any one got ideas for building a clojure app for a newlearner coming from Ruby? [1:04] maybe suggest porting some existing Ruby gem?

amrit what kind of project?

@samlinncon: anything interesting and easy enough to start off with and iterate

you are familiar with the syntax first?

yes

okay,you can check out luminusweb which is a framework for building web apps in clojure

would prefer building some library

@amrit: Database clients, markdown parser, a custom datatype, ... :)

that am not yt that good

@amrit: what kind of libraries have you built before?

@martinklepsch: have you used luminusweb before?

@samlinncon: briefly

worked with sessions in the framework?i could use some help

@samlinncon: don't remember anything about that. I'd recommend to just ask, some people in here might know and be happy to help :)

@martinklepsch @samlinncon Would you guys have experience in session management using ring middleware?

@udit: as said earlier: you're most likely to get help if you state your problem and ideally provide some code to give context

i’m looking for some ideas to solving a small problem: given a number of length 1 to 8 digits, return an 8 digit number filling in with leading zeros, then split it into two 4 digit pieces

(function 25467) => 0002 5467

making some progress here:

((fn prod-dir [prod-id]
   (loop [p (str prod-id)]
     (if (= 8 (count p))
       p
       (recur (cons 0 p)))))
 22747)

(defn fx
  [n]
  (let [n' (str n)
        c (- 8 (count n'))
        cl (partition 4 (str (clojure.string/join (repeat c 0)) n'))]
    (str (-> cl first clojure.string/join) " " (-> cl second clojure.string/join))))

Just a quick first pass.

(partition 4 (format "%08d" 25467)) ((\0 \0 \0 \2) (\5 \4 \6 \7))

I always forget about format.

Then you have to do the string/join on each of those

Yep. That gets rid of the need for (str n) and the call to count.

woohoo i did it but i should look at what you guy just posted too

(defn prod-dir [prod-id]
  (loop [p (str prod-id)]
    (if (= 8 (count p))
      (str (apply str (take 4 p)) "/" (apply str (take-last 4 p)))
      (recur (cons 0 p)))))

wow this is a lot shorter… (partition 4 (format "%08d" 25467))`

sadly i started with partition but failed to discover format

thnx

(defn fx
  [n]
  (let [cl (partition 4 (format "%08d" n))]
    (str (-> cl first clojure.string/join) " " (-> cl second clojure.string/join))))

Teamwork!

(fx 25467) => “0002 5467”

my solution probably stinks, but it still felt good to glue things together and make it work.

The more you use Clojure, the more you’ll find yourself composing functions rather than writing an iterative approach.

that’s why im practicing

trying to learn to think in that way

Right on. Well, never hesitate to ask questions.

do you use the thread first macro a lot akiva?

When it lends itself to clarity, yeah, so if I’m chaining two or more functions, I usually use it.

And I use it a lot in the REPL because it’s easy to just CTRL-up and add another function to see.

i’ll have to experiment with that. i do find things reasonably readable without it, but my second pass at learning to code i was talked into common lisp (a gentle guide to symbolic computation) — perhaps i’m used to reading inside out

oooh good use case there in repl

hi all (sorry for bashing into the convo @akiva & @chadhs).. i’m hitting a Unable to resolve var: routes issue while following this manual https://devcenter.heroku.com/articles/clojure-web-application.. Does this point to a particular beginners mistake I’m unaware of?

just after ‘web bindings with Compojure'

You need to make sure (defroutes routes …) is set.

Want to paste your code for that section?

Clojure doest't hoist so it'll need to come first in the file

Before it's used.

Yep.

a bit of a tangent but… @timaeus: if you want to know how to push that to a stand alone server and not just heroku i did a quick write up for digitalocean: https://www.digitalocean.com/community/tutorials/how-to-deploy-a-clojure-web-application-on-ubuntu-14-04

there’s a freebsd version too

There is a declare command that allows you to refer to a var that hasn’t yet been defined.

So if you really want routes at the bottom, you can (declare routes) above -main.

It’s not widely used, though. I like having functions in alphabetical order so I use it personally.

@jeff.engebretsen: @akiva thanks, I’m not really set on putting the routes at the bottom but it seems that wherever I put the defroutes i can’t start the server

What's the idiomatic thing to do? I'm coming from Java and I really like having the method definition appear after first use.

It didn't work with defroutes before -main?

doesn’t seem so

Jeff, I don’t see declare used a lot in the wild. Seems most people put the actual definition right before its first call from another function.

Unable to resolve symbol: index

Same issue. You need index then defroues then -main

Yep.

Since routes references index

okey yes it works

thanks !

I wasn’t aware of the strict ordering

I guess I'll just get used to the Clojure way.

does order you define functions in in a file matter?

like if fn2 uses fn1

fn1 should be def’d first

is that correct?

Correct.

Unless you use declare then you can do

(declare f1)
(defn f2
[]
(f1 …))

(defn f1
[]
…)

How do datomic and Clojure tend to work together if you're not ready to make your front end stack Om or Om Next?

I’d be surprised if Datomic cares about anything beyond receiving and sending data.

Whether it’s through a back-end API or something like Om.

(I’ve not used it, mind you; I just doubt the idea of it being tightly coupled to a particular front-end library.)

i’m trying to add a result processor for yesql (and luminus) like this:

(db/get-tenant {:tenantid tenantid} {:result-set-fn first})

@akiva: I agree I'm just not sure about interfacing with it I guess is my major question

@kamuela Datomic will take/give plain old Clojure data structures.

Found my problem. In case somebody finds it useful it turns out that conman (used by luminus) adds a wrapper to yesql. https://github.com/luminus-framework/conman/commit/73098c925b61971b41df0ebe41f7fc612acea4eb this is how i am using

(db/get-tenant {:tenantid tenantid} @db/*db* {:result-set-fn first})