/* 

  Monkey and bananas problem in Picat.

  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 util.
% import cp.
import bplan.

main => go.


go => 
   initial_state(Init),
   % time(bplan(Init,L)),
   time(plan2(Init,L,Cost)),
   write(L), nl,
   writeln(len=L.length),
   writeln(cost=Cost),
   nl.


%  This is the monkey and bananas as a planning problem.

% The bananas, monkey, and box are at different locations.
% The monkey is not on the box and has no bananas.
initial_state(Init) => Init=[loc1,loc2,loc3,n,n].


% The goal is any state where the monkey has the bananas.
goal_state(Goal) => Goal=[_,_,_,_,y].

table
% Climbing on the box causes the monkey to be on the box.
legal_move(From,Move,To,Cost) ?=> 
   From=[B,M,M,n,H],Move=climb_on,To=[B,M,M,y,H],Cost=1.

% Climbing off the box causes the monkey to be off the box.
legal_move(From,Move,To,Cost) ?=> 
   From=[B,M,M,y,H],Move=climb_off,To=[B,M,M,n,H],Cost=1.

% Grabbing the bananas causes the monkey to have the bananas.
legal_move(From,Move,To,Cost) ?=> 
   From=[B,B,B,y,n],Move=grab,To=[B,B,B,y,y],Cost=1.

% Pushing the box changes where the monkey and the box are.
legal_move(From,Move,To,Cost) ?=> 
   From=[B,M,M,n,H],Move=$push(X),To=[B,X,X,n,H],Cost=1.

% Going to a location changes where the monkey is.
legal_move(From,Move,To,Cost) =>   
   From=[B,_,L,n,H],Move=$go(X),To=[B,X,L,n,H],Cost=1.