Data commit

Task/Langtons-ant/Bc/langtons-ant.bc

@@ -0,0 +1,50 @@
+define o() {
+    auto i, j
+
+    "P1 "
+    w
+    h
+    for (j = 0; j < h; j++) {
+        for (i = 0; i < w; i++) {
+            a[j * w + i]
+        }
+    }
+}
+
+define l(w, h, x, y) {
+    auto a[], d, i, x[], y[]
+
+    /* d represents one of the four possible directions:
+     *             0
+     *             ⇑
+     *           3⇐ ⇒1
+     *             ⇓
+     *             2
+     * The arrays x[] and y[] contain the changes to the x and y direction for
+     * each value of d.
+     */
+    x[1] = 1
+    x[3] = -1
+    y[0] = -1
+    y[2] = 1
+
+    while (1) {
+        i = y * w + x
+        if (a[i] == 0) d += 1   /* turn right if white */
+        if (a[i] == 1) d -= 1   /* turn left if black */
+        if (d < 0) d = 3
+        if (d > 3) d = 0
+        x += x[d]
+        y += y[d]
+        a[i] = 1 - a[i]         /* toggle cell colour */
+        if (x < 0) break
+        if (x == w) break
+        if (y < 0) break
+        if (y == h) break
+    }
+
+    o()
+}
+
+l(100, 100, 50, 50)
+quit