does
17:21	justin_smith	no, it doesn't
17:21	justin_smith	(just checked)
17:22	rhg135	justin_smith: actually vim already does a bit of window management
17:22	Somelauw	rhg135: :r !python insert-char.py prints the char after a newline for me
17:23	justin_smith	rhg135: right, my point was he was trying to get vim-style char insertion everywhere (thus the dwm thing...) and a vim solution only helps if all his other apps are inside vim
17:23	justin_smith	but maybe I misunderstood the task
17:25	rhg135	Isn't this why input managers exist?
17:26	Somelauw	if an input-manager can do this or has a plugin system to do this or something that would be great
17:26	rhg135	Well, I wasted time getting uim working
17:27	Somelauw	For some reason, gtk and qt use a different input than the rest of x
17:27	rhg135	Let's me bug people with infinite amounts of Greek letters
17:27	Somelauw	rhg135: How have you set uim up?
17:28	rhg135	I think I just launched it and set some variables from my profile
17:28	Somelauw	how do you enter a greek char from uim?
17:29	rhg135	The arch wiki was useful here
17:29	Somelauw	at least in xim, you need to write your own .XCompose
17:29	rhg135	Compose key is how I do it
17:29	rhg135	C-S-u
17:29	Somelauw	because the standard composing have a very limited set
17:30	rhg135	Yup
17:30	Somelauw	I already made xim use vim digraphs using some script
17:34	Somelauw	the arch wiki page about uim only talks about Japanese
17:37	rhg135	I looked at all the input manager pages
17:39	Somelauw	it might be that uim has more features than xim I don't know
17:39	Somelauw	rhg135: Is there anything xim doesn't do that you need?
17:39	rhg135	I couldn't get xim to work in some apps
17:41	Somelauw	yeah, gtk and kde use their own input methods by default for some reason, you could force them to use xim or uim
17:42	rhg135	I'll try that when I'm at my computer later
17:50	Somelauw	⤴
17:51	Somelauw	☃
17:51	Somelauw	that's supposed to be snowman
17:51	Somelauw	okay, played enough
18:09	rhg135	I see
18:23	justin_smith	yes, that was a snowman
18:26	RedNifre	Hey there. First time using leiningen, I try to use Compojure by following this guide: https://adambard.com/blog/sinatra-docs-in-clojure/ but I get this error, what is the problem? http://pastebin.com/Xn54awdU
18:27	justin_smith	RedNifre: how did you add compojure to your dependencies?
18:27	justin_smith	that error means that the clojure compiler could not find the compojure files
18:27	RedNifre	good question, the tutorial wasn't that clear so I improvised. One second...
18:28	RedNifre	Ah, I'm pasting too much. Anyway, here is my project.clj: http://pastebin.com/mNyyRNaV
18:30	RedNifre	I did not follow the tutorial exactly, it said to run "lein new myapp" but I thought since that would create a library project where I surely want an executable I went with "lein new app myapp" instead. Was that wrong?
18:30	justin_smith	RedNifre: if the project.clj is what you shared, and it is in the directory with the project, lein should have downloaded compojure (or used the copy already on your cache)
18:31	RedNifre	I won't have a copy in my cache since this is the first time I use compojure. I should do "lein run" in the project directory i.e. the directory that contains the project.clj, right?
18:31	justin_smith	RedNifre: can you share the output of 'lein cp' - or at least check if compojure is actually in that output?
18:32	justin_smith	RedNifre: right
18:33	RedNifre	Ah, never mind. It seems that the project.clj wasn't properly saved m/
18:33	RedNifre	Seems to work properly now, sorry.
18:34	justin_smith	that would explain it
18:36	RedNifre	Regarding tutorials, I did not like "Clojure for the brave and true" at all. I heard "the joy of clojure" might be good, can you recommend it? Or what might be a good next step for me?
18:36	justin_smith	joy of clojure is good, but it's not a slow intro
18:37	RedNifre	Sounds good. I'm looking for something that is as in-your-face overwhelming as the Haskell tutorials.
