Algol 68 Genie

hilbert-curve-latex.a68

     
   1  COMMENT
   2  
   3  @section Synopsis
   4  
   5  Generate LaTeX code to plot a Hilbert curve.
   6  
   7  
   8        ╭───╮   ╭───╮   ╭───╮   ╭───╮   ╭───╮   ╭───╮   ╭───╮   ╭───╮
   9        │   │   │   │   │   │   │   │   │   │   │   │   │   │   │   │
  10        │   ╰───╯   │   │   ╰───╯   │   │   ╰───╯   │   │   ╰───╯   │
  11        │           │   │           │   │           │   │           │
  12        ╰───╮   ╭───╯   ╰───╮   ╭───╯   ╰───╮   ╭───╯   ╰───╮   ╭───╯
  13            │   │           │   │           │   │           │   │    
  14        ╭───╯   ╰───────────╯   ╰───╮   ╭───╯   ╰───────────╯   ╰───╮
  15        │                           │   │                           │
  16        │   ╭───────╮   ╭───────╮   │   │   ╭───────╮   ╭───────╮   │
  17        │   │       │   │       │   │   │   │       │   │       │   │
  18        ╰───╯   ╭───╯   ╰───╮   ╰───╯   ╰───╯   ╭───╯   ╰───╮   ╰───╯
  19                │           │                   │           │        
  20        ╭───╮   ╰───╮   ╭───╯   ╭───╮   ╭───╮   ╰───╮   ╭───╯   ╭───╮
  21        │   │       │   │       │   │   │   │       │   │       │   │
  22        │   ╰───────╯   ╰───────╯   ╰───╯   ╰───────╯   ╰───────╯   │
  23        │                                                           │
  24        ╰───╮   ╭───────╮   ╭───────╮   ╭───────╮   ╭───────╮   ╭───╯
  25            │   │       │   │       │   │       │   │       │   │    
  26        ╭───╯   ╰───╮   ╰───╯   ╭───╯   ╰───╮   ╰───╯   ╭───╯   ╰───╮
  27        │           │           │           │           │           │
  28        │   ╭───╮   │   ╭───╮   ╰───╮   ╭───╯   ╭───╮   │   ╭───╮   │
  29        │   │   │   │   │   │       │   │       │   │   │   │   │   │
  30        ╰───╯   ╰───╯   │   ╰───────╯   ╰───────╯   │   ╰───╯   ╰───╯
  31                        │                           │                
  32        ╭───╮   ╭───╮   │   ╭───────╮   ╭───────╮   │   ╭───╮   ╭───╮
  33        │   │   │   │   │   │       │   │       │   │   │   │   │   │
  34        │   ╰───╯   │   ╰───╯   ╭───╯   ╰───╮   ╰───╯   │   ╰───╯   │
  35        │           │           │           │           │           │
  36        ╰───╮   ╭───╯   ╭───╮   ╰───╮   ╭───╯   ╭───╮   ╰───╮   ╭───╯
  37            │   │       │   │       │   │       │   │       │   │    
  38         ───╯   ╰───────╯   ╰───────╯   ╰───────╯   ╰───────╯   ╰──  
  39  
  40  COMMENT
  41  
  42  INT points = 384;
  43  
  44  PROC draw member = (INT n) VOID:
  45     BEGIN INT d = points OVER (2 ^ n);
  46        MODE POINT = STRUCT (INT x, y);
  47        POINT origin := (d OVER 2, d OVER 2);
  48        print (("\begin{picture}(", whole (points, 0), ", ", whole(points, 0), ")", newline));
  49        go right (n);
  50        print (("\end{picture}"));
  51  
  52        PROC line to = (POINT end) VOID: 
  53           (POINT vector = (x OF end - x OF origin, y OF end - y OF origin);
  54            print (("\put(", whole (x OF origin, 0), ", ", whole (y OF origin, 0), "){",
  55               "\line(", whole(SIGN x OF vector, 0), ", ", whole (SIGN y OF vector, 0), "){",
  56               whole (ENTIER sqrt (x OF vector ^ 2 + y OF vector ^ 2), 0), "}}", newline));
  57            origin := end
  58           );
  59  
  60        PROC go up = (INT n) VOID:
  61           IF n > 0
  62           THEN go right (n - 1);
  63              line to ((x OF origin + d, y OF origin));
  64              go up (n - 1);
  65              line to ((x OF origin, y OF origin + d));
  66              go up (n - 1);
  67              line to ((x OF origin - d, y OF origin));
  68              go left (n - 1)
  69           FI;
  70  
  71        PROC go down = (INT n) VOID:
  72           IF n > 0
  73           THEN go left (n - 1);
  74              line to ((x OF origin - d, y OF origin));
  75              go down (n - 1);
  76              line to ((x OF origin, y OF origin - d));
  77              go down (n - 1);
  78              line to ((x OF origin + d, y OF origin));
  79              go right (n - 1)
  80           FI;
  81  
  82        PROC go left = (INT n) VOID:
  83           IF n > 0
  84           THEN go down (n - 1);
  85              line to ((x OF origin, y OF origin - d));
  86              go left (n - 1);
  87              line to ((x OF origin - d, y OF origin));
  88              go left (n - 1);
  89              line to ((x OF origin, y OF origin + d));
  90              go up (n - 1)
  91           FI;
  92  
  93        PROC go right = (INT n) VOID:
  94           IF n > 0
  95           THEN go up (n - 1);
  96              line to ((x OF origin, y OF origin + d));
  97              go right (n - 1);
  98              line to ((x OF origin + d, y OF origin));
  99              go right (n - 1);
 100              line to ((x OF origin, y OF origin - d));
 101              go down (n - 1)
 102           FI;
 103        SKIP
 104     END;
 105  
 106  draw member(4)
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