Hey, what is the go-to Ring logger? https://github.com/nberger/ring-logger ?

noob question: ((fn [a b] [a b]) 1 2) eval to [1 2], (#(vector %1 %2) 1 2) eval to [1 2] too, why (#([%1 %2]) 1 2) got clojure.lang.ArityException: Wrong number of args (0) passed to: PersistentVector

and what does (#(-> [%1 %2]) 1 2) mean?

just like #(+ %1 %2) expands to (fn [x y] (+ x y)) #([%1 %2]) expands to (fn [x y] ([x y])) - #() keeps the outer parens

-> is a macro also known as thread-first and it's being abused here to be able to use a vector literal where it would otherwise not work

I got it~ so (#(do [%1 %2]) 1 2) works too

yes - do is better than -> here (in this context do and -> are the same)

so the [%1 %2] was evaled in place and used as the initial value of ->, but there is no further functions, so it got returned

with more forms,-> would be writing each form into the one after it

@leira exactly

hmmm I thought about this, but was not very sure I thought it was kinda an abuse too~

thanks @noisesmith!

Is there any sane way of handling repeated date conversions between java.sql.date and java.util.Date or should I give up and use timestamps instead (if that would be better)? Every sql update query rotates the date back a full day because of the time zone getting chopped off and re-added.

@tjscollins The only sane solution is to have all your servers set to UTC and your database set to UTC, and work entirely in UTC date/times -- and only convert to/from local date/times on the fringe.

I was afraid it would be something like that.

Our data center is East Coast and we have everything set to UTC across the board.

Thanks

What database are you using?

Postgres. Wanted to use datomic, but my organization's purchasing rules wouldn't allow it without too many headaches.

I don't know about Postgres but with MySQL you have to explicitly set the DB to UTC separately from the O/S. Just FYI.

Thanks, I'm digging into the docs now to figure it out.

I'm not a big fan of how the javadoc UI works for browing java functions.

Is there a clojure library for parsing javadocs into clojure data (so I can build my own search system) ?

dont think so, that'd be a useful library tho 🙂

greetings, [finite state machines] can anyone describe the difference between "composite state" and "(sub) machine"? UML spec says those are basically the same thing, however, there are 2 names, which is suspicious:

A submachine State implies a macro-like insertion of the specification of the corresponding submachine StateMachine. It is, therefore, semantically equivalent to a composite State. The Regions of the submachine StateMachine are the Regions of the composite State.

I'm trying to "live at the REPL" more. One common debugging issue is how to quickly evaluate forms within functions or let bindings, where the symbols are not defined. ProtoREPL has a whole feature around this, and it looks like Cider does too.... (We use Cursive as we've come from a Java shop and deal with lots of Java code still.) Is this something people use a lot? Is there a repl independent approach to this?

@apbleonard You should be able to do this in Cursive - if there’s something missing (or if you have a link to some doc about ProtoREPL’s approach to this) I’d be very interested to see it.

You can select any form and that will be sent, or there’s the “Send form before caret” action. Cursive doesn’t do anything clever with missing symbols though, is that what you’re referring to?

Sorry I meant to quote this discussion https://github.com/clojure-emacs/cider/issues/1809

@apbleonard So that’s sort of what I had in mind. If you send a form for evaluation, I can check if any of its bindings are not defined in that form. I had envisioned a popup dialog when you evaluate the form which would allow you to enter a value for each one. Does that sound like what you had in mind?

That sounds nice 🙂

Definitely. Could you file an issue for that and I’ll see what I can do?

I think this is related to tracing though. In protorepl (sorry to mention the competition!) you stick a (save) form in your code and it can remember values flowing through code as a test runs say, and then you can def these values so you can evaluate forms and debug as you go.

No problem at all, ProtoREPL is awesome, it’s by far my second favourite Clojure environment 🙂

Ok, I see - I think that should be possible. One issue with that is that IntelliJ’s ability to paint things over the editor isn’t as slick as Atom’s yet.

But that’s just a UI issue that can be worked around.

Hi, how to do optimistic locking in java.jdbc, write a sql that update by id and version field?

@cfleming I think tools like this would really help the team debug efficiently. Experienced Java developers used to debuggers balk at the debugging approaches we resort to - still generally sprinkling printlns in the code. We know evaluating forms in the REPL is the way, but it feels like it's hard work to be efficient. Not sure if Sayid's approach to tracing, where every function call's arguments is saved is too "omniscient" or could be drawn upon? https://github.com/jasongilman/proto-repl-sayid

Sure, I think Sayid is great too - there are lots of different ways to skin the cat.

Cursive does offer a traditional Java-style debugger, FWIW

It works very well, with some caveats.

Yes - perhaps I should stop being so purist and get better at using it!