18:41	ridcully	if you are battle hardened in other languages i found clojure applied very nice
18:42	justin_smith	yes, that's a good one too
18:45	RedNifre	So what's the theme of "joy of clojure" compared to "clojure applied"?
18:45	justin_smith	joc gets more into the design philosophy, clojure applied has more about typical incidental things you should know if you are going to develop and deploy clojure
18:50	RedNifre	Well, the situation I find myself in is this: I write large things in Haskell (solid, difficult) and small scripts in Ruby (messy, easy). Clojure looks interesting to me because it's functional. I'm skeptical about the dynamic typing but I think I should give it a chance. Macros seem amazing, though the only use case I can think of so far would be Haskell's do-notation. What I find very fascinating is this "code is data" thing; edn is muc
18:50	RedNifre	h more elegant than json so the idea of writing config files in the same data format that I use to write the small tools that use them is appealing.
18:52	RedNifre	So basically I wonder if Clojure can replace Ruby for me (I only use Ruby for small tools) and if that works out I might check how far it scales i.e. whether I can write code as robust as Haskell code but quicker (because of dynamic typing).
18:53	RedNifre	I'm not sure if I can judge those two books yet, but maybe I should read joc first to understand the philosophy and "clojure applied" after that?
18:55	TEttinger	RedNifre: the only annoyance I have with clojure for small tools is the somewhat long startup time, though there are good ways around that now. I do spend much less time writing the tools though, relative to OOP langs like Java, so that's a benefit :)
18:55	TEttinger	https://github.com/technomancy/leiningen/wiki/Faster
18:56	RedNifre	TEttinger do you always create jars or do you have very tiny scripts that you run interpreted?
18:56	RedNifre	Regarding lein, is it a build tool / dependency resolver like all the others (cabal, npm etc.) or does it differ?
18:56	TEttinger	I almost never create jars unless I have to
18:57	TEttinger	I run with 'lein run' usually, sometimes 'lein repl' and paste in some snippet
18:57	TEttinger	for tiny stuff I just paste it into a lazybot instance I have running
18:58	TEttinger	lein is a built tool and dep resolver, it doesn't do much too different. it does have good creation of uberjars
18:58	RedNifre	I like Ruby's shell interop, you can run shell commands just by using backticks: `curl -bla`. How shell friendly is Clojure?
18:58	TEttinger	it emphasizes cross-platform stuff, and shell commands are not that at all, so...
18:59	TEttinger	there is shell support in the standard lib
18:59	RedNifre	Okay, so it might not be the best choice for glorified bash scripts, huh?
18:59	TEttinger	http://clojuredocs.org/clojure.java.shell/sh
18:59	TEttinger	maybe. that's largely what I use it for, I suppose
19:00	justin_smith	ProcessBuilder is super powerful, but it is also stupidly limited by portability
19:00	justin_smith	eg. you can't find out the PID of a process you launched
19:02	RedNifre	sh looks good. But what for do you people use Clojure? Do you use it for the tiniest tools or do you write those in bash or a traditional scripting language? Or do you use Clojure for large projects? Something in between?
19:04	TEttinger	I've been meaning to use it for larger projects, but mostly I currently use Clojure for small things that I want to get working fast
19:04	TEttinger	clojure is definitely good as projects start to get bigger
19:06	TEttinger	an example is this spreadsheet data turned into TSV: https://dl.dropboxusercontent.com/u/11914692/input.txt I run a small, messy script on it to convert it to much more usable text https://dl.dropboxusercontent.com/u/11914692/class-formatter.clj and the output is like https://dl.dropboxusercontent.com/u/11914692/classes200-final.txt
19:09	RedNifre	The problem sounds like the kind of thing that I solve with Ruby, but the Clojure code looks surprising to me. I'll have to stare at it for a moment...
19:10	RedNifre	Ah, so inp is the file stream and the -> macro funnels it through several processing steps?
19:11	TEttinger	it was never meant to be read!
