However, you use an item index of -1 to insert an item at the end of the list. To remove an item from a queue, use the POPN, POPC, POPL, or POPO function. As with stacks, you should use the ITEMTYPE ...

The ConcurrentStack and ConcurrentQueue classes, lock-free and thread-safe implementations of the Stack and Queue classes, build thread safe collections in .Net Thread safe collections were first ...