pop.m

function self = pop(self)
%increase the stack pointer and return 'top' node data
% usage :
%   stack = pop(stack)
%   element = element(stack)

% $Id$

if isempty(self.stack_pointer)
  self.element = {};
else
  self.element = data(self.stack_pointer);
  self.stack_pointer = next(self.stack_pointer);
end