@sundarj yes

@gdeer81 could you elucidate further?

yes

creating an example right now

ah, thanks!

https://gist.github.com/gdeer81/02484a9e9f6631cea3a381bce40e1d40

neat!

is there a way to do it without a conditional?

I'm sure of it, one moment please

no rush 🙂

@sundarj I updated the same gist

ah, multimethods, of course - very nice 😄

that's satisfying. thank you muchly :~)

That's what we call thirst quenching code. Clojure, it's what editors crave

@sundarj with Specter:

user=> (def numbers (s/walker number?))
#'user/numbers
user=> (s/transform numbers inc [1 2 3])
[2 3 4]
user=> (s/transform numbers inc [[1 2] [3 4 5]])
[[2 3] [4 5 6]]
user=> (s/transform numbers inc [[1 2] [3 4 5] 6 [7]])
[[2 3] [4 5 6] 7 [8]]

Hi, folks, I try to run migrations on the server, I need to run function forest-community-blog.db/migrate but on server I have only server.jar which I start by running java -jar server.jar, is it possible somehow run function which is not main from the jar file? 🙂

On local env I run migrations through lein run -m forest-community-blog.db/migrate

I should install lein and upload sources for accomplishing this task? 🙂

@crashtown I'd probably modify main to either run migrations automatically on run, or let it run the migration function when a certain command line flag is given

@crashtown java -cp server.jar clojure.main forest-community.blog.db

the key here is that forest-community.blog.db must have a -main function - but I'm sure you could arrange that

And I guess i should use :gen-class option for this module? 🙂

no!

clojure.main is sufficient

avoid gen-class whenever possible

Ok, thank you very much 🙂

also if you skip the last arg you get a bare bones repl where you can require any of your namespaces that are in the jar

Nice hint, ty 🙂

@rorysmith reduce takes a function, a collection, and optionally a starting value

so reduce will keep calling your function with values from a collection and passing the resulting value into the function you are reducing with

so (reduce str ["a" "b" "c"]) will not see an initial value and it will use the first value of your collection, "a". So this will start the reduction with "a". And reduce will call your function, here str, with the value that's been accumulated and the next value of the coll

so this will call (str "a" "b") which is the initial value of the collection and then the next value of the collection. This yields "ab" as str will just concatenate

and then reduce passes this accumulated value to your function str along with the next value in the collection, "c"

so it will call (str "ab" "c")

oh yeah!

it's the concatenation that got me

cool

but i remember that passing in multiple args to str will yield a concatenation

i never know what level understanding there is so i didn't mean to explain things you already knew

yeah that was really useful, thanks

no problemo!

have you used str with lazy seq's yet though?

that's kinda a gotcha with it

no, what is a lazy seq?

clojure has some lazy datastructures, meaning it tries to only perform computatoins that you actually consume

can you give an example?

(range) returns an infinite list of the non-negative integers, which is obviously impossible without some kind of bound

oh yeah

(map inc (range)) then would return (1 2 3 .....)

and if you call str on one of these you'll get its string representation, which is something like #lazysez[] or something

ah i see

its usually a gotcha at the beginning. wanted to point it out to you

:thumbsup:

for sure. happy coding!

thanks, i'm going through some exercises on codewars and very much enjoying functional programming

@rorysmith a nice aid to understanding reduce is another function called reductions - which is just like reduce except it returns a lazy sequence of every result (and the last one will be the same one reduce would return)

@noisesmith nice, thanks

(I would have used your example with the bot, but the bot breaks when you give it strings sadly)

got it

didn't know that. awesome

@noisesmith @rorysmith I personally like the fold name sometimes used in place of reduce. It’s very visual

also the name "reduce" implies you can't use it to create outputs with larger or more complex structures than the inputs, which tends to make people less likely to realize when it's useful

Yeah. I am not sure about the reasons why some people prefer the word “reduce”, I am sure there are some very valid ones, but for a beginner “fold” is more visual imo

and conveys the intent better

as you said

it's one of the "historical reasons" things - making clojure more like lisp

like cons

ah

i’ve got a lein project; i’ve written some tests in test/mover.clj, but lein can’t find them

i tried lein test test.mover

do i need to put something in my project.clj?