19:11	TEttinger	this was meant to be written once, clumsily, using regexes to make regexes lol
19:11	TEttinger	I probably have cleaner scripts
19:11	RedNifre	heh
19:12	RedNifre	Indentation would be nice :)
19:12	TEttinger	that's just one I've used a bunch and produced very very quickly
19:12	TEttinger	that one I just paste into the repl
19:12	RedNifre	I see.
19:12	TEttinger	so the indentation doesn't affect it
19:12	TEttinger	(it wouldn't anyway I guess)
19:13	RedNifre	Personally I'm still not used to Lisp's ((()()))()()()))))) but I solved it with this thing called "parinfer": I just use indentation and parinfer just places the parens for me.
19:13	TEttinger	what I pasted is a terrible example of what makes clojure powerful, there'
19:13	TEttinger	what I pasted is a terrible example of what makes clojure powerful, there's a lot better examples I can probably dredge up
19:14	RedNifre	Sure, I only understand it up to "(def fin" so far.
19:14	RedNifre	Does "fin" stand for "finishing touches"?
19:15	TEttinger	hehe yep. I would probably recommend this instead, in retrospect http://ideone.com/L0eHc6
19:15	TEttinger	h.p.lovecraft-style rambling generator
19:15	RedNifre	weird, the syntax highlighting is almost completely pink.
19:16	TEttinger	that can technically be compressed down to one IRC message, about 400 chars. I won't paste it since it's super illegible that compressed
19:16	TEttinger	yeah ideone is broken with '
19:16	TEttinger	it thinks ' is a paired quote somehow
19:19	TEttinger	output is below
19:19	RedNifre	What is "#(do["? Wasn't "#(" the beginning of a lambda and doesn't do usually look like (do (bla) (blaa) (bleh))?
19:20	justin_smith	RedNifre: both of these things are correct
19:20	TEttinger	that might have been to produce a vector in a lambda with a little less code
19:20	justin_smith	RedNifre: #([...]) will error when called, because it calls a vector with no args
19:20	TEttinger	,(map #(do [% %]) [1 2 3])
19:20	clojurebot	([1 1] [2 2] [3 3])
19:21	justin_smith	,([:a :b :c] 1)
19:21	clojurebot	:b
19:22	RedNifre	I don't understand why #(do [%]) should be fine but #([%]) isn't. To me, both look like the lambda would just return the vector with the parameter inside.
19:22	TEttinger	another repacement would be
19:22	TEttinger	,(map #(vector % %) [1 2 3])
19:22	justin_smith	RedNifre: try expanding
19:22	clojurebot	([1 1] [2 2] [3 3])
19:22	justin_smith	,'#([:a])
19:22	clojurebot	(fn* [] ([:a]))
19:23	justin_smith	RedNifre: see the problem?
19:23	justin_smith	,'#(do [:a])
19:23	clojurebot	(fn* [] (do [:a]))
19:24	TEttinger	unless there's a quote preventing it from being run, parentheses in clojure go before fn or macro calls. vectors and maps actually can be used as fns, but they need an index or key as an argument to that fn
19:24	justin_smith	[] is callable, if #([]) was not an error, and returned [], then #(println) would return the println function, instead of calling it
19:25	RedNifre	Oh, that makes sense.
19:25	TEttinger	I think the do[ was a relic from when I ported it from the one-liner
19:25	RedNifre	That also means that if I actually want a lambda that returns the println function I have to write (fn [] println) instead? Or maybe #('println) ?
19:26	justin_smith	RedNifre: 'println is a symbol
19:26	justin_smith	not a function
19:26	justin_smith	,('println "hello" "world")
19:26	clojurebot	"world"
19:26	justin_smith	sorry, that was evil
19:26	RedNifre	My bad, I confused the quote with "don't execute it yet".
19:26	justin_smith	RedNifre: with symbols it means "don't resolve it yet"
19:27	TEttinger	,(constantly println) ; this is a nice way to return a fn that when called will return the value you want, every time
19:27	clojurebot	#object[clojure.core$constantly$fn__4614 0x7e9f909b "clojure.core$constantly$fn__4614@7e9f909b"]
19:27	justin_smith	,((resolve 'println) "hello" "world")
19:27	clojurebot	hello world\n
19:27	TEttinger	,(map (constantly 11) [1 2 3])
19:27	clojurebot	(11 11 11)
19:27	RedNifre	Why did clojurebot just say "world"?
