PriorityQueue

Construct with an item schema in front of the module name, for example Int32 PriorityQueue.

Fields

• data: backing array storage that stores the heap elements.

Public methods

• push (item --): inserts one item and restores heap order.
• top (-- ref): returns Ref to the current top item.
• pop (--): removes the current top item and restores heap order.
• getSize (-- count): returns the current item count.
• empty (-- isEmpty): reports whether the queue has no items.

Internal helpers

• swap (i1 i2 --): swaps two heap positions.
• parent (ordinal -- parentOrdinal): parent-ordinal helper.
• lchild (ordinal -- childOrdinal): left-child ordinal helper.
• rchild (ordinal -- childOrdinal): right-child ordinal helper.
• lift (ordinal --): restores heap order upward from one ordinal.

Ordering and empty state

• The queue compares items through <.
• The top item is the greatest item according to that comparison.
• push preserves that maximal-item property.
• top and pop require one non-empty queue.
• No stable order is guaranteed among equal items.
• top returns one Ref into the current heap array storage.
• push and pop may move stored items while restoring heap order, so earlier references into the queue storage must be treated as invalid after those operations.
• pop removes the current top item and then repairs heap order with the remaining items.

Examples

Runtime example: empty state, size, and top

"PriorityQueue" use
"String" use
"control" use

{} Int32 {} [
  q: Int32 PriorityQueue;
  ("empty0=" q.empty LF) printList
  10 @q.push
  3 @q.push
  20 @q.push
  ("size=" q.getSize LF
   "top=" @q.top new LF
   "empty1=" q.empty LF) printList
  0
] "main" exportFunction

Expected Output

empty0=TRUE
size=3
top=20
empty1=FALSE

See also

• Array: Growable array.
• Deque: Double-ended queue data structure.
• algorithm: Collection interfaces, comparison helpers, iteration adapters, and view slicing utilities.
• HashTable: Hash-based map and set module.