/* 

  Global constraint sum_ctr in Picat.

  From Global Constraint Catalogue:
  http://www.emn.fr/x-info/sdemasse/gccat/Csum_ctr.html
  """

  sum_ctr(VARIABLES, CTR, VAR)
  
  Constraint the sum of a set of domain variables. More precisely, let S denote the sum of the 
  variables of the VARIABLES collection. Enforce the following constraint to hold: S CTR VAR.
  
  [CTR are: [=, !=, <, >=, > , <=]
  
  Example
   (<1, 1,4>, =, 6)
  
  The sum_ctr constraint holds since the condition 1+1+4=6 is satisfied.
  """


  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 = 3,
  X = new_list(N),
  X :: 1..5,
  
  S #>= 0, % the sum

  % X = [1,1,4],
  sum_ctr(X, 1, S),
  S #= 6,

  solve(X ++ [S]),

  println(x=X),
  println(s=S),
  nl,
  fail,
  
  nl.

%
% sum_ctr
% 
% CTR coding:
%  -2:  <
%  -1:  <=
%   0:  =
%   1:  >=
%   2:  >
% else: !=
%
sum_ctr(X, Ctr, S) =>
  SS #= sum(X),
  if     Ctr == -2 then
    SS #< S
  elseif Ctr == -1 then
    SS #<= S
  elseif Ctr ==  0 then
    SS #= S
  elseif Ctr ==  1 then
    SS #>= S
  elseif Ctr ==  2 then
    SS #> S
  else 
    SS #!= S
  end.