我写了一个名为＆＃39; my-append＆＃39;它取两个列表L1，L2 并将L2的每个元素附加到L1的末尾。 （换句话说，它将L1与L2结合）
该函数似乎表现正常，但我似乎得到了一个奇怪的输出。
(my-append '(a b '(1 2 3)) (list '(4 5 6) 7 8 9)) ==>
(list 'a 'b (list 'quote (list 1 2 3)) (list 4 5 6) 7 8 9)
我是计划的新手，无法判断这是正确还是现在。 请注意我在博士里面使用高级学生语言。 这是函数的代码。 （它使用两个辅助函数）
;my-append
;takes two lists L1,L2 and returns concat of L2 to L1
;it first checks if either list is empty if so it returns the non empty one
;if both are empty returns empty
;if both are non empty determine which list has smaller length
;calls my-append-helper with first arg as smaller second larger
;append-element
;takes a list L and element x and adds x
; to the end of L
; I am super limited on which operations i can use
; so i must resort to this O(n) algorithm
;my-append-helper
;takes either two non empty lists L1 L2 then
;builds the concatenation of L1 L2
;by stripping of first element of L2
;and adding it to L1
(define (append-element L x)
(cond ((equal? L '())
(list x) )
(else
(cons (first L)
(append-element (rest L) x)))))
(define my-append-helper
(lambda (L1 L2)
(cond ( (equal? '() L2)
L1)
(else (my-append-helper (append-element L1 (first L2)) (rest L2))))))
(define my-append
(lambda (L1 L2)
(cond ( (and (equal? L1 '()) (equal? L2 '()))
'() )
( (equal? L1 '() )
L2 )
( (equal? L2 '() )
L1)
( else
(my-append-helper L1 L2)))))