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

    1: #
    2: #   Implement a simple stack in terms of a list.
    3: # 
    4: 
    5: =pod
    6: 
    7: =head1 Stack 
    8: 
    9: An object oriented implementation of a Stack data structure.
   10: Stacks are first in last out data structures.
   11: 
   12: =head1 Member functions:
   13: 
   14: =cut
   15: 
   16: package Stack;
   17: 
   18: =pod
   19: 
   20: =head2 new  
   21: 
   22:     Creates a new instance of a stack. 
   23:   
   24:     my $stack = Stack->new();
   25: 
   26: =cut
   27: 
   28: sub new {
   29:     my $class = shift;		# Class name.
   30:     my $self  = [];		# Create an empty list to represent the stack.
   31:     bless($self, $class);	# Turn this into an object and..
   32:     return $self;		# Return it.
   33: }
   34: 
   35: =pod
   36: 
   37: =head2 push
   38: 
   39:     takes an item and pushes it onto the back end of the stack.
   40: 
   41:     my $stack = Stack->new();
   42:     $stack->push(something);
   43: 
   44: =cut
   45: 
   46: sub push {
   47:     my $self = shift;		# Gets the list...
   48:     my $item = shift;		# The item to push.
   49:     push(@$self,$item);
   50: }
   51: 
   52: =pod
   53: 
   54: =head2 pop
   55: 
   56:     Returns the item at the top of the stack: does a pop.
   57: 
   58:     my object = Stack->new();
   59:     my $item = object->pop();
   60: 
   61: =cut
   62: 
   63: sub pop {
   64:     my $self = shift;
   65:     return pop(@$self);
   66: }
   67: 
   68: 
   69: 1;
   70: 
   71: =pod
   72: 
   73: =head1 Internal implementation details
   74: 
   75: Stacks are implemented as lists.  Thus a stack is a thinly disguised
   76: list with push and pop wrappers.  Since PERL is a dynamically typed
   77: language, stacks can contain any data type ... including a
   78: heterogenous collection of types.
   79: 
   80: =cut
   81: