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Up to [LON-CAPA] / loncom / types

Move these type implementing classes to the mainline cvs from the experimental
sandbox.

    1: #
    2: #  Implement a simple queue in terms of a list.
    3: #
    4: 
    5: =pod
    6: 
    7: =head1 Queue
    8: 
    9: An object oriented implementation of a queue data structure.  queues
   10: are first in last out data structures.
   11: 
   12: =head1 Member functions:
   13: 
   14: =cut
   15: 
   16: package Queue;
   17: 
   18: 
   19: =pod
   20: 
   21: =head2 new 
   22: 
   23:   Construct a new queue.
   24: 
   25: =cut
   26: 
   27: sub new {
   28:     my $class = shift;		# Class name to bless into.
   29:     my $self  = [];		# Our data is a reference to an anon. array.
   30: 
   31:     bless($self, $class);	# Type this as an object.
   32: 
   33:     return $self;
   34: }
   35: 
   36: =pod
   37: 
   38: =head2 enqueue
   39: 
   40:    Add an element to the tail of the queue.
   41: 
   42: =cut
   43: 
   44: sub enqueue {
   45:     my $self = shift;		# Get object reference.
   46:     my $item = shift;		# Get the item to enqueue...
   47:     push(@$self, $item);		# Push the item to the back of the array.
   48: 
   49: 
   50: }
   51: 
   52: =pod
   53: 
   54: =head2 dequeue
   55: 
   56:    Remove an element from the front of the queue.
   57: 
   58: =cut
   59: 
   60: sub dequeue {
   61:     my $self = shift;		# Get object reference....
   62:     return shift @$self;		# Remove from the front of the queue.
   63: }
   64: 
   65: 
   66: 1;
   67: 
   68: =pod
   69: 
   70: =head1 Theory
   71: 
   72: The queue is implemented as an array... enqueue is a thinly disguised
   73: push, and dequeue is a thinly disguised shift.  This is probably quite
   74: in efficient for large queues, but should be fine for reasonably sized
   75: queues.
   76: 
   77: Note that since Perl is a dynamically typed language, queues can
   78: contain objects of any data type and can even be heterogenously typed.
   79: 
   80: =cut