19:28	justin_smith	,('a 'b 'c)
19:28	clojurebot	c
19:28	TEttinger	I don't know either, haha
19:28	justin_smith	,(get 'a 'b 'c)
19:28	clojurebot	c
19:28	justin_smith	err
19:28	justin_smith	,(get 'b 'a 'c) ; this is actually equivalent
19:28	clojurebot	c
19:28	RedNifre	well, I don't understand that one either.
19:28	justin_smith	RedNifre: when a symbol is called, it acts as get of itself
19:28	justin_smith	,('a '{a 0})
19:28	clojurebot	0
19:28	TEttinger	justin_smith: is that the default get thing?
19:28	justin_smith	,('a '{b 0} 'c)
19:29	clojurebot	c
19:29	justin_smith	TEttinger: yup
19:29	justin_smith	RedNifre: here's an amazing bug
19:29	justin_smith	,('or nil false)
19:29	clojurebot	false
19:29	justin_smith	,('or true false)
19:29	clojurebot	false
19:29	justin_smith	haha
19:29	justin_smith	(bug being using 'or instead of or of course)
19:29	TEttinger	,(get {:a 1} :a)
19:29	clojurebot	1
19:30	TEttinger	,(get {:b 1} :a)
19:30	clojurebot	nil
19:30	TEttinger	,(get {:b 1} :a :not-found)
19:30	clojurebot	:not-found
19:30	TEttinger	does that make it a bit clearer?
19:30	RedNifre	I only know why (:a {a 0}) would be 0, I don't understand what happens in ('a '{a 0}). How does clojurebot execute quoted forms?
19:30	justin_smith	RedNifre: you don't get quote
19:31	TEttinger	to be honest I don't either :)
19:31	justin_smith	'{a 0} is the same as {'a 0}
19:31	justin_smith	since 0 is self-evaluating
19:31	justin_smith	for that matter, '{:a 0} is the same as {:a 0} because all parts of the form are self-evaluating
19:32	RedNifre	Okay, I only understood quote as "Don't run this code" and that I can run it later with eval which I shouldn't.
19:32	justin_smith	quoting prevents lists from evaluating, and it prevents symbols from being resolved
19:32	justin_smith	RedNifre: no, it is not "don't run this code" it's "don't execute lists (just leave them as lists) and don't resolve symbols (just leave them as symbols)"
19:32	TEttinger	where something like (a b c) is a list of symbols, and unless quoted, would try to resolve them
19:33	TEttinger	,(a b c) ; will fail
19:33	clojurebot	#error {\n :cause "Unable to resolve symbol: a in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: a in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6688]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol: a in this context"\n ...
19:33	TEttinger	,'(a b c) ; will not fail
19:33	clojurebot	(a b c)
19:33	TEttinger	,'(a b) ; will not fail
19:33	clojurebot	(a b)
19:33	justin_smith	RedNifre: now it does turn out that eval uses lists and symbols, but we have reader macros, which means that certain things still happen, even inside quoted data - eg '{} still constructs a hash-map because that's part of reading not eval
19:34	RedNifre	So '(+ 1 2) is a list containing +,1,2, right? What exactly is '+? I guess '+ is not the function yet, it's just ... the symbol... but what does that mean? Does it sort of mean it's something like a String containing the character "+" and resolving the symbol will find the + function? Or is the symbol a more technical thing like the memory location of the function or something?
