1 files changed, 86 insertions, 0 deletions
diff --git a/lib/List.ck b/lib/List.ck
new file mode 100644
index 0000000..539fe75
--- /dev/null
+++ b/lib/List.ck
@@ -0,0 +1,86 @@
+/*
+ * (Double-linked) list data structure with Queue and Stack operations
+ */
+public class List {
+	Element head @=> Element @tail;
+
+	/*
+	 * Stack operations
+	 */
+	fun void
+	push(Object @data)
+	{
+		Element el;
+		tail @=> el.prev;
+		el @=> tail.next @=> tail;
+
+		data @=> el.payload;
+	}
+
+	fun Object @
+	getTail()
+	{
+		/* NOTE: null for tail == head */
+		return tail.payload;
+	}
+
+	fun Object @
+	pop()
+	{
+		tail @=> Element @el;
+		if (el.prev == null)
+			/* empty */
+			return null;
+
+		el.prev @=> tail;
+		null @=> tail.next;
+
+		return el.payload;
+	}
+
+	/*
+	 * Queue operations
+	 */
+	fun void
+	put(Object @data)
+	{
+		data => push;
+	}
+
+	fun Object @
+	getHead()
+	{
+		if (head.next == null)
+			/* empty */
+			return null;
+		else
+			return head.next.payload;
+	}
+
+	fun Object @
+	get()
+	{
+		head.next @=> Element @el;
+		if (el == null)
+			/* empty */
+			return null;
+
+		el.next @=> head.next;
+		if (el.next == null)
+			/* but now it's empty! */
+			head @=> tail;
+		else
+			head @=> el.next.prev;
+
+		return el.payload;
+	}
+
+	/*
+	 * Common operations
+	 */
+	fun void
+	flush()
+	{
+		while (pop() != null);
+	}
+}