Vala: EvenNumbers.

vala/EvenNumbers/main.vala

@@ -0,0 +1,47 @@
+public class EvenNumbers {
+	public int get(int index) {
+		return index * 2;
+	}
+
+	public bool contains(int i) {
+		return i % 2 == 0;
+	}
+
+	public string to_string() {
+		return "[This object enumerates even numbers]";
+	}
+
+	public Iterator iterator() {
+		return new Iterator(this);
+	}
+
+	public class Iterator {
+		private int index;
+		private EvenNumbers even;
+
+		public Iterator(EvenNumbers even) {
+			this.even = even;
+		}
+
+		public bool next() {
+			return true;
+		}
+
+		public int get() {
+			this.index++;
+			return this.even[this.index - 1];
+		}
+	}
+}
+
+void main() {
+	var even = new EvenNumbers();
+	stdout.printf("%d\n", even[5]);
+	if (4 in even) {
+		stdout.printf(@"$even\n");
+	}
+	foreach (var i in even) {
+		stdout.printf("%d\n", i);
+		if (i == 20) break;
+	}
+}