/* 

  2x3-puzzle in Picat.

  This is a stripped down 8-puzzle,
  inspired by the Prolog code in Thinking as Computation. 

  This Picat model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/


import planner.

main => go.

go => 
   nolog,
   initial_state(Init),
   time(best_plan(Init,L)),
   write(L), nl,
   writeln(len=L.length),
   nl.

go2 => 
   nolog,
   initial_state(Init),
   time(best_plan_nondet(Init,L)),
   write(L), nl,
   writeln(len=L.length),
   fail,
   nl.


% This is a 2x3 version of the 15 puzzle.
% Initial state:
%%%%%%%%%
%   1 5 %
% 4 3 2 %
%%%%%%%%%
initial_state(Init) => Init=[0,1,5,4,3,2].
final(Goal) => Goal=[1,2,3,4,5,0].

% Up <-> Down
action(From,To,Move,Cost) ?=> 
   Cost=1, From=[0,B,C, X,E,F],Move=$up(X),To=[X,B,C, 0,E,F].
action(From,To,Move,Cost) ?=> 
   Cost=1, From=[A,0,C, D,X,F],Move=$up(X),To=[A,X,C, D,0,F].
action(From, To, Move,Cost) ?=> 
   Cost=1, From=[A,B,0, D,E,X],Move=$up(X),To=[A,B,X, D,E,0].
action(From,To,Move,Cost) ?=> 
   % From=S1,Move=$down(X),To=S2,
   % action(S2,$up(X),S1).
   Cost=1, Move=$down(X),
   action(To, From, $up(X),Cost).

% Left <-> Right
action(From,To,Move,Cost) ?=> 
   Cost=1, From=[0,X,C, D,E,F],Move=$left(X),To=[X,0,C, D,E,F].
action(From,To,Move,Cost) ?=> 
   Cost=1, From=[A,0,X, D,E,F],Move=$left(X),To=[A,X,0, D,E,F].
action(From,To,Move,Cost) ?=>
   Cost=1, From=[A,B,C, 0,X,F],Move=$left(X),To=[A,B,C, X,0,F].
action(From,To,Move,Cost) ?=> 
   Cost=1, From=[A,B,C, D,0,X],Move=$left(X),To=[A,B,C, D,X,0].
action(From,To,Move,Cost) => 
   % From=S1,Move=$right(X),To=S2,
   % action(S2,$left(X),S1).
   Cost=1, Move=$right(X),
   action(To,From,$left(X),Cost).