It’s essential to my work, definitely. Fortunately we don’t have to choose, we can have both!

hey, I have a function f that calls g, and g calls f, how to order defn's so the compiler knows about all definitions?

Declare

declare I mean

@featalion that's it, thanks

Hello. I'm trying to set up a project for both client and server development, using compojure and http-kit. Since I already had a project going, I decided to modify my own project.clj to match the the one I would get using lein new compojure .., but I'm getting some errors from ring regarding jetty. Here is my project.clj: https://gist.github.com/dea054c015658d4ed3295b40b12c8fd5 Here are the errors: https://gist.github.com/f3f62cb6633979ebbfb849a8b6b20861

This is upon running lein ring server

I also just noticed that lein deps :tree seems to output a good deal of warnings regarding my dependencies. I'm honestly not sure what the best way to fix that would be, so I'll post that as well: https://gist.github.com/87f04f1805c2cc20e1dee2a9defe0462

Hmm. This seems to have something to do with datomic. I added exclusions like this: [com.datomic/clj-client "0.8.606" :exclusions [org.eclipse.jetty/jetty-http]] and eventually got it to run. Now the lein ring server starts but attempting to connect to it just results in a connection reset

Why does (if-let [x y] ...) expands to

(let*
 [temp__4655__auto__ y]
 (if temp__4655__auto__ (clojure.core/let [x temp__4655__auto__] ...) nil))

(let [x y]
  (if x ...))

so that x doesn't have to be re-evaluated multiple times

Different question: Is this an ok way to access both the first arg and all args? (fn [& [head :as all]])

how would x be re-evaluated multiple times in that scenario?

@pesterhazy ^

user=> (macroexpand-1 '(if-let [x (do (prn :foo) true)] [x x] (prn :no)))
(clojure.core/let [temp__6751__auto__ (do (prn :foo) true)] (if temp__6751__auto__ (clojure.core/let [x temp__6751__auto__] [x x]) (prn :no)))

i.e. in cases where x is used in the body of the if-let

@pesterhazy it still wouldn’t get evaluated multiple times with

(let [x (do (prn :foo) true)] (if x [x x]))

?

isn't that pretty much what the actual implementation does?

@hmaurer that binds x in the else branch

if-let doesn't

that's what the extra local binding is for

@bronsa oh, I see. that makes sense; thanks!

I am getting a StackOverflow error when trying to use log4j with Leiningen, could someone please take a look at the stacktrace? https://gist.github.com/hmaurer/40c1bc6d08550222f65e06a6366f0eb9

fixed it by removing a few dependencies… still strange though, I would like to understand why simply adding dependencies to project.clj could cause a stackoverflow error when launching the repl

Hi everyone, I've been doing some experiments on visualizing clojure.spec fails and ended up wrapping them in a library

https://github.com/jpmonettas/inspectable

maybe it's useful to someone else

Given that I have figwheel set up to use a ring handler via :ring-handler, and that handler is also set to auto reload via ring.middlware.reload/reload, is there some way I can make it reload everything? Basically restart the whole deal. I'm working with a library called sente which is for websocket communications, and it doesn't look like the code that initializes everything related to that is being re-run, so it's kind of painful to iterate.

what I do is put all the code that has a lifecycle into https://github.com/stuartsierra/component so I have a way to restart the entire thing

@jpmonettas Hmm, alright. I'll see if I can whip something up that works. Thanks 🙂

don't know if you are currently using something like components or mount

but I've done that with sente

you create something like a web-server component, and in the start/stop of that component you start/stop http-kit server, sente channels etc

Nah, not using anything like that. I'm pretty new to all of this, so still trying to figure out best practices and what people are doing etc. Okay, I see. Is it possible to get that to play well with figwheel using :ring-handler?

I mean, if you move all the stuff that deals with state into components, and then create a system(a bunch of components) you end up with a restart fn you can use wherever you want

I never fired it from that reload middleware but can't see any issues with that

I see. I guess I just don't quite grok how all these things work together. But I'm sure I can come up with something from what you've told me. Thanks!

does anyone have a pro-tip/link to an example of using core.async with ring? or some other http server? like how does one wait for input on a channel and flush said result to a response?

aleph actually has an async request handler infrastructure - and it uses manifold that is designed to integrate easily with core.async

if you use eg. jetty your async code will run but there will still be a blocking thread per request until you respond

the real question I guess is why you are using async, then you can use that answer to guide how you integrate that with a ring server

for the go-loop as you show it, you end up with a single block of code that can only deal with one request at a time - there’s valid reasons to do this sometimes but it’s a pretty severe bottleneck

awesome - I will look into aleph. I was thinking of using core.async as a general abstraction on input/output

something like that

when I say “one request at a time in the block” I mean globally, only one of your requests can be in that block - so if you have five concurrent clients, it takes 5x as long to complete

which usually isn’t the kind of behavior you want in a web server at all

yeah 😕

trying to figure out how to use the results of (>! out) in that example

with manifold, you can set up a function that gets called with an input channel and an output channel, and it is instantiated as many times as you get requests, which is a more reasonable pattern of behavior

