scheme - Lisp Scheme -cannot reference undefined identifier 错误

Question

我是 Lisp Scheme 的新手。 我正在尝试在 DrRacket IDE 上使用 Lisp Scheme 编写 Caesar 密码程序。 我得到以下信息

paragraph: undefined;
cannot reference undefined identifier

我的代码如下

    ;; ENVIRONMENT
    ;; contains "ctv", "vtc",and "reduce" definitions
    (load "include.ss")

    ;; contains a test document consisting of three paragraphs. 
    (load "document.ss")

    ;; contains a test-dictionary, which has a much smaller dictionary for testing
    ;; the dictionary is needed for spell checking
    (load "test-dictionary.ss")

    (load "dictionary.ss") ;; the real thing with 45,000 words

    ;; -----------------------------------------------------
    ;; HELPER FUNCTIONS

    ;; returns a function to "spin" arg "letter" by "val"
    (define spin
      (lambda (val)
        (lambda (letter)
          (vtl(modulo (+ val (ltv letter)) 26)))))

    ;; returns a function to spin current letter to value of 'e'
    (define spin_to_e
      (lambda (pos)
        (+ (- 26 pos) 4)
        ))

    ;;counts how many of a target letter are in a word. (count_letter 'x) returns a func that counts x in a list. ((count_letter 'x) '(list)) counts x in list
    (define count_letter
      (lambda (ltr)
        (lambda (lis)
          (if (null? lis)
              0
              (if (equal? (car lis) ltr)
                  (+ 1 ((count_letter ltr) (cdr lis)))
                  (+ 0 ((count_letter ltr) (cdr lis)))))
          )))

    ;;counts how many elements in a list == #t
    (define count_true
      (lambda (l)
        (reduce + (map (lambda (x) (if (equal? x #t) 1 0)) l) 0) )) ;;HERE'S MY USE OF REDUCE. Count's how many #t's are in a list

    ;;show me the truth
    (define containstrue?
      (lambda (l)
        (if (null? l)
            #f
            (if (equal? (car l) #t)
                #t
                (containstrue? (cdr l))))
        ))

    (define (sortappend l piece) ;;adds one by one, putting element at the head if >= current head
      (if (null? l) (append '() l)
          (if (>= piece (car l))
              (cons piece l)
              (append l (list piece)))))

    (define find_index ;;finds target element, returns its "index" from 0 26
      (lambda (l t)
        (if (null? l) 0
            (if (equal? t (car l))
                0
                (+ 1 (find_index (cdr l) t)) ))
        ))


    ;; *** CODE FOR ANY HELPER FUNCTION GOES HERE ***

    ;; -----------------------------------------------------
    ;; SPELL CHECKER FUNCTION

    ;;check a word's spell correctness
    ;;INPUT:a word(a global variable "dictionary" is included in the file "test-dictionary.ss", and can be used directly here)
    ;;OUTPUT:true(#t) or false(#f)
    (define spell-checker 
      (lambda (w)
        (if (member w dictionary) #t #f)
        ;; DONE
        ))

    ;; -----------------------------------------------------
    ;; ENCODING FUNCTIONS

    ;;(define (multiplyBy n) (lambda (x) (* n x)))
    ;;((multiplyBy 5) 2)       ^^how to ret a function

    ;;generate an Caesar Cipher single word encoders
    ;;INPUT:a number "n"
    ;;OUTPUT:a function, whose input=a word, output=encoded word
    (define encode-n
      (lambda (n);;"n" is the distance, eg. n=3: a->d,b->e,...z->c
        (lambda (w);;"w" is the word to be encoded
          (map (spin n) w) ;;performs helper func 'spin' on every letter in given word w
          )))

    ;;encode a document
    ;;INPUT: a document "d" and a "encoder"
    ;;OUTPUT: an encoded document using a provided encoder
    (define encode-d;;this encoder is supposed to be the output of "encode-n"
      (lambda (d encoder)
        (if (null? d) '() ;;catches recursive base case, returns empty list
            (append (cons(map encoder (car d)) '()) (encode-d (cdr d) encoder) )) ;;encode first para, concat w/ recursive call on rest
        ))

    ;; -----------------------------------------------------
    ;; DECODE FUNCTION GENERATORS
    ;; 2 generators should be implemented, and each of them returns a decoder

