#clojure – 2017-06-21

2017-06-21

08:40	ragojae	Why should one chose Aleph of Http-kit for a webapp?
08:41	dysfun	http-kit integrates with sente, so if you use sente, it's a good choice. aleph uses manifold, so if you use manifold or core.async, it might be a good choice
08:41	ragojae	Isn't it possible to get streams out of http-kit as well - thus making it compatible with manifold & core.async?
08:41	ragojae	If I'm not wrong it even defaults to giving you java streams
08:42	dysfun	it wouldn't surprise me if you could. aleph seems better maintained
08:44	dysfun	in general i am fond of ztellman libraries
09:23	foodoo	Hi, I need a fn that takes a hash-map {:ns ns :name name} and translates this to (find-var (:ns m)/(:name m)); how can I accomplish this?
09:24	foodoo	I want to declare a Var and resolve it later once it is bound at runtime.
09:35	foodoo	Or, to ask differently: What is the best way to achieve late binding?
09:36	dysfun	give it a var object
09:41	foodoo	(declare foo); (def bar foo); (def foo 42); bar -> still unbound
09:41	foodoo	Maybe I need to elaborate a bit
09:42	foodoo	(declare foo-step bar-step baz-step)
09:42	foodoo	(def pipeline-steps [foo-step bar-step baz-step])
09:43	foodoo	when I later create bindings to foo-step, bar-step and baz-steps, the object references in pipeline-steps will still point to the old, uninitialized objects.
09:44	foodoo	My current idea is to define foo-step etc. as placeholders that will use find-var to evaluate to the latest binding
09:45	foodoo	(declare-step foo-step); --> {:ns ns :name foo-step}
09:48	foodoo	But I do not know which Clojure constructs I could use to implement this.
09:51	Frozenlock	dysfun: IIRC Sente now has an Aleph adapter.
09:51	Frozenlock	https://github.com/ptaoussanis/sente/blob/master/src/taoensso/sente/server_adapters/aleph.clj
09:52	Frozenlock	ragojae:
09:55	foodoo	I found (ns-resolve). That should do the job :)
11:07	osan	when running (require '[clojure.string :as clj-str]) in the repl i get a return of nil but then if i try to call (clj-str/subs "hello, world!" 0 5) i get a runtime exception saying no such var as clj-str/subs
11:07	osan	anyone got any idea why?
11:07	noncom	but are you sure there's such a var?
11:08	foodoo	osan: Because subs is part of clojure.core and not clojure.string?
11:08	noncom	iirc subs is available without requiring anything
11:08	osan	oh it is?
11:08	osan	my bad, cheers
11:08	foodoo	osan: Intuition has led you astray ;)
11:08	osan	indeed :P
11:09	foodoo	It would indeed make more sense to have subs in clojure.string
11:09	osan	i agree
13:27	osan	guys which style do you prefer, which do you think is easier to debug, which do you prefer aesthetically?
13:32	osan	https://pastebin.com/WMZZJFFX
13:33	justin_smith	I think you're missing something on line 6
13:34	justin_smith	usually I used the second one, but with parens (-> login-url (http/get) (:body) (json/read-str))
13:34	justin_smith	also, often with line breaks
13:45	runejuhl[m]	IMO it depends on the context, but I prefer the threaded one. It makes it really to add a line of debug printing (e.g. `taoensso.timbre/spy`), although stepping through the function in the CIDER debugger becomes a bit harder
13:48	ridcully_	you can also do that okish with let: _ (println prevvar)
13:48	ridcully_	or put a doto around
13:49	runejuhl[m]	Yes, lots of ways to skin that cat :)
13:51	ridcully_	yet i'd got for the threading too. but i would just name it load-json or something -- other than the naming of the function and the param this is not that much special to login flows
13:51	justin_smith	if anything the let version is more flexible than the threaded one
13:51	justin_smith	you can spy inside a let too
13:55	runejuhl[m]	Not sure if the let version is more flexible, but visually it can easily get a bit messy with a bunch of let statements compared to threading. Knowing that the expressions are processed top-down without any unrelated variables in between (as you could have in a let) makes it easy to skim and get an idea about what's happening
13:56	justin_smith	runejuhl[m]: "not sure" - I'm 100% sure it is more flexible, let allows operations that can't be done directly in threading
13:56	dysfun	like "do this, then do this"
13:57	justin_smith	of course, things that are more powerful are often more messy - the weaker tool is usually preferrable if both work
13:57	dysfun	rather than do this, then do this on that
13:57	ridcully_	also to be extra picky, the naming there in the let is overly verbose and it's off (first name e.g.)
13:58	ridcully_	some crisp wording would give the let version more appeal in that case
13:58	ridcully_	e.g. response, body, payload
13:59	runejuhl[m]	...and a `C-c space` to align it
13:59	justin_smith	right, when you only use the symbols locally they don't need to be as specific because their context is clear in that block
14:02	osan	justin_smith: no it works i ran the code both ways
14:03	justin_smith	osan: (json/read-str) should be throwing an error
14:03	justin_smith	either that or it's super weird and just giving you nil or something
14:03	justin_smith	to duplicate the other code you'd have to call it on login-flows-json-str
14:05	osan	justin_smith: there's a (:require [] :as json) in (:ns)
14:05	osan	justin_smith: why do you think it should be throwing an error?