19:34	TEttinger	,('a 'b) ; but this doesn't quote the list, so it's trying to call the quoted symbol 'a now
19:34	clojurebot	nil
19:34	justin_smith	RedNifre: symbols are like keywords, but they also resolve to vars in a namespace
19:35	TEttinger	,`+
19:35	clojurebot	clojure.core/+
19:35	justin_smith	and also to locals inside a bound body
19:35	TEttinger	+ actually knows what its namespace is, I think, which is how ` (backtick, aka syntax-quote) can get the namespaced fn name
19:36	justin_smith	TEttinger: '+ has no namespace, eval decides what the namespace is based on the mappings in the current context
19:36	TEttinger	ohh
19:36	justin_smith	TEttinger: for example what if it's bound to a local? then it has no namespace
19:36	TEttinger	mm
19:36	justin_smith	what if you used :refer-clojure [:exclusions [+]] or however that works
19:36	RedNifre	So if I define my own + in my own namespace and then do '+ I'll get a symbol for my own + and even if I throw this '+ over to another namespace it will there not mean the standard clojure +, it will still mean my own + from the other namespace?
19:37	TEttinger	so '+ doesn't know, the environment produced from things like require is what knows
19:37	RedNifre	ah, so the opposite of what I said.
19:37	justin_smith	RedNifre: '+ isn't even "for" anything yet - you prevented the resolving step
19:37	justin_smith	if you used + it would resolve to the one in the same namespace, sure
19:37	justin_smith	RedNifre: for the last part, no, absolutely not
19:37	justin_smith	symbols know nothing
19:38	RedNifre	So '+ is more like the String containing the character plus?
19:38	justin_smith	namespaces decide what symbols mean
19:38	justin_smith	kind of, yeah, with some special behaviors that strings dont' have, of course
19:38	TEttinger	I think the last statement is closest yea
19:39	TEttinger	it does seem like you're picking this up pretty quickly, RedNifre
19:39	TEttinger	the quote thing can get kinda complex at first
19:39	justin_smith	RedNifre: maybe it would help to mention that a namespace owns a hash-map, and the keys are symbols, the values are vars, and vars are dereffed to get values created with def
19:39	RedNifre	Right, so when the symbol gets resolved, Clojure checks the current namespace for a function or variable that kinda has the same String name like what's in the symbol.
19:39	RedNifre	So quoted symbols can lead to disasters when using code obfuscation?
19:39	justin_smith	RedNifre: and when you call def, you are mutating the hash-map to add a new symbol as a key
19:39	RedNifre	Thanks, TEttinger.
19:42	RedNifre	Okay, now I'll ponder about "'{a 0} is the same as {'a 0}" for a moment...
19:42	justin_smith	,(= '0 0)
19:42	clojurebot	true
19:43	justin_smith	,(= '{} {})
19:43	clojurebot	true
19:43	justin_smith	,(= ':a :a)
19:43	clojurebot	true
19:43	RedNifre	See, to me it looks like '{a 0} is a symbol and {'a 0} is a map that maps the symbol 'a to 0. I also don't understand what the hint "0 evaluates to self" means.
19:43	justin_smith	it's what I was saying about the reading step
19:43	justin_smith	the reading step happens before resolve, and resolve happens as the first step of eval
19:43	justin_smith	' does not prevent reading - "" prevents reading
19:44	RedNifre	Are '0 and 0 really the same or does = turn the '0 into 0 before comparing?
19:44	justin_smith	RedNifre: '0 is 0
19:44	justin_smith	the reader creates 0
19:44	justin_smith	it has nothing to do with eval
19:44	justin_smith	reading has to happen before ' can be applied
19:44	justin_smith	actually, reading turns 'x into (quote x)
19:44	justin_smith	,''x
19:45	clojurebot	(quote x)
19:45	RedNifre	And (quote 0) is 0?
19:45	justin_smith	will, the one above is the list '(quote 0)
19:45	justin_smith	but yes
19:45	justin_smith	,(quote 0)
19:45	clojurebot	0
19:45	justin_smith	,(quote (quote 0))
19:45	clojurebot	(quote 0)
19:46	justin_smith	(quote just quoted another quote)
19:46	justin_smith	but 0 above is still 0!
19:46	RedNifre	Which 0 above?
19:46	justin_smith	but of course "0" contains no 0 - that actually prevented reading
19:47	RedNifre	You mean the String "0" containing the character with the unicode value 32?
19:47	justin_smith	RedNifre: the one generated by (quote (quote 0)) is a regular 0 - it is created before the quote is applied
19:47	justin_smith	RedNifre: yes, "" is what prevents reading
19:47	justin_smith	once reading happens, all literals have been created
19:47	justin_smith	this includes data structures and numbers and symbols and keywords - all self-evaluating things
19:48	justin_smith	RedNifre: remember it's a REPL
19:48	justin_smith	R happens first
19:49	RedNifre	Just to be sure, are we talking about something that only behaves like this in the REPL or is it the same in regular compiled clojure?
19:49	justin_smith	RedNifre: most languages have something like this (in the compiler), but lisps have the annoying / cool property that you end up needing to care, because forms are first class in the language.
19:49	justin_smith	RedNifre: there is no such distinction
19:49	justin_smith	the repl is regular compiled clojure in every aspect
19:49	justin_smith	there is no compiler / interpreter split
19:50	RedNifre	Is '0 just syntactic sugar for (quote 0) or is this a change or does it make no difference because resolving syntactic sugar is kinda what other things like macros are doing?
19:50	justin_smith	RedNifre: yes, ' is synctactic sugar for (quote)
19:50	justin_smith	just like @ is syntactic sugar for (deref)
19:51	RedNifre	Does Clojure even have a distinction between syntactic sugar and macros/reader stuff?
19:51	justin_smith	RedNifre: we have the reader itself (for things like ' and data structures and @), reader macros (all things that start with # are reader-macros), then macros, and then finally functions to evaluate
19:52	justin_smith	I might have missed something there, but I think that's most of it
19:52	RedNifre	Okay, so there is a hierarchy and '0 meaning (quote 0) is more language featurey than the macros I can define myself...
19:53	justin_smith	yes
19:54	RedNifre	So I take it that when I write (= '0 0) what happens is that it first turns into (= (quote 0) 0). I assume quote is also a macro which resolves it to (= 0 0). That is the final code that gets compiled and when it gets run it evaluates to true?
19:58	justin_smith	RedNifre: well, it resolves to true at compilation time
19:58	justin_smith	so no byte code is generated - it just returns true
19:58	RedNifre	But that's just an arbitrary optimization, right?
19:58	justin_smith	so yeah, you have the idea
19:58	justin_smith	RedNifre: sure, yeah, but it would be a silly one to leave out
19:58	RedNifre	Fair point.
19:59	justin_smith	RedNifre: and it's a gotcha - people expect the clojure compiler to emit byte code for things that have top level side effects, but instead the side effects are invoked while compiling
19:59	justin_smith	common newcomer pitfall
19:59	RedNifre	huh?
19:59	RedNifre	THat sounds surprising.
19:59	justin_smith	RedNifre: (def war (launch-the missiles))
19:59	justin_smith	that launches the missiles in order to compile the def form
20:00	justin_smith	RedNifre: the lesson here is don't ever do top level side effects, unless you are trying to do things at compilation time explicitly
20:00	RedNifre	The code looks wrong, it should be (defn war [] (launch-the-missiles)), right?
20:01	justin_smith	right
20:01	justin_smith	RedNifre: but it's usually (def connection (connect-to db))
20:01	justin_smith	works great in a repl!
20:01	justin_smith	works at dev time if you just run the project
20:01	RedNifre	I have to think about what I would expect (def war (launch)) to do actually.
20:01	justin_smith	works poorly when compiling ahead of time to make a jar that java can invoke
20:02	RedNifre	Okay, well, Haskell would launch the missiles lazily when you try to print the value of the war variable... hm...
20:02	justin_smith	heh, yeah
20:03	RedNifre	Clojure uses eager evaluation so I would actually expect the missiles to launch when the jar gets loaded into the JVM, not at compile time. Hm...
20:03	justin_smith	it launches at the time you are creating the jar
20:03	justin_smith	unless you are doing a non-aot packaging
20:03	RedNifre	So compiling evil source code can format my hard drive?
20:06	RedNifre	It seems like this makes compilation quite complicated. I'm surprised that parts of the program can run before other parts are even compiled. I guess it compiles the easy parts first and invokes the tricky parts last?
