Detecting statis with blinkers or beacons or some other 2-period oscillator

conway/go/conways-game-of-life/main.go

@@ -15,10 +15,18 @@ var (
 	height  = flag.Int("height", 40, "Game height")
 	width   = flag.Int("width", 80, "Game width")
 	mutate  = flag.Bool("mutate", false, "Mutate every other generation")
-	sleepMs = flag.Int("sleep.millis", 200,
+	sleepMs = flag.Int("sleep.ms", 200,
 		"Millisecond sleep interval per generation")
 )
 
+func pushChecksum(checksum string, checksums []string) {
+	first2 := make([]string, 2)
+	copy(first2, checksums[:2])
+	checksums[0] = checksum
+	checksums[1] = first2[0]
+	checksums[2] = first2[1]
+}
+
 func main() {
 	flag.Parse()
 
@@ -29,7 +37,9 @@ func main() {
 		os.Exit(2)
 	}
 
-	cksum := game.Checksum()
+	checksums := make([]string, 3)
+	checksums[0], checksums[1], checksums[2] = "foo", "bar", "baz"
+	pushChecksum(game.Checksum(), checksums)
 
 	ticks := time.Tick(time.Duration(*sleepMs) * time.Millisecond)
 	generations := 0
@@ -39,12 +49,20 @@ func main() {
 
 		game.EvaluateGeneration()
 
-		if cksum == game.Checksum() {
+		curChecksum := game.Checksum()
+
+		if checksums[0] == curChecksum {
 			fmt.Println("Stasis!")
 			os.Exit(0)
 		}
 
-		cksum = game.Checksum()
+		if checksums[1] == curChecksum || checksums[2] == curChecksum {
+			fmt.Println("Checksum found in last 2")
+			fmt.Println("Stasis with blinkers or beacons or some such!")
+			os.Exit(0)
+		}
+
+		pushChecksum(curChecksum, checksums)
 
 		if *mutate && generations%2 == 0 {
 			game.Mutate()