Clojure Remove item from Vector at a Specified Location

Question

Is there a way to remove an item from a vector based on index as of now i am using subvec to split the vector and recreate it again. I am looking for the reverse of assoc fo

Answer 1

subvec is fast ; combined with transients it gives even better results.

Using criterium to benchmark:

user=> (def len 5)
user=> (def v (vec (range 0 5))
user=> (def i (quot len 2))
user=> (def j (inc i))

; using take/drop
user=> (bench
         (vec (concat (take i v) (drop j v))))
;              Execution time mean : 817,618757 ns
;     Execution time std-deviation : 9,371922 ns

; using subvec
user=> (bench
         (vec (concat (subvec v 0 i) (subvec v j len))))
;              Execution time mean : 604,501041 ns
;     Execution time std-deviation : 8,163552 ns

; using subvec and transients
user=> (bench
         (persistent!
          (reduce conj! (transient (vec (subvec v 0 i))) (subvec v j len))))
;              Execution time mean : 307,819500 ns
;     Execution time std-deviation : 4,359432 ns

The speedup is even greater at greater lengths ; the same bench with a len equal to 10000 gives means: 1,368250 ms, 953,565863 µs, 314,387437 µs.