tasks a-s

Task/Queue-Usage/D/queue-usage-1.d

@@ -0,0 +1,44 @@
+class LinkedQueue(T) {
+    private static struct Node {
+        T data;
+        Node* next;
+    }
+
+    private Node* head, tail;
+
+    bool empty() { return head is null; }
+
+    void push(T item) {
+        if (empty())
+            head = tail = new Node(item);
+        else {
+            tail.next = new Node(item);
+            tail = tail.next;
+        }
+    }
+
+    T pop() {
+        if (empty())
+            throw new Exception("Empty LinkedQueue.");
+        auto item = head.data;
+        head = head.next;
+        if (head is tail) // Is last one?
+            // Release tail reference so that GC can collect.
+            tail = null;
+        return item;
+    }
+
+    alias push enqueue;
+    alias pop dequeue;
+}
+
+void main() {
+    auto q = new LinkedQueue!int();
+    q.push(10);
+    q.push(20);
+    q.push(30);
+    assert(q.pop() == 10);
+    assert(q.pop() == 20);
+    assert(q.pop() == 30);
+    assert(q.empty());
+}