prototype.c

   1 #include <stdint.h>
   2 #include <stdio.h>
   3 #include <string.h>
   4 #include <time.h>
   5
   6 #define COLS 80
   7 #define ROWS 25
   8
   9 #define DEAD ' '
  10 #define ALIVE '#'
  11
  12 #define INIT_RATIO 4
  13
  14 #define STR(x) _STR (x)
  15 #define _STR(x) #x
  16
  17 static uint16_t xss; /* xs() state */
  18
  19 static uint16_t
  20 xs () /* xorshift prng */
  21 {
  22   xss ^= (xss << 1);
  23   xss ^= (xss >> 3);
  24   xss ^= (xss << 10);
  25
  26   return xss;
  27 }
  28
  29 static void
  30 clearscr ()
  31 {
  32   printf ("\e[1;1H\e[2J");
  33 }
  34
  35 static void
  36 print_row (char row[COLS])
  37 {
  38   printf ("%." STR (COLS) "s\n", row);
  39 }
  40
  41 static void
  42 print_grid (char grid[COLS * ROWS])
  43 {
  44   for (int i = 0; i < ROWS; i++)
  45     print_row (grid + i * COLS);
  46 }
  47
  48 static void
  49 init_grid (char grid[COLS * ROWS])
  50 {
  51   for (int i = 0; i < COLS * ROWS; i++)
  52     {
  53       if (xs () % INIT_RATIO)
  54         grid[i] = DEAD;
  55       else
  56         grid[i] = ALIVE;
  57     }
  58 }
  59
  60 static char
  61 get_state (char grid[COLS * ROWS], int row, int col)
  62 {
  63   if (row < 0 || row >= ROWS || col < 0 || col >= COLS)
  64     return DEAD;
  65
  66   return grid[row * COLS + col];
  67 }
  68
  69 static int
  70 alive_neighbours (char grid[COLS * ROWS], int idx)
  71 {
  72   int row = idx / COLS;
  73   int col = idx % COLS;
  74   int neighbours = 0;
  75
  76   for (int i = -1; i <= 1; i++)
  77     for (int j = -1; j <= 1; j++)
  78       if (get_state (grid, row + i, col + j) == ALIVE)
  79         neighbours++;
  80
  81   if (get_state (grid, row, col) == ALIVE)
  82     neighbours--;
  83
  84   return neighbours;
  85 }
  86
  87 static char
  88 next_state (char grid[COLS * ROWS], int idx)
  89 {
  90   int n = alive_neighbours (grid, idx);
  91
  92   if (get_state (grid, idx / COLS, idx % COLS) == ALIVE)
  93     {
  94       if (n < 2 || n > 3)
  95         return DEAD;
  96
  97       return ALIVE;
  98     }
  99
 100   if (n == 3)
 101     return ALIVE;
 102
 103   return DEAD;
 104 }
 105
 106 static void
 107 update_grid (char grid[COLS * ROWS])
 108 {
 109   char new[COLS * ROWS];
 110
 111   for (int i = 0; i < COLS * ROWS; i++)
 112     new[i] = next_state (grid, i);
 113
 114   memcpy (grid, new, COLS * ROWS);
 115 }
 116
 117 int
 118 main ()
 119 {
 120   char grid[COLS * ROWS];
 121
 122   xss = time (0);
 123   init_grid (grid);
 124
 125   do
 126     {
 127       clearscr ();
 128       print_grid (grid);
 129       update_grid (grid);
 130     }
 131   while (getchar () != 'q');
 132
 133   return 0;
 134 }