Non destructive subsequence-except in lisp

Question

I know subseq in lisp return a subsequence through a range. Is there anything which will return the subsequence except that range and should be non-destructive? Any help is appreciated.

Answer 1

You can do it for any sequence with concatenate and subseq:

(defun sequence-except (sequence start end)
  (concatenate (sequence-type sequence)
               (subseq sequence 0 start)
               (subseq sequence end)))

The following should be enough to determine the type of the input sequence for bit-vectors, strings, etc:

(defun sequence-type (sequence)
  (etypecase sequence
    (list 'list)
    (array `(array ,(array-element-type sequence) (*)))))

Tests:

(loop for test in (list
                   #*10101001
                   "abcd"
                   '(0 3 2)
                   nil
                   #(1 2 3 4)
                   (make-array 4
                               :adjustable t
                               :fill-pointer T
                               :initial-contents
                               '(a b c d)))
      collect (concatenate (sequence-type test) test))