DragonFly On-Line Manual Pages

cl_queue(1)            DragonFly General Commands Manual           cl_queue(1)

       Authors: Enrique Marcote (enrique.marcote@erlang-consulting.com) Miguel
       Rodriguez (miguel@erlang-consulting.com)

MODULE
       cl_queue

DESCRIPTION
       cl_queue is a library application to implement memory queues with
       priority.

       Elements are inserted with a priority.  Elements with higher priority
       are extracted first.  Priority 0 is the highest and decreases as the
       number increases.  There is not a predefined maximun value.

ARQUITECTURE
       cl_queue is a data structure and no intermediate process is created.
       The client application is responsible for creating a controlling
       process for the cl_queue if desired.  The module cl_queue_srv provides
       a generic queue controlling process.

       cl_queue is basically a lists of standard queues, one queue per
       priority.

                +------------+
                |   queue    |
                | priority 0 |
                +------------+

                +------------+
                |   queue    |
                | priority 1 |
                +------------+

                     ...

                +------------+
                |   queue    |
                | priority n |
                +------------+

DESIGN
       cl_queue acts as a single queue with priorities.  First elements from
       the highest priority queue are extracted.  If no elements available on
       that queue, the queue with the next priority is selected, and so on.

       Homonymous functions in queue use the same return values than those in
       the standard queue module.

ORIGINAL EXPORTS
       Exported functions.

   in(Item, Q1) -> Q2
       Types

       Item = term()

       Q1 = Q2 = queue()

       Inserts an Item in the rear of Q1 with the highest priority.  Returns
       the resulting Q2

   in(Item, Q1, Priority) -> Q2
       Types

       Item = term()

       Q1 = Q2 = queue()

       Priority = int()

       Inserts an Item in the rear of Q1 with a given Priority.  Returns the
       resulting Q2

       This function fails if Priority is not an integer.

   is_queue(Term) -> true | false
       Types

       Term = term()

       Returns true if Term is a queue, false otherwise.

   is_empty(Q) -> true | false
       Types

       Q = queue()

       Returns true if Q is empty, false otherwise.

   join(Q1, Q2) -> Q3
       Types

       Q1 = Q2 = Q3 = queue()

       Returns a queue Q3 that is the result of joining Q1 and Q2  with Q1 in
       front of Q2.

   len(Q) -> N
       Types

       Q = queue()

       N = int()

       Returns the length of the queue Q

   new() -> Q
       Types

       Q = queue()

       Returns an emtpy queue.

   out(Q1) -> Result
       Types

       Q1 = Q2 = queue()

       Result = {{value, Item}, Q2} | {empty, Q1}

       Removes the item at the front of queue  Q1.  Returns  the  tuple
       {{value,  Item},  Q2},  where Item is the item removed and Q2 is the
       resulting queue. If Q1 is empty, the tuple  {empty,  Q1}  is returned.

       The item at the front is the one at the front among those with the
       highest priority.

   out_r(Q1) -> Result
       Types

       Q1 = Q2 = queue()

       Result = {{value, Item}, Q2} | {empty, Q1}

       Removes the item at the rear of queue  Q1.  Returns  the  tuple
       {{value,  Item},  Q2},  where Item is the item removed and Q2 is the
       resulting queue. If Q1 is empty, the tuple  {empty,  Q1}  is returned.

       The item at the rear is the one at the rear among those with the lowest
       priority.

EXTENDED EXPORTS
       Extended API functions.

   get(Q) -> Item
       Types

       Q = queue()

       Item = term()

       Returns the Item at the front of queue  Q.

       Fails with reason empty if Q is empty.

   get_r(Q) -> Item
       Types

       Q = queue()

       Item = term()

       Returns the Item at the rear of queue  Q.

       Fails with reason empty if Q is empty.

SEE ALSO
       common_lib(1)

common_lib                      Version: 3.3.4                     cl_queue(1)