20:06	RedNifre	Hang on, does that mean that compiling a throw away script will run at compile time and the jar will only contain one large print statement with the result?
20:07	justin_smith	RedNifre: the compiler can be made to execute arbitrary code, this is the premise of a lisp
20:07	justin_smith	def is just a trivial example of this, but it goes much deeper
20:07	RedNifre	:)
20:07	RedNifre	It's getting more and more interesting.
20:08	RedNifre	That's exactly the stuff I was looking for: strange concepts I'm not familiar with yet.
20:08	justin_smith	RedNifre: you could easily test what it does in a project with a top level println in the same ns as -main with a freshly created app
20:09	RedNifre	Does the joc book cover all this?
20:09	justin_smith	yes, and probably makes a more coherent explanation of how these things all fit together and why
20:10	RedNifre	I'm sold, I'll order the book and come back when I have less basic questions to ask :)
20:11	RedNifre	Thank you two for taking the time to clear up my questions. It changed my view.
20:12	RedNifre	Have a good night!
20:12	justin_smith	you too
20:25	justin_smith	TEttinger: https://twitter.com/voxel/status/586452796125265921
20:28	rhg135	Heh, any you say?
20:30	justin_smith	"
20:30	justin_smith	err
20:31	justin_smith	"this is , but we call him bom"
20:33	rhg135	I think I knew a guy called bom
20:34	rhg135	The school's IT system must have had fun
20:35	blockzombie	lol
20:38	TEttinger	@voxel @buzzert I noticed "a baby" is not on that list.
21:08	rhg135	Whoa
21:16	gilch	Can anybody explain where "#=" is documented? It's ungoogleable.
21:16	blockzombie	lol
21:16	blockzombie	it's on the cheat sheet
21:16	blockzombie	... getting
21:17	blockzombie	http://clojure.org/api/cheatsheet
21:17	gilch	I don't see it on grimore
21:17	justin_smith	gilch: it's a reader macro, and is covered in the part of the clojure.org docs about reader macros. Everything that starts with # is a reader macro.
21:17	blockzombie	ah it's not there sorry
21:19	justin_smith	gilch: oh, wow, it's missing here too http://clojure.org/reference/reader
21:19	gilch	justin_smith: you mean http://clojure.org/reference/reader ? The string "#+" not found on page :(
21:20	gilch	*"#="
21:20	justin_smith	,(read-string "#=(+ 1 1)")
21:20	clojurebot	#error {\n :cause "EvalReader not allowed when read-eval is false."\n :via\n [{:type java.lang.RuntimeException\n :message "EvalReader not allowed when read-eval is false."\n :at [clojure.lang.Util runtimeException "Util.java" 221]}]\n :trace\n [[clojure.lang.Util runtimeException "Util.java" 221]\n [clojure.lang.LispReader$EvalReader invoke "LispReader.java" 1100]\n [clojure.lang.LispRe...
21:20	justin_smith	anyway, that's what that is - in your repl the above returns 2
21:20	justin_smith	it's for evaluating arbitrary code at read time
21:20	justin_smith	it's kind of a terrible feature actually
21:21	gilch	Oh, like common lisp
21:21	gilch	#.
21:22	gilch	It seriously isn't documented anywhere?
21:22	justin_smith	sorry to mislead, I was sure it would be described with the other reader dispatch in the section on the reader
21:23	justin_smith	it has to be documented, I'm just wondering where...
21:23	justin_smith	gilch: this isn't searchable for obvious reasons, but it's described here https://clojuredocs.org/clojure.core/read-eval
21:24	justin_smith	gilch: aha!
21:24	justin_smith	gilch: in your repl, try (find-doc "#=")
21:25	justin_smith	that's clojure.repl/find-doc, but most repls auto-use clojure.repl for obvious reasons
21:27	amalloy	i think the reason it's not mentione with the reader macros is it's one you're not supposed to use as a feature; rather it's really just for the runtime's internal use
21:29	gilch	How am I supposed to tell what's API and what's implementation detail?
21:29	gilch	read-eval is documented
21:30	gilch	I wonder if I'm missing any other dispatches not on the cheatsheet?
