/* 

  Array concatenation in Picat.
 
  From Rosetta Code:
  http://rosettacode.org/wiki/Array_concatenation
  """
  Show how to concatenate two arrays in your language. If this is as simple 
  as array1 + array2, so be it. 
  """

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

*/


% import util.
% import cp.


main => go.


go => 
   L1 = [1,2,3,4,5],
   L2 = [6,7,8,9],

   % The tradtional concatenation
   writeln(L1 ++ L2),

   % Using built-in append
   append(L1,L2,L3),
   writeln(L3),

   % User defined append
   append2(L1,L2,L4),
   writeln(L4),

   nl.

append2(Xs,Ys,Zs) ?=> Xs=[], Ys=Zs.
append2(Xs,Ys,Zs) => Xs=[X|XsR], Zs=[X|Zss], append2(XsR,Ys,Zss).