I have difficulty in using keep-indexed with multiple arguments:
Using:
(keep-indexed #(if (= %1 3) %2) [1 2 3 4 5])
I can get the value with index 3, namely (4).
If the index should be given as an argument, for example for index 3:
(keep-indexed #(if (= %1 ???) %2) 3 [1 2 3 4 5])
How should I modify the ???-part?
You would need to factor it out as keep-indexed expects a two argument function.
(defn my-nth [index coll] (keep-indexed #(if (= %1 index) %2) coll))
(my-nth 3 [1 2 3 4 5])
;=> (4)
If you are just trying to access by index, then for a vector
(get [1 2 3 4 5] 3) ;=> 4
Or indeed simply
([1 2 3 4 5] 3) ;=> 4
If you, say wanted the values at index 1 and 3.
(map (partial get [1 2 3 4 5]) [1 3])
;=> (2 4)
Or, if you like
(map [1 2 3 4 5] [1 3])
;=> (2 4)
For a list or sequence type, use nth.
