LISP "Error Illegal function object..."

Question

我刚刚开始在课堂上学习LISP。我正在进行作业作业，其中我必须使用一些原始操作（例如CAR，CDR，CONS，APPEND，REVERSE，REVERSE，ATOM，EQ，EQ，2LOSE和NULL）来编程一些非常基本的功能。

所以这是我到目前为止的代码：

(defun union2 (l1 l2)
  (cond ((null l1) l2)
        ((member((car l1) l2)) (union2((cdr l1) l2)))
        (t (cons (car l1) (union2((cdr l1) l2)))))
  )

当我尝试进行测试时：

(union2 '(5 7 2 3 1) '(3 2 4 6 9))

我得到一个"错误：非法函数对象：（汽车L1）"。我的印象是我正确编写了代码。我究竟做错了什么？谢谢您的宝贵时间。

Answer 1

不要在参数列表周围放上额外的括号。

• (member((car l1) l2))应该是(member (car l1) l2)
• (union2((cdr l1) l2))应该是(union2 (cdr l1) l2)

Answer 2

尝试使用编译器，例如SBCL：

* (defun union2 (l1 l2)
  (cond ((null l1) l2)
        ((member((car l1) l2)) (union2((cdr l1) l2)))
        (t (cons (car l1) (union2((cdr l1) l2)))))
  )
; in: DEFUN UNION2
;     ((CAR L1) L2)
; 
; caught ERROR:
;   illegal function call
;     (MEMBER ((CAR L1) L2))
; 
; caught WARNING:
;   The function was called with one argument, but wants at least two.
;     ((CDR L1) L2)
; 
; caught ERROR:
;   illegal function call
;     (UNION2 ((CDR L1) L2))
; 
; caught WARNING:
;   The function was called with one argument, but wants exactly two.
;     ((CDR L1) L2)
; 
; caught ERROR:
;   illegal function call
;     (UNION2 ((CDR L1) L2))
; 
; caught WARNING:
;   The function was called with one argument, but wants exactly two.
; 
; compilation unit finished
;   caught 3 ERROR conditions
;   caught 3 WARNING conditions