Is there a way to quickly run tests when a file changes? Manually running lein test takes about 10s to boot for me, and using https://github.com/weavejester/lein-auto take the same time

I assume the delay is coming from the jvm boot time, but I don’t know how to avoid it

@hmaurer fyi lein test just uses clojure.test, and you can require that and run (clojure.test/run-all-tests) in your repl (after requiring your test namespaces of course)

@hmaurer I'd recommend running tests from a persistent repl, and using something like clojure.tools.namespace to ensure code is reloaded and up to date

you could hook up the run-all-tests to run as part of your system refresh if you have such defined

@noisesmith ah, good point. Thanks!

are there any “good practice” I should be aware of regarding testing clojure? (either tools/libs or approaches). Or should I just get started with clojure.test?

Also, is it advisable to place pre/post conditions on every “core” functions of an app? Including spec checks on arguments.

one thing to keep in mind is that testing functional code is easier than what you are probably used to

good functional design in general separates the mutable / side effecting source and sink of your data from the immutable guts

if you do that right, you can unit test the immutable guts easily, and separately verify that the mutable input and output logic works

where the input and output would likely be integration tests, or even better they can be verified by the tests on the separate code implementing the i/o

@hmaurer what that looks like in the big picture is a bunch of immutable code that does no io or side effects, and a top level “driver” that connects that to data - which can easily be subbed out by a lambda or direct function argument in your test

@noisesmith Ok, I’ll try to follow that idea. I have done some FP before so it’s not completely unfamiliar. The app I am currently working on is very much CRUD, so I don’t think there will be that much distinction to make betwen i/o code and pure functions (almost everything does i/o)

Last but not least, is Midje worth looking into?

I don’t like midje at all

some people like it, especially if they are used to that kind of dsl for testing

I like midje. but it wasn't widely embraced and the lead developer is done with clojure. I would not start a new project with it

lazy question: @seancorfield is there any notion of "business time" in clj-time?

in my past ruby life I used this: https://github.com/bokmann/business_time

<deleted>

Ah, sorry, I guess I’ll delete that and post it to #clojure-spec

I have a Clojure design problem which I’d love some feedback on. I have a SeriesStore record and corresponding SeriesStore protocol. There are different stores for different accounts etc, so I need some way to create these stores. I’m considering two options: 1. Have a regular fn that is a closure around all dependencies of the store, and then pass that fn around 2. Create another record which contains all the dependencies, e.g SeriesStoreFactory, and then pass an instance of that record around. i.e regular fn closure vs. record, which is preferable and why?

Records almost always win @schmee for the simple reason that functions are opaque. Once you close over something with a function there's no way to introspect the closure to see what you closed over.

Sometimes you need that for debugging, other times just to do keys or to otherwise get the state out inside some function.

hello everyone while using clojure.test its possible to share data between tests? something like

(def data (atom :none))
(deftest t1 ... (reset! data 10))
(deftest t2 ... (do-stuff 10))

(do-stuff data) *

If I wish to set up some data that should be accessible to all tests (either set up once before all tests or set up and tear down before and after each test), how can I do it with clojure.test? with-fixtures doesn’t appear to let me pass data down to the test. I could use a global atom but that seems nasty

@plins oh wow, haha, I hadn’t read your message before posting

looks like we have the exact same question

@tbaldridge sounds reasonable. but sometimes you want it opaque though? my main concern with records is that I want to keep it as functional as possible, and I worry that my code will start to look like OO if there are too many records all over the place. what’s your experience on striking the right balance between records and fns?

@schmee records are still immutable. they're still functional

@schmee in clojure Ive never been like, I wish I had less information at my disposal

Right, you got to separate out "is a protocol" from "looks like OOP"

polymorphism is orthogonal from "functional" imo

also I would recommend checking out stuart sierra's component or weavejesters integrant

OOP = information hiding, local mutation, and inheritence

records and protocols don't do any of that.

true, true. and I actually have polymorphism in this case, so I’ll go with records. thanks for the input!

@owen I’ve tried the whole gamut of state management libs in clojure, I’m currently experimenting with https://github.com/vspinu/commix which I think is fantastic so far!

