/* 

  Explanation-Based Generalization (EBG) in Picat v3.

  This is a port of the program minihyper.pl in
  I. Bratko, "Prolog Programming for Artificial Intelligence", 4th edn.,
  Pearson Education / Addison-Wesley 2012
  Page 621ff (Figures 25.6, 25.7)

  This is the lift movement example from figure 25.6.

  Note: I redefined 'A =:= ' to eq(A,B)

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

*/

import ebg_v3.

main => go.


go ?=>
  load_lift_movement,
  Goal = $go(3,6,Moves),
  GenGoal = $go(Level1,Level2,GenMoves),
  ebg(Goal,GenGoal,Condition),
  bp.asserta($(GenGoal :- Condition)),
  number_vars([Level1,Level2,GenMoves]),

  println([level1=Level1,level2=Level2]),
  println(goal=Goal),
  println(genGoal=GenGoal),  
  println(condition=Condition),
  println(moves=Moves),
  nl,
  % fail, aleternative solutions (1+1+1+1-1) etc)
  
  nl.

go => true.


go2 ?=>
  go,


  Goal = $go(7,10,Moves),
  GenGoal = $go(Level1,Level2,GenMoves),
  ebg(Goal,GenGoal,Condition),
  bp.asserta($(GenGoal :- Condition)),
  number_vars([Level1,Level2,GenMoves]),

  println([level1=Level1,level2=Level2]),
  println(goal=Goal),
  println(genGoal=GenGoal),  
  println(condition=Condition),
  println(moves=Moves),
  
  nl.

go2 => true.



%  Figure 25.6  Two problem definitions for explanation-based generalization.

load_lift_movement :-
  bp.assertz($(go(Level, GoalLevel, Moves)  :-
               move_list( Moves, Distance),   
               % (Distance =:= GoalLevel - Level))), 
               eq(Distance,GoalLevel - Level))), % hakank          
  bp.assertz($(move_list( [], 0))),
  bp.assertz($(move_list( [Move1 | Moves], Distance + Distance1)  :-
               move_list( Moves, Distance),
               move( Move1, Distance1))),
  bp.assertz($(move(up, 1))),
  bp.assertz($(move(down, -1))).

eq(A,B) :- A =:= B.

%%  go( Level, GoalLevel, Moves)  if
%%    list of moves Moves brings lift from Level to GoalLevel
%%
% go(Level, GoalLevel, Moves)  :-
%                move_list( Moves, Distance),   
%                % Distance =:= GoalLevel - Level.
%                eq(Distance, GoalLevel - Level).               
%
% move_list( [], 0).

% move_list( [Move1 | Moves], Distance + Distance1)  :-
%   move_list( Moves, Distance),
%   move( Move1, Distance1).

% move( up, 1).
% move( down, -1).

% operational( A == B) :- println($operational(A,B)).
operational( eq(A, B)). % hakank