go =>
  println("Test 1"),
  queue_test1,
  nl.

empty(Q) => Q = [].
push(Queue, Value) = Q2 =>
  Q2 = [Value] ++ Queue.
pop(Q,_) = _, Q==[] ; var(Q) =>
   throw $error(empty_queue,pop,'Q'=Q).
pop(Queue,Q2) = Queue.last() =>
   Q2 = [Queue[I] : I in 1..Queue.len-1].

queue_test1 =>

    % create an empty queue
    println("Start test 2"),
    empty(Q0),
    printf("Create queue %w%n%n", Q0),

    % add numbers 1 and 2
    println("Add numbers 1 and 2 : "),
    Q1 = Q0.push(1),
    Q2 = Q1.push(2),

    % display queue
    printf("Q2: %w\n\n", Q2),

    % pop element
    V = Q2.pop(Q3),

    % display results
    printf("Pop : Value: %w Queue: %w\n\n", V, Q3),

    % test the queue
    print("Test of the queue: "),
    ( Q3.empty() -> println("Queue empty"); println("Queue not empty") ),
    nl,

    % pop the elements
    print("Pop the queue : "),
    V1 = Q3.pop(Q4),
    printf("Value %w Queue : %w%n%n", V1, Q4),

    println("Pop empty queue:"),
    catch(_V = Q4.pop(_Q5),Exception,println(Exception)),
    nl,

    println("\nEnd of tests.").