A little problem of the clojure koans. The only one that I cannnot solve :

"You can also create a new object from another object with metadata"
  (= {:league "National League" :park "AT&T Park"}
     (meta (vary-meta giants
                      assoc {"test" "National Leaque"}))) 

now I see this error : 'ArityException Wrong number of args (2) passed to: core/assoc--4371 clojure.lang.AFn.throwArity (AFn.java:429)'

You almost got it. To fix the arity exception, drop the curlies.

... assoc "test" "National Leaque" )))

@johnny.martin thanks

you brought me on the right track

Can this be improved :

(fn [key map]  (if (contains? map key) (nil? (map key)) false)) 

its my solution to 4clojure challenge 134

There are other ways to write it but most of them are not as succinct

wouldn't (nil? (get map key ::not-found)) work?

@agile_geek sorry, my English is not very good, What does succint mean

@verma : I do not think so, the answer of the challenge need to be true or false

@roelofw most of the other versions are more code and/or not as clear

@roelofw nil? does return true or false though

yes, but if they key is not in the map , I think your code returns ::not-found and it suppose to return false

@agile_geek thanks

I love to write clear code

@verma (nil? (get map key false)) would probably do the job tho

@roelofw ::not-found is then evaluated through nil? which returns false.

true... or is that false?

@agile_geek sure, that works as well, get returning anything other than nil for no key found is good :thumbsup:

::not-found is not nil so (nil? ::not-found) is false

You can even drop the get if map is never nil (fn [key map] (nil? (map key :not-found))

:thumbsup:

oke, learned another thing

@roelofw a map (the datastructure) is itself a function that takes a key and looks up the value for that key in itself. Also keywords (e.g. :this-is-a-keyword) are functions that look themselves up in a map.

i.e. ({"key" "this works"} "key") => "this works" and (:key {:key "this works"}) => "this works" both work

but this ("key" {"key" "this throws exception"}) doesn't

as "key" is just a java.lang.String which doesn't implement IFn i.e. it's not a function

@agile_geek thanks for the explanation

np

That's what I like about clojure. Always people who wants to explain things or help with problems

@agile_geek did you ever work with boot and if so, which "ide" do you use ?

@roelofw I've not really used boot, mainly lein and I use Emacs but I have friends who much prefer IntelliJ with Cursive (and some who use Vim and Fireplace or Spacemacs)

However, Emacs is a steep learning curve all of it's own

Oke, I use Cursive but I like to try this framework : https://github.com/framework-one/fw1-clj

but I seems to only be working with boot

There's no reason boot can't be used in Cursive but I've no idea how. Might be worth posting a specific question in the #boot channel?

i.e. "I'm a beginner using Cursive. How do I get started with Boot?"

or conversely ask in the #cursive channel!

it can be done with a trick : https://slack-redir.net/link?url=https%3A%2F%2Fgithub.com%2Fboot-clj%2Fboot%2Fwiki%2FFor-Cursive-Users&v=3

Im stuck at 4clojure , challenge 156 , I have to solve this :

(= (__ 0 [:a :b :c]) {:a 0 :b 0 :c 0}) 

(fn [v m](map (assoc % v) m )) 

anyone a tip how to solve it ?

@roelofw do you mean #(assoc...)?

Could be . What I try to do is to add the zero to every item of the list

that is why I have used a map

@tom : you mean that I have to use a anymious function .

And then the current item . can I call that item ?

the % is for the parameter for anonymous functions of the style #(function-name %). since you are using the (fn [param1 param2] ...) you use whatever you named your parameters

in your case, you called them v and m

@dpsutton so I do not need a map ?

i'm just telling you why the % doesn't work in the (fn [v m]) style

what functions you need are up to you

oke

i'm solving your syntax issue

No problem thanks