21:31	gilch	Is there a list of the builtin edn tags somewhere?
21:32	justin_smith	#= is not an edn tag - the main difference between core/read and edn/read is that it does not respect that flag
21:32	gilch	So edn will work on all the other #x
21:32	justin_smith	that I know of, yeah
21:33	gilch	#@? / #?
21:33	justin_smith	one moment, testing
21:33	gilch	I can't think of a use edn would have for that
21:34	justin_smith	oh, just now I tested it, and #? failed
21:34	justin_smith	so yeah, good instinct on that one
21:35	amalloy	,(require 'clojure.edn)
21:35	clojurebot	nil
21:35	amalloy	,(clojure.edn/read-string "#_1 2")
21:35	clojurebot	2
21:36	gilch	I saw #inst and #uuid on the github spec. I thought I saw a #js in code somewhere, but... Maybe find-doc
21:36	gilch	nope
21:38	gilch	https://github.com/edn-format/edn explicitly says it does support "#_"
21:38	justin_smith	gilch: also the e stands for extensible, people can add their own readers for # things
21:39	gilch	but they have to use namespace/
21:39	gilch	but #inst doesn't use namespace/
21:39	gilch	what else doesn't?
21:39	gilch	just #uuid so far?
22:21	rhg135	#= can be useful for derived constants, like if you need a char code but are too lazy
22:23	rhg135	You can either write a macro, or insert seemingly random numbers
22:33	gilch	does weird things when nested (quote #=(symbol (str foo . bar)))
22:34	gilch	=>unmatched delimiter?
22:35	gilch	(quote #= (symbol #=(str foo . bar)))
22:36	gilch	foo.bar
22:59	rhg135	,(str . " what?")
22:59	clojurebot	#error {\n :cause "Unable to resolve symbol: . in this context"\n :via\n [{:type clojure.lang.Compiler$CompilerException\n :message "java.lang.RuntimeException: Unable to resolve symbol: . in this context, compiling:(NO_SOURCE_PATH:0:0)"\n :at [clojure.lang.Compiler analyze "Compiler.java" 6688]}\n {:type java.lang.RuntimeException\n :message "Unable to resolve symbol: . in this context"\n ...
22:59	rhg135	I thought so
23:00	justin_smith	,(str 'foo '. 'bar)
23:00	clojurebot	"foo.bar"
23:03	rhg135	Ah
23:05	justin_smith	hmm
23:05	justin_smith	,(intern 'sanbox '. "dot")
23:05	clojurebot	#error {\n :cause "No namespace: sanbox found"\n :via\n [{:type java.lang.Exception\n :message "No namespace: sanbox found"\n :at [clojure.core$the_ns invokeStatic "core.clj" 4032]}]\n :trace\n [[clojure.core$the_ns invokeStatic "core.clj" 4032]\n [clojure.core$intern invokeStatic "core.clj" 6071]\n [clojure.core$intern invoke "core.clj" 6071]\n [sandbox$eval72 invokeStatic "NO_SOURCE_FILE"...
23:05	justin_smith	,(intern 'sandbox '. "dot")
23:05	clojurebot	#'sandbox/.
23:05	justin_smith	,.
23:05	clojurebot	"dot"
23:05	rhg135	Box-san!
23:07	rhg135	Those are a few reasons why I no longer write code after dark
23:07	justin_smith	oh, wait
23:07	justin_smith	,(def . "dotty")
23:07	clojurebot	#'sandbox/.
23:08	rhg135	,(def . '.)
23:08	clojurebot	#'sandbox/.
23:08	justin_smith	,(defn . [] .)
23:08	clojurebot	#'sandbox/.
23:08	justin_smith	,(apply . ())
23:08	clojurebot	#object[sandbox$_DOT_ 0x50807f2e "sandbox$_DOT_@50807f2e"]
23:08	justin_smith	that is so weird
23:09	rhg135	That'd totally mess with elispers
23:09	justin_smith	seriously
23:09	justin_smith	I mean it scans really weird even to me as a clojurist
23:12	rhg135	.s are symbols too!