%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% The three barrels in B^{MV}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%         Change the value of max_lit:        %%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% 8  (=>5, 3) - 7 actions
%%% 12 (=> 7, 5 standard) - 11 actions
%%% ...
%%% 64 (=> 64, 33, 31) - 63 actions ~3.7s
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Coded by DFP, 2007
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

max_lit(64).

barrel(M) :- max_lit(N), M is N//2 - 1.
barrel(M) :- max_lit(N), M is N//2 + 1.
barrel(N) :- max_lit(N).

%%%%%%%%%%%%%%%%%%%%%

fluent(contains(B),0,B):- barrel(B).

%%%%%%%%%%%%%%%%

action(pour(X,Y)):-  barrel(X),barrel(Y), neq(X,Y).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

causes(pour(X,Y), contains(X) eq 0,
        [ Y - contains(Y) geq contains(X)]):-
        action(pour(X,Y)).
causes(pour(X,Y), contains(Y) eq contains(Y)^(-1) + contains(X)^(-1),
        [Y - contains(Y) geq contains(X)]):-
        action(pour(X,Y)).
causes(pour(X,Y), contains(Y) eq Y,
        [Y - contains(Y) lt contains(X)]):-
        action(pour(X,Y)).
causes(pour(X,Y), contains(X) eq contains(X)^(-1) - Y + contains(Y)^(-1),
        [Y - contains(Y) lt contains(X)]):-
        action(pour(X,Y)).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

executable(pour(X,Y),[contains(X) gt 0, contains(Y) lt Y ]) :-
        action(pour(X,Y)).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

caused([], contains(B) eq B - contains(B1) - contains(B2)) :-
     max_lit(B), B1 is B//2-1, B2 is B//2+1.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

initially(contains(N) eq  N) :-
    max_lit(N).

%%%%%%%%%%%%%%%

goal(contains(N) eq M) :- max_lit(N), M is N//2.
goal(contains(P) eq M) :- max_lit(N), M is N//2, P is M + 1.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Heuristics:
%action_cost(pour(X,Y), X ) :- action(pour(X,Y)).
%cost_constraint(plan leq 170).