I know this is a clojure channel but maybe someone will know the answer. I'm trying to ssh into a server, run a shell script, and the disconnect from the server and have the script continue to run

ssh + nohup?

#off-topic 🙂

tmux or screen

Hello! I am reading clojure.core’s source cdoe and the beginning confuses me. Could someone explain this out?

;during bootstrap we don't have destructuring let, loop or fn, will redefine later
(def
  ^{:macro true
    :added "1.0"}
  let (fn* let [&form &env & decl] (cons 'let* decl)))

there are a number of those declarations

https://github.com/clojure/clojure/blob/master/src/clj/clojure/core.clj#L31

Is there a std lib function to pick a number of keys out of a map? e.g. Map -> [Key] -> Map

select-keys

@bronsa thanks! I really miss a Hoogle-like tool for Clojure 😞 https://www.haskell.org/hoogle/

@henrik can it be that you are not on the latest version? it is fixed in v0.22.4 https://github.com/atom/language-clojure/commit/70e83b27444da31d6367a0aa447a216836eafc05

I'm trying to use transducers... The original code:

(->> m 
     (map :my-key)
     (map #(clojure.edn/read-string %)) )

translating to transducers:

(let [xf (comp (map :my-key)
                (map #(clojure.edn/read-string %))))]
  (transduce xf concat m)

oh wait... it's not the same.

concat gives that stackoverflowerror...

@kurt-o-sys (into [] xf m)

right, thx.

also: https://stuartsierra.com/2015/04/26/clojure-donts-concat

funny... I read that last week. stupid me 😛

🙂

well, actually it's (flatten (into [] xf m) I was after.

@kurt-o-sys or second map should be mapcat 🙂

nice.

is there something builtin or better for this?

(defn least-common-ancestor [path1 path2]
  (let [i (min (count path1) (count path2))]
    (reduce
      (fn [p idx]
        (let [v1 (nth path1 idx)
              v2 (nth path2 idx)]
          (if (= v1 v2)
            (conj p v1)
            (reduced p))))
      [], (range i))))

(least-common-ancestor
  [:a :b :c]
  [:a :b :d])
=> [:a :b]

@misha (take-while some? (map (fn [a b] (when (= a b) a)) [0 1 2] [0 1 3]))

This one has much better runtime performance, mostly stemming from the omission of nth

Well you could avoid one nth call here if you use reduce-kv and you can guarantee it's a vec

not worth it. on the other hand, count being > 10 is highly unlikely (in my case).

Yeah then the map version will be quicker. Reduce is often slower for smallish input

And if you want to avoid the intermediate sequence: (sequence (comp (map #(when (= %1 %2) %1) ) (take-while some?)) [0 1 2] [0 1 3])

@rauh on such small inputs it is not worth it:

(time  (dotimes [n 1000]    (take-while some? (map (fn [a b] (when (= a b) a)) [0 1 2] [0 1 3]))))
"Elapsed time: 1.166446 msecs"
(time  (dotimes [n 1000]    (sequence (comp (map #(when (= %1 %2) %1) ) (take-while some?))   [0 1 2] [0 1 3])))
"Elapsed time: 7.258858 msecs"

@misha Don't forget a doall 🙂

(time  (dotimes [n 1000]    (doall (take-while
"Elapsed time: 3.356031 msecs"

omg what am I doing right now?

if you want to measure calculation time (or run for side effects) and don’t need the result, use dorun instead of doall

also, sequence is not typically more efficient than regular lazy ops in most cases iirc

So this is fun: when using postwalk, map entries are just vectors (so map-entry? returns false), so there is no way to distinguish a map entry from a map value that is a vector… Anyone else run into this?

I suppose a map key could also be a vector, which adds a 3rd case of ambiguity

@cpmcdaniel It's a known issue in JIRA...

@seancorfield say no more, and thank you

https://dev.clojure.org/jira/browse/CLJ-2031

(go vote for it!)

ah, prewalk works for my use case

(and I voted)

if I am implementing something that is meant to be used in place of a function, is it enough to implement IFn or should I implement AFn too?

it sort of depends on how you are implementing it, AFn is an abstract class so dealing with it from clojure is kind of a pain, but from java that is where I would start

OK - this is clojure code, so I hope I’m safe ignoring AFn

AFn provides defaults for a lot of things like the applyTo machinery and such

I often will implement IFn and just particular invoke arity that I expect to be used

but such an object will not always behave like a function

I think apply won't work, and you will get some weird brokeness with more than 20 args, and maybe fn? will return false

yeah - this is a macro implementing generally something you recommended earlier (making a record that can be called like a function but unlike a lexical closure you can also look at the data in its keys) - trying to make it a convenient to use replacement for code that uses partials extensively

I just verified I implemented things properly to make apply work for over 20 args

but returning false for fn? is acceptable

I think you can fix that too, if I recall fn? checks some marker interface

instance? clojure.lang.Fn

easy enough to extend that, it has no methods

sweet!

yep

thanks - I think this will be a handy little one macro lib, just need a snappy marketable name

@noisesmith big note: you probably want ifn? if you want to check if something is a function. fn? does something different (and is normally wrong, imo).

