lisp - 非破坏性子序列——lisp 除外

Question

我知道 lisp 中的 subseq 返回一个范围内的子序列。除了那个范围之外，有什么东西会返回子序列并且应该是非破坏性的吗？感谢您的帮助。

Answer 1

您可以使用 concatenate 和 subseq 对任何序列执行此操作:

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

以下应该足以确定位向量、字符串等的输入序列的类型:

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

测试:

(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))