/* 

  Global constraint consecutive_values in Picat.

  From Global Constraint Catalog:
  http://www.emn.fr/z-info/sdemasse/gccat/Cconsecutive_values.html
  """
  Purpose:
  Constraint the difference between the largest and the smallest values of the 
  VARIABLES collection to be equal to the number of distinct values assigned 
  to the variables of the VARIABLES collection minus one (i.e., there is no holes 
  at all within the used values).
  
  Example: (5,4,3,5)
  """


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

*/

import cp.


main => go.

go ?=>
  N = 4,

  X = new_list(N),
  X :: 1..9,

  % X = [5,4,3,5],  % should be accepted
  % X = [1,4,3,5],  % should fail
  
  consecutive_values(X),

  solve(X),
  println(X),
  fail,

  nl.

go => true.

consecutive_values(X) =>
   NV :: 1..X.len,
   nvalue(NV, X),
   max(X) - min(X) #= NV - 1.