Drop with Axes R←X↓[K]Y

Y may be any non-scalar array. X must be a simple integer scalar or vector. K is a vector of zero or more axes of Y.

R is an array of the elements of Y with the first or last X[i] elements removed. Elements are removed from the beginning or end of Y according to the sign of X[i].

The rank of R is the same as the rank of Y:

       ⍴⍴R ←→ ⍴⍴Y

The size of each axis of R is determined by the corresponding element of X:

      (⍴R)[,K] ←→ 0⌈(⍴Y)[,K]-|,X

Examples

      ⎕←M←2 3 4⍴⍳24
 1  2  3  4
 5  6  7  8
 9 10 11 12

13 14 15 16
17 18 19 20
21 22 23 24

      1↓[2]M
 5  6  7  8
 9 10 11 12

17 18 19 20
21 22 23 24

      2↓[3]M
 3  4
 7  8
11 12

15 16
19 20
23 24

      2 1↓[3 2]M
 7  8
11 12

19 20
23 24