Common Lisp lambda 表达式错误

Question

我正在尝试制作一个程序，它将重写给定的行而不在输出行中重复。我正在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)

我花了最后 2 个小时在堆栈上检查这段代码和其他答案，但是我不知道我在这里遗漏了什么。

我收到这个错误：

*** - 系统::%EXPAND-FORM:<br> (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)))) 应该是lambda表达式

抱歉格式化，我是函数式编程和 Lisp 的新手，我不知道应该如何正确完成。

Answer 1

您的代码：

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？

您还记得基本 Lisp 表达式的 Lisp 语法吗？

(operator argument0 argument1 ... argumentn)

不是

((operator argument0 argument1 ... argumentn))

Sorry for the formatting, i am novice in functional programming and LISP, and i have no idea how it should be done properly.

从 Touretzky 下载介绍 Lisp 的书：https://www.cs.cmu.edu/~dst/LispBook/

然后在那里学习 Lisp 代码的样子。

您也可以使用 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))
        )
    )
)
))

这是格式化后的代码：

(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))))))

不过写成这样会更好：

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

Common Lisp lambda 表达式错误

Common Lisp lambda expression error

common-lisp

syntax-error