3% Initial situtation
    4
    5% const grippers=2.
    6% const lasttime=3.
    7%block(1..6).
    8block(1).
    9block(2).
   10block(3).
   11block(4).
   12block(5).
   13block(6).
   14
   15% DEFINE
   16on(1,2,0).
   17on(2, 'table', 0).
   18on(3,4,0).
   19on(4, 'table', 0).
   20on(5,6,0).
   21on(6, 'table', 0).
   22
   23% Goal Situation
   24
   25% TEST
   26:- not on(3,2,3).
   27:- not on(2,1,3).
   28:- not on(1,'table',3).
   29:- not on(6,5,3).
   30:- not on(5,4,3).
   31:- not on(4,'table',3).
   32
   33% GENERATE
   34
   35%time(0..3).
   36time(0).
   37time(1).
   38time(2).
   39time(3).
   40location(B) :- block(B).
   41location('table').
   42
   43% GENERATE
   44
   45% { move(B,L,T) : block(B) , location(L) } 2 :-
   46%       time(T),
   47%       T<3.
   48move(B,L,T) :-
   49    block(B) ,
   50    location(L),
   51    time(T),
   52    T < 3, not neg_move(B,L,T).
   53neg_move(B,L,T) :-
   54    block(B),
   55    location(L),
   56    time(T),
   57    T < 3, not move(B,L,T).
   58
   59% DEFINE
   60
   61% effect of moving a block
   62on(B,L,T1) :-
   63    block(B),
   64    location(L),
   65    time(T),
   66    move(B,L,T),
   67    T1 is T + 1,
   68    T < 3.
   69
   70% inertia
   71on(B,L,T1) :-
   72    location(L),
   73    block(B),
   74    time(T),
   75    on(B,L,T),
   76    T1 is T + 1,
   77    not neg_on(B,L,T1),
   78    T < 3.
   79
   80% uniqueness of location
   81neg_on(B,L1,T) :-
   82    block(B),
   83    location(L),
   84    location(L1),
   85    time(T),
   86    on(B,L,T),
   87    L \= L1.
   88
   89% TEST
   90
   91% neg_on is the negation of on
   92:- block(B), location(L), time(T), on(B,L,T), neg_on(B,L,T).   93
   94% two blocks cannot be on top of the same block
   95:- block(B), time(T), on(B1,B,T), block(B1), on(B2,B,T), block(B2), B1 \= B2.   96
   97% a block can’t be moved unless it is clear
   98:- location(L), time(T), T < 3, move(B,L,T), on(B1,B,T), block(B), block(B1).   99
  100% a block can’t be moved onto a block that is being moved also
  101:- block(B), block(B1), location(L), time(T), T < 3, move(B,B1,T), move(B1,L,T).  102
  103?- move(A,B,L).