0. #lang racket
1.  
2. (require math/array)
3.  
4. (define (world dimensions)
5.   (array->mutable-array
6.    (make-array dimensions 7)))
7.  
8. (define (tiles elevation)
9.   (cond
10.     [(elevation . < . 8)
11.      "~"]
12.     [(elevation . < . 10)
13.      ":"]
14.     [(elevation . < . 12)
15.      " "]
16.     [(elevation . < . 14)
17.      "n"]
18.     [else
19.      "A"]))
20.  
21. (define (view-world map south east height width)
22.   (define (view-row south east width)
23.     (if (= width 1)
24.         (array-ref map south east)
25.         (append
26.          (list (array-ref map #(south east)))
27.          (view-row south (+ east 1) (- width 1)))))
28.   (if (= height 1)
29.       (view-row south east width)
30.       (append
31.        (list->string (view-row south east width))
32.        "\n"
33.        (view-world map (+ south 1) east (- height 1) width))))
34.  
35. (define out
36.   (open-output-file "myData" #:exists 'truncate))
37. (write world out)
38. (close-output-port out)
39.  
40. (define in
41.   (open-input-file "myData"))
42. (display (view-world (read in) 1 1 5 5))
43. (close-input-port in)

=>

open-output-file: `write' access denied for myData

out: undefined;

cannot reference an identifier before its definition

in module: 'm

out: undefined;

cannot reference an identifier before its definition

in module: 'm

open-input-file: cannot open input file

path: /home/pasterack/racket68/share/pkgs/web-server-lib/w

eb-server/default-web-root/htdocs/myData

system error: No such file or directory; errno=2

in: undefined;

cannot reference an identifier before its definition

in module: 'm

in: undefined;

cannot reference an identifier before its definition

in module: 'm