Common Lisp lambda表达式错误

Question

我正在尝试创建一个程序,它将在输出行中重写给定行而不重复.我使用这个网站作为编译器:https: //www.tutorialspoint.com/execute_lisp_online.php

这是我的代码

(SETQ X (LIST  2 -3 (LIST 4 3 0 2) (LIST 4 -4) (LIST 2 (LIST 2 0 2))-3))'
(DEFUN SEARCHDEEP (WHAT WHERE) ;Function will find out if atom `WHAT`is in a row `WHERE` => works fine
(COND
    ((NULL WHERE) NIL)
    (T (OR 
            (COND 
                ((ATOM (CAR WHERE)) (EQUAL WHAT (CAR WHERE)))
                (T (SEARCHDEEP WHAT  (CAR WHERE)))
            )
            (SEARCHDEEP WHAT (CDR WHERE))
        )
    )
)
)

(DEFUN REMDOUBLES (INPUT OUTPUT)
(
(COND 
    ((NULL INPUT) NILL) ;recursion exit
    (T                  ; funstion
        (OR             ; step into or go forward
            (COND 
                ((ATOM (CAR INPUT)) (COND 
                                        ((NOT (SEARCHDEEP (CAR INPUT) OUTPUT)) (APPEND OUTPUT INPUT)) ;if this atom wasn't added => append
                                    )
                )
                (T (REMDOUBLES (CAR INPUT) OUTPUT)) ; step into (car input => list
            )
            (REMDOUBLES (CRD INPUT) OUTPUT) ; go forward, car input is anatom
        )
    )
)
)
)

(SETQ OUT (QUOTE)) ;Empty row
(REMDOUBLES X OUT)
(PRINT OUT)

我花了最近2个小时在堆栈上查看这段代码和其他答案,但我不知道我在这里缺少什么.

我收到此错误:

*** - SYSTEM::%EXPAND-FORM:
(COND ((NULL INPUT) NILL)(T(OR (COND ((ATOM (CAR INPUT)) (COND ((NOT (SEARCHDEEP (CAR INPUT) OUTPUT))(APPEND OUTPUT INPUT)))) (T (REMDOUBLES (CAR INPUT) OUTPUT))) (REMDOUBLES (CRD INPUT) OUTPUT)))) should be a lambda expression

对不起格式化,我是函数式编程和Lisp的新手,我不知道它应该如何正确完成.

Answer 1

你的代码:

第一行:

(DEFUN REMDOUBLES (INPUT OUTPUT)

第二行:你能解释一下单括号应该做什么吗？

(

你还记得基本Lisp表达式的Lisp语法吗？

(operator argument0 argument1 ... argumentn)

不是

((operator argument0 argument1 ... argumentn))

对不起格式化,我是函数式编程和LISP的新手,我不知道它应该如何正确完成.

从Touretzky下载Lisp的入门书籍:https://www.cs.cmu.edu/~dst/LispBook/

然后了解Lisp代码的外观.

您还可以使用Lisp为您格式化代码:

这是您未格式化的代码:

[4]> (pprint '(DEFUN SEARCHDEEP (WHAT WHERE) ;Function will find out if atom `WHAT`is in a row `WHERE` => works fine
(COND
    ((NULL WHERE) NIL)
    (T (OR 
            (COND 
                ((ATOM (CAR WHERE)) (EQUAL WHAT (CAR WHERE)))
                (T (SEARCHDEEP WHAT  (CAR WHERE)))
            )
            (SEARCHDEEP WHAT (CDR WHERE))
        )
    )
)
))

这是格式化的代码:

(DEFUN SEARCHDEEP (WHAT WHERE)
 (COND ((NULL WHERE) NIL)
  (T
   (OR
    (COND ((ATOM (CAR WHERE)) (EQUAL WHAT (CAR WHERE)))
     (T (SEARCHDEEP WHAT (CAR WHERE))))
    (SEARCHDEEP WHAT (CDR WHERE))))))

但它会更好地写成:

(DEFUN SEARCHDEEP (WHAT WHERE)
  (WHEN WHERE
    (OR (IF (ATOM (CAR WHERE))
            (EQUAL WHAT (CAR WHERE))
          (SEARCHDEEP WHAT (CAR WHERE)))
        (SEARCHDEEP WHAT (CDR WHERE)))))