1 files changed, 48 insertions, 0 deletions
diff --git a/lib/Queue.ck b/lib/Queue.ck
new file mode 100644
index 0000000..f05ae5e
--- /dev/null
+++ b/lib/Queue.ck
@@ -0,0 +1,48 @@
+/*
+ * Queue data structure
+ */
+public class Queue {
+	class Element {
+		Element @next;
+		Object @payload;
+	}
+	Element head @=> Element @tail;
+
+	fun void
+	push(Object @data)
+	{
+		new Element @=> tail.next @=> tail;
+		data @=> tail.payload;
+	}
+
+	fun Object @
+	peek()
+	{
+		if (head.next == null)
+			/* empty */
+			return null;
+		else
+			return head.next.payload;
+	}
+
+	fun Object @
+	pop()
+	{
+		head.next @=> Element @el;
+		if (el == null)
+			/* empty */
+			return null;
+
+		el.next @=> head.next;
+		if (el == tail)
+			/* but now it's empty! */
+			head @=> tail;
+		return el.payload;
+	}
+
+	fun void
+	flush()
+	{
+		while (pop() != null);
+	}
+}