Data commit

Task/Queue-Definition/Icon/queue-definition.icon

@@ -0,0 +1,34 @@
+# Use a record to hold a Queue, using a list as the concrete implementation
+record Queue(items)
+
+procedure make_queue ()
+  return Queue ([])
+end
+
+procedure queue_push (queue, item)
+  put (queue.items, item)
+end
+
+# if the queue is empty, this will 'fail' and return nothing
+procedure queue_pop (queue)
+  return pop (queue.items)
+end
+
+procedure queue_empty (queue)
+  return *queue.items = 0
+end
+
+# procedure to test class
+procedure main ()
+  queue := make_queue()
+
+  # add the numbers 1 to 5
+  every (item := 1 to 5) do
+    queue_push (queue, item)
+
+  # pop them in the added order, and show a message when queue is empty
+  every (1 to 6) do {
+    write ("Popped value: " || queue_pop (queue))
+    if (queue_empty (queue)) then write ("empty queue")
+  }
+end