Queue/Usage: Difference between revisions

=={{header|PL/I}}==

<lang PL/I>

test: proc options (main);

/* To implement a queue. */

define structure

1 node,

2 value fixed,

2 link handle(node);

declare (head, tail, t) handle (node);

declare null builtin;

declare i fixed binary;

head, tail = bind(:node, null:);

do i = 1 to 10; /* Add ten items to the tail of the queue. */

if head = bind(:node, null:) then

do;

head,tail = new(:node:);

get list (head => value);

put skip list (head => value);

head => link = bind(:node, null:); /* A NULL link */

end;

else

do;

t = new(:node:);

tail => link = t; /* Point the tail to the new node. */

tail = t;

tail => link = bind(:node, null:); /* Set the tail link to NULL */

get list (tail => value) copy;

put skip list (tail => value);

end;

end;

/* Pop all the items in the queue. */

put skip list ('The queue has:');

do while (head ^= bind(:node, null:));

put skip list (head => value);

head = head => link;

end;

end test;

</lang>

The output:

<lang>

1

3

5

7

9

11

13

15

17

19

The queue has:

1

3

5

7

9

11

13

15

17

</lang>