/* 

  Sequence puzzle in Picat.

  From the ECLiPSe book "Constraint Logic Programming using ECLiPSe", 
  page 109. Exercise 6.2
  """
   Find a permutation of numbers 1,..,10 such that
   - 6 is put on 7th place
   - each number starting from the second one is either bigger by 3 or smaller
     by 2 than its predecessor.
  """


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

*/

import cp.

main => go.

go =>

  N = 10,
  X = new_list(N),
  X :: 1..N, 

  all_different(X),
  X[6] #= 7,
  foreach(I in 2..N)
      X[I] - X[I-1] #= 3 #\/
      X[I] - X[I-1] #= -2 
  end,

  solve(X),

  println(X),
  fail,
  
  nl.