@jaihindh.reddy Check out this library that does this for all the java time types https://github.com/magnars/java-time-literals Also, if you print it as #inst and read it back in it'll change type, and lose the offset information.

hi, i was hoping this snippet would access one key or use another if it is missing

but the (or) bit doesn’t ever seem to return if the first value is missing

the second entry always comes out as blank

i think it’s to do with how i’m accessing the key values inside the map function?

the expression (or :login :id) always returns :login

So your line 10 is equivalent to (map :login users)

You need to turn (or :login :id) into an actual function (e.g. anonymous), so that its outcome is dependent on some input

@christopher.paul do you know how to do that? (hint: you're close)

sorry was in dm with sundar

he helped me

i needed to use some-fn

as the key reference always returns true as it is a function

Oh TIL. That's cleaner than what I had in mind, thanks! For transparency: (map (some-fn :login :id) [{:id "1"}]) -> ("1") vs (map #(or (:login %) (:id %)) [{:id "1"}]) -> ("1")

i ended up writing my own ropey version of some-fn

but then found that some-fn existed 🙂

hey all, I am off work from Wednesday till the new year, do you recon there is a project I can do in that time (because I have 0 life)?

I have a pattern in Clojure that keeps popping up and I'm not sure the best "clojure-esque" way to do it. Say, for example, I have the following:

user=> (println my-map)
{12 3, 10 4, 8 1, 7 1, 6 1, 4 1}

maps are unordered

an "index" for a map makes no sense

well it does… from a key to a value :)

well yes, I meant not an "index" in the sense he's talking about

an ordered index :)

You can use https://github.com/clj-commons/ordered if you want ordered maps though

Ok, then how do I get it "ordered" so that I can get the one I'm interested in?

well, you might also consider sorted-maps, not sure if they would satisfy

What specifically do you want the order for?

FWIW @joseph.hance if you're actually using maps as if they were ordered, it's not just a conceptual issue, the insertion order actually does get shuffled around randomly

user=> {1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9}
{7 7, 1 1, 4 4, 6 6, 3 3, 2 2, 9 9, 5 5, 8 8}

Let me take a step back, I have:

user=> (println my-map)
{12 3, 10 4, 8 1, 7 1, 6 1, 4 1}

right, then you don't need an index at all

Note: beginner talking here.

What if you just take “10” as the “index” you want? Will that meet your needs?

user=> (apply max-key val {12 3, 10 4, 8 1, 7 1, 6 1, 4 1})
[10 4]

let me know if you need help understanding why that works

lol, this is the first I’ve heard that there was a max-key fn in clojure core.

it annoys me a lot that it works on varargs rather than on a single sequence :)

Yeah I can see where that would be annoying.

it's the way it is because it's an "enhanced" max, but it feels closer to a filter-like function to me

@joseph.hance can you give a bigger-picture example of a case where you run into this pattern? I have a feeling we may be missing the forest for the trees and it sounds like you may have an interesting question behind your question.

...looking up max-key. Thanks.

hey guys

how can I do something like this:

(rename-keys (function-gives-map arg1) {:key1 :keey})

(-> arg1 function-gives-map ...)

??

(-> arg1 function-gives-map (rename-keys {:key1 :keey}))

user=> (macroexpand-1 '(-> arg1 function-gives-map (rename-keys {:key1 :keey})))
(rename-keys (function-gives-map arg1) {:key1 :keey})

there's no problem with arity ordering?

-> will always insert the piped argument as the first argument to the function

->> as the last

yeah, but rename-keys takes map and another map of keys that I rename]

if I wanted to put in the second arg of rename-keys I would use ->> ?

if you (-> arg1 (f arg2)) you'll get (f arg1 arg2)

thanks 😃

(->> argN (f arg1 arg2)) will give you (f arg1 arg2 argN)

play with macroexpand-1 as I've shown above to get a feel if you're not sure what a macro does

ok 😃

thanks!

np

Hey! People who are learning clojure and doing Advent of Code! Last week I did a code review on stream, and I found it to be a fun and interesting exercise. https://www.twitch.tv/videos/349004355?t=55m30s If anyone wants me to do the same for their Advent of Code code, please let me know! I won’t do one every day (and I won’t do one today), but I’d like to do one a couple times a week if enough submissions roll in.

Is there a better way to write this utility function?

(defn read-int-from-envvar-with-fallback [env_var_name default_val]
	(min
		(try
			(. Integer parseInt (System/getenv env_var_name))
			(catch Exception e default_val))
		default_val))

why the min?

Values more than default-value are invalid

(if-some [txt (System/getenv env_var_name)]
  (min 
    (Long/parseLong env_var_name 10) ;; NOTE you should pass the radix explicitly
    default-val)
  default-val)

Is there a version of assoc that only sets the key if it's empty?

Maybe something like this? (merge my-map {:add-key-if-new 7, :another-key-but-only-if-new 23})

merge will overwrite existing keys right?

oh, but probably the other way around on the args there. sorry

Yup

and that isn't necessarily the fastest way to achieve what you asked, for a single key.

Maybe (defn assoc-default [m k v] (if (get m k) m (assoc m k v)))

Just curious if there was something in the standard library

I can't think of anything off hand that is already there, like that.

Ok, thanks

@jstaab maybe update? (update m k #(or % v)) Also, these functions will not work if nil or false are valid values in the map. You could support those by changing from (get m k) to (contains? m k)

(update-in m [k] (fnil identity v))

ooh nice @hiredman

I'll probably use the merge version in most places, but that's pretty elegant

Hey guys, I'm wondering if you can help me out. I am trying to play around with luminus and get that running. I can create a new app from template lein new luminus firsttest +postgres and I have a postgres url string set as the :database-url "" I can start the app and run the default user migrations, but

user=> (firsttest.db.core/create-user! { :id "fun1" :first_name "me" :last_name "me" :pass "secret" :email "" })

IllegalArgumentException db-spec mount.core.DerefableState@548f4400 is missing a required parameter  clojure.java.jdbc/get-connection (jdbc.clj:409)