    ;;generate a decoder using brute-force-version spell-checker
    ;;INPUT:an encoded paragraph "p"
    ;;OUTPUT:a decoder, whose input=a word, output=decoded word
    (define Gen-Decoder-A
      (lambda (p)
        (define return_decoder
          (lambda (i)
            (encode-n i)
            ))

        (define valid_wordcounts
          (map count_true
               (list
                (map spell-checker (map (encode-n 0) p))
                (map spell-checker (map (encode-n 1) p))
                (map spell-checker (map (encode-n 2) p))
                (map spell-checker (map (encode-n 3) p))
                (map spell-checker (map (encode-n 4) p))
                (map spell-checker (map (encode-n 5) p))
                (map spell-checker (map (encode-n 6) p))
                (map spell-checker (map (encode-n 7) p))
                (map spell-checker (map (encode-n 8) p))
                (map spell-checker (map (encode-n 9) p))
                (map spell-checker (map (encode-n 10) p))
                (map spell-checker (map (encode-n 11) p))
                (map spell-checker (map (encode-n 12) p))
                (map spell-checker (map (encode-n 13) p))
                (map spell-checker (map (encode-n 14) p))
                (map spell-checker (map (encode-n 15) p))
                (map spell-checker (map (encode-n 16) p))
                (map spell-checker (map (encode-n 17) p))
                (map spell-checker (map (encode-n 18) p))
                (map spell-checker (map (encode-n 19) p))
                (map spell-checker (map (encode-n 20) p))
                (map spell-checker (map (encode-n 21) p))
                (map spell-checker (map (encode-n 22) p))
                (map spell-checker (map (encode-n 23) p))
                (map spell-checker (map (encode-n 24) p))
                (map spell-checker (map (encode-n 25) p)))))

        (return_decoder
         (find_index valid_wordcounts (apply max valid_wordcounts)))

        ))

    ;;generate a decoder using frequency analysis
    ;;INPUT:same as above ;;sample of a doc, so a para
    ;;OUTPUT:same as above
    (define Gen-Decoder-B
      (lambda (p)
        (define return_decoder
          (lambda (i)
            (encode-n i)
            ))

        (define lettercounts
          (list
           (reduce + (map (count_letter 'a)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'b)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'c)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'd)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'e)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'f)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'g)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'h)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'i)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'j)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'k)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'l)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'm)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'n)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'o)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'p)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'q)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'r)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 's)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 't)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'u)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'v)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'w)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'x)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'y)(reduce append (list p) '())) 0)
           (reduce + (map (count_letter 'z)(reduce append (list p) '())) 0)))

        (return_decoder (spin_to_e (find_index lettercounts (apply max lettercounts))))
        ))

    ;; -----------------------------------------------------
    ;; CODE-BREAKER FUNCTION

    ;;a codebreaker
    ;;INPUT: an encoded document(of course by a Caesar's Cipher), a decoder(generated by functions above)
    ;;OUTPUT: a decoded document
    (define Code-Breaker
      (lambda (d decoder)
        (if (null? d) '() ;;catches recursive base case, returns empty list
            (append (cons(map decoder (car d)) '()) (Code-Breaker (cdr d) decoder)) ) ;;encode first para, concat w/ recursive call on rest
        ))

    ;; -----------------------------------------------------
    ;; EXAMPLE APPLICATIONS OF FUNCTIONS
    (spell-checker '(h e l l o))
    (define add5 (encode-n 5))
    (encode-d document add5)
    ;(define decoderSP1 (Gen-Decoder-A paragraph))
    (define decoderFA1 (Gen-Decoder-B paragraph))
    (Code-Breaker document decoderSP1)

IDE 在代码的倒数第二行显示错误

(define decoderFA1 (Gen-Decoder-B paragraph)).

错误是由于段落。

帮我解决这个错误。在此先感谢您的帮助 我有必要的外部文件，但那些只包含列表

Answer 1

您正在使用 DrRacket 编写 Scheme 程序。由于 DrRacket 可以与多种语言一起使用，因此您需要选择 R5RS Scheme 作为您的语言:

1. In the lower left corner of DrRacket, click the drop down menu.
2. Click "Choose Language..."
3. Choose R5RS Scheme.

还要记住将文件“include.ss”、“document.ss”、“test-dictionary.ss”和“dictionary.ss”复制到与您自己的源文件相同的目录中。

PS:是这个项目吗？ https://github.com/T-G-P/CaeserDawg/blob/master/proj2.pdf