我将如何在球拍中创建取反二进制函数

Question

我对如何使用此功能感到困惑

函数negate-binary使用自然数列表，alist并产生一个列表，其中包含列表中有效二进制数字的补码（即仅包含0和1的数字）。

产生的清单中的补码必须与清单中出现的原始二进制数字的相对顺序相同。

假定所有数字都没有前导0；换句话说，列表将不包含任何数字，例如0001

• 数字->字符串和字符串->数字可能会有用*

(negate-binary (list 1000 101010 123 111)) ⇒ (list 111 10101 0)
(negate-binary (list 95 137 401)) ⇒ empty

Answer 1

#lang racket

; 1String is a String of length 1.

; [List-of Number] -> [List-of Number]
(define (negate-binary lon)
  (map ones-complement (filter is-binary? lon)))

; Number -> Boolean
; is `num` a binary number?
(define (is-binary? num)  
  (andmap is-binary-1string? (num->1string-list num)))

; Number -> [List-of 1String]
; number to a list of 1strings
(define (num->1string-list num)
  (explode (number->string num)))

; String -> [List-of 1String]
; convert a string to a list of 1strings
(define (explode str)
  (map string (string->list str)))

; 1String -> Boolean
; is 1string a binary 1string?
(define (is-binary-1string? 1string)
  (or (string=? 1string "0") (string=? 1string "1")))

; Number -> Number
; one's complement of a number
(define (ones-complement num)
  (str-list->number (flip-bits (num->1string-list num))))

; [List-of 1String] -> [List-of 1String]
; "0" to "1" and "1" to "0" in list of 1strings
(define (flip-bits lo1s)
  (map flip-bit lo1s))

; 1String -> 1String
; convert "0" to "1" and "1" to "0"
(define (flip-bit 1string)
  (if (string=? 1string "0") "1" "0"))

; [List-of 1String] -> Number
; convert the list of 1strings to a number
(define (str-list->number lo1s)
  (string->number (apply string-append lo1s)))


(module+ test
  (require rackunit)
  (check-equal? (negate-binary (list 1000 101010 123 111)) (list 111 10101 0))
  (check-equal? (negate-binary (list 95 137 401)) empty))

Edit：删除了所有更高阶的列表抽象，例如map，andmap，filter和apply。 
#lang racket

; 1String is a String of length 1.

; [List-of Number] -> [List-of Number]
(define (negate-binary lon)
  (ones-complement* (binary-only lon)))

; [List-of Number] -> [List-of Number]
; only keep the binary numbers
(define (binary-only lon)
  (cond
    [(empty? lon) '()]
    [else (if (is-binary? (first lon))
              (cons (first lon) (binary-only (rest lon)))
              (binary-only (rest lon)))]))

; [List-of Number] -> [List-of Number]
; one's complement for all numbers in lon
(define (ones-complement* lon)
  (cond
    [(empty? lon) '()]
    [else (cons (ones-complement (first lon))
                (ones-complement* (rest lon)))]))

; Number -> Boolean
; is `num` a binary number?
(define (is-binary? num)  
  (all-binary-1strings? (num->1string-list num)))

; [List-of 1String] -> Boolean
; are all 1strings in lo1s binary?
(define (all-binary-1strings? lo1s)
  (cond
    [(empty? lo1s) #true]
    [else (and (is-binary-1string? (first lo1s))
               (all-binary-1strings? (rest lo1s)))]))

; Number -> [List-of 1String]
; number to a list of 1strings
(define (num->1string-list num)
  (explode (number->string num)))

; String -> [List-of 1String]
; convert a string to a list of 1strings
(define (explode str)
  (charlist->string-list (string->list str)))

; [List-of Char] -> [List-of 1String]
; convert a list of characters to a list of 1strings
(define (charlist->string-list charlist)
  (cond
    [(empty? charlist) '()]
    [else (cons (string (first charlist))
                (charlist->string-list (rest charlist)))]))

; 1String -> Boolean
; is 1string a binary 1string?
(define (is-binary-1string? 1string)
  (or (string=? 1string "0") (string=? 1string "1")))

; Number -> Number
; one's complement of a number
(define (ones-complement num)
  (str-list->number (flip-bits (num->1string-list num))))

; [List-of 1String] -> [List-of 1String]
; "0" to "1" and "1" to "0" in list of 1strings
(define (flip-bits lo1s)
  (flip-all-bits lo1s))

; [List-of 1String] -> [List-of 1String]
; flip bits of all 1strings in lo1s
(define (flip-all-bits lo1s)
  (cond
    [(empty? lo1s) '()]
    [else (cons (flip-bit (first lo1s))
                (flip-all-bits (rest lo1s)))]))

; 1String -> 1String
; convert "0" to "1" and "1" to "0"
(define (flip-bit 1string)
  (if (string=? 1string "0") "1" "0"))

; [List-of 1String] -> Number
; convert the list of 1strings to a number
(define (str-list->number lo1s)
  (string->number (join-all lo1s)))

; [List-of 1String] -> String
; join all 1strings in lo1s into a single string
(define (join-all lo1s)
  (cond
    [(empty? lo1s) ""]
    [else (string-append (first lo1s)
                         (join-all (rest lo1s)))]))


(module+ test
  (require rackunit)
  (check-equal? (negate-binary (list 1000 101010 123 111)) (list 111 10101 0))
  (check-equal? (negate-binary (list 95 137 401)) empty))