cross-post from lein channel --- Hello all, I have this specific use case where i need to run $ lein run with sudo (i know bad idea, but its just for testing). does anyone know what this warning is trying to tell me:

WARNING: You're currently running as root; probably by accident.
Press control-C to abort or Enter to continue as root.
Set LEIN_ROOT to disable this warning.

the former @dviramontes

@ghadi does it look like: LEIN_ROOT=true ?

yeah any value will do

LEIN_ROOT=dviramontes lein repl

@dviramontes: you can also set it just one time if you add it before lein run LEIN_ROOT=true lein run

that way you don’t have to change any configs just to try something out

How about (into [:ul [:li :first-item]] list-items)?

^ @naomarik

yeah i'm aware that works, but wondering if there's a way to do it the other way... perhaps writing a macro? I'm just being a bit stubborn about it

(let [t []](dotimes [i 10] (conj t i))t)
=> []

why doesn't this populate a vector?

whereas the following does:

(let [t (transient [])]
  (dotimes [i 10]
    (conj! t i))
  (persistent! t))
=> [0 1 2 3 4 5 6 7 8 9]

Blithely, because t in the former is an immutable vector

conj takes an immutable data structure and returns a new immutable data structure that contains the given value

It does not change the immutable data structure argument

so how to display the contents of the t at the end of let?

You need to accumulate the intermediate t values if you want all the integers from 0 to 9 in it

dotimes won’t let you do that. It’s used when you want side effects.

(mapv (fn [i] i) (range 10)) would be one way to do it immutably

I see, thanks

(into [] (range 10)) might be more idiomatic

Or simply (range 10) if you don’t need it to be a vector, just a seq

note that into will do transients under the hood for you too

Interesting. I just wanted to wrap both of them into a time to do a side-by-side comparison, but apparently it's not as easy as it seems 🙂

Performance testing in the JVM is something of a dark art

For quick and dirty analyses though, try the criterium library

took a mental note of that library, thanks!

@alexmiller funny you mentioned it, I am just reading the 2nd chapter of your Clojure Applied where you are explaining it and doing various experimentations with code snippets of my own. Serendipitous...

Random question, I’m working my way through Clojure for the Brave and True

and I noticed this little difference when repl-ing through the examples

why would the space between (inc 199) and (/ 100 (-7 2) cause the solutions to differ by 5000?

The author expects 220 as a solution

there's no way that can happen @dmbennett

could the 5 be from a previous println?

no, I just replicated it again

but it requires the paren spacing at the end

open a new repl from scratch, try putting and removing how many spaces you want, there's no way that can happen

k

well, there's your problem

/100 is not a valid clojure expression

evaluation gets aborted

evaluation resumes at (- 7 2) which is 5

you get 2 other errors because )) is invalid code

and then you get the result for your next expression which is 220

did you miss that last line?

the repl you're using causes the 5 and 220 to be printed in the same line

stille evals to 5220 after fixing the space issue

oh

no, that's just 5 and 220

interesting, it only holds the 5 after it errors from the /100 form and then when eval-ing the next runs (+ (inc 199)(/ 100 (- 7 2))) returns the 5 and 220

I don't know what repl you're using, but the default clojure REPL doesn't exhibit that behaviour

I’m using lein repl

user=> (+ (inc 199) (/100 5))
RuntimeException Invalid token: /100  clojure.lang.Util.runtimeException (Util.java:221)
5
RuntimeException Unmatched delimiter: )  clojure.lang.Util.runtimeException (Util.java:221)
RuntimeException Unmatched delimiter: )  clojure.lang.Util.runtimeException (Util.java:221)

¯\(ツ)/¯

iDave-MBP:~ dmbennett$ which lein repl
/usr/local/bin/lein
iDave-MBP:~ dmbennett$ lein -version
Leiningen 2.6.1 on Java 1.8.0_25 Java HotSpot(TM) 64-Bit Server VM

use `

yeah, dunno. might be a known bug with lein/nREPL

well thanks for that

np

Question: why would I not be able to make this function: (defn valid-args? [function-name] (:arglists (meta (var function-name)))) the result I get is clojure.lang.Compiler$CompilerException: java.lang.RuntimeException: Unable to resolve var: function-name in this context

I wanted to make a short cut for calling (:arglists (meta #’map)) for any function, that would normally respond with ([f] [f coll] [f c1 c2] [f c1 c2 c3] [f c1 c2 c3 & colls]).