Common lisp =of（NIL 1）参数中的错误应为NUMBER类型。通用口齿不清

我有一个菜单，它是在选项功能中创建的，它的功能是让用户输入一个数字（1或2或3），以便用所选方法（DFS、BFS、BESTFS）解决问题。这个方法应该返回用户在这一行代码中选择的内容（SearchProblem'（0 0 2 6 4）'（0 0 0 0）（选项））。问题是，当我编译这个问题时，它会显示这个错误：“In=of（NIL 1）参数应该是NUMBER类型。”。我怎样才能解决这个问题

;----------Otptions menu------------------------------------------------------ 
(defun Options ()
  ( print "Searching methods." )
  ( print "For DFS method press 1." )
  ( print "For BFS method press 2." )
  ( print "For BESTFS method press 3." )
  ( print "Choose searching method" )
  ( let (opt (read))
      (cond 
        ( ( = opt 1 )  'DFS )
        ( ( = opt 2 )  'BFS )
        ( ( = opt 3 )  'BESTFS ) 
      ) 
  )
)

---

有很多事情你需要改进：

(defun Options ()                        ; Lisp does not use uppercase
  ( print "Searching methods." )         ; don't add whitespace around parentheses
                                         ; don't use print,
                                         ;   since it prints string quotes
  ( print "For DFS method press 1." )    ; users don't 'press', they 'enter'
  ( print "For BFS method press 2." )
  ( print "For BESTFS method press 3." )
  ( print "Choose searching method" )
                                         ; after print you READ
                                         ;  but you have to deliver the ouput first,
                                         ;  in case it is buffered
  ( let (opt                             ; you define two variables OPT and READ
         (read))                         ; both are set to NIL            
      (cond 
        ( ( = opt 1 )  'DFS )            ; if OPT is NIL -> ERROR. Use EQL
        ( ( = opt 2 )  'BFS )
        ( ( = opt 3 )  'BESTFS ) 
      )                                  ; no dangling parentheses in Lisp,
                                         ; this is not C
  )
)

让我为您修复此代码：

(defun options ()
  (write-string              ; we write a multiline string
"
Searching methods.
For DFS method enter 1.
For BFS method enter 2.
For BESTFS method enter 3.

Choose searching method:
")
  (finish-output)            ; deliver all output
  (let ((opt (read)))        ; define a variable OPT
    (case opt                ; CASE uses EQL
      (1  'DFS)
      (2  'BFS)
      (3  'BESTFS))))

或

或

---

有很多事情你需要改进：

(defun Options ()                        ; Lisp does not use uppercase
  ( print "Searching methods." )         ; don't add whitespace around parentheses
                                         ; don't use print,
                                         ;   since it prints string quotes
  ( print "For DFS method press 1." )    ; users don't 'press', they 'enter'
  ( print "For BFS method press 2." )
  ( print "For BESTFS method press 3." )
  ( print "Choose searching method" )
                                         ; after print you READ
                                         ;  but you have to deliver the ouput first,
                                         ;  in case it is buffered
  ( let (opt                             ; you define two variables OPT and READ
         (read))                         ; both are set to NIL            
      (cond 
        ( ( = opt 1 )  'DFS )            ; if OPT is NIL -> ERROR. Use EQL
        ( ( = opt 2 )  'BFS )
        ( ( = opt 3 )  'BESTFS ) 
      )                                  ; no dangling parentheses in Lisp,
                                         ; this is not C
  )
)

让我为您修复此代码：

(defun options ()
  (write-string              ; we write a multiline string
"
Searching methods.
For DFS method enter 1.
For BFS method enter 2.
For BESTFS method enter 3.

Choose searching method:
")
  (finish-output)            ; deliver all output
  (let ((opt (read)))        ; define a variable OPT
    (case opt                ; CASE uses EQL
      (1  'DFS)
      (2  'BFS)
      (3  'BESTFS))))

或

或

---

您可能会受到支持这种可怕的括号用法的各种CAD lisp示例的影响。本样式指南可能会有所帮助。您可能会受到支持这种可怕的括号用法的各种CAD lisp示例的影响。本样式指南可能会有所帮助。“用户不‘按’，他们‘输入’”-这是我从长xD以来看到的最好的样式更正“用户不‘按’，他们‘输入’”-这是我从长xD以来看到的最好的样式更正