Question

我找到了在http://rosettacode.org/wiki/Sierpinski_carpet#Scheme生成Sierpinski地毯的代码 - 但它不会在DrRacket环境或WeScheme中运行。有人可以为这两种环境提供解决方案吗？

Answer 1

在预先添加

后，看起来这个代码在DrRacket中运行良好

#lang racket

表示代码是用Racket编写的。如果这还不够，我可以提供更多细节。

Answer 2

我已将该程序翻译为在WeScheme下运行。我做了一些改动：而不是使用（显示）和（换行），我使用WeScheme提供的图像基元来制作更好的图像。你可以view the running program and its source code。为方便起见，我还在此处提供了来源：

;; Sierpenski carpet.
;; http://rosettacode.org/wiki/Sierpinski_carpet#Scheme

(define SQUARE (square 10 "solid" "red"))
(define SPACE (square 10 "solid" "white"))

(define (carpet n)
  (local [(define (in-carpet? x y)
           (cond ((or (zero? x) (zero? y))
                  #t)
                 ((and (= 1 (remainder x 3)) (= 1 (remainder y 3)))
                  #f)
                 (else
                  (in-carpet? (quotient x 3) (quotient y 3)))))]

  (letrec ([outer (lambda (i)
                    (cond
                      [(< i (expt 3 n))                       
                       (local ([define a-row
                                 (letrec ([inner 
                                           (lambda (j)
                                             (cond [(< j (expt 3 n))
                                                    (cons (if (in-carpet? i j)
                                                              SQUARE
                                                              SPACE)
                                                          (inner (add1 j)))]
                                                   [else
                                                    empty]))])
                                   (inner 0))])
                         (cons (apply beside a-row)
                               (outer (add1 i))))]
                      [else
                       empty]))])
    (apply above (outer 0)))))


(carpet 3)

Answer 3

以下是WeScheme的修改代码。 WeScheme不支持do循环语法，所以我使用srfi-1展开

(define (unfold p f g seed)
  (if (p seed) '()
    (cons (f seed)
          (unfold p f g (g seed)))))

(define (1- n) (- n 1))

(define (carpet n)
  (letrec ((in-carpet?
             (lambda (x y)
               (cond ((or (zero? x) (zero? y))
                      #t)
                     ((and (= 1 (remainder x 3)) (= 1 (remainder y 3)))
                      #f)
                     (else
                       (in-carpet? (quotient x 3) (quotient y 3)))))))
    (let ((result
            (unfold negative?
                    (lambda (i)
                      (unfold negative?
                              (lambda (j) (in-carpet? i j))
                              1-
                              (1- (expt 3 n))))
                    1-
                    (1- (expt 3 n)))))
      (for-each (lambda (line)
                         (begin
                           (for-each (lambda (char) (display (if char #\# #\space))) line)
                           (newline)))
                result))))

Sierpinski地毯方案代码的翻译

3 个答案: