Update README.md

README.md

@@ -32,6 +32,54 @@ together with path compression. This reduces storage consumption
 by almost two orders of magnitude in comparison to ART with
 similar lookup times for the longest prefix match.
 
+## Example
+
+```golang
+func ExampleTable_Contains() {
+	// Create a new routing table
+	table := new(bart.Table[struct{}])
+
+	// Insert some prefixes
+	prefixes := []string{
+		"192.168.0.0/16",       // corporate
+		"192.168.1.0/24",       // department
+		"2001:7c0:3100::/40",   // corporate
+		"2001:7c0:3100:1::/64", // department
+		"fc00::/7",             // unique local
+	}
+
+	for _, s := range prefixes {
+		pfx := netip.MustParsePrefix(s)
+		table.Insert(pfx, struct{}{})
+	}
+
+	// Test some IP addresses for black/whitelist containment
+	ips := []string{
+		"192.168.1.100",      // must match, department
+		"192.168.2.1",        // must match, corporate
+		"2001:7c0:3100:1::1", // must match, department
+		"2001:7c0:3100:2::1", // must match, corporate
+		"fc00::1",            // must match, unique local
+		//
+		"172.16.0.1",        // must NOT match
+		"2003:dead:beef::1", // must NOT match
+	}
+
+	for _, s := range ips {
+		ip := netip.MustParseAddr(s)
+		fmt.Printf("%-20s is contained: %t\n", ip, table.Contains(ip))
+	}
+
+	// Output:
+	// 192.168.1.100        is contained: true
+	// 192.168.2.1          is contained: true
+	// 2001:7c0:3100:1::1   is contained: true
+	// 2001:7c0:3100:2::1   is contained: true
+	// fc00::1              is contained: true
+	// 172.16.0.1           is contained: false
+	// 2003:dead:beef::1    is contained: false
+}
+```
 ## API
 
 The API has changed in ..., v0.10.1, v0.11.0, v0.12.0, v0.12.6, v0.16.0