Clojurians Log v2

Watching this video, what is reified mean:

@i In general, “to reify” means “to make (something abstract) more concrete or real”.

In this case, it means to turn each possibly implicit “event” or “state change” into an explicit, concrete record of that event that is recorded.

Does that help?

Thanks.

I wonder how to publish datomic transaction with at least once semantics. Does datomic itself support this functionality?

Can you please clarify? What do you mean by “publish” ?

What's the recommended way to structure a project that's divided between "library" and "application" code? I see a lot of repos with /src and /app folders, but I want them to live in separate git repositories and at the same time share a common REPL and dependencies during development. Or is that a bad idea in the first place?

@qythium This can be easily accomplished using deps.edn/tools.deps :local/root which allows you to develop an app and libraries in one REPL

Oh! great that we're already using tools.deps 🙂 Do you mean something like this:

foo/
  lib/
    .git/
    src/
    deps.edn
  app/
    .git/
    src/
    deps.edn - {:deps {foo :local/root {"../lib"}}}

yes

and then I start a REPL in the app/ folder, and tell Cider to sesman-link-with-project

or I don't suppose you can specify :paths ["../lib"] paths in the deps.edn as well

no, you're not allowed to specify paths outside of the current dir. Why do you need sesman-link. Just a REPL should be sufficient

So I can interactively redefine things in the lib/ folder while I'm in app/

yes

you can already do that

oh, you can indeed! Thanks for the help 🙂

@vemv, Yes, this is an interesting comment, I do feel the same way. That article made me waver but every developers dream is for their website to go viral. If that happens, and multiple machines need to be spun up, scaling postgres is quick, so it is probably a better choice.

How to change a process’s working directory?

If you mean in a running JVM process, then this StackOverflow question seems to describe some ways you can at least partially get that behavior, but perhaps not for all file accessing API calls, maybe only a subset of them: https://stackoverflow.com/questions/840190/changing-the-current-working-directory-in-java

Came across this too. Seems no easy way.

Hello all. When calling Java code from clojure, is reflection always used? I’ve come across this in my profiling: Function code: https://github.com/tel/clatrix/blob/master/src/clatrix/core.clj#L214 Profiler says it uses reflection 100% of the time:

Seems odd with all the type hints…

Matrix is a deftype with a field called me. Maybe if you use (.-me m) instead of (.me m) it won't use the reflection.

You might be quite right… the thing is that if I (set! *warn-on-reflection* true) and reload the namespace clatrix.core it doesn’t give any warnings

Are people using 🅰️ lein new or 🅱️ clj -X new or 🅾️ other to start projects?

We're using https://github.com/cookiecutter/cookiecutter

@jayzawrotny Can I vote for: none of the above? I usually bootstrap new projects just by using mkdir -p src/foo and writing a deps.edn file.

I think that falls into other 😛

ok

Seems like it doesn’t make a difference:

(time (do (doall (repeatedly 10000000 #(.x ^A x)))
          1))
"Elapsed time: 2543.122789 msecs"
=> 1
(time (do (doall (repeatedly 10000000 #(.-x ^A x)))
          1))
"Elapsed time: 2470.688716 msecs"

it’s bizarre

If you're willing to debug the compiler, I think the relevant place is clojure.lang.Compiler$InstanceFieldExpr. Maybe someone else has some ideas on why you see that behavior, but I don't.

With just

(deftype X [a])
(def x (X. 1))
(.-a ^X x)

Yeah but as soon as I do this:

(time (do
        (doall (repeatedly 10000000 #(.-a ^X x)))
        1))

An unrelated thing - you can use dotimes instead of repeatedly or dorun instead of wrapping doall in do.

I can't reproduce it at all with Clojure 1.10.3.

The whole code:

(deftype X [a])
(def x (X. 1))
(defn xxx [] (.-a ^X x))
(dotimes [_ 10000000000] (xxx))

I checked both B and O because my O is just mkdir, cd, edit deps.edn sometimes, but it’s still a CLI/`deps.edn` project.

Yeah that works without reflection. But if I just go (doall (repeatedly xxx 1000000)) it is back again… it’s just weird… maybe the profiler is pulling my leg…

Still can't reproduce it on 1.10.3 with repeatedly. invokeNoArgInstanceMember isn't in the results at all on my end.

Yeah i dont know. I’ll keep looking

@jayzawrotny lately, been using lein new app.... But building a custom scaffolding tool to setup the full stack for web dev.

Git submodules can be really tricky.... They leave the head in a detached state. Your app code is an MVC web stack? With lib in clojure ?

Nothing to do with web... it's just some library code with a bunch of example uses and extensions of the library that aren't part of the main library logic. My plan now is to move them to separate git repos (not submodules) in the same parent folder.

i've been using @seancorfield’s clj-new. is that clj -X new or other?