🙂 there are alot, I havent even heard of this option

It’s less than a week old 😄

sounds ready for production to me

I wouldn’t, but hey, I won’t judge you 😉

Better than most node libraries! #burn

> Commix was built as a response to a range of limitations in Integrant which in turn was designed to overcome limitations in Component.

turns out dependencies are hard?

I’ve been using integrant for a couple of days, it has been great so far

I liked it as well when I compared it with component

I tried using Integrant but I immediately found myself working around it instead of with it, then I stumbled over commix here: https://github.com/weavejester/integrant/issues/21

I recognized some of the problems I encountered in the “differences from Integrant” section

anyways, more options on the table, more innovation = win for everyone

Does anyone have a recommendation for me on how to share some stuff between tests? e.g. a database connection

well if is something static i think you can just

(def db-spec (..))

(deftest test
   (jdbc/query db-spec ..))

@plins why would you want to do that?

im trying to do some sort of all-or-nothing integration api integration test imagine that i do a request to create an user, and it returns me an id afterwards in another test id like to user this id to create a bank account for this user (or something like that)

@plins ah, I was planning on doing the same thing. It seems to me this should be done within one test block? I don’t think there are much guarantees as to in which order tests will run

and you would rely on order there

im trying to avoid a giant let with tons of implicit tests, but i seems that i got no other option

@plins I am a newb, but what do you think would be the issue? You can nest testing calls to create context

dynamic vars and a fixture would be another option but probably not a very good one

and from what I just inferred from the source of testing, it returns its last expression

so you could use that to pass values around

not sure though…

like

the last line of deftest is returned?

(defn- create-user-account []
  (testing "Create a user account"
    (let [user-account (app/create-user-account)]
      (is (= ....))
      user-account)))

(defn- create-bank-account [user-account]
  (testing "Create bank account"))

(deftest scenario-1
  (let [user-account (create-user-account)
        bank-account (create-bank-account user-account)]))

I don’t know if you can use testing outside a deftest though

if you can’t, just move it to within the deftest

I haven’t tried it though, and completely new to clojure.test, so don’t take my word on it

i wanst aware of the testing function / macro

will check it out thanks 😄

@plins I just tried to use testing inside a defn- function called from a deftest and it worked, but the doc says `May be nested, but must occur inside a test function (deftest).`, so I am not sure how to take it

maybe it means it will work so long as it’s called within the callstack of a deftest function

or maybe I am doing something very wrong 😄

@hmaurer I just did a macroexpand of (testing "foo" body) and it looks like it relies on dynamic calls for context so I think you're OK -- but it's definitely a bit unorthodox.

(macroexpand '(clojure.test/testing "foo" (something)))

(let* 
 [] 
 (clojure.core/push-thread-bindings 
  (clojure.core/hash-map 
   (var clojure.test/*testing-contexts*) 
   (clojure.core/conj clojure.test/*testing-contexts* "foo"))) 
 (try (something) (finally (clojure.core/pop-thread-bindings)))) 

@seancorfield so deftest sets a dynamic var which is available anywhere within the callstack during its execution?

thanks for checking it!

do you have a better suggestion to do what I was trying to do? (split a test in this way)

is it “not ok” for some reason to split a test in multiple functions that way?

it seems that it improves composability

I haven't seen it done that way before -- so it looks unfamiliar -- but if clojure.test manages all of its testing context dynamically, I guess it's fine. I guess I would have a specific test for each creation function that asserted whatever behavior I expected (and cleaned up after itself), and then in the main test I'd just call the creation functions without worrying about testing or is...

In other words, I'd only have "one" test for those common things, rather than repeating the tests every time they are called.

Ah, I see.

How should a regex look for the :aot option in leiningen?

The way I used it seems to have no effect

are you sure you want to aot compile?

if you don't have :gen-class in a ns form, compile is a nop, and if you don't have gen-class I doubt you really want to aot compile

@hiredman I'm sure. I'm trying to minimize startup time in resulting jar.

I noticed that most ns don't necessarily get aot'd, when I stripped out clj files jar started to fail

does anyone know of a library for doing set-like operations (`intersect`, union) on possibly infinite sets?

f.e. (set/union inf/all #{1}) => inf/all or (set/intersect inf/all #{1}) => #{1}

I'm crawling through a clojars search but figured I'd ask

I suspect what you want is a symbolic logic library

how so?

I didn't find anything in my quick searching, but rolling my own shouldn't be too hard

just gotta figure out what infinity looks like

oh, just because that is a more logic based representation of a set vs. a datastructure

ah

for my use case, 95% of the time it'll fall back to regular set ops

can you recommend a good primer on the topic of symbolic logic programming?

the core.logic readme mentions The Reasoned Schemer

core.logic isn't really that, the little prover (which shares an author) would be more like it

thanks

I actually have enough time to read this before I have to tackle this problem for real