@tbaldridge so if I am making something that is a drop in replacement for a function returned from partial, would it be a bad idea to make fn? return true from someone else’s check?

I guess that’s a style issue

nah, just code against IFn, and then ifn? will return true, which is what most people should be using

:thumbsup:

@tbaldridge on thing though, in my code, checking ifn? would lead to surprising results here

=> (ifn? :hi)
true

that could be a sign of doing other things wrong I guess…

that doesn't surprise me, a keyword is a function

(What @ghadi said)

I suppose the fn? stole the good name early, but had the wrong semantics

yeah fn? really means "something that was created with (fn ...)"

fn? was added when trampoline was added

continue-trampolining?

yeah, I guess the answer of (defmulti foo first) (fn? foo) can be a guide there

----------------------------------------------- Sooooooooo who here has played with tools.deps.alpha and what do they think? ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

i looked at the version compare and it seems like it will return 1.1 > 1.9

but i don't know how to crank it up since it's based on the pom file rather than a project file

10541c0254973ce045305499d4b5622073ede622 (is the trampoline commit fyi)

i'm not a java guy

it also specifies its own deps in the new edn format. does that make it "self-hosted"?

@dpsutton if you have mvn installed you can crank it up using the commands in the README. Use of mvn/pom is a one-time thing at setup. (It will probably be handled by the package manager when this stuff filters over there)

thanks. i'll get that going tonight

yeah i wanted to play with it and do a PR for

;; TODO - choose better
(defn- choose-coord
  [coord1 coord2]
  (if coord1
    (if coord2
      (let [v1 (:version coord1)
            v2 (:version coord2)]
        (if (pos? (compare (str v1) (str v2)))
          coord1
          coord2))
      coord1)
    coord2))

once you have it installed, you can use it in a project folder (using $PWD/deps.edn) or globally (using $HOME/.clojure/deps.edn)

The version comparison seems intentionally naive, no need to poke fun at that yet 😃

oh i know. i wasn't doing it in the notion of sniping

If you specify versions explicitly you won't invoke that code

but let alex and others figure out the hard stuff and I could help out with the easy solved stuff

I would like to write a function (if possible with the stdlib) to check if a map “matches” a pattern. More specifically, I would like to describe a map in terms of another map with the same structure, whose values can either be ints/bools/strings or regexs. If the value are ints/bools/strings they they should be compared for equality with the target map, and if they are regexs they should match

i meant "take this off their plate" not like "i can't believe they coded this"

e.g.

{:first-name "john"
 :last-name #".*"}

{:first-name "john"
 :last-name "doe"}

it should work for deeply nested maps

spec?

(I would use it to write tests checking the expected output of an API)

there are a few options

(for the map thing)

mmh yes specs would work but it seems a bit overkill for what I need

you could just take two maps, the first being the shape and the second being the data and recurse through them

@hiredman that’s precisely what I’m wondering how to do. Is there an easy way to express this recursion procss with stdlib functions?

you can take the description map and turn it to into a sequence of paths and predicates and reduce over that with the data

or to turn it into a sequence of paths

ah, found an example. http://blog.jayfields.com/2010/09/clojure-flatten-keys.html

(defn f [m1 m2]
  (letfn [(g [p m]
            (if (map? m)
              (for [[k v] m
                    i (g (conj p k) v)]
                i)
              [[p m]]))]
    (reduce
     (fn [x [path predicate]]
       (and x (predicate (get-in m2 path))))
     true
     (g [] m1))))

dictated but not read, etc

that assumes the description map is a map of keys to predicates, so you will have to change it to do your regex and = compares instead

great. It’s sane to convert it to a map of predicates anyway

thank you!

I was thinking of writing my tests in a descriptive form as EDN, using tags for different types of predicates

(e.g. regex)

with your approach it should extend nicely to other predicates

Is there a protocol I can implement to get peek/pop/conj to work on a queue like datastructure I'm building?

conj maps to the cons method of IPersistentCollection java interface

peek and pop map to the IPersistentStack java interface (with the same method names)

Thank you