X-Git-Url: https://git.wirehaze.ovh/lifeboot.git/blobdiff_plain/693fc5383745f0999d9fa5348c2a3d6ffc2f8e5e..a8cfbb9937178d02aa35816ac8607b2525ba7263:/prototype.c?ds=sidebyside

diff --git a/prototype.c b/prototype.c
index 405654e..83b9398 100644
--- a/prototype.c
+++ b/prototype.c
@@ -1,5 +1,6 @@
+#include <stdint.h>
 #include <stdio.h>
-#include <stdlib.h>
+#include <string.h>
 #include <time.h>
 
 #define COLS 80
@@ -8,41 +9,126 @@
 #define DEAD ' '
 #define ALIVE '#'
 
-#define INIT_RATIO 10
+#define INIT_RATIO 4
 
-#define STR(x) _STR(x)
+#define STR(x) _STR (x)
 #define _STR(x) #x
 
-static void clearscr() {
-  printf("\e[1;1H\e[2J");
+static uint16_t xss; /* xs() state */
+
+static uint16_t
+xs () /* xorshift prng */
+{
+  xss ^= (xss << 1);
+  xss ^= (xss >> 3);
+  xss ^= (xss << 10);
+
+  return xss;
+}
+
+static void
+clearscr ()
+{
+  printf ("\e[1;1H\e[2J");
 }
 
-static void print_row(char row[COLS]) {
-  printf("%." STR(COLS) "s\n", row);
+static void
+print_row (char row[COLS])
+{
+  printf ("%." STR (COLS) "s\n", row);
 }
 
-static void print_grid(char grid[COLS * ROWS]) {
+static void
+print_grid (char grid[COLS * ROWS])
+{
   for (int i = 0; i < ROWS; i++)
-    print_row(grid + i * COLS);
+    print_row (grid + i * COLS);
+}
+
+static void
+init_grid (char grid[COLS * ROWS])
+{
+  for (int i = 0; i < COLS * ROWS; i++)
+    {
+      if (xs () % INIT_RATIO)
+        grid[i] = DEAD;
+      else
+        grid[i] = ALIVE;
+    }
+}
+
+static char
+get_state (char grid[COLS * ROWS], int row, int col)
+{
+  if (row < 0 || row >= ROWS || col < 0 || col >= COLS)
+    return DEAD;
+
+  return grid[row * COLS + col];
+}
+
+static int
+alive_neighbours (char grid[COLS * ROWS], int idx)
+{
+  int row = idx / COLS;
+  int col = idx % COLS;
+  int neighbours = 0;
+
+  for (int i = -1; i <= 1; i++)
+    for (int j = -1; j <= 1; j++)
+      if (get_state (grid, row + i, col + j) == ALIVE)
+        neighbours++;
+
+  if (get_state (grid, row, col) == ALIVE)
+    neighbours--;
+
+  return neighbours;
 }
 
-static void init_grid(char grid[COLS * ROWS]) {
-  for (int i = 0; i < ROWS * COLS; i++) {
-    if (rand() % INIT_RATIO)
-      grid[i] = DEAD;
-    else
-      grid[i] = ALIVE;
-  }
+static char
+next_state (char grid[COLS * ROWS], int idx)
+{
+  int n = alive_neighbours (grid, idx);
+
+  if (get_state (grid, idx / COLS, idx % COLS) == ALIVE)
+    {
+      if (n < 2 || n > 3)
+        return DEAD;
+
+      return ALIVE;
+    }
+
+  if (n == 3)
+    return ALIVE;
+
+  return DEAD;
+}
+
+static void
+update_grid (char grid[COLS * ROWS])
+{
+  char new[COLS * ROWS];
+
+  for (int i = 0; i < COLS * ROWS; i++)
+    new[i] = next_state (grid, i);
+
+  memcpy (grid, new, COLS * ROWS);
 }
 
-int main () {
+int
+main ()
+{
   char grid[COLS * ROWS];
 
-  srand(time(0));
-  init_grid(grid);
+  xss = time (0);
+  init_grid (grid);
 
-  clearscr();
-  print_grid(grid);
+  do
+    {
+      clearscr ();
+      print_grid (grid);
+      update_grid (grid);
+    }
+  while (getchar () != 'q');
 
   return 0;
 }