常见的Lisp Lambda表达式错误 [英] Common Lisp lambda expression error

问题描述

我正在尝试制作一个程序，该程序将重写给定的行，而输出行中没有重复项。我使用此网站作为编译器：
https://www.tutorialspoint.com/execute_lisp_online。 php

I am trying to make a program, which will rewrite given row without duplicates in an output row. I am using this website as a compiler: 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)

我上次用过2小时在堆栈上检查此代码和其他答案，但是我不知道这里缺少什么。

I have spent last 2 hours checking this code and other answers here, on stack, however I have no clue what am I missing here.

我收到此错误：

***-SYSTEM ::％扩展格式：

（COND（（NULL INPUT）NILL））（T（OR（COND [[ATOM（CAR INPUT））（COND（[NOT（SEARCHDEEP（CAR INPUT）OUTPUT）] [APPEND OUTPUT INPUT））））（[T（REMOUUBLES（CAR INPUT）OUTPUT））））（REMOUBLES（CRD INPUT）OUTPUT） ）））应该是lambda表达式

很抱歉，我是函数式编程和Lisp的新手，我也不知道该怎么做

Sorry for the formatting, I am novice in Functional Programming and Lisp, and I have no idea how it should be done properly.

推荐答案

您的代码：

第一行：

(DEFUN REMDOUBLES (INPUT OUTPUT)

第二行：您能解释单括号应该做什么吗？

(

您还记得基本Lisp表达式的Lisp语法吗？

You remember the Lisp syntax for basic Lisp expressions?

(operator argument0 argument1 ... argumentn)

不是

((operator argument0 argument1 ... argumentn))

很抱歉，我是函数式编程和LISP的新手，我也不知道应该如何正确完成操作。

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Lisp入门书籍： https://www.cs.cmu.edu/~dst/LispBook/

Download the introductory Lisp book from Touretzky: https://www.cs.cmu.edu/~dst/LispBook/

然后在那里学习Lisp代码的样子。

Then learn there how Lisp code looks like.

您还可以使用Lisp为您格式化代码：

You can also use Lisp to format the code for you:

这是您未格式化的代码：

This is your unformatted code:

[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))))))

但是最好写成这样：

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

这篇关于常见的Lisp Lambda表达式错误的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！