/*

  Scheduling speakers in Picat.

  From Rina Dechter, Constraint Processing, page 72
  Scheduling of 6 speakers in 6 slots.

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

*/

import cp.

main => go.

go =>

   N = 6, % number of speakers

   % the available slots 
   Available = 
       [
                  % Reasoning:        
         [3,4,5,6],    % 2) the only one with 6 after speaker F -> 1
         [3,4],   % 5) 3 or 4
         [2,3,4,5],    % 3) only with 5 after F -> 1 and A -> 6
         [2,3,4],      % 4) only with 2 after C -> 5 and F -> 1 
         [3,4],   % 5) 3 or 4
         [1,2,3,4,5,6] % 1) the only with 1
       ],

   L = findall(X,$schedule_speakers(N,Available,X)),
   foreach(S in L) writeln(S) end,
   nl.


schedule_speakers(N,Available,Xs) =>

   % the alotted speaker slot
   Xs = new_list(N),
   Xs :: 1..N,

   all_different(Xs),

   foreach({X,A} in zip(Xs,Available))
      element(_,A,X)
   end,

   solve([], Xs).