14:06	ridcully_	in the code you pasted earlier, you are calling (json/read-str) in the let example
14:06	osan	justin_smith: clojure.data.json.read-str takes one arg
14:06	ridcully_	one would expect, that json/read-str would take one argument of a string, that is the actual json to parse
14:06	osan	oh yeah
14:06	osan	you guys are right
14:07	osan	dno how that happened
14:26	amalloy	osan: you don't have to pick one or the other. give names to intermediate variables that can be given useful names, and leave the others anonymous by threading them through
14:27	osan	amalloy: true
14:28	amalloy	and even when making something anonymous, you don't have to thread it. i would probably have written something like (-> (:body (http/get login-url)) (json/read-str)), to emphasize the important :body and http/get stuff and deemphasize json/read-str, which feels like more of a bookkeeping detail to me
14:45	osan	amalloy: good advice
14:45	osan	amalloy: thanks
16:24	lxsameer	hey guys, I'm looking forward to design an extensible library. but I'm not sure which is the best approach to it, do you know any reading matterial about this ?
16:31	amalloy	that is quite a broad, generic question, which can really only be answered in a broad, generic way: use functions
16:32	lxsameer	amalloy: ok, then how my user can extend the lib based on his/her needs
16:32	dysfun	by writing more functions!
16:33	dysfun	functions are extensible because you can build new functions that use them
16:33	amalloy	yes, i don't just mean that you should defn things. your functions should accept functions as arguments, and you should have functions that return functions so that you can compose them in interesting ways
16:35	lxsameer	aha now i get it
16:35	dysfun	your basic categories of extensibility are higher order functions, prototypes/interfaces, inheritance and multimethods
16:35	dysfun	pick and choose according to what problem you're trying to solve
16:35	amalloy	(and all of those are just special cases of higher-order functions)
16:36	dysfun	and indeed if you can just keep it as higher order functions, it would be easier
16:36	lxsameer	dysfun: amalloy cool, thanks guys
17:24	osan	what do you guys think of this code? anyways to improve it you think? https://share.riseup.net/#vzf4LaY_yKLH2O4Xv1iBWg
17:26	justin_smith	I would find it a lot more readable if the forms weren't all one liners
17:26	justin_smith	and threading a function literal into map is weird
17:27	justin_smith	just use mapv
17:27	justin_smith	use seq instead of (not (empty? ...))
17:28	justin_smith	(which is explicitly mentioned in the doc of empty?)
17:30	justin_smith	for example, the body of get-all-login-types-strings would be much more readable as (mapv #(get % "type") (get-all-login-types-hasmaps login-url))
17:31	justin_smith	for personaly preference, I find that names that long make things less readable
17:31	osan	justin_smith: thanks, any suggestions for alternative name?
17:31	justin_smith	for example, the namespace ends in "login" and every single thing you define in the namespace has "login" in the name and every function binds an arg to a name with "login" in it
17:32	justin_smith	I think the code would become more readable if "login" were just assumed context based on the ns and doc strings, and the word login were removed from all other names
17:33	osan	justin_smith: thanks i agree
18:24	technomancy	I have a test that's 50 lines of "make this HTTP request and then check the response and use the response to generate another response" and it's just a huge let block with a bunch of res (http/get ...)\n _ (is (= 200 (:status res)))\n res (http/get ...) back and forth
18:26	technomancy	anyone have a preferred way to clean this up? http://p.hagelb.org/let-tests.html
18:27	hiredman	I have been writing the same kind of tests, and I feel like you should be able to do something with as->, but haven't nailed it down
18:31	hiredman	another thought I've had is to make your tests in to a finite state transducer (responses are inputs, requests are ouputs) and then assert it reaches an accepted state at the end
18:32	paolo`	?
18:33	hiredman	(which would support some level of non-determinsm in the tests, a response could be X or Y sort of things)
18:33	technomancy	that would certainly make them shorter =)
19:09	lxsameer	is it possible to attach meta data to hash-map keys
19:10	justin_smith	only if the keys are instances of IMeta
19:10	justin_smith	for example keywords can't take metadata
19:11	lxsameer	justin_smith: thanks
19:12	justin_smith	lxsameer: but symbols can have metadata
19:12	justin_smith	people might think you are weird for using symbols though
19:12	amalloy	i would think you're weird for putting metadata on keys of a map specifically
19:12	lxsameer	justin_smith: hmmmm i have big hash-map containing some configuration, i wanted to some how attach some docs to each key
19:13	lxsameer	amalloy: :)) thanks for the heads up
19:13	amalloy	like if you're using a symbol as a key, sure, and the symbol happens to already have some metadata on it, and you put that in a map: no problem
19:13	amalloy	but in your hashmap you already have plenty of space to store information about an entry: in the value!
19:14	lxsameer	amalloy: yeah that's right
19:14	lxsameer	thanks
19:14	amalloy	{:max-memory {:doc "how much memory" :value 1000000}, :language {:doc "what language to speak to the user in" :value "english"}}
19:17	lxsameer	amalloy: thanks man