%% 
%% riverpuzzle.pl (hw #9, problem 3)
%%
%% Author: 
%% 
%% Comments:
%%


% some "nice" prolog settings...  see assignment 8's
% description for the details on what these do
% -- but it's not crucial to know the details of these Prolog internals
:- set_prolog_flag( prompt_alternatives_on, groundness ).
:- set_prolog_flag(toplevel_print_options, [quoted(true), 
     portray(true), attributes(portray), max_depth(999), priority(699)]).


%% A good place to start is with the
%% towers-of-hanoi example code covered in class
%% (and provided from the website)



%% This problem can take advantage of
%
%  assert and retract
%
%  After solving, you will need to use retractall( marked(_) )
%  -- or its equivalent -- in order to "clean the slate" for
%  using this to solve subsequent instances of the problem...

% Here, we declare marked to be a 1-argument dynamic predicate:
:- dynamic marked/1.