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namespace;
include rt;
// conway's life on a 10 x 20 torus, with typed 2d arrays in a struct.
// a glider walks diagonally and wraps around the edges.
const H = 10, W = 20;
struct board { int[10][20] c; };
int get(board* b, int y, int x) { return b.c[(y + H) % H][(x + W) % W]; }
void step(board* from, board* to) {
for (int y = 0; y < H; y++)
for (int x = 0; x < W; x++) {
int n = 0;
for (int dy = 0 - 1; dy <= 1; dy++)
for (int dx = 0 - 1; dx <= 1; dx++)
if (dy || dx) n += get(from, y + dy, x + dx);
to.c[y][x] = n == 3 || (n == 2 && from.c[y][x]);
}
return;
}
void show(board* b, int gen) {
rt.put_s("generation "); rt.put_n(gen); rt.put_c(10);
for (int y = 0; y < H; y++) { for (int x = 0; x < W; x++) rt.put_c(b.c[y][x] ? '#' : '.'); rt.put_c(10); }
return;
}
void main() {
board* a = rt.new(board), b = rt.new(board);
a.c[0][1] = 1; a.c[1][2] = 1; a.c[2][0] = 1; a.c[2][1] = 1; a.c[2][2] = 1;
// two generations a pass, a -> b -> a: owned boards can't be swapped
// through a temporary, since the analyzer can't follow that
for (int g = 0; g <= 40; g += 2) {
if (g % 20 == 0) show(a, g);
step(a, b);
step(b, a);
}
rt.free(a); rt.free(b);
return;
}
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